Temperature induced-masculinisation in the Nile tilapia causes rapid up-regulation of both dmrt1 and amh expressions

Nile tilapia has primarily a XX/XY sex determining system but minor genetic factors as well as temperature can override the major factors. Female XX progenies can be sex-reversed into functional males by rearing at high temperatures (>34 degrees C) from 10 dpf onwards. Temperature effects on the molecular pathways during sex differentiation in teleosts need to be deciphered. The temporal expression profiles of cyp19a1a and foxl2, two ovarian-developmental genes and dmrt1 and amh, two testes-developmental genes were analysed during key stages of the sex differentiation of genetic all-females, all-males and temperature-masculinised XX females (TM) tilapia. Overall QPCR analysis was similar between gonads and trunks. Both amh and dmrt1 expressions were up-regulated simultaneously in TM already at 1315 dpf. Dmrt1 expression became markedly elevated similar to 3-fold higher than XY male levels at 20-26 dpf whereas amh had similar levels to XY males. Foxl2 and cyp19a1a expression profiles were similar. Both were up-regulated at early stages in TM but repressed after 17-19 dpf, whilest levels continued to increase in XX-females. Our results show that temperature action on tilapia testis development induces the rapid increase of both dmrt1 and amh expressions followed by the down-regulation of fox12 and cyp19a1a. This suggests that dmrt1 and/or amh may be the modulator(s) of the down-regulation of foxl2 and/or cyp19a1a. (C) 2013 Elsevier Inc. All rights reserved.