TULP2 deletion mice exhibit abnormal outer dense fiber structure and male infertility

PURPOSE: Tulp2 (tubby‐like protein 2) is a member of the tubby protein family and expressed predominantly in mouse testis. Recently, it was reported that Tulp2 knockout (KO) mice exhibited disrupted sperm tail morphology; however, it remains to be determined how TULP2 deletion causes abnormal tail formation. METHODS: The authors analyzed male fertility, sperm morphology, and motility of two Tulp2 KO mouse lines that were generated using the conventional method that utilizes homologous recombination in embryonic stem (ES) cells as well as the clustered regularly interspaced short palindromic repeats/CRISPR‐associated protein 9 (CRISPR/Cas9) system. Furthermore, the authors observed the spermatogenesis of Tulp2 KO mice in more detail using scanning and transmission electron microscopy (SEM and TEM). RESULTS: Both mouse lines of Tulp2 KO exhibited male infertility, abnormal tail morphology, and impaired sperm motility. No overt abnormalities were found in the formation of the mitochondrial sheath in Tulp2 KO mice using the freeze‐fracture method with SEM. In contrast, abnormal outer dense fiber (ODF) structure was observed in Tulp2 KO testis with TEM. CONCLUSIONS: TULP2 may play roles in the correct formation and/or maintenance of ODF, which may lead to abnormal tail morphology, impaired sperm motility, and male infertility.