A scRNA-seq Approach to Identifying Changes in Spermatogonial Stem Cell Gene Expression Following in vitro Culture

Spermatogenic Stem Cells: Core Biology, Defining Features, and Utilities

The actions of spermatogenic stem cells (SSCs) provide the foundation for continual spermatogenesis and regeneration of the cognate lineage following cytotoxic insult or transplantation. Several decades of research with rodent models have yielded knowledge about the core biology, morphological features, and molecular profiles of mammalian SSCs. Translation of these discoveries to utilities for human fertility preservation, improving animal agriculture, and wildlife conservation are actively being pursued. Here, we provide overviews of these aspects covering both historical and current states of understanding.

Sertoli cell-only syndrome: advances, challenges, and perspectives in genetics and mechanisms

Male infertility can be caused by quantitative and/or qualitative abnormalities in spermatogenesis, which affects men's physical and mental health. Sertoli cell-only syndrome (SCOS) is the most severe histological phenotype of male infertility characterized by the depletion of germ cells with only Sertoli cells remaining in the seminiferous tubules. Most SCOS cases cannot be explained by the already known genetic causes including karyotype abnormalities and microdeletions of the Y chromosome. With the development of sequencing technology, studies on screening new genetic causes for SCOS are growing in recent years. Directly sequencing of target genes in sporadic cases and whole-exome sequencing applied in familial cases have identified several genes associated with SCOS. Analyses of the testicular transcriptome, proteome, and epigenetics in SCOS patients provide explanations regarding the molecular mechanisms of SCOS. In this review, we discuss the possible relationship between defective germline development and SCOS based on mouse models with SCO phenotype. We also summarize the advances and challenges in the exploration of genetic causes and mechanisms of SCOS. Knowing the genetic factors of SCOS offers a better understanding of SCO and human spermatogenesis, and it also has practical significance for improving diagnosis, making appropriate medical decisions, and genetic counseling. For therapeutic implications, SCOS research, along with the achievements in stem cell technologies and gene therapy, build the foundation to develop novel therapies for SCOS patients to produce functional spermatozoa, giving them hope to father children.

Single-cell transcriptomics reveals male germ cells and Sertoli cells developmental patterns in dairy goats

Spermatogenesis holds considerable promise for human-assisted reproduction and livestock breeding based on stem cells. It occurs in seminiferous tubules within the testis, which mainly comprise male germ cells and Sertoli cells. While the developmental progression of male germ cells and Sertoli cells has been widely reported in mice, much less is known in other large animal species, including dairy goats. In this study, we present the data of single cell RNA sequencing (scRNA-seq) for 25,373 cells from 45 (pre-puberty), 90 (puberty), and 180-day-old (post-puberty) dairy goat testes. We aimed to identify genes that are associated with key developmental events in male germ cells and Sertoli cells. We examined the development of spermatogenic cells and seminiferous tubules from 15, 30, 45, 60, 75, 90, 180, and 240-day-old buck goat testes. scRNA-seq clustering analysis of testicular cells from pre-puberty, puberty, and post-puberty goat testes revealed several cell types, including cell populations with characteristics of spermatogonia, early spermatocytes, spermatocytes, spermatids, Sertoli cells, Leydig cells, macrophages, and endothelial cells. We mapped the timeline for male germ cells development from spermatogonia to spermatids and identified gene signatures that define spermatogenic cell populations, such as AMH, SOHLH1, INHA, and ACTA2. Importantly, using immunofluorescence staining for different marker proteins (UCHL1, C-KIT, VASA, SOX9, AMH, and PCNA), we explored the proliferative activity and development of male germ cells and Sertoli cells. Moreover, we identified the expression patterns of potential key genes associated with the niche-related key pathways in male germ cells of dairy goats, including testosterone, retinoic acid, PDGF, FGF, and WNT pathways. In summary, our study systematically investigated the elaborate male germ cells and Sertoli cells developmental patterns in dairy goats that have so far remained largely unknown. This information represents a valuable resource for the establishment of goat male reproductive stem cells lines, induction of germ cell differentiation in vitro, and the exploration of sequential cell fate transition for spermatogenesis and testicular development at single-cell resolution.