The Chromatoid Body in Spermatogenesis: Nucleo-Cytoplasmic Transport of Haploid Gene Products and Its Cytoskeletal Regulation

Abstract

All cells of the germ line are characterized by specific cytoplasmic components, germ cell determinants, that are called polar granules in insects, germinal plasm in amphibians and nuage in mammals (Beams and Kessel, 1974). The chromatoid body is a germ cell determinant; it is characteristic for mammalian spermatocytes and spermatids (Eddy, 1974; Söderström, 1981, for review, see Sud, 1961). In early spermatids, it is a lobulated cytoplasmic structure with l–2µm in diameter (Figure 1). During the first appearance of the chromatoid material in mid-pachytene spermatocytes (Russell and Frank, 1978; Head and Kresge, 1985), it is often seen to be intimately associated with mitochondria (Fawcett et al., 1970). During early spermiogenesis, the chromatoid body is located on the surface of the nucleus close to the Golgi complex and the developing acrosome (Susi and Clermont, 1970). During this period, two cytochemically distinct compartments of the Golgi cortex, characterized by acid phosphatases, nicotinamide adenine dinucleotide phosphatase (NADPase) and cytidine mono-phosphatase (CMPase), independently contribute to the formation of the vesicular component of the chromatoid body (Thorne-Tjomsland et al., 1988). Towards the end of spermiogenesis, the chromatoid body diminishes in size and is found in the region of the developing flagellum. It becomes separated from the spermatozoon at spermiation in the residual body.