Functions of TBX1:an update

Antonio Baldini & Elizabeth IllingworthTelethon Institute of Genetics and Medicine

&Institute of Genetics and Biophysics

Napoli, Italy

Goals of Basic Research

• Molecular diagnostics• Identification of the disease genes• Fnctional studies• Develop the basis for future treatments

(conventional or gene therapy)

22

del

Diagnosis of del22q11

FISH

Gene A Gene B

A B D EC

Del22q11.2

T10

PRODH

DGCR6

IDD

STK22A

GSCL

RANBP1

SLC25A1

ARVCF

COMT

TRXR2

GNB1L

TBX1GPIB

CDCREL1

CLD5

CDC45

UFD1L

NLVCF

ES2EL

HTF9C

ZNF74

HIRA

CRKL

LZTR1

CLTCL

3Mb (90%)

Cen

1.5Mb (10%)

HCF2

Genes and clinical findings in multigene deletion syndromes

Deleted region

Genes

a b c d e f g h

Clinical findings

?

Mouse models and human genetic diseases

“Chromosome engineering”

Generation of the first animal modelof del22q11.2 (Lindsay-Illingworth, 1999)

Df1 mouse-Interrupted aortic arch-Small Thymus-Small parathyroids-Neurobehavioral abnormalities

Identification of the critical gene

in the mouse

Df1

Es2el Ufd1l HiraComtIdd Tbx1Cdcrel1

del22q11

Lindsay-Illingworth et al., 2001Jerome et al., 2001 Merscher et al., 2001

Mutations of TBX1found in VCFS patients

without deletion

Yagi et al., 2003

Paylor et al., 2006

Zweier et al., 2007

TBX1 mutations

T-box

T-box

T-box

F157Y G319S

1250delC

1320-1342del

TBX1 NLS1

H194Q

L411P

Gene Functions

• Definition of developmental processes that require Tbx1.

• Definition of the critical time(s) when Tbx1 should carry out its function.

The developmental process(heart)

Progenitor cells Specialized,

differntiated cells(e.g. cardiac muscle

cells)

expansion differentiation

Tbx1

+ -

Proliferation Differentiation

Tbx1

Cardiac Progenitors (SHF)

How does it work (I)

Tbx1

Target gene

How does it work (I)

Tbx1Target gene

Activation of “target genes”

How does it work (II)

Tbx1 X

Y

How does it work (II)

Tbx1X

Y

Protein-protein interactionsleading to functional modification

of the proteins involved

Tbx1Target gene

Tbx1X

A

B

(e.g. Fgf8)

(e.g. Smad1)

Tbx1-M

Target gene

Tbx1X

A

B

(e.g. Fgf8)

(e.g. Smad1)

Tbx1Target gene

Tbx1-MX

A

B

(e.g. Fgf8)

(e.g. Smad1)

Mutation in a VCFSpatient

Tbx1 ?

How to re-establis the balance (in the mouse)?

• Increase Tbx1 dosage– Excess of Tbx1 is deleterious (published examples)

• Increase the dosage of target genes– Many genes involved (e.g. Fgf8).

• Intervene on developmental processes– Inhibit genes that enhance differentiation or that

reduce proliferation. • Reduce the sensitivity of tissues to Tbx1 dosage

– ?

7 8 9 10 11

Mouse

Heart defects Cleft palate

12

16 20 24 28 33

Humans

41

Critical times

Gestation days

Psychiatric disease ?

Future goals

• Exactly define the (molecular) damage from the loss of Tbx1.

• If and when there are irreversible damages.• Identify mechanisms to “boost” the one

remaining copy of Tbx1, or its target genes.

Funding

National Institutes of Health (NIH), USA

Telethon Italia

European Community

Italian Ministry of University and Research

Acknowledgments

COLLABORATORSElizabeth Lindsay-Illingworth

Peter J ScamblerRobert Schwartz

(Baylor and IBT/TexasA&M) Houston

Huansheng XuZhen ZhangFrancesca VitelliLi ChenHedda LeemingTom Huynh

Gabriella LaniaGabriella FulcoliCinzia CaprioLuna PaneRosa SerrentinoDiego CircoloSara Cioffi