Decreased expression of SAM68 in human testes with spermatogenic defects

Testicular hypoplasia in Nellore Cattle: Genetic analysis and functional analysis of genome-wide association study results

Characterized by the incomplete development of the germinal epithelium of the seminiferous tubules, Testicular hypoplasia (TH) leads to decreased sperm concentration, increased morphological changes in sperm and azoospermia. Economic losses resulting from the disposal of affected bulls reduce the efficiency of meat production systems. A genome-wide association study and functional analysis were performed to identify genomic windows and the underlying positional candidate genes associated with TH in Nellore cattle. Phenotypic and pedigree data from 207,195 animals and genotypes (461,057 single nucleotide polymorphism, SNP) from 17,326 sires were used in this study. TH was evaluated as a binary trait measured at 18 months of age. A possible correlated response on TH resulting from the selection for scrotal circumference was evaluated by using a two-trait analysis. Thus, estimated breeding values were calculated by fitting a linear-threshold animal model in a Bayesian approach. The SNP effects were estimated using the weighted single-step genomic BLUP method. Twelve non-overlapping windows of 20 adjacent SNP that explained more than 1% of the additive genetic variance were selected for candidate gene annotation. Functional and gene prioritization analysis of the candidate genes identified genes (KHDRBS3, GPX5, STAR, ERLIN2), which might play an important role in the expression of TH due to their known roles in the spermatogenesis process, synthesis of steroids and lipid metabolism.

Hepatic Sam68 Regulates Systemic Glucose Homeostasis and Insulin Sensitivity

Hepatic glucose production (HGP) is an important component of glucose homeostasis, and deregulated HGP, particularly through gluconeogenesis, contributes to hyperglycemia and pathology of type-2 diabetes (T2D). It has been shown that the gluconeogenic gene expression is governed primarily by the transcription factor cAMP-response element (CRE)-binding protein (CREB) and its coactivator, CREB-regulated transcriptional coactivator 2 (CRTC2). Recently, we have discovered that Sam68, an adaptor protein and Src kinase substrate, potently promotes hepatic gluconeogenesis by promoting CRTC2 stability; however, the detailed mechanisms remain unclear. Here we show that in response to glucagon, Sam68 increases CREB/CRTC2 transactivity by interacting with CRTC2 in the CREB/CRTC2 complex and occupying the CRE motif of promoters, leading to gluconeogenic gene expression and glucose production. In hepatocytes, glucagon promotes Sam68 nuclear import, whereas insulin elicits its nuclear export. Furthermore, ablation of Sam68 in hepatocytes protects mice from high-fat diet (HFD)-induced hyperglycemia and significantly increased hepatic and peripheral insulin sensitivities. Thus, hepatic Sam68 potentiates CREB/CRTC2-mediated glucose production, contributes to the pathogenesis of insulin resistance, and may serve as a therapeutic target for T2D.

Ablation of Sam68 in adult mice increases thermogenesis and energy expenditure

Genetic deletion of Src associated in mitosis of 68kDa (Sam68), a pleiotropic adaptor protein prevents high-fat diet-induced weight gain and insulin resistance. To clarify the role of Sam68 in energy metabolism in the adult stage, we generated an inducible Sam68 knockout mice. Knockout of Sam68 was induced at the age of 7-10 weeks, and then we examined the metabolic profiles of the mice. Sam68 knockout mice gained less body weight over time and at 34 or 36 weeks old, had smaller fat mass without changes in food intake and absorption efficiency. Deletion of Sam68 in mice elevated thermogenesis, increased energy expenditure, and attenuated core-temperature drop during acute cold exposure. Furthermore, we examined younger Sam68 knockout mice at 11 weeks old before their body weights deviate, and confirmed increased energy expenditure and thermogenic gene program. Thus, Sam68 is essential for the control of adipose thermogenesis and energy homeostasis in the adult.

