Talk Abstracts

How the olivocerebellar circuit represents predictable stimuli 4

Aalok Varma | PhD Student | NCBS 4

Precise excitation-inhibition balance - computational implications for feedforward circuits 5

Aanchal Bhatia | PhD Student | NCBS 5

The effect of temporal patterns and noisy inputs on stereotypic sensory responses in the insect olfactory system 6

Aarush Mohit Mittal | PhD Student | IIT Kanpur 6

Electrical synapses modulate free-running rhythms in Drosophila melanogaster. 7

Aishwarya Ramakrishnan | PhD Student | JNCASR 7

LSD 1-BDNF activity in LH-MFB area is essential for reward seeking behavior by intracranial self-stimulation 8

Amul Sakharkar | Faculty | Pune University 8

Egr-1, a candidate molecular player involved in time-related learning and memory processes in honey bees 9

Aridni Shah | PhD Student | NCBS 9

Postnatal Fluoxetine evokes structural and functional changes in the rodent hippocampus 10

Ashmita Chatterjee | Master's Student | TIFR Mumbai 10

Building the brain: Role of Transcription factors and chromatin regulators 11

Bhavana Muralidharan | Faculty | inStem Bangalore 11

The Visible Burrow System: assessing behavioural, physiological and neurobiological correlates of hierarchical ranking position in wild-type Groningen rats 12

Deepika Patel | PhD Student | University of Groningen 12

Cytoskeletal remodeling protein Formin-2 in development of neural circuits in zebrafish 13

Dhriti Nagar | PhD Student | IISER Pune 13

Analyzing the role of sensory feedback in the initiation of zebra finch song. 14

Divya Rao | PhD Student | IISER Pune 14

A ribosomal tag in zebrafish Purkinje neurons for in vivo imaging and translatomic profiling 15

Gnaneshwar V. Yadav | Post Doctoral Fellow | NCBS 15

Heparan sulfate modifications determine navigation properties of thalamocortical axons in the developing mouse forebrain. 17

Mallika Chatterjee | Faculty | Amity University 17

Ameliorating early life stress mediated olfactory deficits using an environment enrichment housing 18

Meenakshi Pardasani | PhD Student | IISER Pune 18

α-Synuclein fibrils induced disruption of pacemaker firing in dopamine neurons is dependent on selective K-ATP channel activation 19

Poonam Thakur | Wellcome Trust-DBT India Alliance Fellow | CCMB 19

A gene candidate for social memory deficit 20

Prakash Devaraju | Post Doctoral Fellow | St Jude Children's Research Hospital 20

Understanding the representation of innate valence of monomolecular odors and their binary mixtures in the activity of antennal lobe neurons 21

Pranjul Singh | PhD Student | IIT Kanpur 21

A resource to facilitate the cellular basis of mental illness in humans 22

Raghu Padinjat | Faculty | NCBS 22

Differential propagation of ripples along the proximo-distal and septo-temporal axes of dorsal CA1 of rats 23

Sachin Deshmukh | Faculty | IISc 23

Robustness properties of chemical switches 24

Sahil Moza | PhD Student | NCBS 24

A novel function of rodent olfactory system: airflow detection and discrimination in mice. 25

Sarang Mahajan | PhD Student | IISER Pune 25

Neto-mediated intracellular interactions sculpt postsynaptic composition at the Drosophila neuromuscular junction 26

Saumitra Dey Choudhury | Post Doctoral Fellow | NATIONAL INSTITUTES OF HEALTH, BETHESDA 26

Regulation of Synapse Development by DYRK1A/mnb Kinase 27

Sayantan Datta | PhD Student | TIFR Hyderabad 27

Understanding the origin of introductory vocalisations in male zebra finch song 28

Shikha Kalra | PhD Student | IISER Pune 28

A novel genetic pathway where SYD-2/Liprin-α acts downstream of LRK-1/LRRK2 and along with AP complexes to mediate polarized cargo trafficking in neurons 29

Shirley Bharat Dixit | Junior Research Fellow | TIFR Mumbai 29

Understanding ALS using Drosophila Tripartite Synapse. 30

Shweta Tendulkar | PhD Student | IISER Pune 30

Role of STIM1 in regulating gene expression and synaptogenesis in Cerebellar Purkinje neurons 31

Sreeja Kumari Dhanya | PhD Student | NCBS 31

Transcription factor LHX2 is required in early cortical progenitors for normal thalamocortical innervation 32

Suranjana Pal | Post Doctoral Fellow | TIFR Mumbai 32

Are tungsten wires suitable as recording electrodes? 33

Swikriti Saran Singh | PhD Student | IIT Kanpur 33

Gain of function of β-catenin in the dorsal telencephalic midline has opposing effects on the hippocampus and choroid plexus 34

Varun Suresh | PhD Student | TIFR Mumbai 34

How the olivocerebellar circuit represents predictable stimuli  

Aalok Varma | PhD Student | NCBS  The well-conserved olivo-cerebellar circuit, composed of the inferior olive and the cerebellum

among other brain regions, plays an important role in motor control and other cognitive

processes. Work from our lab has shown that when presented with optic flow in a predictable

fashion, larval zebrafish respond to successive stimuli progressively faster. Calcium imaging of

the principal neurons of the cerebellum (Purkinje cells, PCs) has shown that about a third of

these cells respond when an expected stimulus is not presented, i.e. during “probe” trials. This

suggests that these neurons either compute or receive a copy of a “prediction error signal”.

Calcium transients imaged in PCs are electrophysiologically ambiguous, arising either from an

increased parallel fiber (PF)-induced simple spike rate, or from large climbing fiber (CF) EPSPs.

Larval zebrafish are amenable to simultaneous behaviour and electrophysiology, which has

shown that PCs respond to both optic flow and probe trials to some degree. However, the probe

response signature cannot be identified simply by averaging firing rates across all trials, given its

sparse encoding, so we developed and validated a method to reconstruct calcium imaging from

zebrafish Purkinje cell recordings to unambiguously identify probe responding trials.

We find that optic flow predominantly modulates PC simple spike rate, with a minor effect on CF

input rate. Probe responding trials, however, show a modulation of CF input, suggesting that the

prediction error signal is climbing fiber mediated. Whether the computation occurs at the level

of the inferior olive, or at the level of Purkinje cells is yet to be determined. We hypothesize that

these responses come from feed-forward connections from the cerebellum to the inferior olive

(the olivocerebellar loop). We are now trying to interrogate this well-conserved olivo-cerebellar

circuit using optogenetic tools to understand how this circuit is poised to encode prediction and

prediction error responses.

Precise excitation-inhibition balance - computational implications for feedforward circuits  

Aanchal Bhatia | PhD Student | NCBS  Balanced excitation and inhibition (EI) are seen in several brain areas, including sensory cortices

and hippocampus. However, it is unknown if EI balance emerges only in response to specific

stimuli, or if all presynaptic input neuron combinations are balanced.

