title: Timing of SOX9 downregulation and female sex determination in gonads of the sea turtle Lepidochelys olivacea.
abstract: The SRY-related gene SOX9 is involved in the differentiation of Sertoli cells in male gonads of vertebrates with different kinds of sex determination. In the olive ridley Lepidochelys olivacea, a species with temperature sex determination (TSD), the SOX9 protein is expressed at stages 21-24 in medullary cells in gonads of embryos incubated at both male-(MPT) or female-promoting temperatures (FPT). However, at FPT the expression of SOX9 protein decreases at stage 25 and disappears at stage 26, suggesting this as the critical period for SOX9 regulation by temperature. Here, we used reverse transcriptase polymerase chain reaction (RT-PCR) to detect SOX9 transcripts in gonads of embryos switched from MPT to FPT at stage 23 and sampled at days 6-14. Simultaneously, groups of embryos were switched back to MPT and gonadal sex was established. SOX9 transcripts were detected at days 6-12 of switching, when embryos reached stage 25 and were no longer detected at day 14, when the embryos were at stage 26. Embryos switched back to MPT at days 6 or 8 formed testes, whereas embryos switched at days 10 or 14 developed ovaries. Results suggest that at MPT the male sex-determining pathway that maintains SOX9 expression in male gonads is established at stage 24. In contrast, at FPT, the female sex-determining pathway involved in downregulation of SOX9 in female gonads occurs within two days at stage 25. J. Exp. Zool. 290:498-503, 2001.
authors.affiliation: Departamento de Biologia Celular, Instituto de Investigaciones Biomedicas, UNAM, Mexico 04510.
authors.forename: L
authors.initials: L
authors.lastname: Torres-Maldonado
authors.forename: N
authors.initials: N
authors.lastname: Moreno-Mendoza
authors.forename: A
authors.initials: A
authors.lastname: Landa
authors.forename: H
authors.initials: H
authors.lastname: Merchant-Larios
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA; D004625:Embryo, Nonmammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006066:Gonads / Q000196:embryology* / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor; D017386:Sequence Homology, Amino Acid; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000235:genetics*; D013696:Temperature; D013995:Time; D014157:Transcription Factors / Q000235:genetics*; D014426:Turtles / Q000196:embryology*
chemical_list: D006609:High Mobility Group Proteins; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D014157:Transcription Factors; D004247:DNA