MCB 186CIRCADIAN BIOLOGY

Week 1

Biological rhythms & Circadian Clocks

Free running period & environmental effects

September 19, 2007J. W. Hastings

THERE ARE MANY DIFFERENT BIOLOGICAL RHYTHMS WITH

PERIODS RANGING FROM MILLISECONDS TO YEARS

BIOLOGICAL CYCLES SHORTER (ULTRA) & LONGER(INFRA) THAN CIRCADIAN

YEAST ULTRADIAN OSCILLATION of DISSOLVED OXYGEN

2001 Murray et al. J. Bacteriol.~44 min/cycle

GOLDEN MANTLED SQUIRRELS - CIRCANNUAL RHYTHMS OF HIBERNATION

ANNUAL RHYTHM: DINOFLAGELLATE CYST GERMINATIONAlexandrium fundyense PATRICIA MATRAI,

MENSTRUAL PERIODS (FOUR BIRTHS; WINFREE, 1980)

MOST ORGANISMS also EXHIBIT CIRCADIAN RHYTHMS in

MANY DIFFERENT PROCESSES

SUCH RHYTHMS CONTINUE in CONSTANT CONDITIONS = FREE RUNNING RHYTHM

PERIOD NOT EXACTLY 24 HOURS

CIRCA = ABOUT

DIAN = ONE DAY

FREE RUNNING RHYTHMS HUMAN IN CONSTANT CONDITIONS FOR 24 DAYS

How can we more easily measure or visualize the period (tau)?

RASTER PLOTS

Double, triple etc. raster plots

Modulo tau raster plots

SLEEP-WAKE RHYTHM IN HUMAN: LD & LL

Variability in sleeponset has meaning

CIRCADIAN LEAF MOVEMENT RHYTHM

BACTERIAL COLONIES EXPRESSING BIOLUMINESCENCE

NIGHTPHASE

DAYPHASE

BACTERIAL LUCIFERASE as a REPORTER of a CIRCADIAN RHYTHM of GENE EXPRESSION in BACTERIA

KONDO, STRAYER,KULKARNI, TAYLOR, ISHIURA, GOLDEN & JOHNSON, 1993

CIRCADIAN PHOTOACCUMULATION IN PARAMECIUM Hasegawa et al.

The clock controls an overt developmental rhythm in Neurospora.

movie courtesy of Van Gooch

DROSOPHILA PERIOD GENE: FIRST CLOCK MUTANTS

WILD TYPE per+

ARHYTHMIC pero

SHORT PERIOD perS

LONG PERIOD perL

NOTE: SLOPEis a MEASUREof PERIOD (tau)

CIRCADIAN CLOCKS TIMING MAY BE VERY PRECISE DECOURSEY, 1961

SLEEP-WAKE RHYTHM IN HUMAN: LD & LL

Variability in sleeponset has meaning

NIGHT HAULING by ANDREW WYETH showing BIOLUMINESCENCE

DINOFLAGELLATE BIOLUMINESCENCE (Hastings’Lab)

GONYAULAX CELL AT DAY (LEFT) AND NIGHT PHASE FLUORESCENCE OF LUCIFERIN IN SCINTILLONS

DINOFLAGELLATE FLASH & GLOW BIOLUMINESCENCEand its CIRCADIAN EXPRESSION

scale: ~ 24 hours peak to peak

CIRCADIAN RHYTHM of LUMINESCENCE: top, LD; below, LL

LD

DD

GONYAULAX PEAK TIMES OF GLOW UNDER ENTRAINED AND FREE RUNNING CONDITIONS

Academic Press, New York, 1970

View 1: Environmental signals detected by organisms Provide information on time of day

View 2: Organisms have internal biological clocks

THE BIOLOGICAL CLOCK

POSTULATED CELLULAR MECHANISMRESPONSIBLE FOR DAILY RHYTHMS

CIRCADIAN RHYTHMS CIRCADIAN CLOCK

To be called circadian the organism must be kept under constant conditions

CIRCA-: ABOUT -DIAN: ONE DAY

Other circa- periodicitiesCIRCALUNAR: ~MONTHLY

CIRCANNUAL: ~YEARLY

FUNCTIONS OF THE CIRCADIAN CLOCKOrigin and Evolution of Circadian Rhythms

TIME ACTIVITIES TO CERTAIN TIMES OF DAY OR NIGHT

- Insect eclosion, Drosophila (temperature compensation) - Plant rhythms, flower openings, bee visitations - Cyanobacteria, photosynthesis by day, nitrogen fixation by night

CELESTIAL NAVIGATION - Animal migration, sun compass; knowledge of time of day required

PHOTOPERIODISM: MEASURE DURATION OF DAY AND NIGHT - Plant rhythms: seasonal flowering, spring summer or fall - Animal seasonal reproduction; hamster only once per year

