Sohlh1 is essential for spermatogonial differentiation

Single-cell RNA-seq and pathological phenotype reveal the functional atlas and precise roles of Sox30 in testicular cell development and differentiation

Sox30 has recently been demonstrated to be a key regulator of spermatogenesis. However, the precise roles of Sox30 in the testis remain largely unclear. Here, the specific functions of Sox30 in testicular cells were determined by single-cell sequencing and confirmed via pathological analyses. Sox30 loss appears to damage all testicular cells to different extents. Sox30 chiefly drives the differentiation of primary spermatocytes. Sox30 deficiency causes spermatocyte arrest at the early phase of meiosis I, with nearly no normally developing second spermatocytes and three new spermatocyte -subclusters emerging. In addition, Sox30 seems to play important roles in the mature phenotypes of Sertoli and Leydig cells, and the proliferation and differentiation of spermatogonia. The developmental trajectory of germ cells begins with spermatogonia and splits into two different spermatocyte branches, with Sox30-null spermatocytes and wild-type spermatocytes placed at divergent ends. An opposite developmental trajectory of spermatocyte subclusters is observed, followed by incomplete development of spermatid subclusters in Sox30-null mice. Sox30 deficiency clearly alters the intercellular cross-talk of major testicular cells and dysregulates the transcription factor networks primarily involved in cell proliferation and differentiation. Mechanistically, Sox30 appears to have similar terminal functions that are involved mainly in spermatogenic development and differentiation among major testicular cells, and Sox30 performs these similar crucial roles through preferential regulation of different signalling pathways. Our study describes the exact functions of Sox30 in testicular cell development and differentiation and highlights the primary roles of Sox30 in the early meiotic phase of germ cells.

Clinical phenotype and genetic analysis of patients with severe oligoasthenospermia carrying heterozygous SOHLH1 c.346-1G>A mutation

Introduction

Severe oligoasthenospermia (SOA) is a prevalent cause of male infertility. However, the underlying causes of most SOA cases remain unclear due to the complexity of germ cell development and the significant genetic heterogeneity associated with male infertility. Therefore, in this study, we aimed to elucidate the genetic etiology of two cases of male infertility resulting from SOA and clarify the novel clinical phenotype associated with a heterozygous mutation at the c.346-1G>A site of the SOHLH1 gene.

Methods and results

Through whole-exome sequencing, we found that patients with SOA carried heterozygous mutations at the c.346-1G>A site. This variant is classified as pathogenic based on disease database records and literature reports. Notably, our study demonstrated that patients with heterozygous mutations at the c.346-1G>A site exhibited severely reduced sperm counts, significantly impaired sperm motility, and pronounced morphological deformities. One patient underwent assisted reproductive treatment through an intracytoplasmic sperm injection and achieved a favorable outcome, resulting in a successful pregnancy.

Discussion

In conclusion, our study provides the first evidence that the heterozygous mutation at the c.346-1G>A site of SOHLH1 is associated with SOA, and elucidates the new clinical phenotype associated with this mutation.

Single-cell RNA sequencing unveils dynamic transcriptional profiles during the process of donkey spermatogenesis and maturation

INTRODUCTION

With the increasing demand for donkey production, there has been a growing focus on the breeding of donkeys. However, our current understanding of the mechanisms underlying spermatogenesis and maturation in donkeys during reproduction remains limited.

OBJECTIVES

This study is to provide a comprehensive single-cell landscape analysis of spermatogenesis and maturation in donkeys.

METHODS

In this study, we employed single-cell RNA sequencing to investigate cell composition, gene expression patterns, and regulatory roles during spermatogenesis and maturation in donkeys.

RESULTS

The expression patterns of CDK1, CETN3, and UBE2J1 were found to be indicative of specific germ cells during donkey spermatogenesis. Additionally, the DEFB121, ELSPBP1, and NPC2 genes were specifically identified in the principal cells of the donkey epididymis.

CONCLUSIONS

We performed single-cell RNA sequencing to analyze the cellular composition and spatial distribution of donkey testis and epididymis, thereby generating comprehensive transcriptional atlases at the single-cell resolution.

Single-cell RNA sequencing reveals the critical role of alternative splicing in cattle testicular spermatagonia

Spermatogonial stem cells (SSCs) form haploid gametes through the precisely regulated process of spermatogenesis. Within the testis, SSCs undergo self-renewal through mitosis, differentiation, and then enter meiosis to generate mature spermatids. This study utilized single-cell RNA sequencing on 26,888 testicular cells obtained from five Holstein bull testes, revealing the presence of five distinct germ cell types and eight somatic cell types in cattle testes. Gene expression profiling and enrichment analysis were utilized to uncover the varied functional roles of different cell types involved in cattle spermatogenesis. Additionally, unique gene markers specific to each testicular cell type were identified. Moreover, differentially expressed genes in spermatogonia exhibited notable enrichment in GO terms and KEGG pathway linked to alternative splicing. Notably, our study has shown that the activity of the YY1 regulation displays distinct expression patterns in spermatogonia, specifically targeting spliceosome proteins including RBM39, HNRNPA2B1, HNRNPH3, CPSF1, PCBP1, SRRM1, and SRRM2, which play essential roles in mRNA splicing. These results emphasize the importance of mRNA processing in spermatogonia within cattle testes, providing a basis for further investigation into their involvement in spermatogonial development.

Decabromodiphenyl ether induces the chromosome association disorders of spermatocytes and deformation failures of spermatids in mice

The environmental presence of decabromodiphenyl ether (BDE-209), which is toxic to the male reproductive system, is widespread. The current study investigated its mechanism of toxicity in mice. The results showed, that BDE-209 induced DNA damage, decreased the expression of the promoter of meiosis spermatogenesis- and oogenesis-specific basic helix-loop-helix 1 (Sohlh1), meiosis related-factors Lethal (3) malignant brain tumor like 2 (L3MBTL2), PIWI-like protein 2 (MILI), Cyclin-dependent kinase 2 (CDK2), Cyclin A, synaptonemal complex protein 1 (SYCP1) and synaptonemal complex protein 3 (SYCP3), and caused spermatogenic cell apoptosis, resulting in a decrease in sperm quantity and quality. Furthermore, BDE-209 downregulated the levels of anaphase-promoting complex/cyclosome (APC/C), increased the expression of PIWI-like protein 1 (MIWI) in the cytoplasm of elongating spermatids, and decreased the nuclear levels of RING finger protein 8 (RNF8), ubiquitinated (ub)-H2A/ub-H2B, and Protamine 1 (PRM1)/Protamine 2 (PRM2), while increasing H2A/H2B nuclear levels in spermatids. The reproductive toxicity was persistent for 50 days following the withdrawal of BDE-209 exposure. The results suggested that BDE-209 inhibits the initiation of meiosis by decreasing the expression of Sohlh1. Furthermore, the reduced expression of L3MBTL2 inhibited the formation of chromosomal synaptonemal complexes by depressing the expression of meiosis regulators affecting the meiotic progression and also inhibited histone ubiquitination preventing the replacement of histones by protamines, by preventing RNF8 from entering nuclei, which affected the evolution of spermatids into mature sperm.

A Single-Cell Landscape of Spermioteleosis in Mice and Pigs

(1) Background: Spermatozoa acquired motility and matured in epididymis after production in the testis. However, there is still limited understanding of the specific characteristics of sperm development across different species. In this study, we employed a comprehensive approach to analyze cell compositions in both testicular and epididymal tissues, providing valuable insights into the changes occurring during meiosis and spermiogenesis in mouse and pig models. Additionally, we identified distinct gene expression signatures associated with various spermatogenic cell types. (2) Methods: To investigate the differences in spermatogenesis between mice and pigs, we constructed a single-cell RNA dataset. (3) Results: Our findings revealed notable differences in testicular cell clusters between these two species. Furthermore, distinct gene expression patterns were observed among epithelial cells from different regions of the epididymis. Interestingly, regional gene expression patterns were also identified within principal cell clusters of the mouse epididymis. Moreover, through analysing differentially expressed genes related to the epididymis in both mouse and pig models, we successfully identified potential marker genes associated with sperm development and maturation for each species studied. (4) Conclusions: This research presented a comprehensive single-cell landscape analysis of both testicular and epididymal tissues, shedding light on the intricate processes involved in spermatogenesis and sperm maturation, specifically within mouse and pig models.

