Introduction

Spermatogenesis is the process of cellular differentiation in which diploid progenitor cells in the testis differentiate into haploid spermatozoa. During meiosis–one of the central events of spermatogenesis–chromosomes pair, and genetic recombination occurs in the functionally tetraploid pachytene spermatocyte. Numerous cytological studies have described in detail the dramatic morphological changes that the differentiating cells undergo and the unique structures that appear during the development and maturation of the male gamete. These structural data provide an excellent framework on which to investigate at a molecular level the changes in testicular gene expression that underlie the developmental events. Moreover, the testis provides a superior system to study certain eukaryotic control mechanisms. The ordered differentiation of the germ cells allows analysis of the temporal regulation of gene expression for a series of defined proteins in a terminally differentiating system. Furthermore, because transcription terminates early during spermiogenesis, translational regulation of stored mRNA is essential to synthesize many of the proteins appearing during this haploid phase of spermatogenesis. A more complete understanding of the biochemistry of spermatogenesis and the roles played by the plethora of distinct testicular proteins will also disclose many essential regulatory mechanisms unique to the development of the male gamete.

In this chapter, the literature on gene expression during spermatogenesis in mammals will be examined. Although it will be directed toward mammals, pertinent information from nonmammalian species will be included.