Aims: (1) Test if arbitrary combinations of presynaptic CA3 neurons are balanced at CA1. (2)

Measure and analyse the resultant neuronal response due to summation of balanced synaptic

inputs. Methods: We optogenetically stimulated Channelrhodopsin2-expressing CA3 neurons

with hundreds of different input combinations, and monitored CA1 neuron responses

intracellularly in mouse hippocampal slices. We further used computational modelling to

characterize how the EI responses integrate at CA1. Results: We discovered that hundreds of

randomly chosen combinations of presynaptic neurons were balanced, demonstrating a striking

degree of precision in EI balance in the CA3-CA1 network. Integration of these balanced inputs

led to divisive normalization in the subthreshold domain, i.e., larger input amplitudes led to

diminishing changes in CA1 responses. Biophysically, subthreshold divisive normalization (SDN)

based gain control emerged from EI summation, because increasing the input strength advanced

the inhibitory onset toward excitatory onset. This resulted in shared information coding

between response amplitude and timing.

Conclusions: This study shows, (1) the granularity of EI balance is much finer than previously

thought, (2) subthreshold normalization by SDN, provides an analogue gain control and gating

mechanism. In summary, we propose two new fundamental attributes of feedforward circuits:

precise EI balance and SDN.

The effect of temporal patterns and noisy inputs on stereotypic sensory responses in the insect olfactory system 

Aarush Mohit Mittal | PhD Student | IIT Kanpur 

Connections between neuronal populations may be genetically hardwired or random. In the

insect olfactory system, projection neurons of the antennal lobe connect randomly to Kenyon

cells of the mushroom body. Consequently, while the odor responses of the projection neurons

are stereotyped across individuals, the responses of the Kenyon cells are variable. Surprisingly,

downstream of Kenyon cells, mushroom body output neurons show stereotypy in their

responses. In a previous study where we looked at neural responses using a firing rate model,

we established that the stereotypy is enabled by the convergence of inputs from many Kenyon

cells onto an output neuron. Further, the stereotypy emerges in the total response of the

Kenyon cell population using multiple odor-specific features of the projection neuron responses,

benefits from the nonlinearity in the transfer function, depends on the

convergence:randomness ratio, and is constrained by sparseness. We are now working on

understanding the role of temporal patterning in the emergence of stereotypy. Does stereotypy

vary with changes in temporal patterning and which features affect this variation? We also look

at how noisy representations of olfactory information affect the level of stereotypy.

Electrical synapses modulate free-running rhythms in Drosophila melanogaster.  

Aishwarya Ramakrishnan | PhD Student | JNCASR  

Circadian clocks are endogenous time-keeping mechanisms with an intrinsic period of

approximately 24 hrs (in the absence of external environmental cues). They regulate various

physiological and metabolic rhythms in the body and also synchronize them with external daily

environmental cycles. Due to its robust and easily quantifiable circadian rhythms in many

behaviours and a relatively few number of neurons controlling them, Drosophila melanogaster

has been used extensively in understanding the neuronal basis of circadian behaviour. In

Drosophila, these clocks are located in about 7 clusters of bilaterally distributed neurons (~150

cells) in the brain and are classified based on size and anatomical location. Previously, several

studies have investigated the roles of individual clusters of neurons in determining properties of

activity-rest rhythms under different external environmental conditions. However, an interesting

question that remains is how these neurons with slightly different intrinsic periodicities

communicate amongst each other to bring about a coherent behavioural rhythm with a single

period. Although communication via chemical synapses have been well studied in the Drosophila

circadian circuit, there have been no reports on the role of electrical synapses. I am investigating

a previously unreported role played by electrical synapses in communication amongst these

circadian clock neuronal subsets. I have performed a genetic-behavioural screen which has led

to the identification of candidate genes which play important roles in communication amongst

neurons and determine a very core clock property under constant darkness (DD).I will present

the results of the screen, the distribution of these proteins in the clock neuronal network and

the possible mechanisms by which these genes influence circadian clock properties.

LSD 1-BDNF activity in LH-MFB area is             essential for reward seeking behavior by           intracranial self-stimulation  

Amul Sakharkar | Faculty | Pune University  

Sneha Sagarkar, Nagalakshmi Balasubramanian, Amit Choudhary,           Dadasaheb Kokare, Nishikant Subhedar, Amul Sakharkar  Intracranial self-stimulation (ICSS) of the lateral hypothalamus (LH)-medial forebrain bundle

(MFB) is a reliable technique to study reward mechanisms. Reward induces activity-dependant

gene expression and synaptic plasticity-related changes. However, the mechanisms of chromatin

remodelling in the LH-MFB during the reward is not known. Histone modifications in the reward

circuit represent some of the strong and enduring changes in the brain. For example, the

lysine-specific demethylase-1 (LSD 1), an enzyme that demethylates histone proteins, plays a

critical role in regulating transcriptional repression as well as activation in a wide range of

systems including memory and emotional behaviors. The current study focuses on studying the

role of LSD1 within the circuitry of LH-MFB in the ICSS-induced reward.

METHODS: Adult male Wistar rats were conditioned to self-stimulate via an electrode in the

right LH–MFB. The lever press activity, expression of BDNF and LSD1, and histone methylation

(H3K9me2 and H3K4me2) levels in the LH-MFB at the BDNF promoter were measured in the side

ipsilateral to the implantation of electrode. Effects of LSD1 siRNA alone and co-administered

with BDNF peptide on behavioural and epigenetic measures were also examined.

RESULTS: ICSS conditioning increased expression levels of LSD1 and BDNF in the LH area. While

the H3K4me2 levels at the BDNF IVp and BDNF IXp were increased, H3K9me2 levels were found

to be decreased. Treatment with pan LSD1 siRNA post-conditioning inhibited lever press activity

coinciding with the reduction in BDNF expression and levels of H3K4me2 as well as H3K9me2.

Further, the co-administration of BDNF peptide and LSD1 siRNA restored the lever press activity.

All these epigenetic and behavioural changes were resolved in a week after the LSD1 siRNA

administration. The reduction of LSD1 protein and mRNA levels by siRNA reduced the BDNF

expression in LH-MFB of non-conditioned animals.

CONCLUSIONS: These results suggest that the LSD1 regulate BDNF expression in LH-MFB via

H3-K4 and H3-K9 methylation and this mechanism play an important role in the ICSS-induced

reward.

Egr-1, a candidate molecular player involved in             time-related learning and memory processes         in honey bees  

Aridni Shah | PhD Student | NCBS  Honey bee foraging is one of the best studied and most fruitful behavioral paradigms in

understanding the sensory and cognitive capabilities of insects and animals in general. During

the last few years, our lab has developed and used different molecular techniques to identify

neuromodulators and genes involved in foraging-related learning processes.

We demonstrated that continuous foraging in honey bees is accompanied by a sustained

upregulation of the transcription factor Egr-1 (early growth response protein-1) and candidate

downstream genes involved in learning and memory (EcR, DopEcR, Ddc, Dop2).

