MAP4K4/JNK Signaling Pathway Stimulates Proliferation and Suppresses Apoptosis of Human Spermatogonial Stem Cells and Lower Level of MAP4K4 Is Associated with Male Infertility

Research progress on the adverse effects of high-altitude environment to the male reproductive system: a review study

An increasing number of people are being exposed to high-altitude environments as they become more important in economic development, resource exploitation, and other areas. This review is focused on the impact of the high-altitude environment on the male reproductive system. In high-altitude areas, the unique conditions lead to complex and significant changes in male reproductive hormone levels. The secretion of GnRH is inhibited, which in turn affects the levels of FSH and LH, ultimately influencing testosterone synthesis and secretion, thus disrupting the normal endocrine regulatory network. Testicular tissue also shows marked morphological changes. The seminiferous tubule structure becomes disordered, and the number and function of spermatogenic and interstitial cells are damaged. These alterations have a direct impact on sperm quality, resulting in a decrease in sperm density and motility, an increase in the deformity rate, and damage to genetic material integrity. Additionally, sexual function is affected, with symptoms such as decreased libido and erectile dysfunction being common. The underlying mechanisms involve oxidative stress damage, an abnormal increase in apoptosis, and enhanced autophagy. Nevertheless, current research, especially human-based studies, is restricted by small sample sizes and insufficiently in-depth exploration of these mechanisms.

Gene regulation and signaling transduction in mediating the self-renewal, differentiation, and apoptosis of spermatogonial stem cells

ABSTRACT

Infertility has become one of the most serious diseases worldwide, and 50% of this disease can be attributed to male-related factors. Spermatogenesis, by definition, is a complex process by which spermatogonial stem cells (SSCs) self-renew to maintain stem cell population within the testes and differentiate into mature spermatids. It is of great significance to uncover gene regulation and signaling pathways that are involved in the fate determinations of SSCs with aims to better understand molecular mechanisms underlying human spermatogenesis and identify novel targets for gene therapy of male infertility. Significant achievement has recently been made in demonstrating the signaling molecules and pathways mediating the fate decisions of mammalian SSCs. In this review, we address key gene regulation and crucial signaling transduction pathways in controlling the self-renewal, differentiation, and apoptosis of SSCs, and we illustrate the networks of genes and signaling pathways in SSC fate determinations. We also highlight perspectives and future directions in SSC regulation by genes and their signaling pathways. This review could provide novel insights into the genetic regulation of normal and abnormal spermatogenesis and offer molecular targets to develop new approaches for gene therapy of male infertility.

Investigating the effects of COVID-19 on sperm in male smokers: A prospective integrated proteomic and metabolomic study

Notable variations in semen parameters among non-smoking males have been documented post-COVID-19 pandemic. The role of smoking as a significant contributing factor to male infertility has been substantiated. Does the combined effect of smoking and SARS-CoV-2 infection impact male reproductive function? A prospective descriptive cohort study was performed using data from 90 smoking and 90 non-smoking males before and after coronavirus infection in a single center over a period of 3 months. Semen samples were collected before and within 15 days after COVID-19 infection, ensuring no more than three months elapsed between the two collections. The semen parameters evaluated included volume, concentration, progressive motility, normal morphology, and DNA fragmentation rate. Proteomic and metabolomic studies were further used to explore the differences between groups. Both non-smokers and smokers exhibited a marked reduction in sperm concentration, progressive motility, and normal morphology rate. Additionally, an increase in sperm DNA fragmentation index was noted for non-smokers and smokers. In the non-smoking group, dysregulation proteins including SEMG1, SEMG2 and DNAH5, and metabolites including L-glutamine, cis-9-Palmitoleic acid and Linoleamide were observed. In smokers, dysregulation proteins including SMCP, ROPN1B and IZUMO4, alongside metabolites including carnitine, gamma-Glutamylglutamic acid, and hypoxanthine were found. Comparative analysis between smoking and non-smoking patients post-COVID-19 also revealed significant differences in semen concentration, morphology and sperm DNA fragmentation rate. Dysregulated proteins including HSPA5, HSPA2 and PGK2, and metabolites such as acetylcarnitine, oxaloacetate and nicotinate were associated with impaired sperm function. Our study demonstrates that the virus also significantly compromises sperm quality in smoking males, who experience more pronounced declines post-infection compared to their non-smoking counterparts. This research underscores the necessity for comprehensive fertility assessments for smoking males after recovering from COVID-19.

