When we observe the behavior and physiology of living things, we invariably notice that they are rhythmic. The rotation of the earth results in daily periodicity of the environment, and our planet's circuit around the sun imposes seasonal cycles to which organisms must adapt. Thus it is not surprising that plants and animals show daily and annual cycles when we study them in their natural environment. What fascinates me is the finding that such rhythms persist with nearly (but not exactly) the same period even when organisms are placed in constant environmental conditions. Furthermore, the period of these rhythms - and even their persistence - depends upon the expression of specific genes. In addition, these rhythms depend upon particular structures in the central nervous system. My laboratory studies the molecular and neural basis of these endogenous daily (circadian) rhythms in mammals. We focus upon the suprachiasmatic nucleus of the hypothalamus (SCN), a master pacemaker critical not only to general activity rhythms but also to the estrous cycle, the rhythmic secretion of many hormones, and seasonal breeding.
We have recently discovered a recessive mutation that shortens the free running period of circadian rhythms and has remarkable effects upon their entrainment. While wild type animals show only modest (>3 hour) phase shifts in response to light pulses, the duper mutant shifts by as much as 12 circadian hours. Efforts are underway to determine the locus of the mutation; through RNA-Seq and next generation sequencing we have determined that it is not in the coding region of any of the known core circadian clock genes. Additional work is focused on the physiological consequences of the hierarchical organization of the circadian system. The molecular feedback loops that account for rhythmicity of the SCN pacemaker also run in other neurons, including those that control ovulation and wakefulness. We seek to determine whether circadian rhythms in these subordinate oscillators (e.g., GnRH and hypocretin cells) are necessary for normal function, or whether rhythmicity of the SCN is sufficient.
Learn more at www.umass.edu/cns/bittman/index.htm
- Postdoctoral Scholar: University of Michigan at Ann Arbor (Reproductive Endocrinology Program)
- PhD University of California at Berkeley (Psychology & Endocrinology), 1978
- MA University of California at Berkeley (Psychology), 1977
- BA University of Pennsylvania (Biology & Psychology), 1973