title: Chronology, magnitude and duration of expression of putative sex-determining/differentiation genes in a turtle with temperature-dependent sex determination.
abstract: The red-eared slider turtle (Trachemys scripta) possesses temperature-dependent sex determination (TSD) in which the incubation temperature determines gonadal sex. Although a number of mammalian gene homologues have been identified in reptiles with TSD, the exact sex-determining trigger(s) is not known. To date, the current study represents the most comprehensive simultaneous evaluation of the chronology of mRNA expression profiles of putative sex-determining/differentiation genes (Dmrt1, Sox9, Amh, Lhx9, and Foxl2) from gonads incubated at male- and female-producing temperatures in T. scripta. Additionally, sex-reversing treatments with 17β-estradiol and letrozole were examined. At a male-producing temperature, Dmrt1 expression was sexually dimorphic by stage 17, Sox9 by 19 and Amh by 21. In contrast, Foxl2 did not significantly increase until after the thermosensitive period at a female-producing temperature. Treatment with 17β-estradiol resulted in reduced gonad size and/or inhibited gonadal development and differentiation. Gene expression was subsequently low in this group. Sex reversal utilizing letrozole failed to produce testes at a female-producing temperature and as such, gene expression was comparable to ovary. These results indicate that Dmrt1 and Sox9 are potential triggers for testis differentiation and Amh, Lhx9 and Foxl2 represent a conserved core set of genes in the sex-determining/differentiation pathway of TSD species.
authors.affiliation: Department of Biology, University of Alabama at Birmingham, Birmingham, Ala., USA.
authors.forename: Kayla L
authors.initials: KL
authors.lastname: Bieser
authors.forename: Thane
authors.initials: T
authors.lastname: Wibbels
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006066:Gonads / Q000187:drug effects / Q000196:embryology / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D000077289:Letrozole; D008297:Male; D009570:Nitriles / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D019849:Sex Determination Processes / Q000187:drug effects / Q000235:genetics*; D012733:Sex Differentiation / Q000187:drug effects / Q000235:genetics*; D013696:Temperature; D013997:Time Factors; D014230:Triazoles / Q000494:pharmacology; D014426:Turtles / Q000196:embryology / Q000235:genetics*
chemical_list: D009570:Nitriles; D014230:Triazoles; D004958:Estradiol; D000077289:Letrozole