Morphological Changes of Mammalian Nucleoli during Spermatogenesis and Their Possible Role in the Chromatoid Body Assembling

Abstract

Chromatoid body (CB) is a typical cytoplasmic organelle of germ cells, and it seems to be involved in RNA/protein accumulation for later germ-cell differentiation. Despite most of the events in mammals spermatogenesis had been widely described in the past decades and the increase in the studies related to the CB molecular composition and physiology, the origins and functions of this important structure of male germ cells are still unclear. The aims of this study were to describe the nucleolar cycle and also to find some relationship between the nucleolar organization and the CB assembling during the spermatogenesis in mammals. Cytochemical and cytogenetics analysis showed nucleolar fragmentation in post-pachytene spermatocytes and nucleolar reorganization in post-meiotic spermatids. Significant difference in the number and in the size of nucleoli between spermatogonia and round spermatids, as well as differences in the nucleolar position within the nucleus were also observed. Ultrastructural analysis showed the CB assembling in the cytoplasm of primary spermatocytes and the nucleolar fragmentation occurring at the same time. In conclusion our results suggest that the CB may play important roles during the spermatogenesis process in mammals and that its origin may be related to the nucleolar cycle during the meiotic cell cycle.

Structure of nucleoli in first-order spermatocytes of selected free-living animal species

“…The detection of several mitochondrial elements in CB may confirm the relationship between the nuclear and mitochondrial genomes and that this interaction is passed on from generation to generation (Noce et al, 2001). Research (Peruquetti et al, 2012) has also confirmed a relationship between the mitochondria of spermatocytes and CB and the role of CB in the formation of the midpiece and tail of sperm cells. The relationship between CB and mitochondria may also explain the participation of CB in the synthesis and transport of apocytochrome c, an isoform of cytochrome c whose expression is observed in testicular tissue, and the presence of cytochrome c oxidase (COXI), a significant component of mitochondria (Haraguchi et al, 2005).…”

“…Another hypothesis explains that the nucleoli decrease in size because fragments of them migrate to the cytoplasm of the cells towards the end of prophase I (Peruquetti et al, 2012). The literature suggests that CB assembly occurs at the same time as fragmentation of the nucleolus and that the two processes are correlated (Kotaja and Sassone-Corsi, 2007;Peruquetti et al, 2008Peruquetti et al, , 2010.…”

“…These are typical cytoplasmic organelles present in haploid reproductive cells during spermatogenesis up to the differentiation stage. These studies are supplemented by analysis of the precise position of the nucleolus in the spermatogonium and spermatocyte (Peruquetti et al, 2012).…”

“…The nucleolus contains most of the cellular protein Pch2, which detects faulty organization of synaptonemal complexes and prevents segregation of chromosomes during meiotic recombination (Peruquetti et al, 2012).…”

ДИНАМИКА ГИСТОЛОГИЧЕСКОЙ СТРУКТУРЫ СЕМЕН-НИКОВ У ПЕРЕПЕЛОВ (Coturnix coturnix) В ПРОЦЕССЕ СПЕРМА-ТОГЕНЕЗА

“…При сперматогенезе происходит клеточная пролиферация с повторными митотическими делениями, дублированием хромосом, мейотическим делением клеток и т.д. для дальнейшего образования гаплоидных сперматид с их последующей дифференциацией в зрелые спермии (18).…”