Since Egr-1 expression changes were strongly associated with onset of foraging, we asked if the

time of foraging affects Egr-1 expression. We found that Egr-1 expression was upregulated at the

time of training in morning (8-10 am) and evening (4-6 pm) feeder trained foragers even in the

absence of food reward . At all the other tested time points, expression levels were low. In

addition, by training bees to 2 feeders that were separated in space and time, we found that

Egr-1 expression was highly dependent on the individual foraging activity of the bee. Bees that

foraged only in the morning or the evening feeder showed higher expression at the respective

timepoints only whereas bees that visited both the feeders showed higher expression at both

the time points. When we prevented time trained foragers from flying out using an "artificial

rain" set-up, foragers showed slight but significant increases in Egr-1 expression around the time

of feeder training. In-situ hybridization demonstrated that foraging- and feeder time-training

particularly lead to an upregulation of Egr-1 specifically in the small-type Kenyon cells of the

mushroom bodies.

Based on our results, we propose that Egr-1 is a potential molecular link between the output of

the circadian clock and the learning and memory systems involved in foraging.

Postnatal Fluoxetine evokes structural and         functional changes in the rodent hippocampus  

Ashmita Chatterjee | Master's Student | TIFR Mumbai  With the turn of the century, Mood disorders have come to the forefront of discussions

regarding hurdles that are currently impeding human development. Globalisation has put

nations in the arms race of productivity and mental health of the working class is at the eye of

the storm. For more than half a century neurobiologists have aimed to elucidate the underlying

mechanism of emergence of mood disorders, and increasing evidence suggests the role of

Serotonin in both the psychopathology and treatment of depression and anxiety.

Selective serotonin reuptake inhibitors (SSRIs), a class of popularly used antidepressants, that

prevent the clearance of the serotonin from the synapse, are the first line of treatment against

the disease. However, foetal or juvenile exposure to SSRIs, have been linked to increased

incidences of suicidal ideation and hostility. With similar findings validated in rodent models,

postnatal administration of fluoxetine (an SSRI) becomes a powerful tool to investigate the role

of serotonin in the emergence of depression and anxiety. In this study, we aimed to characterise

the Hippocampus, a region highly implicated for its role in regulating the emotional response of

animals, using an integrative approach across the network, cellular and epigenetic levels. We

found changes in the number of interneurons as well as, extracellular matrix components, both

involved in gating the inhibitory tone on the circuit. This suggests an overall dysfunction at the

level of Hippocampal functioning, an indeed we see that the circuit is more sensitive to

environmental input. Our findings indicate that serotonin permanently alters glutamate levels in

the circuit, which controls hippocampal function, ultimately affecting the emergent behavioural

phenotype.

Building the brain: Role of Transcription factors             and chromatin regulators  

Bhavana Muralidharan | Faculty | inStem Bangalore  The cerebral cortex is the seat of sensory perception, decision-making, language, learning and

memory. For a functional cerebral cortex in adulthood, a diverse number of neurons and glia are

to be produced adequately during development. Chromatin level regulations play a very crucial

role in the fate specification of neurons and glia. Several neurodevelopmental disorders stem

from mutations or perturbations to the process of chromatin regulation.

Yet our molecular understanding of these mechanisms is very poor in the developing brain.

To elucidate such mechanisms, I looked at the downstream targets of transcription factor (TF)

Lhx2, that has distinct roles in the two regions of the cerebral cortex namely neocortex and

hippocampus. In my talk, I will describe how this TF along with its association with chromatin

modifiers, regulates its target genes to specify a particular class of cortical neurons, which

project to the spinal cord and are involved in movement, in the neocortex. Whereas, in the

hippocampus, Lhx2 along with 3 other TFs participates in a complex regulatory network to

ensure proper numbers of neurons and glia.

Further, I will discuss how studying the global genome-wide occupancy profiles of TFs and

chromatin remodelers will help us understand the fine-tuning of gene expression and shed light

into the dynamicity of brain development.

Mental illnesses have neurodevelopmental origins and are poorly understood due to the lack of

appropriate mouse models to adequately recapitulate the human disease at multiple levels. As

part of the Accelerator program for Discovery in Brain disorders using Stem cells (ADBS) at

inStem, my lab utilizes the valuable iPSC lines generated from clinically dense families with

Schizophrenia and Bipolar disorder to model neuropsychiatric disorders in a dish.

The Visible Burrow System: assessing         behavioural, physiological and neurobiological       correlates of hierarchical ranking position in           wild-type Groningen rats  

Deepika Patel | PhD Student | University of Groningen  The visible burrow system (VBS) is a habitat containing burrows and an open area for mixed-sex

rat colonies. This study aims to study consequences of differential hierarchical ranking positions

on brain and behavior in wild-type Groningen (WTG) rats living in the VBS for 3 weeks. We

focused on behavioral, physiological and neurobiological indicators of chronic social stress

exposure during colony housing. Formation and maintenance of hierarchy during the colony

period was assessed by scoring of agonistic behaviours among residential male rats. Male

dominancy was validated by agonistic behavior towards an unfamiliar male intruder. We also

introduce the colony-intruder paradigm to defeat proactive male rats that had several prior

winning experience as residents in the resident-intruder paradigm. After 3 weeks of VBS housing

period, animals were sacrificed and their organs were collected and weighed. Brains were

processed for molecular analysis of actin binding protein cofilin to understand the relation

between ranking position and structural remodelling. Behavioral observations showed clear

formation of social hierarchy in male WTG rats. Dominants exhibited offensive behavior towards

subordinate and intruder male rats whereas subordinate males and intruders showed defensive

behavior. Clearly, proactive intruder rats were successfully defeated and telemetrically recorded

cardiovascular data indicate long-term alterations in heart rate, blood pressure as well as body

temperature. Body weight in male dominant as well as subordinate rats was reduced during the

colony period compared to control, pair housed rats. Dominant and subordinate rats had

increased adrenal weight and reduced fat mass compared to control rats. Interestingly, rise in

the expression of phosphorylated cofilin/cofilin proteins was observed in the subordinate rats

compared to dominant and control rats. The colony-intruder paradigm may serve as an

alternative for the resident-intruder paradigm to defeat highly aggressive rats. Housing rats in

semi-natural environment produces large individual differences in ranking position, making this

a promising model to study underlying mechanisms of individual differences in social ranking

and the potential role of high or low ranking in health and disease.

Cytoskeletal remodeling protein Formin-2 in         development of neural circuits in zebrafish  

Dhriti Nagar | PhD Student | IISER Pune  A functional brain comprises of a multitude of hardwired neural circuits with scope for synaptic

plasticity. Activity patterns within neural circuits give rise to behavioural outputs. To achieve

precise connectivity, the newly born neurons are guided to their appropriate targets by a

dynamic structure at their tip, the growth cone, which interrogates the environment to allow

efficient navigation. Active cytoskeletal remodelling is imperative to achieve such dynamicity in

response to environmental cues and is governed by several remodelling proteins, of which

Formin-2 (Fmn2) has been recently characterised (Sahasrabudhe et al., Development,2016).

Using zebrafish, we have evaluated the role of the neuronally enriched Fmn2 in the

development of neural connectivity and associated behaviours. Morpholino-mediated

knockdown of Fmn2 resulted in morphological, locomotor and self-righting defects. We find

deficits in the neural circuits underlying acoustic startle and self-righting. Fmn2 knockdown

causes axonal outgrowth defects in the commissural excitatory interneurons called the spiral

fiber neurons, in the acoustic startle circuit. The absence of Mauthner cell innervation by spiral

fiber neurons leads to increased latency to respond and therefore, impaired escape response.

