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

Transcriptome Analyses Reveal Expression Profiles of Morphologically Undifferentiated and Differentiated Gonads of Yangtze Sturgeon Acipenser dabryanus

Sturgeon is known as a primitive fish with the ZZ/ZW sex determination system and is highly prized for its valuable caviar. Exploring the molecular mechanisms underlying gonadal differentiation would contribute to broadening our knowledge on the genetic regulation of sex differentiation of fish, enabling improved artificial breeding and management of sturgeons. However, the mechanisms are still poorly understood in sturgeons. This study aimed to profile expression patterns between female and male gonads at morphologically undifferentiated and early differentiated stages and identify vital genes involved in gonadal sex differentiation of sturgeons. The sexes of Yangtze sturgeon (Acipenser dabryanus) juveniles were identified via the sex-specific DNA marker and histological observation. Transcriptome analyses were carried out on female and male gonads at 30, 80 and 180 days post-hatching. The results showed that there was a total of 17 overlapped DEGs in the comparison groups of between female and male gonads at the three developmental stages, in which there were three DEGs related to ovarian steroidogenesis, including hsd17b1, foxl2 and cyp19a1. The three DEGs were highly expressed in the female gonads, of which the expression levels were gradually increased with the number of days after hatching. No well-known testis-related genes were found in the overlapped DEGs. Additionally, the expression levels of hsd17b1 and cyp19a1 mRNA were decreased with the knockdown of foxl2 mRNA via siRNA. The results further suggested that foxl2 should play a crucial role in the ovarian differentiation of sturgeons. In conclusion, this study showed that more genes involved in ovarian development than testis development emerged with sexually dimorphic expression during early gonadal sex differentiation, and it provided a preliminary understanding of the molecular regulation on gonadal differentiation of sturgeons.

The molecular regulation mechanism of dmrt1-based on the establishment of the testis cell line derived from two-spot puffer Takifugu bimaculatus

The establishment of fish cell lines can provide an important in vitro model for developmental biology, pathology, and genetics and also an effective tool to investigate the interactions and related functions of genes. Two-spot puffer Takifugu bimaculatus is a high economic and nutritional value marine fish in Fujian in recent years. Nevertheless, dmrt1 plays a key role in the male differentiation from invertebrates to vertebrates. To understand the molecular regulatory mechanisms of dmrt1 in T. bimaculatus, a testis cell line called TBTc from a juvenile testis of this organism was established with modified Leibovitz's L-15 medium supplemented with 20% FBS, fish serum, embryo extract, and other growth factors. The TBTc with a stable karyotype can be passaged continuously, which was composed of fibroblast-like cells and expressed the marker genes of male-special cells, dmrt1, and amh, and the absence of vasa expression may rule out the possibility of the presence of germ cells. Therefore, TBTc appeared to consist of the mixture of the Sertoli cell and germ cell of the testis. The dmrt1 was significantly expressed in the testes and slightly expressed in the late embryonic development, illustrating that the dmrt1 may participate in the molecular regulation of gonads development and sex differentiation. With the high transfection efficiency of TBTc by electroporation, the cell lines could be used effectively in the study for the expression of exogenous and endogenous genes. Meanwhile, after the knockdown of dmrt1, the morphological changes and survival rates of cells proved that dmrt1 could affect the growth of testicular cells. Furthermore, with the loss of dmrt1, the expression of male-bias genes amh, sox9, and cyp11a was significantly decreased, and the expression of female-bias genes foxl2, sox3, and cyp19a was increased, which suggested that dmrt1 upregulates amh, sox9, and cyp11a and downregulates foxl2, sox3, and cyp19a to participate in the testis development. As a first fish gonadal cell lines of T. bimaculatus, which can be a more convenient, efficient, and rapid model for the investigation of the expression and function of genes, the results will lay a foundation for the next study of the molecular regulation mechanism in gonadal development and sex determination of fish in the future.