Evaluation of MYBL1 as the master regulator for pachytene spermatocyte genes dysregulated in interspecific hybrid dzo

Misregulation of spermatogenesis transcription factors (TF) in hybrids can lead to misexpression, which is a mechanism for hybrid male sterility (HMS). We used dzo (male offspring of Bos taurus ♂ × Bos grunniens ♀) in bovines to investigate the relationship of the key TF with HMS via RNA sequencing and assay for transposase-accessible chromatin with high-throughput sequencing analyses. RNA sequencing showed that the widespread misexpression in dzo was associated with spermatogenesis-related genes and somatic or progenitor genes. The transition from leptotene or zygotene spermatocytes to pachytene spermatocytes may be the key stage for meiosis arrest in dzo. The analysis of TF-binding motif enrichment revealed that the male meiosis-specific master TF MYB proto-oncogene like 1 (MYBL1, known as A-MYB) motif was enriched on the promoters of downregulated pachytene spermatocyte genes in dzo. Assay for transposase-accessible chromatin with high-throughput sequencing revealed that TF-binding sites for MYBL1, nuclear transcription factor Y, and regulatory factor X were enriched in the low-chromatin accessibility region of dzo. The target genes of the MYBL1-binding motif were associated with meiosis-specific genes and significantly downregulated in dzo testis. The transcription factor MYBL1 may be the candidate master regulator for pachytene spermatocyte genes dysregulated in interspecific HMS dzo. This study reported that a few upstream TF regulation changes might exert a cascading effect downstream in a regulatory network as a mechanism for HMS.

Sohlh1 loss of function male and female infertility model impacts overall health beyond gonadal dysfunction in mice†

Reproductive longevity is associated with health outcomes. Early menopause, loss of ovarian function, and male infertility are linked to shorter lifespan and increased adverse health outcomes. Here we examined the extragonadal effects of whole animal loss of spermatogenesis and oogenesis specific basic helix-loop-helix 1 (Sohlh1) gene in mice, a well-described mouse model of female and male infertility. Sohlh1 encodes a transcription factor that is primarily expressed in the male and female germline and regulates germline differentiation. The Sohlh1 knockout mouse model, just like human individuals with SOHLH1 loss of function, presents with hypergonadotropic hypogonadism and loss of ovarian function in females and impaired spermatogenesis in males, with a seemingly gonad restricted phenotype in both sexes. However, extragonadal phenotyping revealed that Sohlh1 deficiency leads to abnormal immune profiles in the blood and ovarian tissues of female animals, sex-specific alterations of metabolites, and behavior and cognition changes. Altogether, these results show that Sohlh1 deficiency impacts overall health in both male and female mice.

Postnatal ontogeny of Neuromedin S and its receptors NMUR1 and NMUR2 expression in mouse testis

Neuromedin S (NMS) is a well-known anorexigenic neuropeptide. Despite some reports of the presence of its transcript and precursor protein in testis, the expression and localization of NMS and its receptors during the postnatal development of mammalian testis remains elusive. We investigated the expression patterns and testicular localization of NMS and its receptors NMUR1 and NMUR2, during 5, 10, 20, 30, and 90 days of postnatal development, using real time PCR, immunoblot analysis and immunohistochemistry in mice. NMS and its receptors are present at all age groups at transcript level in mouse testis. At the protein level, NMS and NMUR2 are present in all age groups, whereas NMUR1 is present primarily in 30- and 90-day testis. Immunolocalization study showed that NMS and NMUR2 are expressed in spermatogonia, spermatocytes, Sertoli cells, and Leydig cells, in contrast to NMUR1 which is expressed exclusively in the Leydig cells of 30- and 90-day testis. The results also confirm the intranuclear localization of NMS in spermatogonia and spermatocytes. Although NMS-NMUR2 is expressed in Sertoli cells at all stages of the spermatogenic cycle, they showed a stage-specific expression pattern in spermatogonia and primary spermatocytes. In conclusion, NMS and its receptors NMUR1 and NMUR2 are expressed in the testis and may regulate spermatogenesis, possibly by modulating steroidogenesis and Sertoli cell function in the testis.

Identification of genomic regions associated with total and progressive sperm motility in Italian Holstein bulls

Sperm motility is directly related to the ability of sperm to move through the female reproductive tract to reach the ovum. Sperm motility is a complex trait that is influenced by environmental and genetic factors and is associated with male fertility, oocyte penetration rate, and reproductive success of cattle. In this study we carried out a GWAS in Italian Holstein bulls to identify candidate regions and genes associated with variations in progressive and total motility (PM and TM, respectively). After quality control, the final data set consisted of 5,960 records from 949 bulls having semen collected in 10 artificial insemination stations and genotyped at 412,737 SNPs (call rate >95%; minor allele frequency >5%). (Co)variance components were estimated using single trait mixed models, and associations between SNPs and phenotypes were assessed using a genomic BLUP approach. Ten windows that explained the greatest percentage of genetic variance were located on Bos taurus autosomes 1, 2, 4, 6, 7, 23, and 26 for TM and Bos taurus autosomes 1, 2, 4, 6, 8, 16, 23, and 26 for PM. A total of 150 genes for TM and 72 genes for PM were identified within these genomic regions. Gene Ontology enrichment analyses identified significant Gene Ontology terms involved with energy homeostasis, membrane functions, sperm-egg interactions, protection against oxidative stress, olfactory receptors, and immune system. There was significant enrichment of quantitative trait loci for fertility, calving ease, immune response, feed intake, and carcass weight within the candidate windows. These results contribute to understanding the architecture of the genetic control of sperm motility and may aid in the development of strategies to identify subfertile bulls and improve reproductive success.

SRSF10 is essential for progenitor spermatogonia expansion by regulating alternative splicing

Alternative splicing expands the transcriptome and proteome complexity and plays essential roles in tissue development and human diseases. However, how alternative splicing regulates spermatogenesis remains largely unknown. Here, using a germ cell-specific knockout mouse model, we demonstrated that the splicing factor Srsf10 is essential for spermatogenesis and male fertility. In the absence of SRSF10, spermatogonial stem cells can be formed, but the expansion of Promyelocytic Leukemia Zinc Finger (PLZF)-positive undifferentiated progenitors was impaired, followed by the failure of spermatogonia differentiation (marked by KIT expression) and meiosis initiation. This was further evidenced by the decreased expression of progenitor cell markers in bulk RNA-seq, and much less progenitor and differentiating spermatogonia in single-cell RNA-seq data. Notably, SRSF10 directly binds thousands of genes in isolated THY+ spermatogonia, and Srsf10 depletion disturbed the alternative splicing of genes that are preferentially associated with germ cell development, cell cycle, and chromosome segregation, including Nasp, Bclaf1, Rif1, Dazl, Kit, Ret, and Sycp1. These data suggest that SRSF10 is critical for the expansion of undifferentiated progenitors by regulating alternative splicing, expanding our understanding of the mechanism underlying spermatogenesis.

Casein kinase 1α regulates murine spermatogenesis via p53-Sox3 signaling

Casein kinase 1α (CK1α), acting as one member of the β-catenin degradation complex, negatively regulates the Wnt/β-catenin signaling pathway. CK1α knockout usually causes both Wnt/β-catenin and p53 activation. Our results demonstrated that conditional disruption of CK1α in spermatogonia impaired spermatogenesis and resulted in male mouse infertility. The progenitor cell population was dramatically decreased in CK1α conditional knockout (cKO) mice, while the proliferation of spermatogonial stem cells (SSCs) was not affected. Furthermore, our molecular analyses identified that CK1α loss was accompanied by nuclear stability of p53 protein in mouse spermatogonia, and dual-luciferase reporter and chromatin immunoprecipitation assays revealed that p53 directly targeted the Sox3 gene. In addition, the p53 inhibitor pifithrin α (PFTα) partially rescued the phenotype observed in cKO mice. Collectively, our data suggest that CK1α regulates spermatogenesis and male fertility through p53-Sox3 signaling, and they deepen our understanding of the regulatory mechanism underlying the male reproductive system.

Functional Importance of Mini-Puberty in Spermatogenic Stem Cell Formation

Primordial germ cells nesting in the fetal testis give rise to gonocytes. The gonocytes then transform into spermatogenic stem cells (SSCs) during the neonatal period and thereafter serve as a lifetime source of spermatogenesis. Therefore, gonocyte to SSC transformation is quite an important process that supports fertility in males. During the gonocyte to SSC transformation, morphological and transcriptomic changes sequentially occur and gonocytes migrate from the center to the peripheral region of the seminiferous tubules. However, extrinsic signals which trigger the transcriptomic changes as well as the migration are not yet fully clarified. Recent studies have drawn attention to the temporal activation of the hypothalamic-pituitary-gonadal axis during the neonatal stage which occurs concurrently with SSC formation. This phenomenon is called mini-puberty, and recent studies on human cryptorchid patients as well as animal models partially support the hypothesis that mini-puberty plays pivotal roles in gonocyte-to-SSC transformation. Focusing on this point, here, we aimed to discuss the latest knowledge on the importance of mini-puberty in spermatogenesis in this review.

