Expression profiles of sex differentiation‐related genes during ontogenesis in the European sea bass acclimated to two different temperatures

Abstract

The European sea bass is a teleost fish that lacks sex chromosomes and for which temperature influences sex ratios. However, correlation between temperature, developmental stage at a given age and sex-specific gene expression is hampered by the lack of sex markers. To study this correlation, fish were exposed to feminizing (15 degrees C) or masculinizing temperature (21 degrees C) from 0-120 days post fertilization, throughout the thermosensitive period (TSP). Aromatase (cyp19a1a), 11beta-hydroxylase (cyp11b), androgen receptor (arb) and estrogen receptors (era, erb1 and erb2) were assessed by qPCR prior and during sex differentiation. Canonical discriminant analysis (CDA), with length--as proxy for developmental stage--and cyp19a1a expression as predictors, was validated and used to reliably assign gonadal sex to fish sampled within and outside the TSP. Differences in cyp19a1a and cyp11b expression could be detected 1-month before the first signs of histological sex differentiation. Cyp19a1a and cyp11b were significantly higher in future females and males, respectively, and revealed as robust molecular markers to predict future ovarian and testicular differentiation. In contrast, no association between phenotypic sex and arb, era, erb1 and erb2 expression was found, suggesting that these genes do not contribute to the differentiation of a particular sex. The CDA-based approach implemented here could be used to sex undifferentiated animals in species where genetic sex cannot be known owing to the lack of simple sex determining systems, as it is the case of many fish and reptiles with or without temperature-dependent sex determination, and provide a useful tool to relate gene expression and phenotypic sex.

Sexing Frogs by Real-Time PCR: Using Aromatase <b><i>(cyp19) </i></b>as an Early Ovarian Differentiation Marker

“…In support of this observation, sexually dimorphic levels of GMC cyp19 in G. rugosa have been reported 2 weeks earlier than cyp17 and foxl2 [Ohtani et al, 2003;Iwade et al, 2008;Maruo et al, 2008;Oshima et al, 2008Oshima et al, , 2009Sakurai et al, 2008;Suda et al, 2011b]. Together, these results support the use of cyp19 as an early ovarian differentiation marker in amphibians, as has been proposed for fish [Fernandino et al, 2008;Blázquez et al, 2009].…”

“…Generally, in fish, the gonadal form of cyp19 (cyp19a1a) can be detected in the developing gonads even before morphological sex differentiation occurs Baroiller et al, 1999;Blázquez et al, 2009], with aromatization taking place before sex differentiation and directing the fate of the gonad [Kwon et al, 2000]. Although histological analyses were not carried out in the present analysis, our results suggest that dimorphic patters in the GMC of L. sylvaticus tadpoles can be observed previous to morphological differentiation of the tadpole gonads.…”

Differential expression analysis of genes involved in high-temperature induced sex differentiation in Nile tilapia

“…Therefore, the gonad containing a little peritoneum did not affect the detection for the amplification of CYP19A1A or ERβ. Blázquez et al (2009) found that CYP19A1A among 7 genes was the best variable to discriminate sex in sea bass and CYP19A1A alone was capable of correctly classifying 100% of the fish. Together previous studies and our work indicated that qRT-PCR of CYP19A1A and ERβ could be used for predicting future females and future males of tilapia larvae.…”

“…The real time PCR, the CYP19A1A and ERβ as primer (Table 1) and the gonad cDNA as template were utilized to determine the Ct (cycle threshold) value for CYP19A1A and ERβ in adult or larvae (Ijiri et al, 2008;Blázquez et al, 2009). According to the obtained Ct values from adults, we can set the fold change threshold value of CYP19A1A between females and males.…”

Steroidogenesis and phase II conjugation during the gametogenesis of thicklip grey mullet (Chelon labrosus) from a population showing intersex condition

“…Several authors have categorized the cyp11b1 gene as a gender-specific gene with low or inexistent expression in ovaries (Blázquez et al, 2009;Kusakabe et al, 2002;Liu et al, 2000;Yokota et al, 2005;Zhang et al, 2010). The present work detected low and relatively constant transcription of cyp11b1 in ovaries irrespectively of the reproductive stage.…”