Other components of the acoustic startle circuit were not compromised. This apart, we observe

self-righting defects in the Fmn2 morphants concomitant with decreased branching of the

primary motor neurons and the pectoral fin nerve. We are now exploring the contribution of the

trunk and pectoral fin movement in maintaining postural control in larval zebrafish and how

Fmn2 contributes to the development of the underlying neural circuits.

Our findings implicate the significance of Fmn2 as a specific regulator of axonal outgrowth and

pathfinding in vivo, in turn modulating behavioural outputs in larval zebrafish. In parallel, we are

characterizing CRISPR-Cas9 based mutant lines which will allow us to further dissect the role of

Fmn2 in the development of neural circuits during early development. Recent studies in humans

revealing intellectual disability due to Fmn2 loss of function (Almuqbil et al., Eur J Med Genet.,

2013; Law et al., AJHG, 2014; Marco et al., BMC Med Gen. 2018) emphasise that Fmn2 is

essential for neuronal function. Our findings make the Fmn2 loss-of-function zebrafish a

promising model to investigate the functional significance of Fmn2 in brain development and

function.

Analyzing the role of sensory feedback in the               initiation of zebra finch song.  

Divya Rao | PhD Student | IISER Pune  The song of the adult male zebra finch is a widely established model to study naturally learned

motor sequences. However, how such movements are initiated by the brain remains poorly

understood. Song bouts begin with a variable number of short vocalizations called Introductory

Notes (INs). Sequences of such INs speed up and reach a consistent acoustic “ready” state just

before the start of each song, suggesting a role for INs in motor preparation (Rajan and Doupe

2013). Here, we test a related hypothesis that INs represent a calibration process that uses

peripheral sensory feedback to get the brain “ready” to produce the song. To analyze the role of

feedback, we first characterized baseline changes in IN properties in adult male birds by

recording the same bird multiple times within a 3 year period. We found that the mean number

of INs showed very little day-to-day fluctuations, increased marginally after the first year and

then remained mostly unchanged, suggesting song initiation is a robust phenomenon in adult

birds. Next, we examined the influence of feedback by removing either (1) peripheral

proprioceptive feedback by bilaterally severing the tracheosyringeal (ts) nerve or (2) peripheral

auditory feedback through bilateral removal of the cochlea. The mean number of INs, as well as

the timing and acoustic progression of INs, remained unaffected by both these manipulations.

These results show that song initiation is independent of peripheral sensory feedback and as

such, the acoustics of vocalized INs are not actively used during this process. Further supporting

this hypothesis, we observed that the proximity of other non-song vocalizations to INs can also

facilitate song initiation. Also, in a rare bird that did not vocalize INs, we observed IN-like neural

activity in the premotor area HVC, similar to that seen in birds that produce INs. Together, these

results show that the progression of introductory notes is a reflection of the internal processes

in the brain actively getting the motor system ready for the song, in a sensory feedback

independent manner.

A ribosomal tag in zebrafish Purkinje neurons             for in vivo imaging and translatomic profiling  

Gnaneshwar V. Yadav | Post Doctoral Fellow | NCBS  Ribosomes, macromolecules that are sites of protein synthesis in cells, determine whether a

pool of transcripts expressed from corresponding genes are translated into proteins and

regulate the rate at which this occurs in any cell type. Neurons have a remarkable ability to

spatio-temporally regulate the translation of mRNAs into proteins through ribosomes located

even on distal neurites to support local synapses and neurodevelopment. However, how and

why ribosomes are designated to certain locations on neurites and its impact on the

development and function of neurons is poorly understood (Noma et al.,2017). To understand

the rules of ribosomal distribution on neurites and their influences on local or global translation

and ultimately how it affects neuronal function, it is important to have an in vivo system to track

and pull-down ribosomes in a cell-type specific manner.

Here, we have developed transgenic zebrafish in which ribosomes of Purkinje neurons are

labeled. We have tagged ribosomes by overexpressing a ribosomal protein fused to eGFP (Tryon

et al., 2013) under the control of a Purkinje neuron-specific enhancer (Matsui et al., 2014). First,

we show in vivo that ribosomal puncta are present along dendritic arbors of Purkinje neurons in

3, 5 and 7 dpf larvae. Next, we validate that these puncta co-localize with other ribosomal

markers and a translation initiation marker. We examine in vivo the effect of commonly used

translation inhibitors on the pattern of ribosomal puncta. Further, we could purify translating

ribosomes bound to their respective mRNAs using translating ribosome affinity purification

(TRAP) with a substantial modification from the protocol by Heiman et al., 2014, and sequence

these mRNAs. This allowed us to profile the influence of different mutations and experimental

manipulations on the translatomic profile of Purkinje neurons. Overall, this tool aids in tracking

neuronal ribosomes and in cataloging the translatomic changes occurring in Purkinje neurons in

response to various conditions. Similar approaches to label ribosomes in vivo and to purify them

for sequencing mRNAs can also be used in other neuronal types by exploiting cell-type specific

expression systems.

References:

1) Noma et al., 2017. Microtubule dependent ribosome localization in C. elegans neurons. eLife

2017;6:e26376

2) Tryon et al.,2013. Development of Translating ribosome affinity purification for zebrafish.

Genesis; 51:187-192

3) Heiman et al., 2014. Cell type-specific mRNA purification by translating ribosome affinity

purification (TRAP). Nature Protocols; 9; 1282-1291

Heparan sulfate modifications determine       navigation properties of thalamocortical axons         in the developing mouse forebrain.  

Mallika Chatterjee | Faculty | Amity University  Development of precise topographical connections between the thalamus and the cortex is

imperative for accurate sensory and motor functioning of the vertebrate body. Thalamocortical

axons (TCAs) navigate complex territories before reaching their final cortical destinations. This

complex route is designed by the intricate, context dependent function of various guidance

molecule-receptor complexes like Slit-Robo, Erbb-neuregulin, Nrp2-semaphorin etc.

Of late, heparan sulfate proteoglycans (HSPGs) has been shown to be key functional interactors of

signaling and axon- guidance molecules. Various post translationally modified HSPGs have been shown to

play important roles in determining corpus callosum and optic chiasm development. However, their

function in determining the trajectory of forebrain projection fibers has not been yet looked into. Gbx2, a

homeodomain containing transcription factor is expressed in the developing thalamus. Our microarray

data in mice shows that Gbx2 regulates the thalamic expression of all 3 isoforms of Hs6st -a key enzyme

of the heparan sulfate synthesis pathway known to be involved in the 6O sulfation of heparan sulfate.

Gbx2 loss causes significant down-regulation of expression of all 3 isoforms resulting in aberrant sulfation

pattern within the mutant TCAs. Analyses of Hs6st1/2 mutants reveal significant trajectory defects with

some of these mutant axons being directed ventrally towards the hypothalamus – a partial phenocopy of

Gbx2 mutants. This behavior also recapitulates Slit/Robo mutant TCA defects and using explant cultures

we show that Slit Robo interaction is indeed compromised in Hs6st1/2 mutants. In silico binding studies

of the Slit/Robo/HSPG complex in presence and absence of 6O sulfation using molecular dynamics

simulation further indicate that the increase in flexibility and decrease in stability of the 6O sulfation

lacking triad likely result in disruption of function of the complex.

