Divergent and sex‐dimorphic expression of the paralogs of the Sox9‐Amh‐Cyp19a1 regulatory cascade in developing and adult atlantic cod (Gadus morhua L.)

Abstract

The factors of the Sox9-Amh-Cyp19a1 cascade play a crucial role in the complex process of sex differentiation in mammals. The involvement of Sox9 and Cyp19a1 paralogs and the single Amh ortholog in sex differentiation and development of the gonads and the brain in Atlantic cod was examined by analyzing bimodal and sex-dimorphic gene expression patterns, respectively, during early stages and in maturing males and females. Expression of sox9a and sox9b were initiated at blastulation, and both paralogs were expressed in chondrogenic tissue in the hatched larvae. The male-specific expression of sox9a in the adult gonads supports a conserved role in testis function, while sox9b was expressed in the maturing testes and ovaries at similar levels. Amh was expressed at low, but variable, levels from late gastrulation prior to the onset of cyp19a1a and cyp19a1b expression. Male-biased amh expression was found in the maturing gonads, but the increased ovarian levels during maturation suggest a role also in females. The larval expression of cyp19a1a and cyp19a1b increased at the expected time of sex differentiation, but showed large individual variation. The ovarian expression of cyp19a1a and amh increased concomitant with increased plasma estradiol levels during vitellogenesis. The testis-specific cyp19a1b expression supports the importance of estrogen in the spermatogenesis, while abundant expression in the male and female brain is probably related to the continuous neurogenesis in fish. These divergent and sex-dimorphic expression patterns of the cod sox9 and cyp19a1 paralogs demonstrate the complexity of the genetic network regulating sexual development in fish.

Sexually dimorphic transcription of estrogen receptors in cod gonads throughout a reproductive cycle

“…In contrast, teleosts have two cyp19 genes: cyp19a1a is preferentially expressed in ovaries, whereas cyp19a1b is found predominantly in brain (Tchoudakova & Callard 1998). Our current knowledge of seasonal changes of cyp19a1a expression in fish ovaries throughout a reproductive cycle is still very limited (Sampath Kumar et al 2000, Rocha et al 2009, Johnsen et al 2013. In Atlantic cod, cyp19a1a transcripts are constantly present at higher levels in ovaries than in testes, with a significant increase in expression in ovaries but not in testes towards the spawning season.…”

“…In this report, we focus on the ERs in gonads: ERa (esr1) and two paralogs of ERb (esr2a and esr2b). We also analyzed the relative mRNA levels of ar, which mainly acts in spermatogenesis (Shi et al 2012), and cytochrome P450 aromatase (cyp19a1a) catalyzing the biosynthesis of estrogens (Johnsen et al 2013) to determine their association with esr expression in gonads.…”

Effect of the probiotic Lactobacillus rhamnosus on the expression of genes involved in European eel spermatogenesis

“…Assay characteristics and cross-reactivities of the 17,20bP assay have previously been described by Mazzeo et al [44] and validated for eel plasma by Peñaranda et al [24]. The cross-reactivities of a new 11-KT antiserum used in this work have been previously described by Johnsen et al [45]. To validate 11-KT recovery from plasma in the eel assay, a plasma pool was spiked with 45-ng 11-KT/mL of plasma and then subjected to ether extraction as described in the following.…”

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…The characteristics and crossreactivities of the DHP assay have previously been described by Tveiten et al (2010) and validated for eel plasma by Peñaranda et al (2010). The cross-reactivities of a new 11-KT antiserum used in this work have previously been described by Johnsen et al (2013). To validate the recovery of 11-KT from plasma in the eel assay, a plasma pool was spiked with 45 ng 11-KT/ml of plasma and then underwent ether extraction as described below.…”