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Mahoney, Megan M

Associate Professor
Director of Graduate Studies, Comparative Biosciences

Address and Contact Information

College of Veterinary Medicine
2001 South Lincoln Avenue
3639 Vet Med Basic Sciences Bldg.
Urbana, IL  61802


  • PhD, Michigan State University
  • Post-Doc, University of Michigan
  • BA, Bates College, Maine

Academic Interests

  • Circadian rhythms
  • Female reproduction (mating behavior, hormone surges, neuroanatomy)
  • The effect of jet lag and shift work on health, particularly in females
  • Sleep
  • Clock genes in central and peripheral oscillators
  • Hypothalamus pituitary gonadal axis
  • Comparison of diurnal and nocturnal species
  • Sexual differentiation
  • Xenoestrogens and their effects on reproduction and sexual differentiation of the brain

Research Interests

  • My work focuses on the influence of estrogen on the expression of circadian rhythms. In rodents gonadal steroids modify the timing, strength and period of circadian rhythms. Ovarian hormones appear to have a similar effect in women as diurnal and circadian rhythms including sleep-wake cycles and endocrine rhythms (cortisol, melatonin) change between the follicular and luteal phases of the reproductive cycle. Sex differences in circadian rhythms exist and women are more likely than men to experience insomnia, and women undergoing the menopausal transition have significant disturbances in their sleep onset, quality, and efficiency. Hormone replacement therapy alleviates some of these problems. Despite the gender disparities in sleep-wake patterns, and the known sex differences in circadian rhythms in both rodents and humans, relatively little work has elucidated the specific role of ovarian hormones. We use transgenic mouse models which have impaired estrogen signaling to examine the interplay of estrogen on circadian rhythms.
  • Additionally I am interested in understanding how the circadian timekeeping system regulates reproductive events such as hormone secretion and mating behavior. Reproductive neuroendocrine events occur in a cyclical manner, however, relatively little is known about how the underlying endogenous circadian system regulates reproductive function, or how disruptions in biological rhythms are correlated with changes in fertility, hormone secretion, and pregnancy outcome. Female shift workers and transatlantic travelers are at risk for severe reproductive complications such as reduced conception rates, increased miscarriage rates, smaller birth weight babies, and dysmenorrhea. This is a significant issue for women's health as over 3 million women have flexible or shift work schedules. The number of female reproductive morbidities associated with such altered work schedules is alarming yet the etiology of these health problems is unclear. Our lab examines how disruptions of the circadian clock (jet lag, shift work) decreases reproductive function and alters clock gene expression in female rats.
  • My interests in the effects of estrogen in the developing organism are extended to understanding how exogenous hormones or hormone mimics can alter the expression of proteins or RNA in sexually dimorphic areas of the brain. I am investigating how endocrine disrupting chemicals that may mimic or block hormones can also influence the functions of the timekeeping system. 


Dr. Mahoney attended Smith College (Northampton Mass) and graduated from Bates College (Lewiston ME) with a BA in Biology. She worked as a research assistant at Harvard Medical School for two years before returning to graduate School to get a dual Ph.D. in Zoology and Ecology, Evolutionary Biology, and Behavior at Michigan State University (2003, East Lansing, MI). Dr, Mahoney moved to the University of Michigan for her post-doc where she participated in the Reproductive Sciences Program and Toxicology Training Program. In 2004 Dr. Mahoney was appointed an Assistant Research Scientist in the Department of Psychology. Dr. Mahoney became an Assistant Professor in the Department of Comparative Biosciences (formerly Veterinary Biosciences) at the College of Veterinary Medicine in May of 2006.

Teaching Statement

I believe that learning is enhanced when students are interested in the subject they are studying; and once they are engaged in the material then they can hone their critical thinking skills. I want the students to feel that they are a part of the classroom experience, and I think they will learn better if they are involved in talking and analyzing the material rather than passively listening to a lecture. To that end I work hard to infuse energy into the classroom and to convey my enthusiasm for the topics I teach. My ultimate goals are that first students will know the information and not just recognize it and second they will be able to utilize their knowledge in the analysis of novel information.

