ENVIRONMENTAL INFLUENCES ON BRAIN PLASTICITY

Summary

Principal Investigator: DAVID P CREWS
Abstract: DESCRIPTION (Adapted from applicant's abstract): This research addresses the fundamental question of what determines behavioral variation. Many environmental variables can produce predictable effects on phenotype. One such variable is the incubation temperature of eggs in many reptiles. In the leopard gecko, embryos become male or female depending upon their temperature during development. In addition, between-sex as well as within-sex differences attributable to incubation temperature have been found in morphology, secretion of and sensitivity to steroid hormones, sociosexual behavior, reproductive success, and in the neuroanatomy and metabolic activity of brain areas that mediate sociosexual behaviors. These environmental effects are analogous to the effect of intrauterine environment in mammals, including humans. Given the homology of the endocrine and nervous systems across vertebrates, it is important to determine if homologous mechanisms underlie these analogous effects on behavior. If the mechanism underlying environmental effects on behavior in the leopard gecko is conserved (i.e., via sex steroids), this research will lend new insight into the evolution of sexual differentiation because temperature-dependent sex determination is thought to be the evolutionary precursor to genotypic sex determination (present in birds and mammals) and because reptiles are the ancestors of both birds and mammals. If the mechanism is different (i.e., direct temperature effects), this research would elucidate a novel process of sexual differentiation that may also be present in birds and mammals but, because of homeothermy, is masked. This latter possibility is especially important because young birds and mammals cannot regulate their body temperature as do adults. The proposed research is broadly categorized into three groups: thermoregulation and its relation to sociosexual behaviors (i.e., the degree to which the neural substrates mediating thermoregulatory and sociosexual behavior overlap), the development of the neural phenotypes of these brain regions and hormone milieus, and the effects of hormonal manipulations during development and neural manipulations in adulthood on thermoregulatory and sociosexual behaviors. The final category of experiments is particularly important as it will discern whether the incubation temperature effects are direct or indirect.
Funding Period: 1998-03-10 - 2003-08-31
more information: NIH RePORT

Top Publications

  1. pmc Epigenetic modifications of brain and behavior: theory and practice
    David Crews
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Horm Behav 59:393-8. 2011
  2. pmc Segregating variation for temperature-dependent sex determination in a lizard
    T Rhen
    Section of Integrative Biology, University of Texas at Austin, Austin, TX, USA
    Heredity (Edinb) 106:649-60. 2011
  3. ncbi Constraints on temperature-dependent sex determination in the leopard gecko (Eublepharis macularius): response to Kratochvil et al
    Victoria Huang
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Naturwissenschaften 95:1137-42. 2008
  4. pmc Epigenetics and its implications for behavioral neuroendocrinology
    David Crews
    Section of Integrative Biology and Center of Behavioral Neuroendocrinology, University of Texas at Austin, Austin, TX 78712, USA
    Front Neuroendocrinol 29:344-57. 2008
  5. ncbi Effect of incubation temperature and androgens on dopaminergic activity in the leopard gecko, Eublepharis macularius
    Brian George Dias
    Institute for Neuroscience, University of Texas at Austin, Austin, Texas, USA
    Dev Neurobiol 67:630-6. 2007
  6. ncbi Reproductive tradeoffs and yolk steroids in female leopard geckos, Eublepharis macularius
    T Rhen
    Department of Biology, University of North Dakota, Grand Forks, ND 58202, USA
    J Evol Biol 19:1819-29. 2006
  7. pmc From gene networks underlying sex determination and gonadal differentiation to the development of neural networks regulating sociosexual behavior
    David Crews
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Brain Res 1126:109-21. 2006
  8. ncbi Effects of gonadal sex and incubation temperature on the ontogeny of gonadal steroid concentrations and secondary sex structures in leopard geckos, Eublepharis macularius
    Turk Rhen
    Department of Biology, University of North Dakota, Grand Forks, 58202, USA
    Gen Comp Endocrinol 142:289-96. 2005
  9. pmc The distributions of the duplicate oestrogen receptors ER-beta a and ER-beta b in the forebrain of the Atlantic croaker (Micropogonias undulatus): evidence for subfunctionalization after gene duplication
    M B Hawkins
    Marine Science Institute, University of Texas at Austin, Port Aransas, TX 78373, USA
    Proc Biol Sci 272:633-41. 2005
  10. ncbi Normally occurring intersexuality and testosterone induced plasticity in the copulatory system of adult leopard geckos
    Melissa M Holmes
    Michigan State University, East Lansing, MI 48824 1101, USA
    Horm Behav 47:439-45. 2005

