Sex Maintenance in Mammals Jiménez Medina, Rafael Burgos Poyatos, Miguel Barrionuevo Jiménez, Francisco Javier Mammalian sex maintenance Sex determination Testis differentiation Ovary differentiation Gonadal cells transdifferentiation Gonadal genetic reprogramming This research was funded by the Andalussian Government, Junta de Andalucia with FEDER funds, grants numbers A-BIO-106-UGR18 and BIO109. The crucial event in mammalian sexual differentiation occurs at the embryonic stage of sex determination, when the bipotential gonads differentiate as either testes or ovaries, according to the sex chromosome constitution of the embryo, XY or XX, respectively. Once differentiated, testes produce sexual hormones that induce the subsequent differentiation of the male reproductive tract. On the other hand, the lack of masculinizing hormones in XX embryos permits the formation of the female reproductive tract. It was long assumed that once the gonad is differentiated, this developmental decision is irreversible. However, several findings in the last decade have shown that this is not the case and that a continuous sex maintenance is needed. Deletion of Foxl2 in the adult ovary lead to ovary-to-testis transdifferentiation and deletion of either Dmrt1 or Sox9/Sox8 in the adult testis induces the opposite process. In both cases, mutant gonads were genetically reprogrammed, showing that both the male program in ovaries and the female program in testes must be actively repressed throughout the individual’s life. In addition to these transcription factors, other genes and molecular pathways have also been shown to be involved in this antagonism. The aim of this review is to provide an overview of the genetic basis of sex maintenance once the gonad is already differentiated. 2021-09-20T06:59:33Z 2021-09-20T06:59:33Z 2021-06-29 info:eu-repo/semantics/article Jiménez, R.; Burgos, M.; Barrionuevo, F.J. Sex Maintenance in Mammals. Genes 2021, 12, 999. [https://doi.org/10.3390/genes12070999] http://hdl.handle.net/10481/70285 10.3390/genes12070999 eng http://creativecommons.org/licenses/by/3.0/es/ info:eu-repo/semantics/openAccess Atribución 3.0 España MDPI