Transcriptional control of human gametogenesis

The pathways of gametogenesis encompass elaborate cellular specialization accompanied by precise partitioning of the genome content in order to produce fully matured spermatozoa and oocytes. Transcription factors are an important class of molecules that function in gametogenesis to regulate intrinsic gene expression programs, play essential roles in specifying (or determining) germ cell fate and assist in guiding full maturation of germ cells and maintenance of their populations. Moreover, in order to reinforce or redirect cell fate in vitro, it is transcription factors that are most frequently induced, over-expressed or activated. Many reviews have focused on the molecular development and genetics of gametogenesis, in vivo and in vitro, in model organisms and in humans, including several recent comprehensive reviews: here, we focus specifically on the role of transcription factors. Recent advances in stem cell biology and multi-omic studies have enabled deeper investigation into the unique transcriptional mechanisms of human reproductive development. Moreover, as methods continually improve, in vitro differentiation of germ cells can provide the platform for robust gain- and loss-of-function genetic analyses. These analyses are delineating unique and shared human germ cell transcriptional network components that, together with somatic lineage specifiers and pluripotency transcription factors, function in transitions from pluripotent stem cells to gametes. This grand theme review offers additional insight into human infertility and reproductive disorders that are linked predominantly to defects in the transcription factor networks and thus may potentially contribute to the development of novel treatments for infertility.

Genetics of ovarian insufficiency and defects of folliculogenesis

Primary ovarian insufficiency (POI) is determined by exhaustion of follicles in the ovaries, which leads to infertility before the age of 40 years. It is characterized by a strong familial and heterogeneous genetic background. Therefore, we will mainly discuss the genetic basis of POI in this review. We identified 107 genes related to POI etiology in mammals described by several independent groups. Thirty-four of these genes (AARS2, AIRE, ANTXR1, ATM, BMPR1B, CLPP, CYP17A1, CYP19A1, DCAF17, EIF2B, ERAL1, FANCA, FANCC, FMR1, FOXL2, GALT, GNAS, HARS2, HSD17B4, LARS2, LMNA, MGME1, NBN, PMM2, POLG, PREPL, RCBTB1, RECQL2/3/4, STAR, TWNK, and XRCC4/9) have been linked to syndromic POI and are mainly implicated in metabolism function and meiosis/DNA repair. In addition, the majority of genes associated with nonsyndromic POI, widely expanded by high-throughput techniques over the last decade, have been implicated in ovarian development and meiosis/DNA repair pathways (ATG7, ATG9, ANKRD31, BMP8B, BMP15, BMPR1A, BMPR1B, BMPR2, BNC1, BRCA2, CPEB1, C14ORF39, DAZL, DIAPH2, DMC1, ERCC6, FANCL, FANCM, FIGLA, FSHR, GATA4, GDF9, GJA4, HELQ, HSF2BP, HFM1, INSL3, LHCGR, LHX8, MCM8, MCM9, MEIOB, MSH4, MSH5, NANOS3, NOBOX, NOTCH2, NR5A1, NUP107, PGRMC1, POLR3H, PRDM1, PRDM9, PSMC3IP, SOHLH1, SOHLH2, SPIDR, STAG3, SYCE1, TP63, UBR2, WDR62, and XRCC2), whereas a few are related to metabolic functions (EIF4ENIF1, KHDRBS1, MRPS22, POLR2C). Some genes, such as STRA8, FOXO3A, KIT, KITL, WNT4, and FANCE, have been shown to cause ovarian insufficiency in rodents, but mutations in these genes have yet to be elucidated in women affected by POI. Lastly, some genes have been rarely implicated in its etiology (AMH, AMHR2, ERRC2, ESR1, INHA, LMN4, POF1B, POU5F1, REC8, SMC1B). Considering the heterogeneous genetic and familial background of this disorder, we hope that an overview of literature data would reinforce that genetic screening of those patients is worthwhile and helpful for better genetic counseling and patient management.

Transcription factor-like 5 is a potential DNA/RNA-binding protein essential for maintaining male fertility in mice

Transcription factor-like 5 (TCFL5) is a testis-specific protein that contains the basic helix-loop-helix domain, but the in vivo functions of TCFL5 remain unknown. Herein, we generated CRISPR/Cas9-mediated knockout mice to dissect the function of TCFL5 in mouse testes. Surprisingly, we found that it was difficult to generate homozygous mice with the Tcfl5 deletion since the heterozygous males (Tcfl5+/-) were infertile. We did; however, observe markedly abnormal phenotypes of spermatids and spermatozoa in the testes and epididymides of Tcfl5+/- mice. Mechanistically, we demonstrated that TCFL5 transcriptionally and post-transcriptionally regulated a set of genes participating in male germ cell development via TCFL5 ChIP-DNA and eCLIP-RNA high-throughput sequencing. We also identified a known RBP, FXR1 as an interacting partner of TCFL5 that may coordinate the transition and localization of TCFL5 in the nucleus. Collectively, we herein report for the first time that Tcfl5 is haploinsufficient in vivo and acts as a dual-function protein that mediates DNA and RNA to regulate spermatogenesis.

The microRNA miR-202 prevents precocious spermatogonial differentiation and meiotic initiation during mouse spermatogenesis

Spermatogonial differentiation and meiotic initiation during spermatogenesis are tightly regulated by a number of genes, including those encoding enzymes for miRNA biogenesis. However, whether and how single miRNAs regulate these processes remain unclear. Here, we report that miR-202, a member of the let-7 family, prevents precocious spermatogonial differentiation and meiotic initiation in spermatogenesis by regulating the timely expression of many genes, including those for key regulators such as STRA8 and DMRT6. In miR-202 knockout (KO) mice, the undifferentiated spermatogonial pool is reduced, accompanied by age-dependent decline of fertility. In KO mice, SYCP3, STRA8 and DMRT6 are expressed earlier than in wild-type littermates, and Dmrt6 mRNA is a direct target of miR-202-5p. Moreover, the precocious spermatogonial differentiation and meiotic initiation were also observed in KO spermatogonial stem cells when cultured and induced in vitro, and could be partially rescued by the knockdown of Dmrt6. Therefore, we have not only shown that miR-202 is a regulator of meiotic initiation but also identified a previously unknown module in the underlying regulatory network.

Sheng Jing Decoction Can Promote Spermatogenesis and Increase Sperm Motility of the Oligozoospermia Mouse Model

Sheng Jing Decoction (SJD), as a traditional Chinese medicine prescription, is mainly be used to treat male infertility. However, the pharmacological functions and molecular mechanisms of SJD are poorly understood. In this study, we investigated the functions of SJD on spermatogenesis and sperm motility and explored the potential mechanisms involved. Here, we demonstrated that high, medium, and low doses of SJD are effective in restoring the impairments of the whole body and testicular tissue by cyclophosphamide inducing and to rescue the damage of testicular tissue cells including Sertoli cells and germ cells. SJD can partly restore the decrease in sperm concentration, sperm vitality, sperm motility, and normal sperm morphology rate in oligozoospermic mouse models. Ki67 staining analyses confirm SJD can promote testicular tissue cell proliferation. Real-time RT-PCR analyses also reveal that SJD can upregulate the expression of proliferation-associated gene Lin28a and differentiation-associated genes Kit, Sohlh2, and Stra8. SJD can also reduce the impairment of mitochondrial membrane potential (MMP) and sperm plasma membrane integrity by cyclophosphamide inducing. Our results reveal that SJD is effective in improving both sperm quantity and quality by increasing the sperm concentration, sperm vitality, sperm motility, and normal sperm morphology rate. SJD can promote spermatogenesis by upregulating the expression of the proliferation-associated gene Lin28a and the differentiation-associated genes (Kit, Sohlh2, and Stra8). SJD can sustain MMP and sperm plasma membrane integrity to increase sperm motility.

