Localization of steroidogenic enzymes and Foxl2a in the gonads of mature zebrafish ( Danio rerio )

Abstract

In zebrafish, the identification of the cells expressing steroidogenic enzymes and their regulators is far from completely fulfilled though it could provide crucial information on the elucidation of the role of these enzymes. The aim of this study was to better characterize the expression pattern of steroidogenic enzymes involved in estrogen and androgen production (Cyp17-I, Cyp11c1, Cyp19a1a and Cyp19a1b) and one of their regulators (Foxl2a) in zebrafish gonads. By using immunohistochemistry, we localized the steroid-producing cells in mature zebrafish gonads and determined different expression patterns between males and females. All these steroidogenic enzymes and Foxl2a were detected both in the testis and ovary. In the testis, they were all localized both in Leydig and germ cells except Cyp19a1b which was only detected in germ cells. In the ovary, Cyp17-I, Cyp19a1a and Foxl2a were immunolocalized in both somatic and germ cells while Cyp19a1b was only detected in germ cells and Cyp11c1 in somatic cells. Moreover, Cyp19a1a and Foxl2a did not display exactly the same patterns of spatial localization but their expressions were correlated suggesting a possible regulation of cyp19a1a gene by Foxl2a in zebrafish. Comparative analysis revealed a dimorphic expression of Cyp11c1, Cyp19a1a, Cyp19a1b and Foxl2a between males and females. Overall, our study provides a detailed description of the expression of proteins involved in the biosynthesis of steroidal hormones at the cellular scale within gonads, which is critical to further elucidating the intimate roles of the enzymes and the use of the zebrafish as a model in the field of endocrinology.

Knockout of Zebrafish Ovarian Aromatase Gene (cyp19a1a) by TALEN and CRISPR/Cas9 Leads to All-male Offspring Due to Failed Ovarian Differentiation

“…As expected, all three mutant lines we generated turned out to be all males, supporting the view that gonadal aromatase and the estrogens it produces are critical in directing gonadal differentiation. Interestingly, although aromatase has been reported to be expressed in the testis of both mammals62 and fish including the zebrafish6364, implicating a role in spermatogenesis, we did not observe any abnormalities in spermatogenesis of the mutant fish, which were fertile as normal at 120 dpf. This agrees with the reports in the mouse.…”

Genetic and structural analyses of cytochrome P450 hydroxylases in sex hormone biosynthesis: Sequential origin and subsequent coevolution

“…Thus CYP11A in zebrafish exhibits temporal subfunctionalization, rather than the functional differentiation like that seen for CYP17A1 and CYP17A2. Fish additionally have CYP11C genes, and while CYP11C1 is known to be expressed in zebrafish testicular tissue and the cytoplasm of the follicular cells surrounding vitellogenic oocytes and of interstitial cells (Baudiffier et al, 2012; Caulier et al, 2015), the specific steroid metabolites of CYP11C1 are not known.…”

Foxl2 and Its Relatives Are Evolutionary Conserved Players in Gonadal Sex Differentiation

“…In male salmonids and seabass, a low but significant level of foxl2 expression is detected by sensitive quantitative methods (RT-qPCR) in the adult testis throughout sexual development [Baron et al, 2004;von Schalburg et al, 2010von Schalburg et al, , 2011Crespo et al, 2013]. In zebrafish, Foxl2 expression has been localized to Leydig and germ cells by immunolocalization [Caulier et al, 2015] ( table 1 ). Medaka foxl2 is clearly expressed in a dimorphic fashion with no testicular expression [Nakamoto et al, 2006].…”