Characterization of gonadotropin receptors Fshr and Lhr in Japanese medaka, Oryzias latipes

The occurrence of luteinizing hormone-like molecule and its receptor in the blue swimming crab, Portunus pelagicus

Knowledge of the neuroendocrine system possibly improves the reproductive performance of captivated crustacean broodstock in aquaculture and it may substitute eyestalk ablation. In this study, we explored the luteinizing hormone (LH)-like molecule and proved the existence of the LH receptor (PpelLHR)-like mRNA in the blue swimming crab, Portunus pelagicus. Using the anti-human LH-β antibody, the immunoreactivities were found in the central nervous system (CNS) and ovary of the crab with the strongest signal in the mature ovary. The full-length PpelLHR-like mRNA sequence contained 4818 bp with deduced protein predicted as seven transmembrane G-protein coupled receptor, made of 1605 amino acids. The phylogenetic tree suggested this protein belonged to the clade of invertebrate LHR/FSHR-like proteins. The PpelLHR-like mRNA expressed in various organs and real-time qPCR revealed significantly higher expression of this mRNA in the brain and lower expression in the ovary of the mature crabs. In situ hybridization of this mRNA was demonstrated in neuronal clusters of the brain, ventral nerve cord, and in the oocyte stage 1-4 of the ovary, respectively. This study was preliminary to prove the existence of LH and its receptor in the blue swimming crab. Functional assay of this receptor should be performed as the next part of experiments to firmly conclude its appearance.

Long-term exposure of metamifop affects sex differentiation and reproductive system of zebrafish (Danio rerio)

The extensive use of herbicide metamifop (MET) in rice fields for weeds control will inevitably lead to its entering into water environments and threaten the aquatic organisms. Previous researches have demonstrated that sublethal exposure of MET significantly affected zebrafish development. Yet the long-term toxicological impacts of MET on aquatic life remains unknown. Herein, we investigated the potential effects of MET (5 and 50 μg/L) on zebrafish during an entire life cycle. Since the expression level of male sex differentiation-related gene dmrt1 and sex hormone synthesis-related gene cyp19a1b were significantly changed after 50 μg/L MET exposure for only 7 days, indicators related to sex differentiation and reproductive system were further investigated. Results showed that the transcript of dmrt1 was inhibited, estradiol content increased and testosterone content decreased in zebrafish of both sexes after MET exposure at 45, 60 and 120 dpf. Histopathological sections showed that the proportions of mature germ cells in the gonads of male and female zebrafish (120 dpf) were significantly decreased. Moreover, males had elevated vitellogenin content while females did not after MET exposure; MET induced feminization in zebrafish, with the proportion of females significantly increased by 19.6% while that of males significantly decreased by 13.2% at 120 dpf. These results suggested that MET interfered with the expression levels of gonad development related-genes, disrupted sex hormone balance, and affected sex differentiation and reproductive system of female and male zebrafish, implying it might have potential endocrine disrupting effects after long-term exposure.

Loss of Fshr Prevents Testicular Maturation in Atlantic Salmon (Salmo salar L.)

Early puberty poses a significant challenge for male Atlantic salmon in aquaculture due to its negative impact on growth and welfare. The regulation of puberty in vertebrates involves 2 key reproductive hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and their gonadal receptors. In male mice lacking FSH receptor, testes size is reduced, but fertility is maintained, while medaka and zebrafish with a disrupted fshr gene exhibit near normal testis size and fertility. In these fishes both Fsh and Lh are present during puberty and Lh may rescue fertility, while in salmonid fish only Fsh is present in the circulation during puberty. Using CRISPR-Cas9, we produced crispants with a high prevalence of fshr mutations at the target site, which remained fertile, although more than half showed a testis development deviating from wild-type (wt) males. Crossing out these F0 crispants to each other produced a viable F1 generation showing frameshift (fshr-/-) or in-frame mutations (fshrif/if). Nearly all wt males matured while all fshr-/- males remained immature with small testes containing A spermatogonia as the furthest developed germ cell type and prepubertal plasma androgen levels. Also, the pituitary transcript levels of gnrhr2bba and lhb, but not for fshb, were reduced in the fshr-/- males compared with maturing males. More than half of the fshrif/if mutant males showed no or a delayed maturation. In conclusion, Atlantic salmon show the unique characteristic that loss of Fshr function alone results in male infertility, offering new opportunities to control precocious puberty or fertility in salmon.

Study on the changes of LHR, FSHR and AR with the development of testis cells in Hu sheep

The process of testis development in mammals is accompanied by the proliferation and maturation of Sertoli, Leydig and germ cells. Spermatogenesis depends on hormone regulation, which must bind to a receptor to exert its biological effects. The changes in Hu sheep testis cell composition and FSHR, LHR and AR expression during different developmental stages are unclear (newborn, puberty and adulthood). To address this, using single-cell RNA sequencing, we analyzed testis cell composition and hormone receptor expression changes during three important developmental stages of Hu sheep. We observed significant changes in the composition of somatic and germ cells in different Hu sheep testis developmental stages. Furthermore, we analyzed the FSHR, LHR and AR distribution and expression changes at three important periods and verified them by qRT-PCR and immunofluorescence. Our results suggest that after birth, the proportion of germ cells increased gradually, peaking in adulthood; the proportion of Sertoli cells decreased gradually, reaching the lowest in adulthood; and the proportion of Leydig cells increased and then decreased, reaching the lowest in adulthood. In addition, FSHR, LHR and AR are mainly located in Sertoli, Leydig and germ cells. LHR and FSHR expression decreased with increasing age, while AR expression increased and then decreased with increasing age.