Formation of spermatogonia and fertile oocytes in golden hamsters requires piRNAs

PIWI-interacting RNAs (piRNAs) support the germline by suppressing retrotransposons. Studies of the pathway in mice have strongly shaped the view that mammalian piRNAs are essential for male but not for female fertility. Here, we report that the role of the piRNA pathway substantially differs in golden hamsters (Mesocricetus auratus), the piRNA pathway setup of which more closely resembles that of other mammals, including humans. The loss of the Mov10l1 RNA helicase—an essential piRNA biogenesis factor—leads to striking phenotypes in both sexes. In contrast to mice, female Mov10l1^–/– hamsters are sterile because their oocytes do not sustain zygotic development. Furthermore, Mov10l1^–/– male hamsters have impaired establishment of spermatogonia accompanied by transcriptome dysregulation and an expression surge of a young retrotransposon subfamily. Our results show that the mammalian piRNA pathway has essential roles in both sexes and its adaptive nature allows it to manage emerging genomic threats and acquire new critical roles in the germline.

A set of three papers reports that the piRNA pathway is essential for mammalian female fertility based on genetic perturbation experiments performed in golden hamsters.

The mutation c.346-1G > a in SOHLH1 impairs sperm production in the homozygous but not in the heterozygous condition

Non-obstructive azoospermia (NOA) is an important cause of male infertility, and the genetic pathogenesis is still incompletely understood. The previous study reported that heterozygous mutation of c.346-1G > A in spermatogenesis and oogenesis specific basic helix–loop–helix 1 (SOHLH1) was identified in two NOA patients and suggested it is the pathogenic factor for NOA. However, in our research, this heterozygous mutation was confirmed in three Chinese infertile patients who suffered from teratozoospermia, but they had normal sperm number. Intriguingly, a homozygous mutation of c.346-1G > A in SOHLH1 was detected in a severe oligozoospermia (SOZ) patient, characterized with severely decreased sperm count. Notably, we unprecedently revealed that this homozygous mutation of c.346-1G > A in SOHLH1 leads to the sharp decrease in various germ cells and spermatogenesis dysfunction, which is similar to the phenotype of SOHLH1 knockout male mice. Moreover, western blotting confirmed that the homozygous mutation declined SOHLH1 protein expression. Additionally, we correlated the good prognosis of intracytoplasmic sperm injection (ICSI) in the patients carrying the mutation of c.346-1G > A in SOHLH1. Thus, we suggested that the heterozygous mutation of c.346-1G > A in SOHLH1 is responsible for teratozoospermia, and this homozygous mutation in SOHLH1 impairs spermatogenesis and further leads to the reduced sperm count, eventually causing male infertility, which unveils a new recessive-inheritance pattern of SOHLH1-associated male infertility initially.

Molecular mimicry between SARS-CoV-2 and the female reproductive system

Introduction

Oogenesis, the process of egg production by the ovary, involves a complex differentiation program leading to the production of functional oocytes. This process comprises a sequential pathway of steps that are finely regulated. The question related to SARS‐CoV‐2 infection and fertility has been evoked for several reasons, including the mechanism of molecular mimicry, which may contribute to female infertility by leading to the generation of deleterious autoantibodies, possibly contributing to the onset of an autoimmune disease in infected patients.

Objective

The immunological potential of the peptides shared between SARS‐CoV‐2 spike glycoprotein and oogenesis‐related proteins; Thus we planned a systematic study to improve our understanding of the possible effects of SARS‐CoV‐2 infection on female fertility using the angle of molecular mimicry as a starting point.

Methods

A library of 82 human proteins linked to oogenesis was assembled at random from UniProtKB database using oogenesis, uterine receptivity, decidualization, and placentation as a key words. For the analyses, an artificial polyprotein was built by joining the 82 a sequences of the oogenesis‐associated proteins. These were analyzed by searching the Immune Epitope DataBase for immunoreactive SARS‐CoV‐2 spike glycoprotein epitopes hosting the shared pentapeptides.

Results

SARS‐CoV‐2 spike glycoprotein was found to share 41 minimal immune determinants, that is, pentapeptides, with 27 human proteins that relate to oogenesis, uterine receptivity, decidualization, and placentation. All the shared pentapeptides that we identified, with the exception of four, are also present in SARS‐CoV‐2 spike glycoprotein–derived epitopes that have been experimentally validated as immunoreactive.

Role of microRNAs in etiology of azoospermia and their application as non-invasive biomarkers in diagnosis of azoospermic patients

Azoospermia is a common cause of male infertility without any sperm in the semen and consists of ∼1% of all males and ∼15% of infertile ones. Currently, no accurate non-invasive diagnostic method exists for patients with azoospermia and testis biopsy is mandatory to determine if any spermatozoa exist in the testes. Studies have clarified that the expression of some distinct microRNAs shows alterations in azoospermic patients. MicroRNAs play critical roles during spermatogenesis and their dysregulation can defect this process. Here, we review studied microRNAs involved in the pathogenesis of azoospermia and their target genes. Moreover, we will imply the utility of seminal plasma microRNAs as non-invasive diagnostic biomarkers for azoospermia. We hope such studies could help patients with azoospermia in both diagnosis and treatment, in order that they could father their own biological children.

Analysis of mouse male germ cell-specific or -predominant Tex13 family genes encoding proteins with transcriptional repressor activity

Mammalian spermatogenesis is a highly organized process with successive mitotic, meiotic, and postmeiotic phases. This unique developmental process is characterized by the involvement of spermatogenic cell-specific genes. In this study, we identified and investigated testis expressed gene 13 (Tex13) family genes, consisting of Tex13a, Tex13b, Tex13c1, and Tex13d, in mice. All of these genes were transcribed specifically or predominantly in male germ cells, and their transcription was developmentally regulated. Proteins encoded by the Tex13 genes were predicted to have a conserved domain of ~ 145 amino acids. Tex13a, Tex13c1, and Tex13d encode additional C-terminal regions containing a short conserved sequence termed a zinc finger-RAN binding protein 2 (zf-RanBP2) or zf-RanBP2-like domain. As TEX13B reportedly has transcriptional repressor activity, we examined the effect of the TEX13 proteins on transcriptional regulation using a reporter assay. All of the TEX13 proteins exhibited transcriptional repressor activity. This activity was revealed to reside in the TEX13B-corresponding regions of TEX13A, TEX13C1, and TEX13D. Further, we found that the C-terminal regions of TEX13A, TEX13C1, and TEX13D also have inhibitory activities. These results suggest that male germ cell-specific or -predominant TEX13 proteins commonly function in transcriptional repression as transcription cofactors and/or RNA binding proteins.

Nutrient restriction synergizes with retinoic acid to induce mammalian meiotic initiation in vitro

The molecular machinery and chromosome structures carrying out meiosis are frequently conserved from yeast to mammals. However, signals initiating meiosis appear divergent: while nutrient restriction induces meiosis in the yeast system, retinoic acid (RA) and its target Stra8 have been shown to be necessary but not sufficient to induce meiotic initiation in mammalian germ cells. Here, we use primary culture of mouse undifferentiated spermatogonia without the support of gonadal somatic cells to show that nutrient restriction in combination with RA is sufficient to induce Stra8- and Spo11-dependent meiotic gene and chromosome programs that recapitulate the transcriptomic and cytologic features of in vivo meiosis. We demonstrate that neither nutrient restriction nor RA alone exerts these effects. Moreover, we identify a distinctive network of 11 nutrient restriction-upregulated transcription factor genes, which are associated with early meiosis in vivo and whose expression does not require RA. Our study proposes a conserved model, in which nutrient restriction induces meiotic initiation by upregulating key transcription factor genes for the meiotic gene program and provides an in vitro platform for meiotic induction that could facilitate research and haploid gamete production.

Genetic mutations contributing to non-obstructive azoospermia

Non-obstructive azoospermia is a distinct diagnosis within male infertility in which no sperm is found in the ejaculate as a result of spermatogenesis failure. Because of the increased prevalence of genetic abnormalities in men with non-obstructive azoospermia, male infertility guidelines recommend screening for karyotype abnormalities and Y chromosome microdeletions in this population. Numerous karyotype abnormalities may be present resulting in impaired spermatogenesis, including: Klinefelter syndrome, translocations, and deletions. Y chromosome microdeletions of the AZFa, AZFb, AZFc subregions all can also result in non-obstructive azoospermia with the possibility of sperm being present if only the AZFc subregion is deleted. While these are the two genetic tests recommended by the guidelines, nearly 50%-80% of non-obstructive azoospermia has no identifiable cause and is deemed idiopathic. Several other genetic defects can lead to non-obstructive azoospermia including Kallmann syndrome, mild androgen insensitivity syndrome, and TEX11. While many additional candidate genes have been proposed, many have yet to be verified or are so infrequent in the population that screening is cost-ineffective. Much research is still required in the genetics of non-obstructive azoospermia and will require multi-institutional initiatives to better understand the genetics of condition.

