Expression of insulin-like factor 3 hormone-receptor system in the reproductive organs of male goats

Insulin‐like peptide 3 in domestic animals with normal and abnormal reproductive functions, in comparison to rodents and humans

Background

Methods

Main findings

Conclusion

Evidence for existence of insulin-like factor 3 (INSL3) hormone-receptor system in the ovarian corpus luteum and extra-ovarian reproductive organs during pregnancy in goats

Insulin-like factor 3 (INSL3), initially described as a male hormone, is expressed in female reproductive organs during the estrous cycle and pregnancy but its function has not yet been established. This study explores the function of INSL3 in pregnant Saanen goats by characterizing the expression dynamics of INSL3 and its receptor, relaxin family peptide receptor 2 (RXFP2) and by demonstrating specific INSL3 binding in reproductive organs, using molecular and immunological approaches and ligand-receptor interaction assays. We demonstrate that the corpus luteum (CL) acts as both a source and target of INSL3 in pregnant goats, while extra-ovarian reproductive organs serve as additional INSL3 targets. The expression of INSL3 and RXFP2 in the CL reached maximum levels in middle pregnancy, followed by a decrease in late pregnancy; in contrast, RXFP2 expression levels in extra-ovarian reproductive organs were higher in the mammary glands but lower in the uterus, cervix and placenta and did not significantly change during pregnancy. The functional RXFP2 enabling INSL3 to bind was identified as an ~ 85 kDa protein in both the CL and mammary glands and localized in large and small luteal cells in the CL and in tubuloalveolar and ductal epithelial cells in the mammary glands. Additionally, INSL3 also bound to multiple cell types expressing RXFP2 in the uterus, cervix and placenta in a hormone-specific and saturable manner. These results provide evidence that an active intra- and extra-ovarian INSL3 hormone-receptor system operates during pregnancy in goats.

Physiology and evolution of the INSL3/RXFP2 hormone/receptor system in higher vertebrates

Although the insulin-like peptide hormone INSL3 and its cognate receptor RXFP2 (relaxin-family peptide receptor 2) have existed throughout chordate evolution, their physiological diversification appears to be linked closely with mammalian emergence and radiation. In contrast, they have been lost in birds and reptiles. Both hormone and receptor are expressed from autosomal genes which have maintained their synteny across vertebrate evolution. Whereas the INSL3 gene comprises only two exons closely linked to the JAK3 gene, RXFP2 is normally encoded by 18 exons. Both genes, however, are subject to alternative splicing to yield a variety of possibly inactive or antagonistic molecules. In mammals, the INSL3-RXFP2 dyad has maintained a probably primitive association with gametogenesis, seen also in fish, whereby INSL3 promotes the survival, growth and differentiation of male germ cells in the testis and follicle development in the ovary. In addition, however, the INSL3/RXFP2 system has adopted a typical 'neohormone' profile, essential for the promotion of internal fertilisation and viviparity; fetal INSL3 is essential for the first phase of testicular descent into a scrotum, and also appears to be associated with male phenotype, in particular horn and skeletal growth. Circulating INSL3 is produced exclusively by the mature testicular Leydig cells in male mammals and acts as a potent biomarker for testis development during fetal and pubertal development as well as in ageing. As such it can be used also to monitor seasonally breeding animals as well as to investigate environmental or lifestyle conditions affecting development. Nevertheless, most information about INSL3 and RXFP2 comes from a very limited selection of species; it will be especially useful to gain further information from a more diverse range of animals, especially those whose evolution has led them to express unusual reproductive phenotypes.

