Specialized gene expression in the epididymis.

The metamorphosis of an immature and nonfunctional sperm into a mature sperm capable of progressive motility and fertility is thought to be the result of a highly regulated and complex series of events in the epididymis. It is well established that sperm maturation is not intrinsic to sperm cells themselves but requires the interaction of spermatozoa with proteins that are synthesized and secreted by the epididymal epithelium in a highly regionalized manner. This regional expression of epididymal proteins results in the sperm encountering a unique and ever-changing luminal fluid environment as they progress through the epididymis, which ultimately results in sperm maturation. These maturational events also require the presence of androgens. Although epididymal secretory proteins have been studied for some time, the identity and function of these proteins in sperm maturation and the mechanisms by which their genes are controlled have not been elucidated. The identity and analysis of genes expressed only in discrete regions of the epididymis provide valuable information in the quest to determine the regional-specific functions necessary for sperm maturation. This review will examine several aspects of these epididymal genes including tissue and regional-specific expression, differential regulation by androgens and/or testicular factors, mechanisms by which these genes may be controlled, and the putative functional significance of these genes in the epididymis. Minireview