Ameliorating early life stress mediated         olfactory deficits using an environment         enrichment housing  

Meenakshi Pardasani | PhD Student | IISER Pune  Early life adversity in humans result in long-term maladaptive consequences making them

susceptible to depressive disorders during adulthood. Olfactory impairments are one of the early

symptoms in patients suffering from Major Depressive disorders (MDD). For investigating the

causal link between the altered neural circuits and the behavioral deficits, the well-mapped

mouse olfactory system offers an ideal experimental mode.My primary research interest

involves understanding the effect of stress in modulating sensory information processing by

Olfactory Bulb (OB). Olfactory discrimination learning and memory deficits were observed in

case of our ELS model of maternal separation. In order to investigate the importance of early

environment on the olfactory perception, we employed a novel, inexpensive Environmental

Enrichment (EE) housing to the pups suffering from ELS. Reversal of olfactory learning deficits

through EE was observed. To further investigate the molecular mechanisms, I am using

immunohistochemical techniques to look at the alterations in the integration of adult-born

interneurons in the OB circuitry. To dissect out the precise neural circuitry governing the

olfactory behavioural impairments by ELS and improvement by EE, we are targeting the

Somatostatin releasing interneuron population of OB. We found faster learning in a complex

odor discrimination task when these interneurons were optogenetically activated in ELS mice.

α-Synuclein fibrils induced disruption of         pacemaker firing in dopamine neurons is           dependent on selective K-ATP channel         activation  

Poonam Thakur | Wellcome Trust-DBT India Alliance Fellow |                 CCMB  Parkinson’s disease (PD), one of the most common neurodegenerative disorders, is associated

with α-synuclein aggregation and progressive loss of substantia nigra dopaminergic neurons

(SN DA-neurons). Precise mechanism(s) behind selective vulnerability of SN DA-neurons to

α-synuclein aggregation in comparison to VTA DA-neurons, is not known. SN DA-neurons in

ventro-lateral tier degenerate earlier and to a much larger extent compared to the neurons in

dorso-medial tier. Present study is aimed to delineate the electrophysiological basic of their

differential vulnerability to fibrillar α-synuclein.

Methods:

Male C57Bl/6N mice (3-4 month old) were injected with red fluorescence beads in nucleus

accumbens or dorso-medial striatum or dorso-lateral striatum that retrogradely travel to VTA,

medial-SN and lateral-SN respectively. After 3-4 days of the injection, acute mid-brain slices

were prepared and autonomous pacemaker firing of labelled VTA, medial or lateral SN

DA-neurons was studied. Neurons were exposed to either fibrillar or monomeric α-synuclein.

Results:

Nanomolar concentrations of α-synuclein fibrils, but not its monomeric forms, selectively and

acutely disrupted pacemaker firing of lateral-SN DA neurons. Their firing became irregular and

slow before stopping eventually. This disruption was mediated by activation of K-ATP channels.

On the other hand, firing in other DA subpopulations such as those in medial SN or VTA, was

unaffected. Further, pharmacological inhibition or genetic ablation of K-ATP channels protected

the lateral-SN DA neurons from α-synuclein fibrils induced disruption of their pacemaking

activity.

Conclusion:

Our study suggests that α-synuclein protofibrils, even at nanomolar concentration, selectively

disrupts the pacemaking activity in lateral SN DA-neurons and this effect is largely mediated

through activation of K-ATP channels.

A gene candidate for social memory deficit  

Prakash Devaraju | Post Doctoral Fellow | St Jude Children's                   Research Hospital  Socio-cognitive deficits are a feature of neuropsychiatric disorders such as schizophrenia and

autism spectrum disorders (ASDs). A major predisposition for these disorders is the most

common human microdeletion syndrome known as 22q11.2 deletion syndrome (22q11DS). The

causative gene(s) and the molecular and neural circuit mechanisms by which social behavior

deficits arise in 2211DS is not fully understood. In this study using mouse models, we identified

2510002D24Rik (Rik), a nuclear gene encoding mitochondrial protein as a culprit for

hippocampal CA2-dependent social memory deficits associated with 22q11DS. Rik deficiency

results in reduced firing rate of fast-spiking interneurons in the hippocampal CA2 region and

long-term plasticity deficits in the CA3-CA2 circuitry. Rik protein is enriched in the CA3 and CA2

sub-fields of the hippocampus. Using biochemical approaches, we confirmed the subcellular

localization of Rik protein to the mitochondria and identified ATP23, another interacting

mitochondrial protein as the most downregulated target in Rik deficiency. The recently

developed fluorescent ATP/ADP sensor PercevalHR enabled us to further narrow down the

cellular and molecular loci of the CA2 circuit deficit to reduced interconversion of ATP and ADP

during ongoing neuronal activity in fast-spiking interneurons but not pyramidal neurons.

Atp23+/- mice phenocopied the Rik deficiency induced neural circuit and social memory deficits.

Adeno associated viral vector mediated loss and gain-of function of Atp23, phenocopied and

rescued, respectively, Rik deficiency induced deficits, further supporting Atp23 as a molecular

target. Previously, hippocampal CA2-circuit dependent mechanism has been described as the

cause for social memory deficit in the Df(16)1A+/- mouse model, which harbor a hemizygous

1.3-Mb chromosomal deletion syntenic to the human 22q11.2 critical region. Herein, we

propose Rik as a candidate gene and mitochondrial ATP-ADP interconversion deficit in the CA2

interneurons as a molecular cause for social memory deficits in 22q11DS and the associated

neuropsychiatric conditions.

Understanding the representation of innate         valence of monomolecular odors and their           binary mixtures in the activity of antennal lobe               neurons  

Pranjul Singh | PhD Student | IIT Kanpur  Skin odors along with carbon dioxide, heat, and humidity help mosquitoes locate their host,

resulting in the spread of many deadly diseases. The odors are detected by olfactory receptor

neurons (ORNs) present in antennae and maxillary palp of the insect. ORNs send their axons to

the antennal lobe in the mosquito brain, where they form synapses with Projection neurons

(PNs) and Local neurons (LNs). Projection Neurons carry the odor information to higher brain

centers while local neurons modulate the odor-evoked activity of PNs. Studies in other insects

such as Drosophila have shown that changing the PN activity for an odor changes the behavioral

response to that odor. My research interest includes investigating how innate attractiveness or

aversiveness for an odor is encoded in the antennal lobe neurons of Aedes aegypti, the dengue

mosquito. Previous studies have shown that the behavioral response towards a mixture of odors

often deviates from the linear sum of its component responses. We have designed an acrylic

olfactometer to quantify the behavioral responses of mosquitoes for a set of monomolecular

odors and their binary mixtures. Using whole-cell patch-clamp recordings, the activity of

antennal lobe neurons are recorded for the odor set and the recorded neuron is filled post-hoc

to reveal it’s morphology. So far we have observed that these neurons share physiological and

morphological similarities with Drosophila. Most PNs respond to a subset of odors that include

both attractive and aversive odors. By generating a repertoire of such responses, we are testing

various models for representation of the innate valence of odors in the activity of PNs. This

would also reveal how local neurons modulate the PN responses resulting in deviation of

mixture response from its component responses.

