Temperature Dependent Sex Determination
Sex of many species of turtles and tortoises has been known by reptile stewarts to be determined by incubation temperatures for many years. This was felt to be particularly critical at embryonic stages 17-21affecting aromatse activity with sex being irreversibly determined by embryonic stage 22. In this paper, transcriptional changes were demonstrated as early as embroyonic stage 3 at Female Producing Temperatures (31 degrees C) and stage 5 at Male Producing Temperatures (26 degrees C) in Chrysemys picta (red slider) turtles. Much occured differentialy prior to embryonic stages 17-21. If applicable to other Temperature Dependent Sex Determination turtles and tortoises, this suggests aspects of sexual determination started occuring much earlier in incubation than most of us have previously appreciated.
Thermal Response of Epigenetic Genes Informs Turtle Sex Determination with and without Sex Chromosomes
Srihari Radhakrishnana, Robert Litermanb, Jennifer L. Neuwaldc, Nicole Valenzuelac 2018
http://www.public.iastate.edu/~nval...shnanEtAl2018_EpiGenesThermoTranscription.pdf
Abstract
Vertebrate sexual fate can be established by environmental cues (e.g., temperature-dependent sex determination, TSD) or by genetic content (genotypic sex determination, GSD). While methylation is implicated in TSD, the influence of broader epigenetic processes in sexual development remains obscure. Here, we investigated for the first time the embryonic gonadal expression of the genome-wide epigenetic machinery in turtles, including genes and noncoding RNAs (ncRNAs) involved in DNA/histone acetylation, methylation, ubiquitination, phosphorylation, and RNAi. This ma- chinery was active and differentially thermosensitive in TSD versus GSD (ZZ/ZW) turtles. Methylation and histone acety- lation genes responded the strongest. The results suggest these working hypotheses: (i) TSD might be mediated by epigenetically controlled hormonal pathways (via acetylation, methylation, and ncRNAs), or by (ii) hormonally controlled epigenetic processes, and (iii) key epigenetic events prior to the canonical thermosensitive period may explain differenc- es between TSD and GSD. Novel epigenetic candidate regulators other than methylation were identified, including previously unknown ncRNAs that could potentially mediate gonadogenesis. These findings illuminate the molecular ecology of reptilian sex determination and permitted hypothesis building to help guide future functional studies on the epigenetic transduction of external cues in TSD versus GSD systems.
Sex of many species of turtles and tortoises has been known by reptile stewarts to be determined by incubation temperatures for many years. This was felt to be particularly critical at embryonic stages 17-21affecting aromatse activity with sex being irreversibly determined by embryonic stage 22. In this paper, transcriptional changes were demonstrated as early as embroyonic stage 3 at Female Producing Temperatures (31 degrees C) and stage 5 at Male Producing Temperatures (26 degrees C) in Chrysemys picta (red slider) turtles. Much occured differentialy prior to embryonic stages 17-21. If applicable to other Temperature Dependent Sex Determination turtles and tortoises, this suggests aspects of sexual determination started occuring much earlier in incubation than most of us have previously appreciated.
Thermal Response of Epigenetic Genes Informs Turtle Sex Determination with and without Sex Chromosomes
Srihari Radhakrishnana, Robert Litermanb, Jennifer L. Neuwaldc, Nicole Valenzuelac 2018
http://www.public.iastate.edu/~nval...shnanEtAl2018_EpiGenesThermoTranscription.pdf
Abstract
Vertebrate sexual fate can be established by environmental cues (e.g., temperature-dependent sex determination, TSD) or by genetic content (genotypic sex determination, GSD). While methylation is implicated in TSD, the influence of broader epigenetic processes in sexual development remains obscure. Here, we investigated for the first time the embryonic gonadal expression of the genome-wide epigenetic machinery in turtles, including genes and noncoding RNAs (ncRNAs) involved in DNA/histone acetylation, methylation, ubiquitination, phosphorylation, and RNAi. This ma- chinery was active and differentially thermosensitive in TSD versus GSD (ZZ/ZW) turtles. Methylation and histone acety- lation genes responded the strongest. The results suggest these working hypotheses: (i) TSD might be mediated by epigenetically controlled hormonal pathways (via acetylation, methylation, and ncRNAs), or by (ii) hormonally controlled epigenetic processes, and (iii) key epigenetic events prior to the canonical thermosensitive period may explain differenc- es between TSD and GSD. Novel epigenetic candidate regulators other than methylation were identified, including previously unknown ncRNAs that could potentially mediate gonadogenesis. These findings illuminate the molecular ecology of reptilian sex determination and permitted hypothesis building to help guide future functional studies on the epigenetic transduction of external cues in TSD versus GSD systems.