Regulation of the Mitotic and Meiotic Cell Cycles in the Male Germ Line

Abstract

Mammalian gametogenesis provides a unique system in which to study cell-cycle regulation. Furthermore, understanding the genetic program controlling the mitotic and meiotic divisions of the germ line will provide insight into understanding infertility and new directions for contraception. Male and female germ cells have stages of cell-cycle regulation in common, including a mitotic proliferative stage, entry into meiosis, completion of a reductive division, and entry into a quiescent state awaiting signals at fertilization. However, the timing of these events -and, indeed, even the stage of development at which these events occurs -differs in the two sexes. The genes involved in controlling these specialized mitotic and meiotic cycles of mammalian germ cell differentiation are only now being identified. They include a complex array of kinases, phosphatases, regulatory proteins (e.g., cyclins), and an equally complex array of substrates, including components of the nuclear and cytoplasmic structures involved in cell division. This chapter provides an overview of our current understanding of cell-cycle regulation in mammalian mitotic cells and the importance of restriction points. A summary of observations regarding the expression of various cell-cycle regulatory genes in mouse gametes is provided, along with comments on interesting differences between mitotic and meiotic cells. Finally, the role of the novel A-type cyclin, cyclin A1, during male meiosis is discussed in depth.

DNA replication licensing in somatic and germ cells

“…Thus oogenesis may last for several decades. In contrast, male meiosis begins at puberty and is a continuous process with spermatocytes progressing through prophase I and through the second reduction division in around 22 days (Wolgemuth et al, 2002). Our data and those of Nishitani et al (Nishitani et al, 2001) suggest that all factors required for origin licensing are present within testis.…”

Implication of transcriptome profiling of spermatozoa for stallion fertility

“…This transition is signalled and controlled by cyclins and cyclin-dependent kinases (CDKs) (Neganova and Lako 2008;Wolgemuth et al 2013). Cyclins are the principal cell cycle regulatory proteins, and have been identified in simple as well as higher-order organisms (Wolgemuth et al 2002). Cyclins can be divided into eight classes (cyclin A-H) according to their amino acid similarity and the timing of their appearance during the cell cycle (Wolgemuth et al 2002).…”

“…Cyclins are the principal cell cycle regulatory proteins, and have been identified in simple as well as higher-order organisms (Wolgemuth et al 2002). Cyclins can be divided into eight classes (cyclin A-H) according to their amino acid similarity and the timing of their appearance during the cell cycle (Wolgemuth et al 2002). Although the function of cyclins during mitosis and meiosis has been studied in somatic cells, their function during mitosis and meiosis in the germ line is poorly understood.…”

Hormonal regulation of male germ cell development

“…In meiosis II, both diplotene cells undergo further reduction without DNA synthesis and give rise to four haploid germ cells, marking the completion of the M phase ( Fig. 2; reviewed in Wolgemuth et al (2002)). At the end of the cell cycle, a cell has two potential fates; the cell can enter either a new cycle or into a quiescence phase (G 0 ).…”