Differences in Noradrenaline Receptor Expression Across Different Neuronal Subtypes in Macaque Frontal Eye Field

Cognitive functions such as attention and working memory are modulated by noradrenaline receptors in the prefrontal cortex (PFC). The frontal eye field (FEF) has been shown to play an important role in visual spatial attention. However, little is known about the underlying circuitry. The aim of this study was to characterize the expression of noradrenaline receptors on different pyramidal neuron and inhibitory interneuron subtypes in macaque FEF. Using immunofluorescence, we found broad expression of noradrenaline receptors across all layers of the FEF. Differences in the expression of different noradrenaline receptors were observed across different inhibitory interneuron subtypes. No significant differences were observed in the expression of noradrenaline receptors across different pyramidal neuron subtypes. However, we found that putative long-range projecting pyramidal neurons expressed all noradrenaline receptor subtypes at a much higher proportion than any of the other neuronal subtypes. Nearly all long-range projecting pyramidal neurons expressed all types of noradrenaline receptor, suggesting that there is no receptor-specific machinery acting on these long-range projecting pyramidal neurons. This pattern of expression among long-range projecting pyramidal neurons suggests a mechanism by which noradrenergic modulation of FEF activity influences attention and working memory.

Analysis of transcript and methylation levels of INSL3 and RXFP2 in undescended and descended dog testes suggested promising biomarkers associated with cryptorchidism

Cryptorchidism is the most common disorder of sex development (DSD) in dogs. This malformation is associated with reduced fertility and with a higher risk of gonadal cancer. Testicular descent is a complex process, and the functions of many environmental and genetic factors are crucial for the proper migration of fetal gonads into the scrotum. Among these, the hormone INSL3 (insulin-like peptide 3) and its receptor RXFP2 (relaxin family peptide receptor 2) play crucial roles in the transabdominal migration of the testes. The genetic background of canine cryptorchidism is poorly elucidated. The aim of this study was to compare the transcript and methylation levels of INSL3 and RXFP2 genes in undescended and descended testes of isolated unilateral cryptorchids, and in gonads of control male dogs with scrotal testes. Next, we searched for polymorphic variants in the 5'-regulatory regions of both genes associated with predispositions to cryptorchidism. The INSL3 transcript level was significantly higher in the undescended testes than in the descended testes of both the affected and control dogs. On the other hand, the mRNA level of RXFP2 was significantly lower in the retained gonads of cryptorchids than in the scrotal testes. The methylation level of a single CpG site located 15 bp upstream of the translation start codon in INSL3 was significantly higher in the testes of the control dogs than in both gonads of cryptorchids. The methylation level of 14 CpG sites in the coding region of INSL3 was significantly higher in undescended testes than in the scrotal testes, which may be associated with the higher mRNA levels of INSL3 observed in these samples. The methylation pattern of two CpG sites in the 5'-flanking region of RXFP2 was similar in both descended and undescended testes. We detected three and seven single nucleotide polymorphisms (SNPs) in the 5'-regulatory regions of INSL3 and RXFP2, respectively. Among these, the frequency of A > C substitution (ss7093349755) located 495 bp upstream of the transcription start site of RXFP2 differed significantly between cryptorchids and control dogs. Our study showed two possible genetic biomarkers associated with canine cryptorchidism: a hypomethylation of a single CpG site in the 5'-flanking region of INSL3, and the ss7093349755 SNP in the 5'-flanking region of RXFP2.

Some of the Factors Involved in Male Infertility: A Prospective Review

Infertility is defined as the inability of couples to have a baby after one year of regular unprotected intercourse, affecting 10 to 15% of couples. According to the latest WHO statistics, approximately 50-80 million people worldwide sufer from infertility, and male factors are responsible for approximately 20-30% of all infertility cases. The diagnosis of infertility in men is mainly based on semen analysis. The main parameters of semen include: concentration, appearance and motility of sperm. Causes of infertility in men include a variety of things including hormonal disorders, physical problems, lifestyle problems, psychological issues, sex problems, chromosomal abnormalities and single-gene defects. Despite numerous efforts by researchers to identify the underlying causes of male infertility, about 70% of cases remain unknown. These statistics show a lack of understanding of the mechanisms involved in male infertility. This article focuses on the histology of testicular tissue samples, the male reproductive structure, factors affecting male infertility, strategies available to find genes involved in infertility, existing therapeutic methods for male infertility, and sperm recovery in infertile men.