Novel Gene Regulation in Normal and Abnormal Spermatogenesis

Spermatogenesis is a complex and dynamic process which is precisely controlledby genetic and epigenetic factors. With the development of new technologies (e.g., single-cell RNA sequencing), increasingly more regulatory genes related to spermatogenesis have been identified. In this review, we address the roles and mechanisms of novel genes in regulating the normal and abnormal spermatogenesis. Specifically, we discussed the functions and signaling pathways of key new genes in mediating the proliferation, differentiation, and apoptosis of rodent and human spermatogonial stem cells (SSCs), as well as in controlling the meiosis of spermatocytes and other germ cells. Additionally, we summarized the gene regulation in the abnormal testicular microenvironment or the niche by Sertoli cells, peritubular myoid cells, and Leydig cells. Finally, we pointed out the future directions for investigating the molecular mechanisms underlying human spermatogenesis. This review could offer novel insights into genetic regulation in the normal and abnormal spermatogenesis, and it provides new molecular targets for gene therapy of male infertility.

RNA-Binding Proteins Play an Important Role in the Prognosis of Patients With Testicular Germ Cell Tumor

Testicular germ cell tumors (TGCTs) are common urological neoplasms in young adult males. The outcome of TGCT depends on pathologic type and tumor stage. RNA-binding proteins (RBPs) influence numerous cancers via post-transcriptional regulation. The prognostic importance of RBPs in TGCT has not been fully investigated. In this study, we set up a prognostic risk model of TGCT using six significantly differentially expressed RBPs, namely, TRMT61A, POLR2J, DIS3L2, IFIH1, IGHMBP2, and NPM2. The expression profiles were downloaded from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression datasets. We observed by performing least absolute shrinkage and selection operator (LASSO) regression analyses that in the training cohort, the expression of six RBPs was correlated with disease-free survival in patients with TGCT. We assessed the specificity and sensitivity of 1-, 3-, 5-, and 10-year survival status prediction using receiver operating characteristic curve analysis and successfully validated using the test cohorts, the entire TCGA cohort, and Gene Expression Omnibus (GEO) datasets. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and gene set enrichment analyses were carried out to seek the possible signaling pathways related with risk score. We also examined the association between the model based on six RBPs and different clinical characteristics. A nomogram was established for TGCT recurrence prediction. Consensus clustering analysis was carried out to identify the clusters of TGCT with different clinical outcomes. Ultimately, external validations of the six-gene risk score were performed by using the GSE3218 and GSE10783 datasets downloaded from the GEO database. In general, our study constructed a prognostic model based on six RBPs, which could serve as independent risk factor in TGCT, especially in seminoma, and might have brilliant clinical application value.

Sertoli cell-only syndrome: etiology and clinical management

Almost 50% of infertility cases are due to male factors, and spermatogenesis failure is one of the most severe forms of male infertility. Sertoli cell-only syndrome (SCOS) also known as germ cell aplasia is characterized by azoospermia in which the seminiferous tubules of testicular biopsy are lined only with Sertoli cells. The definitive diagnosis of SCOS is by diagnostic testicular biopsy. Although SCOS may be a result of Klinefelter syndrome, most of the SCOS men have a normal karyotype. Along with genetic aberrations, signaling pathways and endocrine processes might be major factors in the development of SCOS. Sperm retrieval and intracytoplasmic sperm injection (ICSI) are available treatments for SCOS. However, some SCOS patients do not have therapeutic options to help them having a biological child. This review aims to summarize our present knowledge about SCOS and to highlight the importance of future researches in the diagnosis and treatment of this disorder.

Splicing regulation in brain and testis: common themes for highly specialized organs

Expansion of the coding and regulatory capabilities of eukaryotic transcriptomes by alternative splicing represents one of the evolutionary forces underlying the increased structural complexity of metazoans. Brain and testes stand out as the organs that mostly exploit the potential of alternative splicing, thereby expressing the largest repertoire of splice variants. Herein, we will review organ-specific as well as common mechanisms underlying the high transcriptome complexity of these organs and discuss the impact exerted by this widespread alternative splicing regulation on the functionality and differentiation of brain and testicular cells.

