In recent years, it has become increasingly clear that epigenetic regulation of gene expression is critical during spermatogenesis. In this review, the epigenetic regulation and the consequences of its aberrant regulation during mitosis, meiosis and spermiogenesis are described. The current knowledge on epigenetic modifications that occur during male meiosis is discussed, with special attention on events that define meiotic sex chromosome inactivation. Finally, the recent studies focused on transgenerational and paternal effects in mice and humans are discussed. In many cases, these epigenetic effects resulted in impaired fertility and potentially long-ranging affects underlining the importance of research in this area.
Natasha M Zamudio, Suyinn Chong and Moira K O'Bryan
Jessica E M Dunleavy, Moira K O’Bryan, Peter G Stanton and Liza O’Donnell
As germ cells progress through spermatogenesis, they undergo a dramatic transformation, wherein a single, diploid spermatogonial stem cell ultimately produces thousands of highly specialised, haploid spermatozoa. The cytoskeleton is an integral aspect of all eukaryotic cells. It concomitantly provides both structural support and functional pliability, performing key roles in many fundamental processes including, motility, intracellular trafficking, differentiation and cell division. Accordingly, cytoskeletal dynamics underlie many key spermatogenic processes. This review summarises the organisational and functional aspects of the four major cytoskeletal components (actin, microtubules, intermediate filaments and septins) during the various spermatogenic phases in mammals. We focus on the cytoskeletal machinery of both germ cells and Sertoli cells, and thus, highlight the critical importance of a dynamic and precisely regulated cytoskeleton for male fertility.
Duangporn Jamsai, Deborah M Bianco, Stephanie J Smith, Donna J Merriner, Jennifer D Ly-Huynh, Amy Herlihy, Birunthi Niranjan, Gerard M Gibbs and Moira K O'Bryan
Cysteine-rich secretory protein 2 (CRISP2) is a testis-enriched protein localized to the sperm acrosome and tail. CRISP2 has been proposed to play a critical role in spermatogenesis and male fertility, although the precise function(s) of CRISP2 remains to be determined. Recent data have shown that the CRISP domain of the mouse CRISP2 has the ability to regulate Ca2+ flow through ryanodine receptors (RyR) and to bind to MAP kinase kinase kinase 11 (MAP3K11). To further define the biochemical pathways within which CRISP2 is involved, we screened an adult mouse testis cDNA library using a yeast two-hybrid assay to identify CRISP2 interacting partners. One of the most frequently identified CRISP2-binding proteins was gametogenetin 1 (GGN1). Interactions occur between the ion channel regulatory region within the CRISP2 CRISP domain and the carboxyl-most 158 amino acids of GGN1. CRISP2 does not bind to the GGN2 or GGN3 isoforms. Furthermore, we showed that Ggn1 is a testis-enriched mRNA and the protein first appeared in late pachytene spermatocytes and was up-regulated in round spermatids before being incorporated into the principal piece of the sperm tail where it co-localized with CRISP2. These data along with data on RyR and MAP3K11 binding define the CRISP2 CRISP domain as a protein interaction motif and suggest a role for the GGN1–CRISP2 complex in sperm tail development and/or motility.
Lucinda C Aulsebrook, Michael G Bertram, Jake M Martin, Anne E Aulsebrook, Tomas Brodin, Jonathan P Evans, Matthew D Hall, Moira K O'Bryan, Andrew J Pask, Charles R Tyler and Bob B M Wong
Environmental pollution is an increasing problem for wildlife globally. Animals are confronted with many different forms of pollution, including chemicals, light, noise, and heat, and these can disrupt critical biological processes such as reproduction. Impacts on reproductive processes can dramatically reduce the number and quality of offspring produced by exposed individuals, and this can have further repercussions on the ecology and evolution of affected populations. Here, we illustrate how environmental pollutants can affect various components of reproduction in wildlife, including direct impacts on reproductive physiology and development, consequences for gamete quality and function, as well as indirect effects on sexual communication, sexual selection, and parental care. We follow with a discussion of the broader ecological and evolutionary consequences of these effects on reproduction, and suggest future directions that may enable us to better understand and address the effects of environmental pollution.