Diverse functions of myosin VI in spermiogenesis

Abstract

Spermiogenesis is the final stage of spermatogenesis, a differentiation process during which unpolarized spermatids undergo excessive remodeling that results in the formation of sperm. The actin cytoskeleton and associated actin-binding proteins play crucial roles during this process regulating organelle or vesicle delivery/segregation and forming unique testicular structures involved in spermatid remodeling. In addition, several myosin motor proteins including MYO6 generate force and movement during sperm differentiation. MYO6 is highly unusual as it moves towards the minus end of actin filaments in the opposite direction to other myosin motors. This specialized feature of MYO6 may explain the many proposed functions of this myosin in a wide array of cellular processes in animal cells, including endocytosis, secretion, stabilization of the Golgi complex, and regulation of actin dynamics. These diverse roles of MYO6 are mediated by a range of specialized cargo-adaptor proteins that link this myosin to distinct cellular compartments and processes. During sperm development in a number of different organisms, MYO6 carries out pivotal functions. In Drosophila, the MYO6 ortholog regulates actin reorganization during spermatid individualization and male KO flies are sterile. In C. elegans, the MYO6 ortholog mediates asymmetric segregation of cytosolic material and spermatid budding through cytokinesis, whereas in mice, this myosin regulates assembly of highly specialized actin-rich structures and formation of membrane compartments to allow the formation of fully differentiated sperm. In this review, we will present an overview and compare the diverse function of MYO6 in the specialized adaptations of spermiogenesis in flies, worms, and mammals.

Lagging X chromatids specify the orientation of asymmetric organelle partitioning in XX spermatocytes ofAuanema rhodensis

“…All sperm differentiation programs include a postmeiotic, asymmetric partitioning step during which sperm are streamlined by discarding components that are no longer needed into a residual body (RB) (Breucker et al 1985;Steinhauer 2015). Furthermore, the underlying cell polarization and scission events in humans (de Kretser et al 1998), Drosophila (Noguchi et al 2006;Steinhauer et al 2019), and C. elegans (Ward et al 1981;Kelleher et al 2000;Winter et al 2017;Hu et al 2019) all involve common elements such as actin, myosin VI, and microtubules (Zakrzewski et al 2021). Specific to nematode spermatogenesis, RB formation occurs surprisingly early, immediately after anaphase II (Fig.…”

The X chromosome is a potential polarising signal for asymmetric cell divisions in meiotic cells of a nematode

“…This type of cell division found in Auanema spermatogenesis, in which residual material is partitioned to a cell that contains chromosomes, is atypical in metazoans (Gorelick et al, 2016). Residual bodies, which are often observed in ACDs during spermiogenesis, are usually devoid of DNA (Gorelick et al, 2016; Zakrzewski et al, 2021). There are a few exceptions, such as in the nematode Rhabdias , in which one of the X chromosomes is discarded into a residual body during the hermaphrodite spermatogenesis (Runey et al, 1978).…”

TMPRSS12 Functions in Meiosis and Spermiogenesis and Is Required for Male Fertility in Mice

“…Normal spermatogenesis in the testis not only ensures an adequate sperm count but also guarantees sperm quality. During the process of spermiogenesis, round spermatids undergo dramatic morphological, molecular and cellular alterations, thus laying a foundation for the generation of functional sperm ( Ozturk et al, 2017 ; Zakrzewski et al, 2021 ). Due to its predominant expression in spermatids, TMPRSS12 very likely participates in spermiogenesis.…”