Expression of wnt4/5 during reproductive cycle of catfish and wnt5 promoter analysis

Reproduction-associated pathways in females of gibel carp (Carassius gibelio) shed light on the molecular mechanisms of the coexistence of asexual and sexual reproduction

Gibel carp (Carassius gibelio) is a cyprinid fish that originated in eastern Eurasia and is considered as invasive in European freshwater ecosystems. The populations of gibel carp in Europe are mostly composed of asexually reproducing triploid females (i.e., reproducing by gynogenesis) and sexually reproducing diploid females and males. Although some cases of coexisting sexual and asexual reproductive forms are known in vertebrates, the molecular mechanisms maintaining such coexistence are still in question. Both reproduction modes are supposed to exhibit evolutionary and ecological advantages and disadvantages. To better understand the coexistence of these two reproduction strategies, we performed transcriptome profile analysis of gonad tissues (ovaries) and studied the differentially expressed reproduction-associated genes in sexual and asexual females. We used high-throughput RNA sequencing to generate transcriptomic profiles of gonadal tissues of triploid asexual females and males, diploid sexual males and females of gibel carp, as well as diploid individuals from two closely-related species, C. auratus and Cyprinus carpio. Using SNP clustering, we showed the close similarity of C. gibelio and C. auratus with a basal position of C. carpio to both Carassius species. Using transcriptome profile analyses, we showed that many genes and pathways are involved in both gynogenetic and sexual reproduction in C. gibelio; however, we also found that 1500 genes, including 100 genes involved in cell cycle control, meiosis, oogenesis, embryogenesis, fertilization, steroid hormone signaling, and biosynthesis were differently expressed in the ovaries of asexual and sexual females. We suggest that the overall downregulation of reproduction-associated pathways in asexual females, and their maintenance in sexual ones, allows the populations of C. gibelio to combine the evolutionary and ecological advantages of the two reproductive strategies. However, we showed that many sexual-reproduction-related genes are maintained and expressed in asexual females, suggesting that gynogenetic gibel carp retains the genetic toolkits for meiosis and sexual reproduction. These findings shed new light on the evolution of this asexual and sexual complex.

Identification of WNT4 alternative splicing patterns and effects on proliferation of granulosa cells in goat

Increasing ovulation numbers is one of the most important ways to promote reproduction in mammals, and follicular granulosa cells (GCs) provide the necessary nutrients and microenvironment for oocytes to ovulate. WNT4 has been shown to be a key factor in regulating the proliferation of GCs in mammalian ovarian tissues. Our previous transcriptome sequencing (RNA-seq) results have identified two alternatively spliced products of WNT4;however, little is known about the splicing mechanism and its effect on GC proliferation. In this study, two alternatively spliced products of WNT4, designated WNT4-α and WNT4-β, were identified by cloning and analyzed for their function by bioinformatics. The RT-qPCR and Western blot results showed that the expression of WNT4-α was significantly higher than that of WNT4-β in the ovary tissues and GCs of Yunshang black goats. We therefore hypothesized that WNT4-α was the main isoform affecting the proliferation of goat GCs. Subsequently, goat GC proliferation assays showed that overexpression of WNT4-α significantly promoted GC proliferation, and the opposite was true after WNT4-α inhibition. The expression of marker genes of the Wnt signaling pathway was also examined and WNT4-α was found to affect the proliferation and hormone secretion of goat GCs by regulating the Wnt signaling pathway. In addition, a series of splicing factors were involved in in the alternative splicing; in this study, SRSF6 was found to be involved as a splicing factor in the generation of WNT4 alternative splicing. In summary, WNT4 alternative splicing was mediated by the splicing factor SRSF6, and WNT4-α alternative splicing played an important role in follicle development and had a significant effect on the proliferation of goat GCs. The results of this study provide a theoretical foundation for further understanding the molecular regulatory mechanisms of the WNT4 in follicle development in goats.

sox19 regulates ovarian steroidogenesis in common carp

In teleost, ovarian steroidogenesis governed by the neuroendocrine system is also regulated by several transcription factors of gonadal origin. Investigating the synchronized interactions between the transcriptional and the hormonal factors is vital to comprehend the mechanisms that lead to gonadal differentiation. This study signifies the role of sry-related box (sox) 19 in ovarian steroidogenesis regulation of the common carp, Cyprinus carpio. Analysis of tissue distribution displayed higher sox19 expression in brain and ovary, and gonadal ontogeny showed higher expression of sox19 at 80 days post hatch (dph). Higher sox19 mRNA expression during spawning and increase of sox19 post human chorionic gonadotropin induction substantiate gonadotropin dependency. Estradiol-17β treatment but not 17α-methyl-di-hydroxy-testosterone to 50 dph common carp for inducing mono-sex, elevated sox19 expression substantially. Sox19 protein was observed in granulosa cells of the follicular layer in common carp ovary. Higher sox19 expression was detected in isolated granulosa and theca cells, in vitro. Transient gene silencing with sox19-siRNA caused downregulation of various ovary-related genes including those specific to activator protein-1 factors, fibroblast growth factors, wnt-signaling, steroidogenic genes along with certain transcription factors. Serum 17α, 20β-dihydroxy-4-pregnen-3-one and estradiol-17β reduced significantly post sox19 silencing, in vivo. Concomitantly, a decrease in aromatase activity was detected post sox19-siRNA treatment, in vivo. This study demonstrates the impact of sox19 in the regulation of common carp ovarian growth and steroidogenesis.