Stimulated by retinoic acid gene 8 (STRA8) interacts with the germ cell specific bHLH factor SOHLH1 and represses c-KIT expression in vitro

STRA8 (Stimulated by Retinoic Acid Gene 8) controls the crucial decision of germ cells to engage meiotic division up and down‐regulating genes involved in the meiotic programme. It has been proven as an amplifier of genes involved in cell cycle control and chromosome events, however, how STRA8 functions as negative regulator are not well understood. In this study, we demonstrate that STRA8 can interact with itself and with other basic Helix‐Loop‐Helix (bHLH) transcription factors through its HLH domain and that this domain is important for its ability to negatively interfere with the Ebox‐mediated transcriptional activity of bHLH transcription factors. Significantly, we show that STRA8 interacts with TCF3/E47, a class I bHLH transcription factors, and with SOHLH1, a gonadal‐specific bHLH, in male germ cells obtained from prepuberal mouse testis. We demonstrated that STRA8, indirectly, is able to exert a negative control on the SOHLH1‐dependent stimulation of c‐KIT expression in late differentiating spermatogonia and preleptotene spermatocytes. Although part of this results were obtained only ‘in vitro’, they support the notion that STRA8 interacting with different transcription factors, besides its established role as ‘amplifier’ of meiotic programme, is able to finely modulate the balance between spermatogonia proliferation, differentiation and acquisition of meiotic competence.

Molecular genetics of infertility: loss-of-function mutations in humans and corresponding knockout/mutated mice

BACKGROUND

Infertility is a major issue in human reproductive health, affecting an estimated 15% of couples worldwide. Infertility can result from disorders of sex development (DSD) or from reproductive endocrine disorders (REDs) with onset in infancy, early childhood or adolescence. Male infertility, accounting for roughly half of all infertility cases, generally manifests as decreased sperm count (azoospermia or oligozoospermia), attenuated sperm motility (asthenozoospermia) or a higher proportion of morphologically abnormal sperm (teratozoospermia). Female infertility can be divided into several classical types, including, but not limited to, oocyte maturation arrest, premature ovarian insufficiency (POI), fertilization failure and early embryonic arrest. An estimated one half of infertility cases have a genetic component; however, most genetic causes of human infertility are currently uncharacterized. The advent of high-throughput sequencing technologies has greatly facilitated the identification of infertility-associated gene mutations in patients over the past 20 years.

OBJECTIVE AND RATIONALE

This review aims to conduct a narrative review of the genetic causes of human infertility. Loss-of-function mutation discoveries related to human infertility are summarized and further illustrated in tables. Corresponding knockout/mutated animal models of causative genes for infertility are also introduced.

SEARCH METHODS

A search of the PubMed database was performed to identify relevant studies published in English. The term 'mutation' was combined with a range of search terms related to the core focus of the review: infertility, DSD, REDs, azoospermia or oligozoospermia, asthenozoospermia, multiple morphological abnormalities of the sperm flagella (MMAF), primary ciliary dyskinesia (PCD), acephalic spermatozoa syndrome (ASS), globozoospermia, teratozoospermia, acrosome, oocyte maturation arrest, POI, zona pellucida, fertilization defects and early embryonic arrest.

OUTCOMES

Our search generated ∼2000 records. Overall, 350 articles were included in the final review. For genetic investigation of human infertility, the traditional candidate gene approach is proceeding slowly, whereas high-throughput sequencing technologies in larger cohorts of individuals is identifying an increasing number of causative genes linked to human infertility. This review provides a wide panel of gene mutations in several typical forms of human infertility, including DSD, REDs, male infertility (oligozoospermia, MMAF, PCD, ASS and globozoospermia) and female infertility (oocyte maturation arrest, POI, fertilization failure and early embryonic arrest). The causative genes, their identified mutations, mutation rate, studied population and their corresponding knockout/mutated mice of non-obstructive azoospermia, MMAF, ASS, globozoospermia, oocyte maturation arrest, POI, fertilization failure and early embryonic arrest are further illustrated by tables. In this review, we suggest that (i) our current knowledge of infertility is largely obtained from knockout mouse models; (ii) larger cohorts of clinical cases with distinct clinical characteristics need to be recruited in future studies; (iii) the whole picture of genetic causes of human infertility relies on both the identification of more mutations for distinct types of infertility and the integration of known mutation information; (iv) knockout/mutated animal models are needed to show whether the phenotypes of genetically altered animals are consistent with findings in human infertile patients carrying a deleterious mutation of the homologous gene; and (v) the molecular mechanisms underlying human infertility caused by pathogenic mutations are largely unclear in most current studies.

WILDER IMPLICATIONS

It is important to use our current understanding to identify avenues and priorities for future research in the field of genetic causes of infertility as well as to apply mutation knowledge to risk prediction, genetic diagnosis and potential treatment for human infertility.

Conversion from spermatogonia to spermatocytes: Extracellular cues and downstream transcription network

Spermatocyte (spc) formation from spermatogonia (spg) differentiation is the first step of spermatogenesis which produces prodigious spermatozoa for a lifetime. After decades of studies, several factors involved in the functioning of a mouse were discovered both inside and outside spg. Considering the peculiar expression and working pattern of each factor, this review divides the whole conversion of spg to spc into four consecutive development processes with a focus on extracellular cues and downstream transcription network in each one. Potential coordination among Dmrt1, Sohlh1/2 and BMP families mediates Ngn3 upregulation, which marks progenitor spg, with other changes. After that, retinoic acid (RA), as a master regulator, promotes A1 spg formation with its helpers and Sall4. A1-to-B spg transition is under the control of Kitl and impulsive RA signaling together with early and late transcription factors Stra8 and Dmrt6. Finally, RA and its responsive effectors conduct the entry into meiosis. The systematic transcription network from outside to inside still needs research to supplement or settle the controversials in each process. As a step further ahead, this review provides possible drug targets for infertility therapy by cross-linking humans and mouse model.

Intronic variation of the SOHLH2 gene confers risk to male reproductive impairment

OBJECTIVE

To evaluate whether SOHLH2 intronic variation contributes to the genetic predisposition to male infertility traits, including severe oligospermia (SO) and different nonobstructive azoospermia (NOA) clinical phenotypes.

DESIGN

Genetic association study.

SETTING

Not applicable.

PATIENT(S)

Five hundred five cases (455 infertile patients diagnosed with NOA and 50 with SO) and 1,050 healthy controls from Spain and Portugal.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genomic DNA extraction from peripheral blood mononuclear cells, genotyping of the SOHLH2 polymorphisms rs1328626 and rs6563386 using the TaqMan allelic discrimination technology, case-control association analyses using logistic regression models, and exploration of functional annotations in publicly available databases.

RESULT(S)

Evidence of association was observed for both rs6563386 with SO and rs1328626 with unsuccessful sperm retrieval after testicular sperm extraction (TESE-) in the context of NOA. A dominant effect of the minor alleles was suggested in both associations, either when the subset of patients with the manifestation were compared against the control group (rs6563386/SO: P=.021, odds ratio [OR] = 0.51; rs1328626/TESE-: P=.066, OR = 1.46) or against the group of patients without the manifestation (rs6563386/SO: P=.014, OR = 0.46; rs1328626/TESE-: P=.012, OR = 2.43). The haplotype tests suggested a combined effect of both polymorphisms. In silico analyses evidenced that this effect could be due to alteration of the isoform population.

CONCLUSION(S)

Our data suggest that intronic variation of SOHLH2 is associated with spermatogenic failure. The genetic effect is likely caused by different haplotypes of rs6563386 and rs1328626, which may predispose to SO or TESE- depending on the specific allelic combination.

