Antagonists to the Wnt Cascade Exhibit Sex-Specific Expression in Gonads of Sexually Mature Shovelnose Sturgeon

Abstract

Little is known regarding molecular mechanisms involved in sex determination and differentiation in sturgeon species. We addressed this knowledge gap by using next generation pyrosequencing technology to provide transcript libraries and species-specific sequences for mature gonads of shovelnose sturgeon, Scaphirhynchus platorynchus. We then mined these libraries to identify gender-specific transcripts and quantified relative transcript abundance using quantitative real-time polymerase chain reaction (qPCR). We detected a limited number of genes known to play a role in sex differentiation in other species. The sequence for dmrt1 was found only in the testes library. The abundance of dmrt1 differed slightly between the sexes, but the melt curve suggests that there may be different isoforms of dmrt1 in ovaries and testes of shovelnose sturgeon. The transcription factor foxl2 was 5.3-fold greater in ovaries than in testes. Two antagonists to the Wnt cascade, dickkopf-1 (dkk1) and dapper-1 (dact1), were found only in the ovary library. Results from qPCR indicated that dkk1 and dact1 were upregulated 1,819.1- and 207.5-fold, respectively, in ovaries compared with testes. These results suggest that antagonists to the Wnt cascade may play significant roles in sex differentiation and gonadal development in sturgeon and could serve as sex markers in this group of ancient fish.

Discovery and identification of candidate sex-related genes based on transcriptome sequencing of Russian sturgeon (Acipenser gueldenstaedtii) gonads

“…In Alabama shovel sturgeons, VGT and Dmrt1 genes showed no significant differences in the male and female gonads, but foxl2 genes showed female-specific expression. An additional study that also sequenced the transcriptome of Alabama shovel sturgeons came to the same conclusion and found that only two WNT antagonists detected in the female library were considered biomarkers (2).…”

“…Research suggests that the sex-determination system in sturgeons is ZW for female and ZZ for male (58). Sox9, dmrt1, TrA-1, and Foxl2 have been identified as biomarkers for sex determination in some sturgeons (2,3,24,26), but no biomarker has been identified in Russian sturgeons. A previous study found that the stFSHb subunit was expressed at a higher level in 3 and 4 yr old fish than in 1 yr old fish and that the expression level of stFSHb in females was significantly higher than in males (28).…”

Effects of 11-Ketotestosterone on Development of the Previtellogenic Ovary in the Sterlet, Acipenser ruthenus

“…Many studies have shown that foxl2 and cyp19a1 are closely related to sex differentiation, as well as ovarian development and maintenance (40)(41)(42), such as in mammalian (43), avian (44), and teleost (42,45,46) females, but not during male development. There were similar results in the sturgeon, like lake sturgeon (47), shortnose sturgeon (48,49), Russian sturgeon (50), and sterlet (34,51). Moreover, the adult female zebrafish could be sexreversed to male by inhibiting aromatase (52).…”

Molecular characterization and expression pattern of dmrt1 in the immature Chinese sturgeon Acipenser sinensis

“…In addition, dmrt1 exhibited the sexually dimorphic expression pattern and was expressed at a higher level in male gonads, suggesting that it plays an important role in spermatic differentiation. The dmrt1 expression was previously described in sturgeon gonads and shown to be sexually dimorphic in lake sturgeon Acipenser fulvescens Rafinesque 1817 (Hale et al , ), shovelnose sturgeon Scaphirhynchus platorynchus (Rafinesque 1820) (Amberg et al , ) and Siberian sturgeon Acipenser baerii Brandt 1869 (Berbejillo et al , ).…”