Integrated Metabolomics and Transcriptomic Analysis of Hepatopancreas in Different Living Status Macrobrachium nipponense in Response to Hypoxia

As the basic element of aerobic animal life, oxygen participates in most physiological activities of animals. Hypoxia stress is often the subject of aquatic animal research. Macrobrachium nipponense, an economically important aquatic animal in southern China, has been affected by hypoxia for many years and this has resulted in a large amount of economic loss due to its sensitivity to hypoxia; Metabolism and transcriptome data were combined in the analysis of the hepatopancreas of M. nipponense in different physiological states under hypoxia; A total of 108, 86, and 48 differentially expressed metabolites (DEMs) were found in three different comparisons (survived, moribund, and dead shrimps), respectively. Thirty-two common DEMs were found by comparing the different physiological states of M. nipponense with the control group in response to hypoxia. Twelve hypoxia-related genes were identified by screening and analyzing common DEMs. GTP phosphoenolpyruvate carboxykinase (PEPCK) was the only differentially expressed gene that ranked highly in transcriptome analysis combined with metabolome analysis. PEPCK ranked highly both in transcriptome analysis and in combination with metabolism analysis; therefore, it was considered to have an important role in hypoxic response. This manuscript fills the one-sidedness of the gap in hypoxia transcriptome analysis and reversely deduces several new genes related to hypoxia from metabolites. This study contributes to the clarification of the molecular process associated with M. nipponense under hypoxic stress.

Advances in Reproductive Endocrinology and Neuroendocrine Research Using Catfish Models

Catfishes, belonging to the order siluriformes, represent one of the largest groups of freshwater fishes with more than 4000 species and almost 12% of teleostean population. Due to their worldwide distribution and diversity, catfishes are interesting models for ecologists and evolutionary biologists. Incidentally, catfish emerged as an excellent animal model for aquaculture research because of economic importance, availability, disease resistance, adaptability to artificial spawning, handling, culture, high fecundity, hatchability, hypoxia tolerance and their ability to acclimate to laboratory conditions. Reproductive system in catfish is orchestrated by complex network of nervous, endocrine system and environmental factors during gonadal growth as well as recrudescence. Lot of new information on the molecular mechanism of gonadal development have been obtained over several decades which are evident from significant number of scientific publications pertaining to reproductive biology and neuroendocrine research in catfish. This review aims to synthesize key findings and compile highly relevant aspects on how catfish can offer insight into fundamental mechanisms of all the areas of reproduction and its neuroendocrine regulation, from gametogenesis to spawning including seasonal reproductive cycle. In addition, the state-of-knowledge surrounding gonadal development and neuroendocrine control of gonadal sex differentiation in catfish are comprehensively summarized in comparison with other fish models.

Interactive role of Wnt signaling and Zn in regulating testicular function of the common carp, Cyprinus carpio

Wnt signaling is conserved among all species and plays a significant role in various cellular processes including reproduction. The present study identified significant involvement of wnt4a, wnt5b, and wnt8a signaling in the testicular growth of common carp,Cyprinus carpio. Predominant expression of wnt4a, wnt5b, and wnt8a was found in the gonads and Wnt4a was localized in spermatocytes and interstitial cells. Ontogeny and testicular phase-wise analysis signified the importance of wnt isofoms analyzed in this study. Specific pathway activation of Wnt signaling revealed that Wnt4a and Wnt5b act through non-canonical while Wnt8a prefers the canonical pathway. The Wnt signaling regulates several steroidogenic enzyme and testis-related genes which was confirmed by the Wnt blockade experiments. Incidentally, zinc (Zn) is an essential trace element involved in the progression of spermatogenesis in teleosts. In adult male carp, a single administration of Zn at different doses elevated the expression of Wnt and Zn transporter genes and a single-dose (30 μg/g body weight [BW]) of Zn treatment elevated steroidogenic enzyme and testis-related genes which coincided with elevated androgens. Conversely, single-dose administration of Zn chelator to the Zn administered (30 μg/g BW) fish reversed the effects emphasizing a prominent role of Zn in the testicular function perhaps through Wnt signaling. Similar effects were observed in the in vitro experiments using the Zn chelator. Bioaccumulation of Zn and histological analysis revealed the importance of Zn in progression of spermatogenesis and sperm motility. Various assays related to cell viability and proliferation exhibited the role of Zn in promoting spermatogenic cell progression. Flow cytometric analysis confirmed Zn-induced elevation of Wnt and Zn transporter genes in germ and supporting cells. Furthermore, the effects of Zn are dose-related in carp. Taken together, it seems wnt4a, wnt5b, and wnt8a play an important role in testis and exposure of Wnt inhibitor, canonical as well as non-canonical activators, and Zn confirmed that Zn regulates Wnt signaling vis-à-vis promoting spermatogenesis in the common carp.

