Acrosome Biosynthesis in Spermatocytes and Spermatids Revealed by HPA Lectin Cytochemistry

Abstract

The origin of the acrosome is controversial, because of both its lysosomal nature and at the moment of its appearance, which seems to be species-specific. Considering the amazing organization shown by the acrosome of some urodele amphibians, HPA-colloidal gold cytochemistry was used to analyze the biogenesis of the acrosome in the urodele Pleurodeles waltl at electron microscopy level. The results showed that HPA-labeling is useful to label the acrosome and its precursor vesicles and, consequently, HPA-histochemistry could be used as a marker of acrosomal content. Labeling of the Golgi apparatus and precursor vesicles was seen in primary spermatocytes and round (stage I) spermatids, thus contributing solid evidence for the beginning of acrosome biogenesis before meiosis. In both primary spermatocytes and round spermatids, an enigmatic vesicle, probably related to the biosynthesis of the neck piece or the tail, was also labeled. Labeling in elongating spermatids (stage II-IV), showed a homogeneous distribution of colloidal gold particles in the acrosomal cap, but the perforatorium was not positive to the lectin. However, in mature (stage V-VI) spermatids, a regional distribution of labeling in the acrosome was seen, with the apical knob showing a stronger labeling than the lateral barb, and the lateral barb showing a stronger labeling than the principal piece of the acrosomal cap. This regional distribution of the labeling suggests that the acrosome develops several domains with different glycoconjugate compositions.

Identification of N‐Acetylgalactosamine in Carbohydrates of Xenopus laevis Testis

“…Glycoconjugates in postmiotic cells have been reported, with an emphasis on acrosomal‐related carbohydrates (Martínez‐Menárguez et al,1992,1993; Labate and Desantis,1995; Sáez et al,1999,2004; Valbuena et al,2008). In the amphibian Pleurodeles waltl , HPA has been used as an acrosomal marker, which has allowed the analysis of the biosynthesis of the acrosome (Valbuena et al,2008).…”

“…Glycoconjugates in postmiotic cells have been reported, with an emphasis on acrosomal‐related carbohydrates (Martínez‐Menárguez et al,1992,1993; Labate and Desantis,1995; Sáez et al,1999,2004; Valbuena et al,2008). In the amphibian Pleurodeles waltl , HPA has been used as an acrosomal marker, which has allowed the analysis of the biosynthesis of the acrosome (Valbuena et al,2008). The presence of GalNAc in acrosomal carbohydrates is not exclusive to this amphibian species; it has been reported in mammals and insects (Yamamoto,1982; Lee and Damjanov,1984; Arya and Vanha‐Perttula,1984,1985,1986; Malmi and Soderstrom,1987; Malmi et al,1987,1990; Kurohmaru et al,1991,1995,1996; Ertl and Wrobel,1992; Craveiro and Bao,1995).…”

“…There the germ cells synchronously develop forming clusters, called cysts or follicles, each one being enclosed by a capsule formed by follicle (Sertoli) cells, which resemble fibroblasts (Lofts,1974). In recent studies, we have described that some amphibians show a strong expression of GalNAc‐containing glycoconjugates in the acrosome of the developing spermatids (Sáez et al,1999,2004; Valbuena et al,2008). However, Xenopus laevis is the amphibian model most extensively used in biological research, but no report exists about the expression of GalNAc‐containing glycans in the testis of this species.…”

Identification of fucosylated glycoconjugates in Xenopus laevis testis by lectin histochemistry

“…Labelling in spermatocytes and spermatids could be interpreted in terms of fucosylated glycans involved in meiosis and/or spermiogenesis. If we assume that some Fuc moieties are in acrosomal glycoconjugates, this could support an explanation for spermatocyte labelling, because it has been shown that acrosome biogenesis starts in spermatocytes, before completion of meiosis, both in amphibians (Valbuena et al 2008) and mammals (Anakwe and Gerton 1990;Bermúdez et al 1994;Kohn et al 2005).…”

Histochemical identification of sialylated glycans in Xenopus laevis testis

“…In a recent work in another amphibian, Pleurodeles waltl , we have studied the biogenesis of the acrosome by means of HPA cytochemistry, because this lectin can be used as a specific marker (Valbuena et al. ). However, in Xenopus testis, the acrosome was negative, although the rest of the spermatid was positive, as happens with WGA, s‐WGA and DSA.…”