Scientific Experts

Detail Information

Publications11

  1. pmc Epigenetic modifications of brain and behavior: theory and practice
    David Crews
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Horm Behav 59:393-8. 2011
    ..Lastly, it seems intuitive that germline- and context-dependent epigenetic modifications interact, resulting in the individual variation observed in behaviors, but until now this hypothesis has never been tested experimentally...
  2. pmc Segregating variation for temperature-dependent sex determination in a lizard
    T Rhen
    Section of Integrative Biology, University of Texas at Austin, Austin, TX, USA
    Heredity (Edinb) 106:649-60. 2011
    ..These data show for the first time that there is segregating variation for TSD in a reptile and consequently that a quantitative trait locus analysis would be practicable for identifying the genes underlying TSD...
  3. ncbi Constraints on temperature-dependent sex determination in the leopard gecko (Eublepharis macularius): response to Kratochvil et al
    Victoria Huang
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Naturwissenschaften 95:1137-42. 2008
    ..These results suggest that maternal influences on sex determination are secondary relative to incubation temperature effects...
  4. pmc Epigenetics and its implications for behavioral neuroendocrinology
    David Crews
    Section of Integrative Biology and Center of Behavioral Neuroendocrinology, University of Texas at Austin, Austin, TX 78712, USA
    Front Neuroendocrinol 29:344-57. 2008
    ..This work raises the question of how events in generations past can have consequences at both the mechanistic, behavioral, and ultimately evolutionary levels...
  5. ncbi Effect of incubation temperature and androgens on dopaminergic activity in the leopard gecko, Eublepharis macularius
    Brian George Dias
    Institute for Neuroscience, University of Texas at Austin, Austin, Texas, USA
    Dev Neurobiol 67:630-6. 2007
    ..These data indicate that both the embryonic environment as well as the circulating hormonal milieu can modulate neurochemistry, which might in turn be a basis for individual variation in behavior...
  6. ncbi Reproductive tradeoffs and yolk steroids in female leopard geckos, Eublepharis macularius
    T Rhen
    Department of Biology, University of North Dakota, Grand Forks, ND 58202, USA
    J Evol Biol 19:1819-29. 2006
    ..These findings suggest that maternal allocation of DHT could mitigate tradeoffs that lead to poor offspring quality (i.e. poor female condition) and small offspring size (i.e. small egg size)...
  7. pmc From gene networks underlying sex determination and gonadal differentiation to the development of neural networks regulating sociosexual behavior
    David Crews
    Section of Integrative Biology, University of Texas at Austin, Austin, TX 78712, USA
    Brain Res 1126:109-21. 2006
    ....
  8. ncbi Effects of gonadal sex and incubation temperature on the ontogeny of gonadal steroid concentrations and secondary sex structures in leopard geckos, Eublepharis macularius
    Turk Rhen
    Department of Biology, University of North Dakota, Grand Forks, 58202, USA
    Gen Comp Endocrinol 142:289-96. 2005
    ..Furthermore, these data suggest that the organizational effects of incubation temperature on adult female phenotype could be, in part, mediated by incubation temperature effects on steroid hormone levels during juvenile development...
  9. pmc The distributions of the duplicate oestrogen receptors ER-beta a and ER-beta b in the forebrain of the Atlantic croaker (Micropogonias undulatus): evidence for subfunctionalization after gene duplication
    M B Hawkins
    Marine Science Institute, University of Texas at Austin, Port Aransas, TX 78373, USA
    Proc Biol Sci 272:633-41. 2005
    ....
  10. ncbi Normally occurring intersexuality and testosterone induced plasticity in the copulatory system of adult leopard geckos
    Melissa M Holmes
    Michigan State University, East Lansing, MI 48824 1101, USA
    Horm Behav 47:439-45. 2005
    ..Indeed, the system is remarkable in that adult females have normally occurring intersex characteristics and they exhibit substantial steroid-induced morphological plasticity in adulthood...