FIGLA, LHX8 and SOHLH1 transcription factor networks regulate mouse oocyte growth and differentiation

Germ-cell transcription factors control gene networks that regulate oocyte differentiation and primordial follicle formation during early, postnatal mouse oogenesis. Taking advantage of gene-edited mice lacking transcription factors expressed in female germ cells, we analyzed global gene expression profiles in perinatal ovaries from wildtype, FiglaNull, Lhx8Null and Sohlh1Null mice. Figla deficiency dysregulates expression of meiosis-related genes (e.g. Sycp3, Rad51, Ybx2) and a variety of genes (e.g. Nobox, Lhx8, Taf4b, Sohlh1, Sohlh2, Gdf9) associated with oocyte growth and differentiation. The absence of FIGLA significantly impedes meiotic progression, causes DNA damage and results in oocyte apoptosis. Moreover, we find that FIGLA and other transcriptional regulator proteins (e.g. NOBOX, LHX8, SOHLH1, SOHLH2) are co-expressed in the same subset of germ cells in perinatal ovaries and Figla ablation dramatically disrupts KIT, NOBOX, LHX8, SOHLH1 and SOHLH2 abundance. In addition, not only do FIGLA, LHX8 and SOHLH1 cross-regulate each other, they also cooperate by direct interaction with each during early oocyte development and share downstream gene targets. Thus, our findings substantiate a major role for FIGLA, LHX8 and SOHLH1 as multifunctional regulators of networks necessary for oocyte maintenance and differentiation during early folliculogenesis.

Developmental underpinnings of spermatogonial stem cell establishment

BACKGROUND

The germline serves as a conduit for transmission of genetic and epigenetic information from one generation to the next. In males, spermatozoa are the final carriers of inheritance and their continual production is supported by a foundational population of spermatogonial stem cells (SSCs) that forms from prospermatogonial precursors during the early stages of neonatal development. In mammals, the timing for which SSCs are specified and the underlying mechanisms guiding this process remain to be completely understood.

OBJECTIVES

To propose an evolving concept for how the foundational SSC population is established.

MATERIALS AND METHODS

This review summarizes recent and historical findings from peer-reviewed publications made primarily with mouse models while incorporating limited studies from humans and livestock.

RESULTS AND CONCLUSION

Establishment of the SSC population appears to follow a biphasic pattern involving a period of fate programming followed by an establishment phase that culminates in formation of the SSC population. This model for establishment of the foundational SSC population from precursors is anticipated to extend across mammalian species and include humans and livestock, albeit on different timescales.

Loss of Cx43 in Murine Sertoli Cells Leads to Altered Prepubertal Sertoli Cell Maturation and Impairment of the Mitosis-Meiosis Switch

Male factor infertility is a problem in today’s society but many underlying causes are still unknown. The generation of a conditional Sertoli cell (SC)-specific connexin 43 (Cx43) knockout mouse line (SCCx43KO) has provided a translational model. Expression of the gap junction protein Cx43 between adjacent SCs as well as between SCs and germ cells (GCs) is known to be essential for the initiation and maintenance of spermatogenesis in different species and men. Adult SCCx43KO males show altered spermatogenesis and are infertile. Thus, the present study aims to identify molecular mechanisms leading to testicular alterations in prepubertal SCCx43KO mice. Transcriptome analysis of 8-, 10- and 12-day-old mice was performed by next-generation sequencing (NGS). Additionally, candidate genes were examined by qRT-PCR and immunohistochemistry. NGS revealed many significantly differentially expressed genes in the SCCx43KO mice. For example, GC-specific genes were mostly downregulated and found to be involved in meiosis and spermatogonial differentiation (e.g., Dmrtb1, Sohlh1). In contrast, SC-specific genes implicated in SC maturation and proliferation were mostly upregulated (e.g., Amh, Fshr). In conclusion, Cx43 in SCs appears to be required for normal progression of the first wave of spermatogenesis, especially for the mitosis-meiosis switch, and also for the regulation of prepubertal SC maturation.

Silica nanoparticles exacerbates reproductive toxicity development in high-fat diet-treated Wistar rats

To demonstrate the combined adverse effect and the mechanism of silica nanoparticles (SiNPs) with 57.66 ± 7.30 nm average diameter and high-fat diet (HFD) on Wistar rats, 60 male Wistar rats were randomly divided into six groups (n = 10): Control group, SiNPs group, HFD group, 2 mg kg^-1 SiNPs + HFD group, 5 mg kg^-1 SiNPs + HFD group and 10 mg kg^-1 SiNPs + HFD group. HFD was administrated for 2 weeks for the rats in advance and SiNPs were supplied every 3 d for 48 d subsequently. The present study illustrated that both HFD and SiNPs could decrease sperm concentration, mobility rates, increase abnormality rates, damage testicular structure, reduce spermatogonium numbers and spermatoblast numbers, reduce ATP levels, and affect expression of regulatory factors for meiosis in testis. HFD and SiNPs further damaged the sperm and lowered the ATP level and expression of factors associated with meiotic signaling pathway compared with the HFD without SiNPs in testicular tissue of Wistar rats. These results suggested that SiNPs significantly promoted reproductive toxicity induced by HFD in Wistar rats, which provides novel experimental evidence and an explanation for magnified reproductive toxicity triggered by SiNPs in HFD rats.

Genetics of Primary Ovarian Insufficiency in the Next-Generation Sequencing Era

Primary ovarian insufficiency (POI) is characterized by amenorrhea, increased follicle-stimulating hormone (FSH) levels, and hypoestrogenism, leading to infertility before the age of 40 years. Elucidating the cause of POI is a key point for diagnosing and treating affected women. Here, we review the genetic etiology of POI, highlighting new genes identified in the last few years using next-generation sequencing (NGS) approaches. We searched the MEDLINE/PubMed, Cochrane, and Web of Science databases for articles published in or translated to English. Several genes were found to be associated with POI genetic etiology in humans and animal models (SPIDR, BMPR2, MSH4, MSH5, GJA4, FANCM, POLR2C, MRPS22, KHDRBS1, BNC1, WDR62, ATG7/ATG9, BRCA2, NOTCH2, POLR3H, and TP63). The heterogeneity of POI etiology has been revealed to be remarkable in the NGS era, and discoveries have indicated that meiosis and DNA repair play key roles in POI development.

Weighted Single-Step Genome-Wide Association Study of Semen Traits in Holstein Bulls of China

Efficient production of high-quality semen is a crucial trait in the dairy cattle breeding due to the widespread use of artificial insemination. However, the genetic architecture (e.g., distributions of causal variants and their corresponding effects) underlying such semen quality traits remains unclear. In this study, we performed genome-wide association studies to identify genes associated with five semen quality traits in Chinese Holstein population, including ejaculate volume, progressive sperm motility, sperm concentration, number of sperm, and number of progressive motile sperm. Our dataset consisted of 2,218 Holstein bulls in China with full pedigree information, representing 12 artificial insemination centers, with 1,508 genotyped using the Illumina BovineSNP50 BeadChip. We used a weighted single-step genome-wide association method with 10 adjacent Single nucleotide polymorphisms (SNPs) as sliding windows, which can make use of individuals without genotypes. We considered the top 10 genomic regions in terms of their explained genomic variants as candidate window regions for each trait. In total, we detected 36 window regions related to one or multiple semen traits across 19 chromosomes. Promising candidate genes of PSMB5, PRMT5, ACTB, PDE3A, NPC1, FSCN1, NR5A2, IQCG, LHX8, and DMRT1 were identified in these window regions for these five semen traits. Our findings provided a solid basis for further research into genetic mechanisms underlying semen quality traits, which may contribute to their accurate genomic prediction in Chinese Holstein population.

Mechanisms regulating mammalian spermatogenesis and fertility recovery following germ cell depletion

Mammalian spermatogenesis is a highly complex multi-step process sustained by a population of mitotic germ cells with self-renewal potential known as spermatogonial stem cells (SSCs). The maintenance and regulation of SSC function are strictly dependent on a supportive niche that is composed of multiple cell types. A detailed appreciation of the molecular mechanisms underpinning SSC activity and fate is of fundamental importance for spermatogenesis and male fertility. However, different models of SSC identity and spermatogonial hierarchy have been proposed and recent studies indicate that cell populations supporting steady-state germline maintenance and regeneration following damage are distinct. Importantly, dynamic changes in niche properties may underlie the fate plasticity of spermatogonia evident during testis regeneration. While formation of spermatogenic colonies in germ-cell-depleted testis upon transplantation is a standard assay for SSCs, differentiation-primed spermatogonial fractions have transplantation potential and this assay provides readout of regenerative rather than steady-state stem cell capacity. The characterisation of spermatogonial populations with regenerative capacity is essential for the development of clinical applications aimed at restoring fertility in individuals following germline depletion by genotoxic treatments. This review will discuss regulatory mechanisms of SSCs in homeostatic and regenerative testis and the conservation of these mechanisms between rodent models and man.

