Yolk steroid hormones and sex determination in reptiles with TSD.
In reptiles with temperature-dependent sex determination (TSD), the temperature at which the eggs are incubated determines the sex of the offspring. The molecular switch responsible for determining sex in these species has not yet been elucidated. We have examined the dynamics of yolk steroid hormones during embryonic development in the snapping turtle, Chelydra serpentina, and the alligator, Alligator mississippiensis, and have found that yolk estradiol (E(2)) responds differentially to incubation temperature in both of these reptiles. Based upon recently reported roles for E(2) in modulation of steroidogenic factor 1, a transcription factor known to be significant in the sex differentiation process, we hypothesize that yolk E(2) is a link between temperature and the gene expression pathway responsible for sex determination and differentiation in at least some of these species. Here we review the evidence that supports our hypothesis.
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P K
PK
University of Minnesota Crookston, 2900 University Avenue, Crookston, MN 56716-5100, USA. pelf@mail.crk.umn.edu
D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D004530:Egg Yolk / Q000378:metabolism; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D051717:Fushi Tarazu Transcription Factors; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins; D008297:Male; D018160:Receptors, Cytoplasmic and Nuclear; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000502:physiology*; D054339:Steroidogenic Factor 1; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism; D014426:Turtles / Q000196:embryology*
D004268:DNA-Binding Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; D004958:Estradiol