Gatm ablation disrupts spermatogenesis by impairing ribosome biogenesis and coupling defective steroid biosynthesis to immunoglobulin silencing.

Background: Glycine amidinotransferase (GATM) catalyzes the rate-limiting step in creatine biosynthesis, a pathway essential for cellular energy buffering in tissues with high metabolic demands. While its roles in muscle and brain are well established, the function of GATM in testicular development and spermatogenesis remains largely unexplored.Methods: We generated a constitutive Gatm knockout mouse model using CRISPR/Cas9 technology. Comprehensive phenotypic characterization was performed through histological analysis, transmission electron microscopy (TEM), and transcriptomic profiling of whole testes and purified spermatozoa from Gatm, heterozygous (Gatm), and wild-type (WT) mice.Results: Gatm deficiency resulted in severe testicular atrophy, disorganized seminiferous tubules with epithelial thinning (reduced to 2-3 layers), and interstitial edema. Spermatogenesis was arrested, leading to dramatically reduced sperm density. Ultrastructural analysis revealed hallmark features of cacospermia, including mitochondrial depletion in the midpiece and nuclear vacuolization. Transcriptomic profiling demonstrated widespread dysregulation: testicular tissues showed downregulation of ribosome biogenesis and mitochondrial complex assembly pathways, whereas mature spermatozoa exhibited impaired steroid biosynthesis and ion transport. Notably, multiple immunoglobulin variable region genes (e.g., Ighv14-1, Igkv19-93) were completely transcriptionally silenced specifically in Gatm-deficient testes.Conclusion: Our findings establish GATM as a multifunctional regulator of spermatogenesis, integrating creatine-dependent energy metabolism with translational capacity, organelle architecture, and immune-related gene regulation. The coordinated disruption of mitochondrial and ribosomal pathways provides a novel mechanistic framework for understanding the metabolic origins of male infertility.