LncRNA ACVR2B-as1 interacts with ALDOA to regulate the self-renewal and apoptosis of human spermatogonial stem cells by controlling glycolysis activity

Human spermatogonial stem cells (SSCs) have significant applications in reproductive medicine and regenerative medicine because of their great plasticity. Nevertheless, it remains unknown about the functions and mechanisms of long non-coding RNA (LncRNA) in regulating the fate determinations of human SSCs. Here we have demonstrated that LncRNA ACVR2B-as1 (activin A receptor type 2B antisense RNA 1) controls the self-renewal and apoptosis of human SSCs by interaction with ALDOA via glycolysis activity. LncRNA ACVR2B-as1 is highly expressed in human SSCs. LncRNA ACVR2B-as1 silencing suppresses the proliferation and DNA synthesis and enhances the apoptosis of human SSCs. Mechanistically, our ChIRP-MS and RIP assays revealed that ACVR2B-as1 interacted with ALDOA in human SSCs. High expression of ACVR2B-as1 enhanced the proliferation, DNA synthesis, and glycolysis of human SSCs but inhibited their apoptosis through up-regulation of ALDOA. Importantly, overexpression of ALDOA counteracted the effect of ACVR2B-as1 knockdown on the aforementioned biological processes. Collectively, these results indicate that ACVR2B-as1 interacts with ALDOA to control the self-renewal and apoptosis of human SSCs by enhancing glycolysis activity. This study is of great significance because it sheds a novel insight into molecular mechanisms underlying the fate decisions of human SSCs and it may offer innovative approaches to address the etiology of male infertility.

ERK/CREB and p38 MAPK/MMP14 Signaling Pathway Influences Spermatogenesis through Regulating the Expression of Junctional Proteins in Eriocheir sinensis Testis

The hemolymph-testis barrier (HTB) is a reproduction barrier in Crustacea, guaranteeing the safe and smooth process of spermatogenesis, which is similar to the blood-testis barrier (BTB) in mammals. The MAPK signaling pathway plays an essential role in spermatogenesis and maintenance of the BTB. However, only a few studies have focused on the influence of MAPK on crustacean reproduction. In the present study, we knocked down and inhibited MAPK in Eriocheir sinensis. Increased defects in spermatogenesis were observed, concurrently with a damaged HTB. Further research revealed that es-MMP14 functions downstream of ERK and p38 MAPK and degrades junctional proteins (Pinin and ZO-1); es-CREB functions in the ERK cascade as a transcription factor of ZO-1. In addition, when es-MMP14 and es-CREB were deleted, the defects in HTB and spermatogenesis aligned with abnormalities in the MAPK. However, JNK impacts the integrity of the HTB by changing the distribution of intercellular junctions. In summary, the MAPK signaling pathway maintains HTB integrity and spermatogenesis through es-MMP14 and es-CREB, which provides insights into the evolution of gene function during barrier evolution.

FTO promotes gastric cancer progression by modulating MAP4K4 expression via demethylation in an m6A-dependent manner

Gastric cancer (GC) is a serious malignant tumour with a high mortality rate and a poor prognosis. Recently, emerging evidence has suggested that N6-methyladenosine (m6A) modification plays a crucial regulatory role in cancer progression. However, the exact role of m6A regulatory factors FTO in GC is unclear. First, the expression of m6A methylation-related regulatory factors in clinical samples and the clinical data of the corresponding patients were obtained from The Cancer Genome Atlas (TCGA-STAD) dataset, and correlation analysis between FTO expression and patient clinicopathological parameters was subsequently performed. qRT-PCR, immunohistochemistry (IHC) and western blotting (WB) were used to verify FTO expression in GC. CCK-8, EdU, flow cytometry and transwell assays were used to evaluate the effect of FTO on the behaviour of GC cells. Transcriptome sequencing and RNA immunoprecipitation analysis were used to explore the potential regulatory mechanisms mediated by FTO. FTO was highly expressed in GC tissues and cells, and high expression of FTO predicted a worse prognosis than low expression. Functionally, overexpression of FTO promoted the proliferation, migration and invasion of GC cells but inhibited cell apoptosis. Mechanistically, we found that FTO is upregulated in GC and promotes GC progression by modulating the expression of MAP4K4. Taken together, our findings provide new insights into the effects of FTO-mediated m6A demethylation and could lead to the development of new strategies for GC monitoring and aggressive treatment.

UBR4 deficiency causes male sterility and testis abnormal in Drosophila

Introduction

It has been established that UBR4 encodes E3 ubiquitin ligase, which determines the specificity of substrate binding during protein ubiquitination and has been associated with various functions of the nervous system but not the reproductive system. Herein, we explored the role of UBR4 on fertility with a Drosophila model.

Methods

Different Ubr4 knockdown flies were established using the UAS/GAL4 activating sequence system. Fertility, hatchability, and testis morphology were studied, and bioinformatics analyses were conducted. Our results indicated that UBR4 deficiency could induce male sterility and influent egg hatchability in Drosophila.

Results

We found that Ubr4 deficiency affected the testis during morphological analysis. Proteomics analysis indicated 188 upregulated proteins and 175 downregulated proteins in the testis of Ubr4 knockdown flies. Gene Ontology analysis revealed significant upregulation of CG11598 and Sfp65A, and downregulation of Pelota in Ubr4 knockdown flies. These proteins were involved in the biometabolic or reproductive process in Drosophila. These regulated proteins are important in testis generation and sperm storage promotion. Bioinformatics analysis verified that UBR4 was low expressed in cryptorchidism patients, which further supported the important role of UBR4 in male fertility.

Discussion

Overall, our findings suggest that UBR4 deficiency could promote male infertility and may be involved in the protein modification of UBR4 by upregulating Sfp65A and CG11598, whereas downregulating Pelota protein expression.