A resource to facilitate the cellular basis of               mental illness in humans 

Raghu Padinjat | Faculty | NCBS  

I will discuss the progress and resources of a large multi-institutional program that seeks to

create resources to address the genetic and cellular basis of mental illness.

Differential propagation of ripples along the           proximo-distal and septo-temporal axes of         dorsal CA1 of rats  

Sachin Deshmukh | Faculty | IISc  The functional connectivity of the hippocampus with its primary cortical input, the entorhinal

cortex, is organized topographically. In area CA1 of the hippocampus, this leads to different

functional gradients along the proximo-distal and septo-temporal axes of spatial/sensory

responsivity and spatial resolution respectively. CA1 ripples, a network phenomenon, allows us

to test whether the hippocampal neural network shows corresponding gradients in functional

connectivity along the two axes. We studied the occurrence and propagation of ripples across

the entire proximo-distal axis along with a comparable spatial range of the septo-temporal axis

of dorsal CA1. We observed that ripples could occur at any location, but their probability of

co-occurrence and amplitude decreased with increasing distance from the reference tetrode.

This reduction was greater along the proximo-distal axis than the septo-temporal axis.

Furthermore, we found that ripples propagate primarily along the proximo-distal axis. Thus, over

a spatial scale of ̴1.5 mm, the network is anisotropic along the two axes, complementing the

topographically organized cortico-hippocampal connections.

Robustness properties of chemical switches  

Sahil Moza | PhD Student | NCBS  Living systems transform information from the veridical world into relevant action. Biological

Chemical Reaction Networks (CRNs) have been selected over billions of years of evolution to

carry out these computations. Bistable CRNs form a fundamental subgroup of these biochemical

networks with elementary computational functions such as decision making and memory

storage. Several synaptic CRNs implicated with memory storage at the synapse, such as CaMKII

and PKM-zeta have been identified as bistable. Although bistability can be achieved by several

suitable architectures with positive feedback loops, each architecture may have different

degrees of robustness against different kinds of perturbations. Such robustness is thought to

determine a CRN's persistence over evolution and hence occurrence in biological networks. We

compared the robustness of all possible (3561) bistable CRNs with ≤6 reactions between ≤4

reactants in maintaining bistability against perturbation to the network structure (structural)

and reaction rates (parametric). We found that ~98% bistable CRNs always contained one of 24

bistable "root" subnetworks. Further, we discovered that top parametrically robust networks

had a mirror-symmetric network architecture. We found no correlation between structural and

parametric robustness. Then we binarized and counted the unique steady-state concentration

vectors for each CRN across all bistable sets of parameters, called information robustness. We

found that several CRNs with high parametric robustness had low information robustness,

implying poor information retention to parameter variations. Lastly, we looked at the robustness

of bistable CRNs in persisting at a stable fixed point in the presence of various levels of

stochastic noise. In summary, we found very little correlation between the robustness of small

CRNs to different kinds of perturbations, and different structural features were enriched for

different robustnesses. Since the evolutionary perturbations may differ across biochemical

networks according to their environment, their "total" robustness may dictate the enrichment of

functional motifs, and the structure of biochemical reaction networks. Further, we reveal a

robustness map that can be used as an insightful tool to investigate the structural properties of

robust CRNs, to compare alternative CRNs as constructs for synthetic biology, and to search for

bistable motifs across different biochemical networks.

A novel function of rodent olfactory system:             airflow detection and discrimination in mice.  

Sarang Mahajan | PhD Student | IISER Pune  Delivering a needful action requires different prior steps – sensation, perception and

decision-making. Our sense organs collect information from the external environment and

convert the physical/chemical energy to neural representations. Pre-cortical and cortical regions

refine these representations to ease the decision-making process. While most of the sensory

systems encode various features of a single sensory stimulus through multiplexing, the rodent

olfactory system processes completely distinct, yet parallel information – the mechanical

stimulation by the airflow and the chemical sensation of odorants – thereby providing a novel

approach to study the multimodal decisions using a single sensory system. Although the neural

mechanisms of the latter have been investigated in detail, the pathways processing the

mechanical information remains largely elusive. Therefore, probing the multimodal aspects of

olfaction is fundamentally essential. In this study, we focus on investigating the neural

mechanisms of multimodal decision-making by using mouse as the model system. To start with,

we investigated the role of rodent olfactory system in detecting and discriminating airflow rates

in presence and absence of odorant molecules. Our results show that mice can learn to

discriminate a range of airflow rates even in the absence of whiskers, indicating the possibilities

for the airflow information processing without the involvement of whiskers. However, the

discrimination abilities were lost either by the destruction of olfactory sensory neurons by

intranasal application of zinc sulfate or by the removal of olfactory bulb (OB). To investigate the

pre-cortical mechanisms involved, we modified the function of OB inhibitory circuits in a

bidirectional way using optogenetic tools. While enhancement of inhibition resulted in a poor

discrimination of airflow rates, decrease of inhibition caused betterment of discrimination

abilities. This confirms the involvement of OB circuits in the detection and discrimination of

airflow rates.

Neto-mediated intracellular interactions sculpt       postsynaptic composition at the Drosophila         neuromuscular junction  

Saumitra Dey Choudhury | Post Doctoral Fellow | NATIONAL                 INSTITUTES OF HEALTH, BETHESDA  Recruitment of neurotransmitter receptors and organization of postsynaptic densities (PSDs) are

crucial for the formation of neural circuits and for long-term plasticity underlying learning and

memory. The Drosophila neuromuscular junction (NMJ), a glutamatergic synapse similar to

mammalian central synapses, is a powerful genetic system to study synapse assembly and

function. We have previously found that the trafficking and stabilization of ionotropic glutamate

receptors (iGluRs) at the Drosophila NMJ requires Neto, a highly conserved auxiliary protein.

Neto binds to iGluRs and modulates their function, and also engages in intracellular and

extracellular interactions that shape PSD composition and enable iGluRs stabilization at synaptic

sites. Drosophila neto codes for two isoforms, Neto α and Neto β, which have distinct

cytoplasmic domains generated by alternative splicing. The 351-residue cytoplasmic part of Neto

β contains multiple putative phosphorylation sites and docking motifs, including an SH3 binding

motif and a putative CaMKII phosphorylation site. Our previous histological studies have shown

that Neto β, the predominant isoform at the larval NMJ, is key to the recruitment of iGluRs and

PSD components such as p21-activated kinase (PAK) and PAK interacting exchange factor (Pix),

PSD components known to selectively stabilize type A iGluRs. We hypothesize that the

cytoplasmic domain of Neto β provides a signaling platform required for PSD assembly and

function. To test this hypothesis, we have used CRISPR/Cas-9 genome editing and generated a

series of neto β alleles with either progressively truncated intracellular domains, or with small

internal deletions in the putative interaction sites. Loss of the entire Neto β intracellular

domain or truncations that remove the SH3 binding and the CaMKII putative phosphorylation

site abolish the synaptic recruitment of Pix, and thus stabilization of type A iGluRs at the PSD.