Roles of Gonadotropin Receptors in Sexual Development of Medaka

The gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are secreted from the pituitary and bind to the FSH receptor (FSHR) and LH receptor (LHR) to regulate gonadal development in vertebrates. Previously, using fshr-knockout (KO) medaka (Oryzias latipes), we demonstrated that FSH regulates ovarian development by elevating estrogen levels. However, the lhr-KO phenotype in medaka is poorly characterized. Here, we generated lhr-KO medaka using the transcription activator-like effector nuclease (TALEN) technique. We analyzed its phenotype and that of fshr-KO, lhr;fshr double-heterozygotes (double-hetero), and double-KO fish. All genetically male medaka displayed normal testes and were fertile, whereas fshr-KO and double-KO genetically female fish displayed small ovaries containing many early pre-vitellogenic oocytes and were infertile. Although lhr-KO genetically female fish had normal ovaries with full-grown oocytes, ovulation did not occur. Levels of 17α,20β-dihydroxy-4-pregnen-3-one, which is required for meiotic maturation of oocytes and sperm maturation in teleost fish, were significantly decreased in all KO female medaka ovaries except for double-heteros. Further, 17β-estradiol levels in fshr-KO and double-KO ovaries were significantly lower than those in double-heteros. These findings indicate that LH is necessary for oocyte maturation and FSH is necessary for follicle development, but that neither are essential for spermatogenesis in medaka.

Differential gene expression pattern and plasma sex steroids during testicular development in Genyatremus luteus (Perciforme: Haemulidae) (Bloch, 1790)

Abstract The aim of the current study is to evaluate gene expression patterns of LH (lhr) and estrogen (er) receptors and plasma steroid levels during testicular development in Genyatremus luteus. Males were histologically classified as immature (n=7), maturing (n=7) and mature (n=7), based on the cellular structure of their testes. Plasma 11-KT concentration recorded peak at the final maturation stage. The highest plasma 17α-OHP concentrations were observed at the immature stage; they decreased at the maturation and mature stages. On the other hand, 17β-estradiol (E2) recorded higher concentrations at the maturation stage. Er expression has significantly increased along the maturational development of animals’ testes. The mRNA observed for the LH receptor has decreased from immature to maturing stage; it presented expression peak at the mature stage. There was high association between receptor gene expression and plasma steroid levels, mainly E2. The current study was the first to feature different reproductive maturation stages in male G. luteus specimens, based on cellular, endocrine and molecular aspects. In addition, it has shown that the gene expression profile for er and lhr receptors, as well as plasma 11-KT and E2 concentrations, are directly linked to testicular maturation, although they are not necessarily associated with the gonadosomatic index.

Molecular and cellular regulation on sex change in hermaphroditic fish, with a special focus on protandrous black porgy, Acanthopagrus schlegelii

In teleost fish, sex can be determined by genetic factors, environmental factors, or both. Unlike in gonochoristic fish, in which sex is fixed in adults, sex can change in adults of hermaphroditic fish species. Thus, sex is generated during the initial gonadal differentiation stage (primary sex differentiation) and later during sexual fate alternation (secondary sex differentiation) in hermaphroditic fish species. Depending on the species, sex phase alternation can be induced by endogenous cues (such as individual age and body size) or by social cues (such as sex ratio or relative body size within the population). In general, the fluctuation in plasma estradiol-17β (E2) levels is correlated with the sexual fate alternation in hermaphroditic fish. Hormonal treatments can artificially induce sexual phase alternation in sequential hermaphroditic fishes, but in a transient and reversible manner. This is the case for the E2-induced female phase in protandrous black porgy and the methyltestosterone (MT)- or aromatase inhibitor (AI)-induced male phase in protogynous grouper. Recent reviews have focused on the different forms of sex change in fish who undergo sequential sex change, especially in terms of gene expression and the role of hormones. In this review, we use the protandrous black porgy, a nonsocial cue-influenced hermaphroditic species, with digonic gonads (ovarian and testis separated by a connective tissue), as a model to describe our findings and discuss the molecular and cellular regulation of sexual fate determination in hermaphroditic fish.

An ex vivo Approach to Study Hormonal Control of Spermatogenesis in the Teleost Oreochromis niloticus

As the male reproductive organ, the main task of the testis is the production of fertile, haploid spermatozoa. This process, named spermatogenesis, starts with spermatogonial stem cells, which undergo a species-specific number of mitotic divisions until starting meiosis and further morphological maturation. The pituitary gonadotropins, luteinizing hormone, and follicle stimulating hormone, are indispensable for vertebrate spermatogenesis, but we are still far from fully understanding the complex regulatory networks involved in this process. Therefore, we developed an ex vivo testis cultivation system which allows evaluating the occurring changes in histology and gene expression. The experimental circulatory flow-through setup described in this work provides the possibility to study the function of the male tilapia gonads on a cellular and transcriptional level for at least 7 days. After 1 week of culture, tilapia testis slices kept their structure and all stages of spermatogenesis could be detected histologically. Without pituitary extract (tilPE) however, fibrotic structures appeared, whereas addition of tilPE preserved spermatogenic cysts and somatic interstitium completely. We could show that tilPE has a stimulatory effect on spermatogonia proliferation in our culture system. In the presence of tilPE or hCG, the gene expression of steroidogenesis related genes (cyp11b2 and stAR2) were notably increased. Other testicular genes like piwil1, amh, or dmrt1 were not expressed differentially in the presence or absence of gonadotropins or gonadotropin containing tilPE. We established a suitable system for studying tilapia spermatogenesis ex vivo with promise for future applications.