E.O.B.U.: Chronobiology Laboratory
About Chronobiology Chronobiology Links
What is Chronobiology?
Life on earth has evolved in an environment which is spectacularly periodic. The rotation of the earth on its own axis causes the 24-hour day, with its alternating day and night cycles. The revolution of the moon around the earth, once every 29 days, causes the lunar month and the diurnal and semidiurnal ocean tides. The earth itself revolves around the sun once in 365 days accounting for the seasons and the calendar year. Plants, animals, and humans have possibly adapted in the course of millions of years of evolution to these geophysical and cosmic cycles.
Such adaptations express themselves in various biological rhythms such as
[1] The approximately 24 h i.e. circadian rhythms (Latin circa = about; dies = day)
[2] Tidal and lunar rhythm.
[3] Circannual rhythms, with a periodicity of about a calendar year.
The study of how organisms cope physiologically with the temporal order of their environment is called Chronobiology.
Our laboratory is focussed primarily on circadian rhythms. The characteristics of circadian rhythms which make them special are (i) their ability to synchronize to light/dark cycles, (ii) they oscillate in constant conditions of the laboratory with period deviating slightly from 24 h, (iii) they are compensated for temperature changes and show Q10 values close to unity, and (iv) they have a genetic basis.
Major Research Interest of the Chronobiology Laboratory:
Brief Outline of Ongoing Research in the Chronobiology Laboratory:
Experiments are being carried out to investigate the structural and functional aspects of biological clocks in fruit flies, ants and mice. Several rhythms are monitored in fruit flies (eclosion, oviposition, mating, and locomotor activity) and in mice (wheel running, locomotor, feeding and drinking activities) to understand the functioning of biological clocks in flies and mice. Experiments are also being carried out to investigate the interaction of various time cues (light/dark, food availability and other non-photic cues) and the biological clocks.
Behavioural and molecular experiments are conducted to understand the ontogeny of circadian rhythms in fruit flies and mice.
Experiments are also being carried out with ants (Camponotus compressus) to understand the social consequences of circadian rhythms. Circadian rhythms are being assayed in individuals (of different castes) isolated from the colony. The influence of the social structure on the rhythm of individuals in the colony is also being studied. We are also working on the inter- and intra-caste interaction of phase and period of biological rhythm. The effect of numbers on the circadian rhythmicity will also be studied with ants of same caste. Molecular biological tools will be used to understand possible mechanisms regulating plasticity of circadian rhythmicity in individuals of social insect colony.
Activity patterns in a number of organisms are bimodal both under light/dark conditions and in constant conditions. It is also believed that the two components of activity (namely morning and evening) are under different genetic control. Selection lines of Drosophila melanogaster that are selected for their timing of eclosion (the morning type and the evening type) are being maintained to investigate the role of morning and evening oscillators in circadian organisation. Studies are being carried out to look for possible candidate genes and their mechanisms in regulating the morning and evening oscillators of biological clocks.
Using the fruit fly Drosophila melanogaster, laboratory experiments are being carried out to investigate the evolution of circadian organisation. Several populations of D. melanogaster are maintained in six different light regimes (constant light, light/dark cycle of 20 hours, 24 hours, 28 hours and constant darkness) and the eclosion, oviposition and locomotor activity rhythms are assayed every 10 generations in order to find out the role of different environments in shaping the evolution of biological clocks. This work is being carried out in collaboration with the
Evolutionary Biology Laboratory at JNCASR.
Experiments are being carried out on the suprachiasmatic nucleus (SCN; one of the biological clocks of mammals) of mouse, to understand the expression of several clock-output genes like c-fos, VP, VIP etc. Expression of these genes will be studied under a number of light/dark cycles including continuously illuminated environment, which evokes phenomena like lengthening of clock period, splitting of activity and apparent absence of activity. Part of this work is being carried out in collaboration with Prof. William J Schwartz, Department of Neurology, University of Massachusetts, USA.
Studies are also being carried out to understand the connection between psychiatric disorders and circadian clocks and to explore possible modes of treatment. Molecular biological studies are carried out to understand effect of several drugs on the biological clocks. Experiments are also underway to investigate correlation between CLOCK polymorphism and circadian rhythmicity. These experiments are being carried out in collaboration with Dr. Quasar Salim Padiath and Prof. K. VijayRaghavan of NCBS, Bangalore.
Experiments are also underway to understand the possible connection between the circadian organisation and the life history traits like developmental time, fecundity, and longevity. This work is being carried out in collaboration with the
Evolutionary Biology Laboratory at JNCASR on populations of D. melanogaster, which have been subjected to selection for faster development and other demographic attributes in the laboratory.