Abnormal histology in testis from prepubertal boys with monorchidism

BACKGROUND

Little is known about the histology of contralateral descended testes in boys with unilaterally absent testis. We investigated whether absence of one testis is associated with abnormal tissue architecture of the solitary contralaterally descended testis.

DESIGN SETTING AND PATIENTS

For this retrospective study, we examined the results of biopsies of the contralateral descended testis in 43 boys with monorchidism. Data from 26 control testes from boys of matching ages were selected from results published in 1977 and 2009. During surgery, any nubbins were removed. In each case, the scrotal testis was biopsied, and the testis fixed by subdartos pouch or suture.

RESULTS

Of the 43 affected boys, 23 had normal testicular histology in the contralateral descended testis, whereas 20 (46%) had abnormal histology. Eight of the abnormal biopsies matched the criteria for high infertility risk. Samples from three boys in this latter group revealed a Sertoli-cell-only phenotype. Immunohistochemical assays were positive for steroidogenic acute regulatory (STAR) protein in Leydig cells and spermatogonia. STAR expression was stronger in the monorchid group with normal testicular histology.

CONCLUSIONS

Almost half of the patients with unilateral absent testis were at risk for subfertility or infertility. Our results emphasize the need for testicular biopsy of the solitary testis in boys with monorchidism to appropriately assess infertility risk.

Integration of whole-genome DNA methylation data with RNA sequencing data to identify markers for bull fertility

Predicting bull fertility prior to breeding is a current challenge for the dairy industry. The use of molecular biomarkers has been previously assessed. However, the integration of this information has not been performed to extract biologically relevant markers. The goal of this study was to integrate DNA methylation data with previously published RNA-sequencing results in order to identify candidate markers for sire fertility. A total of 1765 differentially methylated cytosines were found between high- and low-fertility sires. Ten genes associated with 11 differentially methylated cytosines were found in a previous study of gene expression between high- and low-fertility sires. Additionally, two of these genes code for proteins found exclusively in bull seminal plasma. Collectively, our results reveal 10 genes that could be used in the future as a panel for predicting bull fertility.

Decreased expression of MRE11 and RAD50 in testes from humans with spermatogenic failure

PURPOSE

To assess testicular mRNA and protein expression levels of MRE11 and RAD50 in human azoospermia patients.

METHODS

Patients diagnosed with maturation arrest at the spermatocyte stage (MA) and Sertoli cell-only syndrome (SCOS) were recruited through diagnostic testicular biopsy. Patients with normal spermatogenesis were studied as controls. In addition, knockdown of MRE11 and RAD50 was performed in GC-2spd(ts) cells to investigate their roles in cellular proliferation and apoptosis.

RESULTS

mRNA and protein expression levels of MRE11 and RAD50 were measured using quantitative polymerase chain reaction, western blotting, and immunohistochemistry, respectively. Knockdown of both MRE11 and RAD50 utilized transfection with small interfering RNAs.

CONCLUSION

Our findings demonstrated altered expression levels of MRE11 and RAD50 in human testes with MA and SCOS, and showed that these alterations might be associated with impaired spermatogenesis. These results offer valuable new perspectives into the molecular mechanisms of male infertility.

[CEP55 may be a potential therapeutic target for non-obstructive azoospermia with maturation arrest]

OBJECTIVE

To explore the effect of small interfering RNA (siRNA)-mediated CEP55 gene silencing on the proliferation of mouse spermatogonia.

METHODS

Six patients with azoospermia diagnosed to have maturation arrest (3 cases) or normal spermatogenesis (3 cases) based on testicular biopsy between January 1 and December 31, 2017 in our center were examined for differential proteins in the testicular tissue using isobaric tags for relative and absolute quantitation (iTRAQ), and CEP55 was found to differentially expressed between the two groups of patients. We constructed a CEP55 siRNA for transfection in mouse spermatogonia and examined the inhibitory effects on CEP55 expressions using Western blotting and qPCR. The effect of CEP55 gene silencing on the proliferation of mouse spermatogonia was evaluated with CCK8 assay.

