TMEM232 is required for the formation of sperm flagellum and male fertility in mice

Asthenoteratozoospermia is a major cause of male infertility. Thus far, the identified related genes can explain only a small share of asthenoteratozoospermia cases, suggesting the involvement of other genes. The transmembrane protein TMEM232 is highly expressed in mouse testes. In the present study, to determine its function of TMEM232 in testes, we constructed a Tmem232-null mouse model using CRISPR–Cas9 technology. Tmem232 knockout (KO) male mice was completely infertile, and their sperm were immotile, with morphological defects of the flagellum. Electron microscopy revealed an aberrant midpiece-principal junction and the loss of the fourth of nine doublet microtubules in the sperm of Tmem232-/-mice. Sperm cells presented an 8+2 conformation and an irregular arrangement of the mitochondrial sheath. Proteomic analysis indicated a downregulation in the expression of proteins associated with flagellar motility, sperm capacitation, and the integrity and stability of sperm structure, as well as an upregulation in the expression of multiple ribosome components in TMEM232-deficient spermatids. Additionally, TMEM232 was observed to be involved in ribophagy by interacting with autophagy-related proteins, such as ATG14 and ARMC3, to regulate ribosome homeostasis during spermiogenesis. These results suggest that TMEM232 is essential for normal sperm flagellum formation and plays an important role in the autophagic elimination of cytosolic ribosomes to provide energy for flagellar motility.