Structural Elements of the Mammalian Sperm Nucleus
During spermiogenesis the spherical nucleus of the germ cell condenses and assumes a configuration that is distinct for each mammalian species. This nuclear transformation, whether yielding a falciform, spatulate or discoid shape, serves to protect the haploid genome and to facilitate penetration of the ovum by the motile sperm cell. Remodeling of the nucleus is complex. The process involves the removal of histones, the selective elimination of most nonhistone chromosomal proteins, the deposition of protamines, and the insertion of novel nuclear proteins (Bellvé, 1979; Bellvé & O’Brien, 1982). A microtubular array, the manchette, exists transiently in association with the condensing nucleus, acting as an external scaffold rather than imposing a direct mechanical force (Myles & Hepler, 1982). Consequently, sperm nuclear shape may be defined intrinsically by nuclear proteins, as suggested previously by Fawcett et al. (1971).
KeywordsGuanidine Hydrochloride Sperm Nucleus Dense Lamina Nuclear Transformation Discoid Shape
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