RESULTS

In the testicular tissues from the 6 patients with azoospermia, iTRAQ combined with LC/MS/MS analysis identified over two hundred differentially expressed proteins, among which CEP55 showed the most significant differential expression between the patients with maturation arrest and those with normal spermatogenesis. The cell transfection experiment showed that compared with the cells transfected with the vehicle or the negative control sequence, the mouse spermatogonia transfected with CEP55 siRNA showed significantly lowered expressions of CEP55 mRNA and protein (P < 0.05) and significantly decreased proliferation rate as shown by CCK8 assay (P < 0.05).

CONCLUSIONS

CEP55 may play a key role in spermatogenesis and may serve as a potential therapeutic target for non-obstructive azoospermia with maturation arrest.

Isobaric tags for relative and absolute quantification-based proteomic analysis of testis biopsies in rhesus monkeys treated with transient scrotal hyperthermia

This study aimed to examine the cellular and molecular events that occur in rhesus monkey testes after scrotal hyperthermia. Eight male adult rhesus monkeys were subjected to scrotal hyperthermia at 43°C for 30 min daily for 6 consecutive days. Sperm concentration, reproductive hormones, and testis histology were examined before hyperthermia (day 0), and at 8, 15, 30, 45, 60, 75, and 90 days after the initiation of hyperthermia. iTRAQ-based proteomic analysis was conducted on testicular tissues collected on days 0, 8, and 60 to identify differentially expressed proteins at the early and recovery stages of testicular damage. The sperm concentration was significantly decreased at days 30 and 45 after treatment (p < 0.01) and recovered to baseline at day 60. When compared with day 0, 101 and 24 differentially expressed proteins were identified at days 8 and 60 after heat treatment, respectively. The molecular functions of the differentially expressed proteins at day 8 were mainly nucleic acid binding, unfolded protein binding, nucleotide binding, and nucleoside phosphate binding. Spliceosome was enriched as the most significant pathway at day 8. CIRBP, PSIP1, Sam68, and Decorin were validated and found to be consistent with the proteomic data, indicating the reliability of the proteomic profiles identified in this study. In summary, we suggest that the proteins identified in this study may play important roles in heat-induced spermatogenic impairment. Some of these proteins, such as CIRBP, PSIP1, Sam68, and Decorin, may be early molecular targets responsible for spermatogenesis suppression induced by heat treatment.

RNA binding proteins in spermatogenesis: an in depth focus on the Musashi family

Controlled gene regulation during gamete development is vital for maintaining reproductive potential. During the complex process of mammalian spermatogenesis, male germ cells experience extended periods of the inactive transcription despite heavy translational requirements for continued growth and differentiation. Hence, spermatogenesis is highly reliant on mechanisms of posttranscriptional regulation of gene expression, facilitated by RNA binding proteins (RBPs), which remain abundantly expressed throughout this process. One such group of proteins is the Musashi family, previously identified as critical regulators of testis germ cell development and meiosis in Drosophila, and also shown to be vital to sperm development and reproductive potential in the mouse. This review describes the role and function of RBPs within the scope of male germ cell development, focusing on our recent knowledge of the Musashi proteins in spermatogenesis. The functional mechanisms utilized by RBPs within the cell are outlined in depth, and the significance of sub-cellular localization and stage-specific expression in relation to the mode and impact of posttranscriptional regulation is also highlighted. We emphasize the historical role of the Musashi family of RBPs in stem cell function and cell fate determination, as originally characterized in Drosophila and Xenopus, and conclude with our current understanding of the differential roles and functions of the mammalian Musashi proteins, Musashi-1 and Musashi-2, with a primary focus on our findings in spermatogenesis. This review highlights both the essential contribution of RBPs to posttranscriptional regulation and the importance of the Musashi family as master regulators of male gamete development.