SMC1A is required for fate determinations of human spermatogonial stem cells and male fertility by interacting with YBX1 and stabilizing HMGA2 mRNA via an m5C modification.

Spermatogonial stem cells (SSCs) are required for initiating and maintaining normal spermatogenesis, and notably, they have significant applications in both reproductive and regenerative medicine owing to their great plasticity with de-differentiation and trans-differentiation potentials. Nevertheless, molecular mechanisms regulating human SSC fate determinations and male fertility remain elusive. Here we report for the first time that structural maintenance of chromosomes 1A (SMC1A) interacts with RNA-binding protein YBX1 to control fate decisions of human SSCs and an association exists between SMC1A dysfunction with male infertility. SMC1A/YBX1 complex stabilizes high mobility group AT-hook 2 (HMGA2) mRNA in an m5C modification-dependent manner to activate the G1/S phase transition, which ultimately mediates human SSC self-renewal and apoptosis. Transplantation of SSCs into the seminiferous tubules of recipient mice without male germ cells reveals that Smc1a silencing impairs SSC colonization and causes differentiation defect. Notably, Smc1a-conditional knockout (Smc1a-cKO) mice assume spermatogenesis disorder and obviously compromise male fertility. Single-cell transcriptomics demonstrates that Smc1a-cKO mice exhibit the downregulation of genes associated with mitosis, meiosis, and m5C regulation. Significantly, whole-exome sequencing (WES) of 2028 non-obstructive azoospermia (NOA) patients identify two deleterious SMC1A variants and one deleterious HMGA2 variant. SMC1A and HMGA2 expression levels were remarkably decreased in testicular tissues from NOA patients with spermatogenic failure compared to obstructive azoospermia (OA) patients with normal spermatogenesis. Collectively, our findings highlight the critical roles and a novel mechanism by the SMC1A/YBX1/HMGA2 axis in regulating human SSC fate decisions and male fertility via an m5C modification. This study is thus of the utmost significance because it would provide novel molecular mechanisms underlying fate determinations of adult stem cells and human spermatogenesis and it could offer network targets for gene targeting male infertility and other diseases.