Common carp pentraxin gene: Evidence for its role in ovarian differentiation and growth

Pentraxins (PTX), belong to an evolutionarily conserved family, containing a PTX protein domain, having role in acute immunological responses and fertility in higher vertebrates. However, information regarding the action of ptx on reproduction is extremely limited in fish. To study this, ptx cDNA was cloned for downstream analysis. Tissue distribution and ontogeny expression analysis indicated the prevalence of ptx in ovary. Varied phase-wise expression during carp ovarian cycle and elevated ptx expression after human chorionic gonadotropin induction, in vitro and in vivo, indicated probable regulation of gonadotropin. In situ hybridization and immunohistochemistry revealed the presence of ptx transcript and protein in the follicular layer of stage-III/IV oocytes indicating a role in ovarian growth. To assess the functional significance of ptx, transient silencing was performed using follicular primary cell culture, in vitro and in common carp, in vivo, through ovary-targeted injection of PEI-siRNA. Transient silencing of ptx-siRNA reduced the expression of various genes/factors related to oogenesis such as transcription factors, several steroidogenic enzymes, and esrs genes. These alterations in expression suggested a plausible role for ptx in ovarian steroidogenesis either, directly or indirectly, which is evident from the changes in the serum estradiol-17β (E₂) and 17α,20β-dihydroxyprogesterone levels. Furthermore, downregulation of aromatase activity was also noticed after transient silencing. Increased ptx expression after E₂ induced sex reversal to juvenile carp showed the correlative role of ptx during ovarian differentiation and development. Taken together, these findings suggest that ptx exerts an important role during ovarian growth, maturation and/or recrudescence of common carp.

Comparative transcriptome reveals the potential modulation mechanisms of estradiol affecting ovarian development of female Portunus trituberculatus

Estradiol is an important sex steroid hormone that is involved in the regulation of crustacean ovarian development. However, the molecular regulatory mechanisms of estradiol on ovarian development are largely unknown. This study performed transcriptome sequencing of ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ of crabs after estradiol treatment (0.1μg g^-1 crab weight). A total of 23, 806 genes were annotated, and 316, 1300, 669, 142, 383 genes were expressed differently in ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ respectively. Differentially expressed gene enrichment analysis revealed several crucial pathways including protein digestion and absorption, pancreatic secretion, insect hormone biosynthesis, drug metabolism-cytochrome P450 and signal transduction pathway. Through this study, some key genes in correlation with the ovarian development and nutrition metabolism were significantly affected by estradiol, such as vitelline membrane outer layer 1-like protein, heat shock protein 70, Wnt5, JHE-like carboxylesterase 1, cytochrome P302a1, crustacean hyperglycemic hormone, neuropeptide F2, trypsin, carboxypeptidase B, pancreatic triacylglycerol lipase-like, and lipid storage droplet protein. Moreover, RT-qPCR validation demonstrated that expression of transcripts related to ovarian development (vitelline membrane outer layer 1-like protein and cytochrome P302a1) and nutrition metabolism (trypsin, glucose dehydrogenase and lipid storage droplet protein) were significantly affected by estradiol treatment. This study not only has identified relevant genes and several pathways that are involved in estradiol regulation on ovarian development of P. trituberculatus, but also provided new insight into the understanding of the molecular function mechanisms of estradiol in crustacean.

Gonadal transcriptome analysis of the common carp, Cyprinus carpio: Identification of differentially expressed genes and SSRs

Common carp (Cyprinus carpio) is a world-wide freshwater fish of eutrophic waters. C. carpio, have various reproductive traits, including early sexual maturity, that may make them excellent, large, realistic, aquaculture model species. In the present work, de novo assembly of gonadal (testicular and ovarian) transcriptomes from juvenile common carp was performed to identify genes involved in gonadal development. A total of 81,757 and 43,257 transcripts with average lengths of 769 and 856 bp, were obtained from the immature testicular and ovarian transcriptomes, respectively. About 84,367 unigenes were constructed after removing redundancy involving representation of transcripts in both gonadal transcriptomes. Gene ontology (39,171 unigenes), clusters of orthologous group's analysis (6651 unigenes) and Kyoto encyclopedia of genes, and genomes automatic annotation server analysis (4783 unigenes) were performed to identify potential genes along with their functions. Furthermore, 18,342 (testis) and 8693 (ovary) simple sequence repeats were identified. About 298 differentially expressed genes were identified, of which 171 and 127 genes were up-regulated in testis and ovary, respectively. Quantitative real-time reverse transcription PCR was performed to validate differential expression of selected genes in testis and ovary. Nearly 809 genes related to reproduction were identified, sex-wise expression pattern of genes related to steroid synthesis, endocrine regulation, germ cell maintenance and others factors related to gonadal differentiation was observed, and expression analysis of nanos, ad4bp/sf-1, and gdf9 was performed. The present study identified certain important genes/factors involved in the gonadal development of C. carpio which may provide insights into the understanding of sex-differentiation and gonadal development processes.