A Standardized Approach for Multispecies Purification of Mammalian Male Germ Cells by Mechanical Tissue Dissociation and Flow Cytometry

Dysregulation of N-glycosylation by Rpn1 knockout in spermatocytes induces male infertility via endoplasmic reticulum stress in mice

N-glycosylation protein modification plays a crucial regulatory role in numerous biological processes, although their contribution to male reproduction in mammals remains largely undefined. Here, we found that Ribophorin I (RPN1), a subunit of oligosaccharyltransferase complex, is indispensable for spermatogenesis in male germ cells. Germ cell-specific Rpn1 knockout results in significant inhibition of the progression of meiosis, consequently disrupting homologous chromosome pairing, meiotic recombination, and DNA double strand breaks repair during meiosis. N-glycoproteomic profiling revealed that glycosylation levels are reduced in endoplasmic reticulum-associated proteins, while functional analyses showed that Rpn1 deficiency could inhibit endoplasmic reticulum function and trigger endoplasmic reticulum stress during meiosis and increasing apoptosis levels in mice. These findings highlight the essential physiological functions of N-glycosylation modification in male spermatogenesis and expand our understanding of its role in male fertility.

Identification of YBX2 and TSKS As STK33 Interacting Proteins in Testicular Germ Cells

Spermiogenesis is a unique process, in which round spermatids undergo morphological changes to form spermatozoa. Serine/Threonine Kinase 33 (STK33), a member of the serine/threonine protein kinase family, plays a pivotal role in spermiogenesis, manifested by the infertile phenotype of Stk33 knockout mice and patients carrying STK33 mutations. To date, the mechanism by which STK33 promotes spermiogenesis is not fully understood. Here we aimed to identify germ cell-specific proteins that interact with STK33. Using immunoprecipitation and mass spectrometry, 13 proteins were identified that potentially interact with STK33 in testicular germ cells. By comparing the expression patterns of the candidate genes in testicular germ cells, we selected Y-Box Binding Protein 2 (YBX2) and Testis Specific Serine Kinase Substrate (TSKS) for validation. When co-expressed in cultured cells, TSKS was immunoprecipitated by STK33, and vice versa. Furthermore, STK33 was recruited to the TSKS foci, likely through interaction with TSKS. Although proximity ligation assay demonstrated that STK33 and YBX2 form the complex in germ cells, their interaction was not recapitulated in cultured cells. Phosphorylation assays showed that STK33 was unable to phosphorylate both YBX2 and TSKS in vitro. Overall, these results suggest that STK33 regulates spermiogenesis through TSKS and YBX2, which warrants further investigation in vivo.

Isolation of stage-specific spermatogenic cells by dynamic histone incorporation and removal in spermatogenesis

Due to the lack of an efficient in vitro spermatogenesis system, studies on mammalian spermatogenesis require the isolation of specific germ cell populations for further analyses. BSA gradient and elutriation have been used for several decades to purify testicular germ cells; more recently, flow cytometric cell sorting has become popular. Although each method has its advantages and disadvantages and is used depending on the purpose of the experiment, reliance on flow cytometric cell sorting is expected to be more prevalent because fewer cells can be managed. However, the currently used flow cytometric cell sorting method for testicular germ cells relies on karyotypic differences via DNA staining. Thus, it remains challenging to separate post-meiotic haploid cells (spermatids) according to their differentiation stage despite significant variations in morphology and chromatin state. In this study, we developed a method for finely separating testicular germ cells using VC mice carrying fluorescently tagged histones. This method enables the separation of spermatogonia, spermatocytes, and spermatids based on the intensity of histone fluorescence and cell size. Combined with a DNA staining dye, this method separates spermatids after elongation according to each spermiogenic stage. Although the necessity for a specific transgenic mouse line is less versatile, this method is expected to be helpful for the isolation of testicular germ cell populations because it is highly reproducible and independent of complex cell sorter settings and staining conditions.

Single-cell multi-omics sequencing of human spermatogenesis reveals a DNA demethylation event associated with male meiotic recombination

Human spermatogenesis is a highly ordered process; however, the roles of DNA methylation and chromatin accessibility in this process remain largely unknown. Here by simultaneously investigating the chromatin accessibility, DNA methylome and transcriptome landscapes using the modified single-cell chromatin overall omic-scale landscape sequencing approach, we revealed that the transcriptional changes throughout human spermatogenesis were correlated with chromatin accessibility changes. In particular, we identified a set of transcription factors and cis elements with potential functions. A round of DNA demethylation was uncovered upon meiosis initiation in human spermatogenesis, which was associated with male meiotic recombination and conserved between human and mouse. Aberrant DNA hypermethylation could be detected in leptotene spermatocytes of certain nonobstructive azoospermia patients. Functionally, the intervention of DNA demethylation affected male meiotic recombination and fertility. Our work provides multi-omics landscapes of human spermatogenesis at single-cell resolution and offers insights into the association between DNA demethylation and male meiotic recombination.

