Identification of genes involved in gonadal sex differentiation and the dimorphic expression pattern in undifferentiated gonads of Russian sturgeonAcipenser gueldenstaedtiiBrandt & Ratzeburg, 1833

Abstract

The establishment of a sexing technique at an early developmental stage is an important issue in sturgeon aquaculture, yet the mechanism of sex differentiation in sturgeons remains poorly understood. This study aimed to identify genes involved in gonadal sex differentiation and to investigate sexually dimorphic gene expression in undifferentiated gonads. RNA-seq analyses using next-generation sequencers were carried out on undifferentiated gonads of five 9-month-old juvenile Russian sturgeon Acipenser gueldenstaedtii. A total of 45 686 832 (8498 Mb) and 79 743 269 (7887 Mb) qualitycontrolled reads were obtained using Ion PGM and HiSeq 2000 sequencers, respectively, and were assembled into 338 648 contigs (N50: 532 b). tBLASTx analyses identified 26 transcripts potentially involved in gonadal differentiation. Read-mapping analyses were performed to obtain relative transcript levels (RPKM values). Multivariate analyses of the RPKM values of five transcripts (gsdf, dmrt1a, dmrt1b, foxl2 and cyp19a1a) showed that the five individuals could be separated into two distinct groups. One group, comprising two individuals, had increased levels of foxl2, hsd17b1 and cyp19a1a, suggesting differentiation into females. Alternatively, levels of gsdf were higher in the other three individuals, suggesting differentiation into males. We describe the levels of 26 transcripts potentially involved in gonadal differentiation in undifferentiated sturgeon gonads and suggest that levels of gsdf, foxl2, hsd17b1 and cyp19a1a are appropriate sexing markers for sturgeon at an early developmental stage. U.S.

Identification of the molecular sex‐differentiation period in the siberian sturgeon

“…It is interesting that ar expression increased during this period, suggesting that androgens are relevant for both male and female gonadal development. In contrast with our previous results in Siberian sturgeon (Berbejillo et al, ), but consistent with previous studies in other sturgeons (Amberg et al, ; Hagihara et al, ), dmrt1 was not sex ‐ dimorphic during this period. We speculate that the differences between the present and previous studies (Berbejillo et al, ) may be related to the age of the fish analyzed.…”

“…When using the presence of invaginations as the criterion for sex differentiation, the age when differentiation occurs was reported to vary from 4 to 9 months among sturgeons species (Chen et al, 2006;Flynn and Benfey, 2007;Grandi et al, 2007;Grandi and Chicca, 2008;Rzepkowska and Ostaszewska, 2013). This superficial distinction does not, however, provide conclusive evidence of morphological sex differentiation (Hagihara et al, 2014). We instead considered the presence of mitotic or meiotic germ cell clusters as a clear sign of ovarian development, whereas the homogeneous distribution of non-meiotic germ cells indicated presumptive males.…”

Sex steroid level and sexual dimorphism expression of genes in gonads of the great sturgeonHuso husoLinneaus, 1758 during maturity developmental stages

“…The present results are consistent with previous studies in Russian sturgeon with no observation of sexual dimorphic expression pattern of sox9 in undifferentiated gonads (Hagihara et al . ). Similarly, our finding is consistent with previous studies on Siberian sturgeon, which states that sox9 play role in late testis differentiation (Berbejillo et al .…”

“…However, several studies investigated the expression of sox9 during gonadal sex differentiation in different fish species (Jorgensen, Morthorst, Andersen, Rasmussen & Bjerregaard ; von Schalburg, Yasuike, Yazawa, De Boer, Reid, So, Robb, Rondeau, Phillips & Davidson ; Smith, Guzmán & Luckenbach ), only few studies have been reported in sturgeons (Berbejillo et al . ; Hagihara, Yamashita, Yamamoto, Ishihara, Abe, Ijiri & Adachi ).…”

Differential expression of foxl2 and cyp19a1amRNA during gonad developmental stages in great sturgeon Huso huso

“…To date, however, all efforts to identify sex determination genes or even a sex‐linked marker in sturgeons have been unsuccessful (Wuertz et al , ; Keyvanshokooh et al , ; McCormick et al , ; Yarmohammadi et al , ). Few studies reported the expression of genes involved in ovarian differentiation such as foxl2 and cyp19a1a in sturgeon species (Hagihara et al , ). The role of ooestrogens, foxl2 and cyp19a1a in ovarian differentiation, however, was not reported in this group of fishes.…”