Yes-associated protein expression in germ cells is dispensable for spermatogenesis in mice

Yes-associated protein (YAP), a key effector of the Hippo signaling pathway, is expressed in the nucleus of spermatogonia in mice, suggesting a potential role in spermatogenesis. Here, we report the generation of a conditional knockout mouse model (Yap^flox/flox ; Ddx4^cre/+ ) that specifically inactivates Yap in the germ cells. The inactivation of Yap in spermatogonia was found to be highly efficient in this model. The loss of Yap in the germ cells had no observable effect on spermatogenesis in vivo. Histological examination of the testes showed no structural differences between mutant animals and age-matched Yap^flox/flox controls, nor was any differences detected in gonadosomatic index, expression of germ cell markers or sperm counts. Cluster-forming assay using undifferentiated spermatogonia, including spermatogonial stem cells (SSCs), also showed that YAP is dispensable for SSC cluster formation in vitro. However, an increase in the expression of spermatogenesis and oogenesis basic helix-loop-helix 1 (Sohlh1) and neurogenin 3 (Ngn3) was observed in clusters derived from Yap^flox/flox ; Ddx4^cre/+ animals. Taken together, these results suggest that YAP fine-tunes the expression of genes associated with spermatogonial fate commitment, but that its loss is not sufficient to alter spermatogenesis in vivo.

Testicular endothelial cells promote self-renewal of spermatogonial stem cells in rats†

Spermatogonial stem cells (SSCs) are the basis of spermatogenesis in male due to their capability to multiply in numbers by self-renewal and subsequent meiotic processes. However, as SSCs are present in a very small proportion in the testis, in vitro proliferation of undifferentiated SSCs will facilitate the study of germ cell biology. In this study, we investigated the effectiveness of various cell lines as a feeder layer for rat SSCs. Germ cells enriched for SSCs were cultured on feeder layers including SIM mouse embryo-derived thioguanine and ouabain-resistant cells, C166 cells, and mouse and rat testicular endothelial cells (TECs) and their stem cell potential for generating donor-derived colonies and offspring was assessed by transplantation into recipient testes. Rat germ cells cultured on TECs showed increased mRNA and protein levels of undifferentiated spermatogonial markers. Rat SSCs derived from these germ cells underwent spermatogenesis and generated offspring when transplanted into recipients. Collectively, TECs can serve as an effective feeder layer that enhances the proliferative and self-renewal capacity of cultured rat SSCs while preserving their stemness properties.

Developmental kinetics and transcriptome dynamics of stem cell specification in the spermatogenic lineage

Continuity, robustness, and regeneration of cell lineages relies on stem cell pools that are established during development. For the mammalian spermatogenic lineage, a foundational spermatogonial stem cell (SSC) pool arises from prospermatogonial precursors during neonatal life via mechanisms that remain undefined. Here, we mapped the kinetics of this process in vivo using a multi-transgenic reporter mouse model, in silico with single-cell RNA sequencing, and functionally with transplantation analyses to define the SSC trajectory from prospermatogonia. Outcomes revealed that a heterogeneous prospermatogonial population undergoes dynamic changes during late fetal and neonatal development. Differential transcriptome profiles predicted divergent developmental trajectories from fetal prospermatogonia to descendant postnatal spermatogonia. Furthermore, transplantation analyses demonstrated that a defined subset of fetal prospermatogonia is fated to function as SSCs. Collectively, these findings suggest that SSC fate is preprogrammed within a subset of fetal prospermatogonia prior to building of the foundational pool during early neonatal development.

In neonatal testes, prospermatogonia generate both spermatogonia for the first wave of spermatogenesis and spermatogonial stem cells (SSCs) for maintenance of spermatogenesis in males. Here the authors characterize the development of mouse SSCs from prospermatogonia using single-cell RNA-seq and transplantation assays.

REC114 Partner ANKRD31 Controls Number, Timing, and Location of Meiotic DNA Breaks

Double-strand breaks (DSBs) initiate the homologous recombination that is crucial for meiotic chromosome pairing and segregation. Here, we unveil mouse ANKRD31 as a lynchpin governing multiple aspects of DSB formation. Spermatocytes lacking ANKRD31 have altered DSB locations and fail to target DSBs to the pseudoautosomal regions (PARs) of sex chromosomes. They also have delayed and/or fewer recombination sites but, paradoxically, more DSBs, suggesting DSB dysregulation. Unrepaired DSBs and pairing failures-stochastic on autosomes, nearly absolute on X and Y-cause meiotic arrest and sterility in males. Ankrd31-deficient females have reduced oocyte reserves. A crystal structure defines a pleckstrin homology (PH) domain in REC114 and its direct intermolecular contacts with ANKRD31. In vivo, ANKRD31 stabilizes REC114 association with the PAR and elsewhere. Our findings inform a model in which ANKRD31 is a scaffold anchoring REC114 and other factors to specific genomic locations, thereby regulating DSB formation.

SOHLHs Might Be Gametogenesis-Specific bHLH Transcriptional Regulation Factors in Crassostrea gigas

The self-renewal and differentiation of germ cells are essential for gametogenesis and reproduction. In mammals, the transcription factors SOHLH1 and SOHLH2, two members of the bHLH family, are specifically expressed in the gonads, and play an important role in spermatocyte and oocyte differentiation. In our previous study, we performed a phylogenetic analysis of the Lophotrochozoa bHLH genes, and two Sohlh were identified in the Pacific oyster Crassostrea gigas. Based on the genomes of other species that have complete genomic information, we further analyzed the phylogenetics of the Sohlh in this study. The results indicate that the Sohlh are ancient genes that were lost in many species during evolution, including in some invertebrates, and lower vertebrates. The phylogenetic tree shows that Sohlh1 and Sohlh2 are located in different scaffolds and that they have low similarity, suggesting early separation in invertebrates. We used RNA-seq and RT-PCR to examine the mRNA expression of the Sohlh in C. gigas (termed Cg-Sohlh), we found that Cg-Sohlh1, and Cg-Sohlh2 are specifically expressed in the gonads. During gonadal development, the mRNA expression levels of both genes increased from the proliferative stage and reached the highest level at the growth stage (P < 0.05). Then, the expression level decreased until the resting stage. In addition, immunohistochemistry was used to determine that the Cg-SOHLH1 protein was specifically expressed in the spermatogonia and spermatocytes. Cg-Sohlh2 mRNA was expressed in both the male and female gonads, while Cg-Sohlh1 mRNA was highly expressed in the female gonads at all developmental stages except for the resting stage. These data indicate that Cg-SOHLH might be gonad-specific regulatory factors, similar to mammalian SOHLH, and that Cg-SOHLH1 might be involved in spermatogonial differentiation. This study lays the foundation to further determine the functional role of SOHLH in mollusk gametogenesis and provides a foundation to better understand the regulatory mechanism of gametogenesis in invertebrates.

Single cell RNA-sequencing identified Dec2 as a suppressive factor for spermatogonial differentiation by inhibiting Sohlh1 expression

Gonocyte-to-spermatogonia transition is a critical fate determination process to initiate sperm production throughout the lifecycle. However, the molecular dynamics of this process has not been fully elucidated mainly due to the asynchronized differentiation stages of neonatal germ cells. In this study, we employed single cell RNA sequencing analyses of P1.5–5.5 germ cells to clarify the temporal dynamics of gene expression during gonocyte-to-spermatogonia transition. The analyses identified transcriptional modules, one of which regulates spermatogonial gene network in neonatal germ cells. Among them, we identified Dec2, a bHLH-type transcription factor, as a transcriptional repressor for a spermatogonial differentiation factor Sohlh1. Deficiency of Dec2 in mice induces significant reduction of undifferentiated spermatogonia, and transplantation assay using Dec2-depleted cells also demonstrated the impaired efficiency of engraftment, suggesting its role in maintaining spermatogonial stem cells (SSCs). Collectively, this study revealed the intrinsic role of a new SSC factor Dec2, which protects germ cells from inadequate differentiation during neonatal testis development.