Attenuation of sodium arsenite mediated ovarian DNA damage, follicular atresia, and oxidative injury by combined application of vitamin E and C in post pubertal Wistar rats

Arsenic being a toxic metalloid ubiquitously persists in environment and causes several health complications including female reproductive anomalies. Epidemiological studies documented birth anomalies due to arsenic exposure. Augmented reactive oxygen species (ROS) generation and quenched antioxidant pool are foremost consequences of arsenic threat. On the contrary, Vitamin E (VE) and C (VC) are persuasive antioxidants and conventionally used in toxicity management. Present study was designed to explore the extent of efficacy of combined VE and VC (VEC) against Sodium arsenite (NaAsO2) mediated ovarian damage. Thirty-six female Wistar rats were randomly divided into three groups (Grs) and treated for consecutive 30 days; Gr I (control) was vehicle fed, Gr II (treated) was gavaged with NaAsO2 (3 mg/kg/day), Gr III (supplement) was provided with VE (400 mg/kg/day) & VC (200 mg/kg/day) along with NaAsO2. Marked histological alterations were evidenced by disorganization in oocyte, granulosa cells and zona pellucida layers in treated group. Considerable reduction of different growing follicles along with increased atretic follicles was noted in treated group. Altered activities ofΔ5 3β-Hydroxysteroid dehydrogenase and 17β-Hydroxysteroid dehydrogenase accompanied by reduced luteinizing hormone, follicle-stimulating hormone and estradiol levels were observed in treated animals. Irregular estrous cyclicity pattern was also observed due to NaAsO2 threat. Surplus ROS production affected ovarian antioxidant strata as evidenced by altered oxidative stress markers. Provoked oxidative strain further affects DNA status of ovary. However, supplementation with VEC caused notable restoration from such disparaging effects of NaAsO2 toxicities. Antioxidant and antiapoptotic attributes of those vitamins might be liable for such restoration.

Modern tools applied to classic structures: Approaches for mammalian male germ cell RNA granule research

First reported in the 1800s, germ cell granules are small nonmembrane bound RNA-rich regions of the cytoplasm. These sites of critical RNA processing and storage in the male germ cell are essential for proper differentiation and development and are present in a wide range of species from Caenorhabditis elegans through mammals. Initially characterized by light and electron microscopy, more modern techniques such as immunofluorescence and genetic models have played a major role in expanding our understanding of the composition of these structures. While these methods have given light to potential granule functions, much work remains to be done. The current expansion of imaging technologies and omics-scale analyses to germ cell granule research will drive the field forward considerably. Many of these methods, both current and upcoming, have considerable caveats and limitations that necessitate a holistic approach to the study of germ granules. By combining and balancing different techniques, the field is poised to elucidate the nature of these critical structures.

Protocol for isolation of spermatids from mouse testes

Post-meiotic spermatids become spermatozoa through developmental stages during spermiogenesis. Isolation of spermatid fractions is required to examine the change of protein expression during spermiogenesis. Here, we present a simple method to isolate spermatid fractions from mouse testes using unit gravity sedimentation in a BSA density gradient. Isolation of spermatid fractions can be used to analyze changes of transcript or protein during spermiogenesis.

For complete details on the use and execution of this protocol, please refer to Kim et al. (2020).

•

A protocol for isolation of post-meiotic spermatids from mouse testes

•

Preparation of single-cell suspension through serial digestion of testes

•

Analysis of cell fractions from unit gravity sedimentation in BSA density gradient

Unified single-cell analysis of testis gene regulation and pathology in five mouse strains

To fully exploit the potential of single-cell functional genomics in the study of development and disease, robust methods are needed to simplify the analysis of data across samples, time-points and individuals. Here we introduce a model-based factor analysis method, SDA, to analyze a novel 57,600 cell dataset from the testes of wild-type mice and mice with gonadal defects due to disruption of the genes Mlh3, Hormad1, Cul4a or Cnp. By jointly analyzing mutant and wild-type cells we decomposed our data into 46 components that identify novel meiotic gene-regulatory programs, mutant-specific pathological processes, and technical effects, and provide a framework for imputation. We identify, de novo, DNA sequence motifs associated with individual components that define temporally varying modes of gene expression control. Analysis of SDA components also led us to identify a rare population of macrophages within the seminiferous tubules of Mlh3-/- and Hormad1-/- mice, an area typically associated with immune privilege.