Abnormal manchette development in spermatids of azh/azh mutant mice

Abstract

A study of manchette development during spermiogenesis in azh/azh mutant mice was carried out by thin-section transmission electron microscopy with the goal of determining which of the initial steps in spermatid development are aberrant. In the homozygous mutant, spermatogenesis was quantitatively normal; but 100% of the sperm nuclei produced had abnormal shapes. The first defect, observed in steps 8-9, was the abnormal positioning of many manchette microtubules. These microtubules were directed towards regions of the plasma membrane not normally associated with manchette formation, in addition to being located at the caudal rim of the acrosome in the normal region of manchette formation. At steps 10-12, sheets of manchette microtubules were often in ectopic positions along the plasma membrane, rather than in association with the nuclear membrane as well. The fine structural appearance of the manchette was generally normal; the defect appeared to be in its positioning within the cell. In many step 8-10 spermatids nuclear invaginations and evaginations were observed, always associated with irregularities in the position of some of the manchette microtubules; these illustrate the capacity of manchette microtubules to deform nuclear shape. The nuclear irregularities remained throughout spermiogenesis. These observations are consistent with the hypothesis that the manchette is involved in at least some aspects of sperm nuclear shaping and that the improper positioning of manchette formation is a likely candidate for the primary abnormality resulting from a defective allele at the azh locus.

A novel 205-kilodalton testis-specific serine/threonine protein kinase associated with microtubules of the spermatid manchette.

“…The significance of the manchette in mammalian spermiogenesis has been inferred from ultrastructural observations of conditions which perturbed the manchette (by using chemical agents or in mutant mice) and consequently affected nuclear shaping (10,32,39). In an attempt to determine the contribution of MAST205 to manchette structure and function, we transiently transfected Cos cells with a full-length construct encoding MAST205 cloned into the mammalian expression vector pcDNAI-neo.…”

“…During spermatogenesis the microtubular cytoskeleton exists in diverse conformations, including two microtubular arrays unique to spermiogenesis, namely the spermatid manchette and flagellum. The manchette temporally forms around the caudal nucleus of round spermatids and has been implicated in the subsequent process of sperm head shaping (9,32,39).We sought to identify proteins which interact with, and potentially modulate the function of, microtubules during spermatogenesis. We describe here the identification and characterization of one such protein, a novel 205-kDa microtubule-associated serine/threonine protein kinase, termed MAST205.…”

“…During spermatogenesis the microtubular cytoskeleton exists in diverse conformations, including two microtubular arrays unique to spermiogenesis, namely the spermatid manchette and flagellum. The manchette temporally forms around the caudal nucleus of round spermatids and has been implicated in the subsequent process of sperm head shaping (9,32,39).…”

Sperm head shaping in ratites: New insights, yet more questions

“…However, disruption or incorrect alignment of the manchette microtubules in birds (McIntosh and Porter, 1967) and mammals (Meistrich et al, 1990;Nozawa et al, 2014;Russell et al, 1991Russell et al, , 1994 displaying this structure results in the formation of abnormally shaped heads, which again points to the possible influence of the manchette on sperm nuclear shaping. The vital contribution of the manchette microtubules to the acrosome-acroplaxome-manchette complex (see below) is illustrated by the fact that removal of the novel manchette-associated protein, Fused, results in abnormal head-shaping and tail morphogenesis (Nozawa et al, 2014).…”

“…Although conflicting evidence has been presented in the literature, morphological data supplied by conventional transmission electron microscopy, supplemented by the use of animal models, have implicated various cellular components and processes in nuclear (head) morphogenesis (Fawcett, et al, 1971;Hermo et al, 2010;Kierszenbaum et al, 2003Kierszenbaum et al, , 2004Kierszenbaum et al, , 2007Meistrich, 1993). These include the role of the forming acrosome ( Kierszenbaum et al, 2003( Kierszenbaum et al, , 2004( Kierszenbaum et al, , 2007Russell et al, 1991) inherent properties of the chromatin condensation process (Fawcett et al, 1971;Prisant et al, 2007;Nozawa et al, 2014;Zhuang et al, 2014) and the involvement of the manchette microtubules (Kierszenbaum, 2002;Meistrich, 1993;Meistrich et al, 1990;Nozawa et al, 2014;Russell et al, 1991Russell et al, , 1994Toshimori and Ito, 2003). In addition, it has been proposed that the ectoplasmic specializations of the Sertoli cells surrounding the sperm head are instrumental in effecting remodeling of the spermatid nucleus (Kierszenbaum et al, 2007;Russell et al, 1994).…”