SOX30 is a prognostic biomarker and chemotherapeutic indicator for advanced-stage ovarian cancer

New potential biomarkers and therapeutic targets for ovarian cancer should be identified. The amplification in chromosomal region 5q31-5q35.3 exhibits the strongest correlation with overall survival (OS) of ovarian cancer. SOX30 coincidentally located at this chromosomal region has been determined as a new important tumor suppressor. However, the prognostic value, role and mechanism of SOX30 in ovarian cancer are unexplored. Here, we reveal that SOX30 is frequently overexpressed in ovarian cancer tissues and is associated with clinical stage and metastasis of ovarian cancer patients. High SOX30 expression predicts better OS and acts as an independent prognostic factor in advanced-stage patients, but is not associated with OS in early-stage patients. Based on the survival analyses, the advanced-stage patients with high SOX30 expression can receive platin- and/or taxol-based chemotherapy, whereas they should not receive chemotherapy containing gemcitabine or topotecan. Functionally, SOX30 strongly inhibits tumor cell migration and invasion in intro and suppresses tumor metastasis in vivo. SOX30 regulates some markers (E-CADHERIN, FIBRONECTIN, N-CADHERIN and VIMENTIN) and prevents the characteristics of epithelial-mesenchymal transition (EMT). SOX30 transcriptionally regulates the expression of E-CADHERIN, FIBRONECTIN and N-CADHERIN by binding to their promoters. Restoration of E-CADHERIN and/or N-CADHERIN when overexpressing SOX30 significantly reduces the anti-metastatic role of SOX30. Indeed, chemotherapy treatment containing platin or gemcitabine combined with SOX30 expression influences tumor cell metastasis and the survival of nude mice differently, which is closely associated with EMT. In conclusion, SOX30 antagonizes tumor metastasis by preventing EMT process that can be used to predict survival and incorporated into chemotherapeutics of advanced-stage ovarian cancer patients.

Sohlh1 is required for synaptonemal complex formation by transcriptionally regulating meiotic genes during spermatogenesis in mice

Gonad-specific transcription factor spermatogenesis- and oogenesis-specific helix-loop-helix transcription factor 1 (SOHLH1) plays a key role in the transcriptional regulation of the expression of differentiating spermatogonial genes. However, its role in spermatocytes (meiotic male germ cells) remains largely unknown. In this study, Sohlh1 knockout (KO) male mice displayed meiotic defects at the zygotene stage during spermatogenesis. Microarray analyses identified 66 upregulated genes and 139 downregulated genes in Sohlh1 KO testes compared with those in wild-type testes at postnatal Day 7.5. Among many of the downregulated genes, Sycp1 and Sycp3, which encode synaptonemal complex proteins 1 and 3 (SYCP1 and SYCP3), respectively, were significantly reduced in Sohlh1 knockout mice. Transmission electron microscopy revealed no formation of the synaptonemal complex in Sohlh1 KO spermatocytes. Luciferase reporter and chromatin-immunoprecipitation assays demonstrated that SOHLH1 enhanced the expression of the Sycp1 and Sycp3 genes by binding the -1276, -708, and -94 basepairs (bp) E-boxes upstream of the Sycp1 promoter and the -64 and -43 bp E-boxes upstream of the Sycp3 promoter. Our data suggest that SOHLH1 transcriptionally regulates the expression of many target genes critical for the meiotic phase of spermatogenesis.

SOX30 specially prevents Wnt-signaling to suppress metastasis and improve prognosis of lung adenocarcinoma patients

BACKGROUND

Different histological subtypes of non-small cell lung cancer (NSCLC) show different molecular characteristics and responses to therapeutic strategy. Identification of specific gene, clarification of its special roles and molecular mechanisms are crucial for developing new therapeutic approach for particular subtype patients.

METHODS

Surgical specimens of 540 NSCLC patients were recruited. Immunohistochemistry was used to detect SOX30 expression, and correlations with clinical parameters were analyzed. Functional experiments and gene ontology analysis were performed to investigate roles of SOX30. Network analysis, TOP/FOP-Flash assays, luciferase reporter assays and ChIP-PCR assays were performed to determine the mechanism. Survival analyses were calculated by Kaplan-Meier and Cox regression. Recovery experiment was investigated the importance of the target of SOX30.

RESULTS

SOX30 expression is closely associated with histological types of NSCLC, and metastasis of adenocarcinoma (ADC) patients but not of squamous cell carcinoma (SCC) patients. SOX30 strongly inhibits cancer cell migration and invasion in ADC cell lines, whrereas not affects cell migration and invasion in SCC cell lines. The genes associated with SOX30 preferentially enrich in metastasis process and Wnt-signaling in only ADC patients. Consistently, SOX30 is negatively associated with the expression of Wnt-signaling and metastasis-related gene CTNNB1 (β-catenin) in ADC, but not in SCC. At the molecular level, SOX30 represses Wnt-signaling by directly transcriptional inhibition of CTNNB1 in ADC, and also not in SCC. In the clinical, SOX30 is a favorable and independent prognostic factor in ADC patients, whereas is an unfavorable and independent prognostic factor in SCC patients. Moreover, SOX30 expression is a double face early-stage prognostic biomarker in ADC and SCC patients. In addition, forcible restoration of CTNNB1 indeed can inhibit the anti-metastatic role of SOX30 in ADC patients.

CONCLUSIONS

In early-stage ADC patients, elevated SOX30 expression inhibits tumor-metastasis by directly binding to CTNNB1 promoter resulting in a favorable prognosis of these patients. However, in early-stage SCC patients, SOX30 has no inhibitory role on tumor-metastasis due to not binding to CTNNB1 promoter leading to an unfavorable prognosis of the patients. This study highlights a special role and prognostic value of SOX30 in ADC, providing a novel therapeutic target for particular subtype NSCLC patients.

Primordial follicle activation is affected by the absence of Sohlh1 in mice

Previous studies have reported that only primordial follicles and empty follicles can be found in 7.5 days postparturition (dpp) Sohlh1^-/- mouse ovaries and females are infertility. There appears to be a defect in follicle development during the primordial-to-primary follicle transition in Sohlh1^-/- mouse ovaries. However, detailed analyses of these phenomena have not been performed. In this study, we used Sohlh1^-/- transgenic mice to explore the role of Sohlh1 in folliculogenesis. The results showed that only primordial follicles and empty follicles can be observed in Sohlh1^-/- ovaries from 0.5 to 23.5 dpp. The expression of Foxo3 and FOXO3 was downregulated; nucleocytoplasmic shuttling of FOXO3 was normal in 7.5-dpp Sohlh1^+/+ but not Sohlh1^-/- ovaries; and primordial follicle activation (PFA) was not observed in 7.5-dpp Sohlh1^-/- mice. The expression levels of KIT, AKT, and P308-AKT were downregulated (p < 0.05), whereas that of P473-AKT was not significantly changed (p > 0.05). The KIT/PI3K/AKT pathway was inhibited. Furthermore, we conducted a dual luciferase assay and chromatin immunoprecipitation. The results showed that SOHLH1 can upregulate the Kit gene by binding to the -3698 bp E-box motif. The absence of Sohlh1 may affect PFA in mouse ovaries via downregulation of Kit and inhibition of the KIT/PI3K/AKT pathway.

A comparative transcriptomic study on developmental gonads provides novel insights into sex change in the protandrous black porgy (Acanthopagrus schlegelii)

Protandrous black porgy (Acanthopagrus schlegelii) is a popular and valuable commercial marine fish in China and East Asian countries. Controlling and managing its breeding has been an imperative step towards obtaining a sustainable supply of this fish in aquaculture production systems. Therefore, study on the molecular mechanisms of sex change in black porgy has both scientific and commercial importance. Previously, we identified some candidate genes related to sex determination and differentiation from a high-quality genome assembly of the black porgy. In the present study, transcriptome sequencing of developmental gonads (including testis, ovotestis and ovary) of black porgy was performed to further investigate the sex-change mechanisms. Our results showed that the highly expressed male-related genes (dmrt1, piwi1, piwi2, sox9, sox30 and amh) at the male phase were significantly down-regulated to a substantial degree at the intersexual stage, and the female-related genes (jnk1, vasa, wnt4, figla and foxl2) were distinctly up-regulated when the fish grows into a female adult, suggesting the potential roles of these genes in sex change of the black porgy. These data also support a previous hypothesis that the femaleness will be switched on when the testis is entering the degenerated stage through the diminished dmrt1 expression. Our transcriptome data provide a very useful genomic resource for future studies on sex change and practical aquaculture in the black porgy.

m6A mRNA modification regulates mammalian spermatogenesis

Mammalian spermatogenesis is a highly specialized differentiation process involving precise regulatory mechanisms at the transcriptional, posttranscriptional, and translational levels. Emerging evidence has shown that N⁶-methyladenosine (m⁶A), an epitranscriptomic regulator of gene expression, can influence pre-mRNA splicing, mRNA export, turnover, and translation, which are controlled in the male germline to ensure coordinated gene expression. In this review, we summarize the typical features of m⁶A RNA modification on mRNA during male germline development, and highlight the function of writers, erasers, and readers of m⁶A during mouse spermatogenesis.