Function of Foxl2 and Dmrt1 proteins during gonadal differentiation in the olive flounder Paralichthys olivaceus

Study on fish sex differentiation is important both from academic and practical aspects. Foxl2 and Dmrt1 are important transcription factors that should be involved in fish gonadal differentiation, but there is still no direct evidence to clarify their protein functions. Olive flounder Paralichthys olivaceus, an important mariculture fish in China, Japan, and Korea, shows sex-dimorphic growth. In this study, the Foxl2 and Dmrt1 proteins were detected in granulosa cells of the ovary and Sertoli cells of the testis, respectively, showing significant sex-dimorphic expression patterns. Then, bioactive high-purity Foxl2 and Dmrt1 recombinant proteins were obtained in vitro. Furthermore, effects of the recombinant Foxl2 and Dmrt1 during gonadal differentiation period were evaluated by intraperitoneal injection in juvenile fish. Compared with the control group, the male rate in the Dmrt1 group increased from 0 % to 82 %, showing for the first time in fish that the recombinant Dmrt1 could alter the sex phenotype. In addition, transcription levels of cyp19a and its transcription factors also changed after the recombinant Foxl2 and Dmrt1 injection. These findings reveal that Foxl2 and Dmrt1 are vital regulators for fish gonadal differentiation by regulating cyp19a expression, and also provide a new approach for sex control in fish aquaculture.

Molecular characterization and expression profiles of six genes involved in vitellogenic deposition and hydrolysis of Chinese sturgeon (Acipenser sinensis) suggesting their transcriptional regulation on ovarian development

Ovary development of Chinese sturgeon (Acipenser sinensis) in controlled breeding has been reported to respond to dietary lipid levels. However, the corresponding molecular regulatory mechanism about ovary development of Chinese sturgeon is still unclear. To elucidate the molecular mechanism of vitellogenic deposition and hydrolysis, six key genes, namely, vtgr (vitellogenin receptor), atp6v1c1 (Vacuolar H⁺-ATPase subunit c1), atp6v1h (Vacuolar H⁺-ATPase subunit h), ctsb (cathepsin B), ctsd (cathepsin D) and ctsl (cathepsin L) involved in vitellogenic deposition and hydrolysis of Chinese sturgeon were cloned and characterized, and their spatio-temporal mRNA expression profiles as well as transcriptional responses to dietary lipid level were investigated. The full-length cDNA sequences of these six genes showed similar domain structure to their respective orthologous genes from other vertebrates. Tissue-specific expression patterns of these genes were observed in ovary, liver, muscle, spleen, brain, gill, intestine, heart, stomach and kidney. Ovarian expression level of vtgr was the highest in stage II, and ctsl expression was the highest in stage IV, while the mRNA expressions of other 4 genes were the highest in stage III. The increase of dietary lipid level promoted ovary development and elevated the expressions of vtgr, atp6v1c1, atp6v1h, ctsb and ctsd in the ovary. The results of the present study indicated that these genes are crucial for vitellogenic deposition, and provided a preliminary understanding on the molecular regulation of vitellogenic deposition and hydrolysis during ovary development of Chinese sturgeon.

The genomic structure of the highly-conserved dmrt1 gene in Solea senegalensis (Kaup, 1868) shows an unexpected intragenic duplication

Knowing the factors responsible for sex determination in a species has significant theoretical and practical implications; the dmrt1 gene (Doublesex and Mab-3 (DM)-related Transcription factor 1) plays this role in diverse animal species. Solea senegalensis is a commercially important flat fish in which females grow 30% faster than males. It has 2n = 42 chromosomes and an XX / XY chromosome system for sex determination, without heteromorph chromosomes but with sex proto-chromosome. In the present study, we are providing the genomic structure and nucleotide sequence of dmrt1 gene obtained from cDNA from male and female adult gonads. A cDNA of 2027 containing an open-reading frame (ORF) of 1206 bp and encoding a 402 aa protein it is described for dmrt1 gene of S. senegalensis. Multiple mRNA isoforms indicating a high variable system of alternative splicing in the expression of dmrt1 of the sole in gonads were studied. None isoforms could be related to sex of individuals. The genomic structure of the dmrt1 of S. senegalensis showed a gene of 31400 bp composed of 7 exons and 6 introns. It contains an unexpected duplication of more than 10399 bp, involving part of the exon I, exons II and III and a SINE element found in the sequence that it is proposed as responsible for the duplication. A mature miRNA of 21 bp in length was localized at 336 bp from exon V. Protein-protein interacting networks of the dmrt1 gene showed matches with dmrt1 protein from Cynoglossus semilaevis and a protein interaction network with 11 nodes (dmrt1 plus 10 other proteins). The phylogenetic relationship of the dmrt1 gene in S. senegalensis is consistent with the evolutionary position of its species. The molecular characterization of this gene will enhance its functional analysis and the understanding of sex differentiation in Solea senegalensis and other flatfish.

