Analysis of the sperm flagellar axoneme using gene-modified mice

Abstract

Infertility is a global health issue that affects 1 in 6 couples, with male factors contributing to 50% of cases. The flagellar axoneme is a motility apparatus of spermatozoa, and disruption of its structure or function could lead to male infertility. The axoneme consists of a “9+2” structure that contains a central pair of two singlet microtubules surrounded by nine doublet microtubules, in addition to several macromolecular complexes such as dynein arms, radial spokes, and nexin-dynein regulatory complexes. Molecular components of the flagellar axoneme are evolutionally conserved from unicellular flagellates to mammals, including mice. Although knockout (KO) mice have been generated to understand their function in the formation and motility regulation of sperm flagella, the majority of KO mice die before sexual maturation due to impaired ciliary motility, which makes it challenging to analyze mature spermatozoa. In this review, we introduce methods that have been used to overcome premature lethality, focusing on KO mouse lines of central pair components.

Structural and Functional Characterization of a Testicular Long Non-coding RNA (4930463O16Rik) Identified in the Meiotic Arrest of the Mouse Topaz1–/– Testes

“…Finally, our ontology analysis of Topaz1 –/– P18-DEGs revealed significant enrichment scores for the several clusters relative to the final structure of spermatozoa such as tetratricopeptide repeat (TPR) and dynein heavy chain (DNAH1) clusters. Dynein chains are macromolecular complexes connecting central or doublet pairs of microtubules together to form the flagellar axoneme, the motility apparatus of spermatozoa (ref in Miyata et al, 2020a ). Dynein proteins have also been identified as being involved in the microtubule-based intracellular transport of vesicles, and in both mitosis and meiosis ( Mountain and Compton, 2000 ).…”

Topaz1, an essential gene for murine spermatogenesis, down-regulates the expression of numerous testis-specific long non-coding RNAs

“…Finally, the ontology analysis of Topaz1 -/-P18-DEGs revealed significant enrichment score for the several clusters referred to the spermatozoa final structure, like tetratricopeptide repeat (TPR) and dynein heavy chain (DNAH1). Dynein chains are macromolecular complexes connecting the central pair or doublet pairs of microtubules together to form the flagellar axoneme, the motility apparatus of spermatozoa (ref in [55]). Dynein proteins have also been identified and involved in microtubule-based, intracellular transport of vesicles, and in both mitosis and meiosis [56].…”

SPATA33 localizes calcineurin to the mitochondria and regulates sperm motility in mice

“…In the female reproductive tract, spermatozoa need to travel a long distance to reach the egg and pass through the zona pellucida (ZP), an extracellular matrix that surrounds the egg. Sperm motility plays critical roles in these processes, which is executed by the flagellum that can be divided into three parts: midpiece, principal piece, and end piece ( 1 , 2 ). The central motility apparatus of the flagellum is the axoneme, a “9+2” microtubule structure, that is found in all the parts of the flagellum.…”

“…The end piece contains no accessory structures. Defects in these structures’ formation or function could lead to impaired sperm motility and male infertility ( 1 , 2 ).…”