Interestingly, Pix recruitment was also altered by a small, 11-residue deletion that removes the

putative CaMKII phosphorylation site. I will reveal my findings using these truncations and

discuss the role of this Neto β motif on PSD assembly and NMJ function. Our study

demonstrates that Neto functions as a critical PSD scaffold and a hub for cellular signaling that

sculpt a developing glutamatergic synapse.

Regulation of Synapse Development by         DYRK1A/mnb Kinase  

Sayantan Datta | PhD Student | TIFR Hyderabad  Down’s Syndrome, mostly caused by a trisomy of Chr. 21 in humans, is one of the most common

neurodevelopmental disorders. One of the genes in the Down’s Syndrome Critical Region on Chr.

21 is DYRK1A (Dual Specificity Tyrosine Phosphorylation Regulated Kinase 1A), the Drosophila

homolog of which is minibrain (mnb). mnb mutants show various neurodevelopmental

phenotypes — reduced head and brain sizes, loss of learning and memory, defects in synaptic

structure and function. Molecular mechanisms behind these phenotypes are not clear, although

there are clues that loss of synaptic structure and/or function maybe involved. Through a

proteomic study of mammalian DYRK1A we have found the TSC (Tuberous Sclerosis) complex

physically interacts with DYRK1A. The TSC complex is an upstream inhibitor of the TOR pathway,

which is a key regulator metabolism and known to regulate growth and development. Using a

combination of biochemical and genetic tools in flies and mammalian cell lines, we are

investigating how the interaction between mnb with TSC complex affects the TOR pathway and

thereby synaptic development in flies. We shall present our preliminary data that attempts to

answer this question, and some hitherto unpredicted insights on DYRK1A activity.

Understanding the origin of introductory         vocalisations in male zebra finch song  

Shikha Kalra | PhD Student | IISER Pune  Many passerine birds initiate their song sequence with a repeated number of simple

introductory vocalizations (Richards DG, Behavior, 1981). These vocalizations have been

hypothesized to function as motor preparation for song sequence initiation (Rajan R, Doupe AJ,

Current Biology, 2013) or as an alerting component for song (Richards DG, Behavior, 1981). It is

known that the acoustic structure and sequencing of song elements are generally learned from a

tutor, though some components of song are unlearned. However, the extent to which

introductory elements are learned or unlearned remains largely unknown.

Here, we address this question using the zebra finch, a songbird that learns its vocalizations

during development. Song bouts of adult male zebra finches begin with a variable number of

introductory notes (INs). To determine the extent to which the number and acoustic structure of

INs is learned, we first compared INs produced by sons (‘pupils’) and their fathers. Number of

INs produced by pupils was positively correlated with the number of INs produced by their

fathers. Further, INs of pupils showed high acoustic similarity with INs of their fathers. Next, we

isolated juvenile zebra finches from their father (starting before day 10 post-hatching) and

experimentally tutored them using one of two different methods: (1) social tutoring with a male

that produced a different number of INs from their father or (2) artificial tutoring with playbacks

of song without INs. Our results demonstrate that the number and acoustic structure of INs of

socially tutored birds were similar to those of their social tutor. Artificially tutored birds with

song without INs, produced INs with both number and structure different from those of their

father. Together, these data suggest that, like song, INs also appear to have both innate and

learned components. The tendency to produce INs is innate while the structure and number can

be learned from the tutor.

A novel genetic pathway where         SYD-2/Liprin-α acts downstream of       LRK-1/LRRK2 and along with AP complexes to             mediate polarized cargo trafficking in neurons  

Shirley Bharat Dixit | Junior Research Fellow | TIFR Mumbai  Distinct compartments of the neuron i.e. dendrites, axons, and the synapse have characteristic

protein compositions that allow them to perform different roles in neurotransmission. Polarised

distribution of proteins to axons and dendrites is a result of protein trafficking events that

happen at the cell body of the neuron. We show that SYD-2/Liprin-α, a synapse assembly

protein, and LRK-1/LRRK-2, a kinase mutated in familial Parkinson’s disease, regulate the

polarized trafficking of axonal cargos at the cell body of the neurons of C. elegans. We show that

LRK-1 acts through SYD-2 and the AP1 complex to restrict the distribution of synaptic vesicle

proteins to axons. Additionally, SYD-2 and AP1 play redundant roles in preventing of synaptic

vesicle protein entry into dendrites. We also show that LRK-1, SYD-2 and the AP3 complex act to

restrict non-axonal cargo, lysosomal proteins, to the cell body. These data suggest that LRK-1

and SYD-2 are regulators of polarised cargo distribution and that they act through two AP

complexes. Furthermore, LRK-1, SYD-2, and the AP3 complex act to facilitate the inclusion of

different synaptic vesicle proteins onto the same transport carrier, thus regulating synaptic

vesicle membrane composition during vesicle biogenesis in the cell body. These early trafficking

events allow synaptic vesicle precursors to depend on their cognate motor, UNC-104/KIF1A, for

their exit out of neuronal cell body.

Understanding ALS using Drosophila Tripartite         Synapse.  

Shweta Tendulkar | PhD Student | IISER Pune  Amyotrophic Lateral Sclerosis (ALS) is a progressive motor neuron degenerative disorder. ALS

patients have a life expectancy of 3-5 years, with no known cure. Research has been focused

primarily on the death of motor neurons, while the other two members of the tripartite synapse,

namely muscle and glia are believed to contribute to the onset and/or progression of the disease

and are not well studied.

We are attempting to understand the molecular and cellular basis of the disease by using

Drosophila melanogaster as a model organism. As a first step, we modulate the levels of fly

orthologs of human genes that cause familial ALS independently in neurons, glia and muscles.

Then, we measure changes in lifespan, bouton morphology and motor function in these animals.

We use, as a sensitized genetic background, a point mutation in the ALS8 causative gene, VAPB.

Drosophila lines carrying the VAPB(P58S) mutation (VAPB(null); +; vapB-promoter>VAPB(P58S))

have a shortened life span, VAPB(P58S) positive inclusions and motor dysfunction that increases

with age (A Moustaqim-Barrette et al., 2014). In this background, using the UAS-Gal4 system, we

have modulated the activity of seven Drosophila genes, namely VAPB, FUS, TBPH, SOD1, VCP,

Alsin and SETX. We find that each cell-type in the synapse shows differential sensitivity to the

modulation of genetic activity for each gene. Our data strongly suggests that ALS mutations

contribute to the disease, from each cell type. Most interestingly, overexpression of a mutant

form of VCP (R152H) (Ritson et al., 2010), in some cell types, but not in others, leads to a distinct

improvement of lifespan and motor function. This suggests that the VCP linked

Ubiquitin-Proteasomal System is involved in the progression of the disease.

