Deficiency of the Tbc1d21 gene causes male infertility with morphological abnormalities of the sperm mitochondria and flagellum in mice

Abstract

Approximately 2-15% of couples experience infertility, and around half of these cases are attributed to male infertility. We previously identified TBC1D21 as a sterility-related RabGAP gene derived from infertile men. However, the in vivo function of TBC1D21 in male fertility remains unclear. Here, we show that loss of Tbc1d21 in mice resulted in male infertility, characterized by defects in sperm tail structure and diminished sperm motility. The mitochondria of the sperm-tail had an abnormal irregular arrangement, abnormal diameter, and structural defects. Moreover, the axoneme structure of sperm tails was severely disturbed. Several TBC1D21 interactors were selected via proteomic analysis and functional grouping. Two of the candidate interactors, a subunit protein of translocase in the outer membrane of mitochondria (TOMM20) and an inner arm component of the sperm tail axoneme (Dynein Heavy chain 7, DNAH7), confirmed in vivo physical co-localization with TBC1D21. In addition, TOMM20 and DNAH7 detached and dispersed outside the axoneme in Tbc1d21-deficient sperm, instead of aligning with the axoneme. From a clinical perspective, the transcript levels of TBC1D21 in sperm from teratozoospermia cases were significantly reduced when compared with those in normozoospermia. We concluded that TBC1D21 is critical for mitochondrial and axoneme development of mammalian sperm.

ARMC12 regulates spatiotemporal mitochondrial dynamics during spermiogenesis and is required for male fertility

“…6 B ) and that KO spermatozoa from the cauda epididymis have an abnormality in the midpiece ( Fig. 6 C ), similar to a recently published study ( 33 ). To check mitochondrial sheath formation in Tbc1d21 KO male mice, we performed freeze-fracture SEM analysis.…”

“…5 C ). Because TBC1 domain family protein TBC1D21 is the only TBC1 domain family protein showing testis-enriched expression in mice ( 20 ) and disruption of Tbc1d21 causes male infertility with morphological abnormalities of the sperm mitochondria ( 33 ), we focused on TBC1D21. We performed RT-PCR and confirmed that Tbc1d21 shows testis-enriched expression in mice and humans ( Fig.…”

“…5 C and F ). TBC1D21 is expressed late in spermatids and localizes to the acrosome and midpiece ( 35 ), and the disruption of TBC1D21 causes male infertility with morphological abnormalities of the sperm mitochondria and flagellum in mice ( 33 ). However, because previous studies did not evaluate the mitochondrial sheath formation of Tbc1d21 -null spermatids, we generated Tbc1d21 KO mice and evaluated the formation.…”

Molecular basis of the morphogenesis of sperm head and tail in mice

“…Armadillo repeat‐containing 12 (ARMC12) and TBC1 domain family member 21 (TBC1D21) are essential for mitochondrial elongation after alignment at mid‐piece in mice. 115 , 116 In Armc12 –KO mice, although spherical mitochondria are normally arranged on mid‐piece, their elongation and interlocking with adjacent mitochondria are impaired. As a result, a disorganized MS is formed, and sperm motility is decreased.…”

Loss of function mutation in DNAH7 induces male infertility associated with abnormalities of the sperm flagella and mitochondria in human

“…Previous studies in animal models have suggested that TBC1D21 is crucial for mitochondrial and axoneme development in mammalian sperm through interaction with TOMM20 and DNAH7. 18 Therefore, we speculate that DNAH7 is vital for the formation of a functional complex with TBC1D21 and TOMM20, and that it might participate in the formation of intact mitochondrial structures in human sperm. From a clinical perspective, positive live birth after ICSI also represents a significant step towards the development of genetic diagnosis and counselling regarding prognosis.…”