Proteomic analyses of ram (Ovis aries) testis during different developmental stages

Male reproductive capacity is essential for animal breeding and reproduction. In males, the testes produce sperm and secrete androgen, processes which require precise regulation by multiple proteins. The composition of proteins in the ram testes has not yet been studied systematically, thus, the application of proteomics to explore differential protein regulation during ram testes development is of great significance. In the present study, ram testes were studied at five different developmental phases to assess postnatal differences in protein regulation. Two dimensional electrophoresis (2-DE) was used to separate ram testes proteins at each developmental phase, yielding 45 different proteins, 37 of which were identified by Matrix Assisted Laser Desorption Ionization-Time of Flight-Time of Flight-Mass Spectrometry (MALDI-TOF/TOF-MS). Gene Ontology (GO) was used to specifically annotate the biological process, cellular composition, and molecular function of each identified protein. Most of the identified proteins were involved in structural formation, development, reproduction, and apoptosis of the testicular spermatogenic tissue and spermatozoa. Quantitative real time PCR (qRT-PCR), western blot and immunohistochemical methods were used to verify the proteins, and the results were consistent with that of 2-DE. The proteins that were different in abundance that were identified in this study can be used as biomarkers in future studies of ram reproduction.

Expression profiling identifies Sertoli and Leydig cell genes as Fsh targets in adult zebrafish testis

Spermatogonial stem cells are quiescent, undergo self-renewal or differentiating divisions, thereby forming the cellular basis of spermatogenesis. This cellular development is orchestrated by follicle-stimulating hormone (FSH), through the production of Sertoli cell-derived factors, and by Leydig cell-released androgens. Here, we investigate the transcriptional events induced by Fsh in a steroid-independent manner on the restart of zebrafish (Danio rerio) spermatogenesis ex vivo, using testis from adult males where type A spermatogonia were enriched by estrogen treatment in vivo. Under these conditions, RNA sequencing preferentially detected differentially expressed genes in somatic/Sertoli cells. Fsh-stimulated spermatogonial proliferation was accompanied by modulating several signaling systems (i.e. Tgf-β, Hedgehog, Wnt and Notch pathways). In silico protein-protein interaction analysis indicated a role for Hedgehog family members potentially integrating signals from different pathways during fish spermatogenesis. Moreover, Fsh had a marked impact on metabolic genes, such as lactate and fatty acid metabolism, or on Sertoli cell barrier components. Fish Leydig cells express the Fsh receptor and one of the most robust Fsh-responsive genes was insulin-like 3 (insl3), a Leydig cell-derived growth factor. Follow-up work showed that recombinant zebrafish Insl3 mediated pro-differentiation effects of Fsh on spermatogonia in an androgen-independent manner. Our experimental approach allowed focusing on testicular somatic genes in zebrafish and showed that the activity of signaling systems known to be relevant in stem cells was modulated by Fsh, providing promising leads for future work, as exemplified by the studies on Insl3.

Functional insulin-like factor 3 (INSL3) hormone-receptor system in the testes and spermatozoa of domestic ruminants and its potential as a predictor of sire fertility

Insulin-like factor 3 (INSL3) is essential for fetal testis descent, and has been implicated in the testicular and sperm functions in adult males; however, similar functions in domestic ruminants remain largely unknown. This study investigated the functional INSL3 hormone-receptor system in adult ruminant testes and spermatozoa, and explored its potential to diagnose the fertility of sires. Testes and spermatozoa were obtained from fertile bulls, rams and he-goats, whereas subfertile testes and spermatozoa were obtained only from bulls. As expected, INSL3 was visualized in Leydig cells, while we clearly demonstrated that the functional receptor, relaxin family peptide receptor 2 (RXFP2), enabling INSL3 to bind was identified in testicular germ cells and in the sperm equatorial segment of bulls, rams and he-goats. In comparison to fertile bulls, the percentage of INSL3- and RXFP2-expressing cells and their expression levels per cell were significantly reduced in the testes of subfertile bulls. In addition, the population of INSL3-binding spermatozoa was also significantly reduced in the semen of subfertile bulls. These results provide evidence for a functional INSL3 hormone-receptor system operating in ruminant testes and spermatozoa, and its potential to predict subfertility in sires.