Courses Taught

  • Structure Function I (Neurobiology portion)
  • Structure Function II (Neurobiology portion)
  • Structure Function III (Neurobiology portion)
  • Animal Behavior
  • Hormones and Behavior
  • Biological Rhythms
  • Research Methods

Research Biography

  • Dr. Mahoney's doctorate and post doctoral work focused on how biological rhythms regulate the timing of female reproductive events in two different diurnal rodents compared to nocturnal lab rats. Her dissertation examined the timing of mating behavior, luteinizing hormone surges and gonadotropin releasing hormone neuron activation in the the diurnal murid rodent Arvicanthis niloticus compared to the nocturnal lab rat. During her post doc work at the University of Michigan Dr. Mahoney extended this research to a second diurnal rodent, Octodon degus. Her interests in estrogen and female reproduction were expanded during her toxicology post-doctoral experience. Using sheep as a model, Dr. Mahoney examined the changes in steroid receptor expression in the hypothalamus of animals prenatally exposed to environmental estrogens (BPA and Methoxychlor).
  • At the University of Illinois Dr. Mahoney has taken her interetest in circadian rhythms, female reproductive cycles, and estrogen in a new direction by 1) examining the effect of disruptions in rhythms (jet lag and shift work) on estrous cyclicity and clock gene expression and 2) characterizing the expression of circadian rhythms in mice with impaired estrogen production or signaling.

Selected Publications

  • Royston, S. E., A. G. Kondilis, S. V. Lord, N. Yasui, J. A. Katzenellenbogen and M. M. Mahoney. 2014. ESR1 and ESR2 differentially regulate daily and circadian activity rhythms in female mice. Endocrinology 155(7): 2613-2623
  • Blattner, M. S. and M. M. Mahoney. 2014. Estrogen receptor 1 modulates circadian rhythms in adult female mice. Chronobiology International 31(5): 637-644
  • Blattner, M. and M. Mahoney. 2013 Phase response curve and cellular activation in response to light-pulse in the suprachiasmatic nucleus of two strains of mice with impaired responsiveness to estrogens. Journal of Biological Rhythms. 28(4), 291-300.
  • Ayelet Ziv-Gal, A. Flaws, J.A., Mahoney, M., Miller, S.R, Zacur, H.A. and L. Gallicchio. 2013. Genetic polymorphisms in the AHR signaling pathway and CLOCK may be associated with sleep disturbances in midlife women. Sleep Medicine 14(9) 883-7
  • Blattner, M. and M. Mahoney. 2012. Circadian parameters are altered in two strains of mice with transgenic modifications of estrogen receptor subtype 1. Genes, Brain and Behavior. 11(7), 828-36.
  • Brockman, R., Bunick, D. and M. Mahoney. 2011. Estradiol deficiency during development modulates the expression of circadian and daily rhythms in male and female aromatase knockout mice. Hormones and Behavior. 60(4), p. 439-47.
  • Mahoney, M.M. and V. Padmanabhan. 2010. Developmental programming: Impact of fetal exposure to endocrine disrupting chemicals on gonadotropin-releasing hormone and estrogen receptor mRNA in sheep hypothalamus. Toxicology and Applied Pharmacology. 247(2):98-104.
  • Mahoney, M.M. 2010. Shift work, jet lag, and female reproduction. International Journal of Endocrinology. Epub 2010 March 8.
  • Mahoney, M.M., Ramanathan, C., Hagenauer, M.H. Thompson, R. Lee, T., and L. Smale. 2009. Daily rhythms and sex differences in vasoactive intestinal polypeptide, VIPR2 receptor, and arginine vasopressin mRNA in the suprachiasmatic nucleus of a diurnal rodent, Arvicanthis niloticus. European Journal of Neuroscience 30(8): 1537-43
  • Mong, J.A., Baker, F.C., Mahoney, M.M., Paul, K.N., Schwartz, M.D., Semba, K., Silver, R. 2011. Sleep, rhythms, and the endocrine brain: influence of sex and gonadal hormones. J Neurosci. 31, 16107-16.
  • Mahoney, M.M., Smale L., and T. Lee. 2009. Daily immediate early gene expression in the suprachiasmatic nucleus of male and female Octodon degus. Chronobiology International. 26(5): 821-837.
  • Gorton, L.M., Mahoney, M.M., Magorien, J.E., Lee, T.M. and R.I. Wood. 2009. Estrogen receptor immunoreactivity in late-gestation fetal lambs. Biology of Reproduction. 80(6): 1152-1159.
  • Mahoney, M.M., Ramanathan, C. and L. Smale. 2007. Tyrosine hydroxylase positive neurons and their contacts with vasoactive intestinal peptide-containing fibers in the hypothalamus of the diurnal murid rodent, Arvicanthis niloticus. Journal of Chemical Neuroanatomy 33:131-139.
  • Hummer, DH, Jechura T., Mahoney, M.M., and T. Lee. 2007. Gonadal hormone effects on entrained and free-running circadian activity rhythms in the developing diurnal rodent, Octodon degus. American Journal of Physiology 292(1):R586-597.
  • Jechura, T.J., Mahoney, M.M, Stimpson, C.D. and T. Lee. 2006. Odor specific effects on re-entrainment following phase advances in the diurnal rodent Octodon degus. American Journal of Physiology 292(6) R1808-1816.
  • Mahoney, M.M. and L. Smale. 2005. Arginine vasopressin and vasoactive intestinal polypeptide fibers make appositions with gonadotropin releasing hormone and estrogen receptor cells in the diurnal rodent Arvicanthis niloticus. Brain Research 1049:156-164.