Our data and analysis should lead to a better understanding of molecular mechanisms that

underpin this disease. We expect to uncover novel genetic interactions between ALS genes and

critical cellular pathways as a well as interactions of ALS genetic sub-networks with anterograde

and retrograde signals in the tripartite synapse.

Role of STIM1 in regulating gene expression             and synaptogenesis in Cerebellar Purkinje         neurons  

Sreeja Kumari Dhanya | PhD Student | NCBS  Calcium plays a significant role in different aspects of neuronal signalling and function. Store

operated Calcium Entry (SOCE) via STIM/Orai Pathway is the major route of calcium entry in

non-excitable cells.Importance of STIM1/Orai mediated SOCE in the context of mature neurons

needs further investigation.Previous studies have proposed that deranged calcium signalling in

cerebellar Purkinje neurons might leads to neuronal degeneration and Spinocerebellar Ataxia

(SCA) .It has been found that STIM1 regulates mGluR1 dependent synaptic transmission and

IP3R dependent calcium signals are strongly attenuated in the absence of STIM1 in Purkinje

neurons , but the molecular mechanisms explaining the deficits is not well understood. We have

used Mouse Purkinje neurons as a mammalian model system to understand how STIM1

modulates neuronal function and how altered function of STIM1 leads to neurodegeneration.

In this talk, I will discuss how selective loss of STIM1 expression in mouse Purkinje neurons

affects behaviour, synaptogenesis and gene expression. Behavioural experiments demonstrate

that loss of STIM1 in Purkinje neurons affects motor learning and coordination where the

phenotype gets more pronounced with age as observed in many neurodegenerative disorders.

Transcriptional profiling of STIM1 knock out Purkinje neurons demonstrated significantly altered

expression levels of 285 genes belonging to pathways related to ion homeostasis, endocytic

recycling, protein transport and neuron projection development.We also observed that loss of

STIM1 in purkinje neurons leads to abnormal climbing fiber innervations on Purkinje dendrites.

Our data suggest that altered expression of genes required for synaptic vesicle endocytosis and

neurotransmitter receptor internalization upon loss of STIM1 affects synaptogenesis of purkinje

dendrites.ThusSTIM1 mediated SOCE appears to physiologically modulate the function of

purkinje neurons. A detailed understanding of the molecular mechanisms involved is expected

to identify potential therapeutic targets for SCA and other neurodegenerative disorders.

Transcription factor LHX2 is required in early             cortical progenitors for normal thalamocortical         innervation  

Suranjana Pal | Post Doctoral Fellow | TIFR Mumbai  Sensory information from the periphery is presented to the cerebral cortex in a highly ordered

manner, providing a topographic representation of the external world. In the mouse, sensory

information from the whiskers is spatially mapped in the brainstem and thalamus and conveyed

to the somatosensory cortex in form of whisker-specific “barrels.” We have discovered a genetic

mechanism that operates in early (E11.5) cortical progenitors that is critical for the regulation of

thalamocortical innervation.

In mice which lack transcription factor LHX2 specifically in the cortex (ctx-specific Lhx2

conditional mutant, Emx1Cre; Lhx2cKO), we reported that the cortical barrels do not form

(Shetty et al., 2013). We sought to examine which component of the LHX2 deficient cortical

plate causes this non-cell-autonomous disruption of incoming thalamic innervation.

We used in utero electroporation of GFP to label thalamic afferents in Lhx2lox/lox mice that also

carried a tamoxifen-inducible CreERT2. By administering tamoxifen at different developmental

stages, we discovered that the Emx1Cre; Lhx2cKO defect is recapitulated only when Lhx2 is

disrupted at E11.5, but not later. Furthermore, we found that a postmitotic NexCre driver is

unable to recapitulate the defect. Therefore, LHX2 function is required in E11.5 progenitors,

which give rise to the subplate, for normal thalamocortical innervation.

Loss of Lhx2 in E11.5 progenitors causes defasciculation and premature innervation of the cortex

at E15.5, a stage when thalamocortical innervation normally "waits" at the subplate. In maturity,

there is a profound deficit in thalamocortical innervation, indicating that mechanisms operating

in the embryonic subplate as early as E15.5 are critical for normal innercation. We find that the

LHX2 deficient subplate neurons are significantly depolarised and have a higher input resistance

compared to controls, suggesting that they are electrically immature. The cortex-specific LHX2

conditional mutant offers new insights into the phenomenon of thalamocortical guidance and

sensory map formation.

Are tungsten wires suitable as recording           electrodes?  

Swikriti Saran Singh | PhD Student | IIT Kanpur  In an insect olfactory system, odors are detected by receptors present on the olfactory sensory

neurons. These neurons are present in thousands of hair-like structures called sensilla located

on the antennae and maxillary palps. Olfactory sensory neurons detect the identity and

concentration of odors and translate this chemical information into electrical signals (spikes),

which are transferred to higher brain centers for eliciting an appropriate behavior.

Electroantennography is commonly used in olfaction research to measure the overall change in

the activity of olfactory sensory neurons upon odor presentation by inserting a blunt recording

electrode into the antennal nerve and a reference electrode in the eye or the thorax. Various

previous studies from different insects have used tungsten wires for recording

electroantennograms. In our investigations of odor-evoked activity in mosquito antenna, we

observed responses for multiple odors. Surprisingly, such activity was present for odors like

propionic acid, linalool, geranyl acetate, and nonanal even when the tungsten wire was dipped

in saline and unattached to any sensillum. This spurious tungsten electrode activity is difficult to

distinguish from odor responses and may interfere with real electroantennogram amplitudes.

We investigate the reason behind these false “odor responses” and analyze the suitability of

tungsten wires as recording electrodes. Our results call into question the correctness of several

previous studies that might be contaminated by the use of tungsten wires.

Gain of function of β-catenin in the dorsal               telencephalic midline has opposing effects on           the hippocampus and choroid plexus  

Varun Suresh | PhD Student | TIFR Mumbai  During telencephalic development, the cortical hem functions as an organizer that is critical for

hippocampal induction. Though Wnt signaling from the hem is critical for hippocampal

induction, the hem does not appear to respond to canonical Wnts. The choroid plexus, which is

derived from the hem, does respond to canonical Wnt signaling.

We tested the effects of constitutive activation of β-catenin in the hem and the choroid plexus

using the Lmx1acre driver (Lmx1a Cre; WntGOF). This resulted in a transformation choroid

plexus to a neuronal identity, and also caused additional defects in the adjacent hippocampus

including an overproliferation of the Ammon’s horn, and a missing dentate gyrus. Behavioral

experiments in the adult indicates that hippocampal mediated behavior such as novel object

recognition is affected in the mutants.

We isolated hippocampus and choroid plexus tissue from control and Lmx1a Cre; WntGOF

embryos at embryonic day (E)14.5 and analysed them using RNA-Seq. The data revealed that the

transcriptome of the mutant choroid plexus, gains neuronal genes, pathways combined with an

altered secretome. We hypothesized that some of these defects may be due to changes in the

cerebrospinal fluid (CSF) secreted by the transformed choroid plexus.

In conclusion, our study highlights the importance of controlled levels of Wnt signaling at the

telencephalic midline.