The effects of 11-ketotestosterone implants on transcript levels of gonadotropin receptors, and foxl2 and dmrt1 genes in the Previtellogenic ovary of cultured beluga (Huso huso)

The in vivo effect of 11-ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshr and lhr) and sex differentiation-related genes (dmrt1 and foxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4-year-old females at the previtellogenic stage (mean body weight 5580 ± 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis of lhr, fshr, dmrt1 and foxl2 were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time-dependent decrease of lhr and dmrt1 mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation of fshr and foxl2 transcript levels. Furthermore, lhr and dmrt1 transcript abundances recovered by 8 weeks of exposure in both blank- and 11KT-implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga.

Gene expression involved in the sexual development of Best Beluga hybrid sturgeons

The scope of this study is to investigate the expression of dmrt1, foxl2, ar, star and sox9 genes in the context of the gonad development stage of 21 month-old Best Beluga individuals. No significant difference was observed between males and females but the cyp17a1 gene showed higher expression in male than in female gonads. The results suggest that during sampling the females were in perinucleolar stage and the males in early spermatogenesis stage which led to specific patterns of expression for the investigated genes.

Expression Characterization of Six Genes Possibly Involved in Gonad Development for Stellate Sturgeon Individuals (Acipenser stellatus, Pallas 1771)

Nowadays, in sturgeon's aquaculture, there is a necessity for sex identification at early stages in order to increase the efficiency of this commercial activity. The basis for a correct identification is studying the different factors that influence the gonad development. The research has been directed towards molecular methods that have been employed with various degrees of success in identifying genes with different expression patterns between male and female sturgeons during their development stages. For the purpose of understanding the sexual development of 4-year-old stellate sturgeon (Acipenser stellatus) individuals, we have selected six genes (foxl2, cyp17a1, ar, dmrt1, sox9, and star). We analysed the gene expression of the selected genes for gonads, anal fin, liver, body kidney, and white muscle. The cyp17a1, ar, dmrt1, and sox9 genes have a significant higher expression in male gonads than in female gonads, while the data shows no significant differences in the expression of the investigated genes in the other organs. We investigate these genes to shed light on aquaculture sturgeon sexual development.

Expression and cellular localization of double sex and mab-3 related transcription factor 1 in testes of postnatal Small-Tail Han sheep at different developmental stages

Double sex and mab-3 related transcription factor 1 (Dmrt1), an evolutionarily conserved gene, is a sex-related gene expressed in male gonads, that is involved in the regulation of sex differentiation, testicular development and reproductive function maintenance. Until now, functional studies on the Dmrt1 gene in sheep (Ovis aries) have been lacking. In this study, testis, heart, liver, spleen, lung, kidney and longissimus dorsi muscle tissues were collected from Small-Tail Han sheep at 0, 2, 5, 12 and 24months after birth (mab). Dmrt1 expression and cellular localization were detected in various testicular tissues by quantitative real time PCR (qRT-PCR), western blot and immunohistochemistry methods. The morphological structures of testicular tissues at different developmental stages were observed by hematoxylin & eosin (HE) staining. The Dmrt1 mRNA expression levels in 12 and 24 mab sheep were significantly higher than those in 0 and 2 mab sheep (P<0.05), and Dmrt1 protein expression showed a similar trend. The qRT-PCR results in various tissues at 12 mab showed that Dmrt1 mRNA was predominantly expressed in testes. Immunohistochemical staining in testes at different developmental stages showed that Dmrt1 protein immunoreactive responses were mainly localized in Sertoli cells and gonocytes at 0, 2 and 5 mab, while they were localized in spermatocytes, sperm cells and some spermatogonia and Sertoli cells at 12 and 24 mab. We speculate that the Dmrt1 gene plays a vital role in postnatal sheep spermatogenesis, perhaps by regulating the maturation and functional maintenance of Sertoli cells, the proliferation and differentiation of gonocytes in prepubertal sheep testes, and the mitosis and meiosis of germ cells in adult sheep, but the specific mechanisms underlying these phenomena must be further studied and verified.

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