Current Projects

  • Determining how hormone mimics or antagonists (endocrine disrupting chemicals) can affect the expression of biological rhythms. 
  • Investigating circadian rhythms in mice with impaired estrogen signaling
  • Determining how and where estrogen acts to modulate the expression of biological rhythms
  • Jet lag effects on reproductive function in rats
  • Developing a novel model of shift work in rats to determine how conflicts in "work" and light:dark schedules affects health
  • The effect of prenatal bisphenol-A on the development of the brain (mice and sheep)

Past Projects

The timing of mating and hormone surges in the diurnal murid rodent Arvicanthis niloticus


  • Morris Animal Foundation First Award for Small Companion Animals, "Biological rhythms in oxidative stress, endocrine, metabolism and immune factors in cats" (Role: PI)
  • University of Illinois Campus Research Board, "Estrogen's influence on the miRNA expression profile in mouse hearts" (Role: Co-PI)
  • Arnold O. Beckman Research Award, "The effect of Shift work and Jet Lag on Reproductive Function and Neuroendocrinology in the Lab Rat" (Role: PI)
  • Arnold O. Beckman Research Award, "The organizational and activational effect of estradiol on circadian rhythms" (Role: PI)
  • University of Illinois Campus Research Board, "The role of ovarian hormones on the development and expression of circadian rhythms" (Role: PI)

Honors and Awards

2012        Arnold O. Beckman Research Award Campus award given to “projects of special distinction”

2012           Chicago Veterinary Medical Association Outstanding Instructor Award

2010-2014   Teachers Ranked as Excellent (at least 4.4/5 pt scale), University of Illinois

2009            Gordon Research Conference travel award

2006            Young Investigator Award, Society for Behavioral Neuroendocrinology

2008            Arnold O. Beckman Research Award  Campus award given to “projects of special distinction”

Other Campus Affiliations

  • Neuroscience Program
  • Reproductive Biology Seminar Group
  • Psychology Department

Professional Affiliations

  • Society for Neuroscience
  • Society for Behavioral Neuroendocrinology
  • Society for Research on Biological Rhythms
  • Society for Study of Reproduction

LDAP Details for Mahoney, Megan M