CIRCADIAN RHYTHMS - KEY PROPERTIES

(1) RHYTHMS CONTINUE IN THE ABSENCE OF LIGHT/DARK

CYCLES WITH PERIODS CLOSE TO BUT NOT EXACTLY 24H

exact period length is a function of environmental conditions

(2) TEMPERATURE ALSO AFFECTS CIRCADIAN PERIOD BUT MUCH

LESS SO THAN FOR TYPICAL BIOCHEMICAL REACTIONS. Cellular

compensation is postulated to be responsible

(3) PHASE can be RESET by LIGHT: ENTRAINED or SYNCHRONIZED to

DAILY LIGHT / DARK or OTHER ENVIRONMENTAL CYCLES

resetting does not need cycles: single exposures or pulses suffice

CIRCADIAN CLOCKS TIMING MAY BE VERY PRECISE DECOURSEY, 1961

BUT PERIOD VALUES VARY WITHIN & ACROSS SPECIES

PERIOD (Tau) DEPENDS on LIGHT INTENSITY

EFFECT of LIGHT INTENSITY on Tau in SPARROWS MENAKER, 1969

EFFECT of INTENSITY of WHITE LIGHT on PERIOD in DIFFERENT SPECIES

EFFECT of INTENSITY on TAU DEPENDS on COLOR of INCIDENT LIGHT

Gonyaulaxpolyedra

PERIOD (Tau) of CIRCADIAN RHYTHM DEPENDS on PRIOR L/D CYCLE PERIOD (T=20)

MOUSEPITTENDRIGH & DAAN

ENTRAINMENTto 20 hr CYCLEMUST be DONEGRADUALLY

PERIOD (Tau) of CIRCADIAN RHYTHM DEPENDS on PERIOD (T=28) OF PRIOR L/D CYCLE

MOUSEPITTENDRIGH & DAAN

ENTRAINMENTto 28 hr CYCLEMUST be DONEGRADUALLY

MOUSE: AFTER EFFECTS ON PERIOD PITTENDRIGH & DAAN

DRUGS MAY ALSO HAVE an EFFECT ON PERIOD e.g., PROTEIN PHOSPHATASE INHIBITORS

PROTEIN KINASE INHIBITORS AFFECT PERIOD

CIRCADIAN RHYTHMS - KEY PROPERTIES

(1) RHYTHMS CONTINUE IN ABSENCE OF LIGHT / DARK CYCLES

WITH PERIODS CLOSE TO BUT NOT EXACTLY 24 HOURS

exact period length is a function of environmental conditions

(2) TEMPERATURE ALSO AFFECTS CIRCADIAN PERIOD BUT MUCH

LESS SO THAN FOR TYPICAL BIOCHEMICAL REACTIONS. Cellular

compensation is postulated to be responsible. THIS GAVE RISE

TO THE CLOCK IDEA

(3) PHASE can be RESET by LIGHT: ENTRAINED or SYNCHRONIZED to

DAILY LIGHT / DARK or OTHER ENVIRONMENTAL CYCLES

resetting does not need cycles: single exposures or pulses suffice

TEMPERATURE HAS ONLY SMALL EFFECT ON PERIOD

PHOTOACCUMULATION IN EUGLENA Bruce & PIttendrigh,1956

GONYAULAX TEMPERATURE COMPENSATIONHastings and Sweeney, 1957

TEMPERATURE EFFECT on TAU in GONYAULAX

TEMPERATURE-COMPENSATED CIRCADIAN PERIOD IN VARIOUS ORGANISMS

LOSS OF RHYTHMICITY

Several environmental conditions, notably low temperature and bright

light, lead to the loss of rhythm; has it stopped or simply not seen?

Return to initial conditions results in the rhythm reappearance of at a fixed phase, CT12, no matter when the return occurs

LOSS OF RHYTHMICITY BELOW 12O C

LOW TEMPERATURE for 12 hr “ STOPS” the CLOCK for 12 hr

“STOPPED” Gonyaulax CLOCK RESTARTS with PHASE at CT12

LOSS OF RHYTHMICITY

Bright light also leads to the loss of rhythmicity and return to initial

conditions causes rhythm to return at a fixed phase, no matter when.

Occurs in many different organisms

EFFECT of WHITE LIGHT INTENSITY on PERIOD and AMPLITUDE in Gonyaulax

680 fc

380 fc

120 fc

JCCP 1957 Fig 3

After an extended period in bright LL, with no detectable bioluminescence rhythm, transfer to

DD re-initiates a rhythm.

Phase is determined by the time of transfer, as if a stopped clock had restarted

RHYTHM in Gonyaulax INITIATED by SHIFT from LL to DD is PHASED STARTING at CT 12

ANOTHER EXAMPLE of a CLOCK “STOPPED” in BRIGHT WHITE LIGHT

Peterson and Saunders J. Theor Biol 1980

Eclosion rhythm of flesh-fly Sarcophaga argyrostoma. White triangle represents time of light exposure. Each point is the median eclosion time for the culture from the end of the light exposure. Note that the duration between end of light exposure and eclosion is constant (11.5 hrs, dotted line), as if the clock is stopped and restarts when the stimulus ends. Note the slight ~24 hr oscillation around the dotted line.