Insights into post-translational modifications of transtition proteins, TP1 and TP2 during mammalian spermiogenesis

Abstract

Spermatogenesis is a male germ cell differentiation process in which a diploid spermatogonial cell differentiates into mature motile haploid spermatozoa through a series of biochemical and morphological changes. Spermatogenesis is a continuous process resulting in the formation of a haploid male gamete which upon its union with the haploid female gamete restores the cellular chromosome number and transfers information from generation to generation (1–4). This process in mammals occurs in the seminiferous tubules of testis where physical association with Sertoli cells (non-germ cell) is critical for the spermatogonia maintenance and its differentiation into spermatids (Figure 1.1). Sertoli cells possess receptor for hormones and mediate their biological effect on the germ cells. Mammalian spermatogenesis is controlled by the hormonal messengers, follicle stimulating hormone (FSH), luteinizing hormone (LH) and androgens (testosterone), which exert their effect via autocrine, paracrine and endocrine pathways (Figure 1.2) (5–9). Cross-sectioning of seminiferous tubules reveals the presence of cell association of germ cells at a defined developmental phase and is referred to as “stage”. Each organism has a characteristic number of stages or cell associations which can be identified by cross-sectioning of the seminiferous tubule over time (4). Time required for the culmination of stages (cell associations) in an ordered manner is called the cycle of seminiferous epithelium and is also a peculiar characteristic of each organism. It requires 4-5 cycles in different organisms for the completion of spermatogenesis from spermatogonia to spermatozoa (4, 10). A comparison of spermatogenesis characteristics of many mammalian species is given in Table 1.1.