The sperm journey in the excurrent duct: functions of microvesicles on sperm maturation and gene expression along the epididymis
Sullivan, RDAmours, OCaballero, JBelleannée, C
Mammalian spermatozoa are differentiated, but unable to fertilize as they leave the testis. In order to acquire fertilizing ability and forward motility properties, the male gamete has to transit the epididymis. This process is collectively known as sperm maturation. The epididymis is a single convoluted tubule located between the vas efferens and the vas deferens; sperm epididymal transit takes 3 to 15 days depending on the species. Protein synthesis in the epididymis is highly active in response to androgen stimulation, and the underlying gene expression pattern shows great variability along this organ. For decades it has been recognized that interactions between the transiting spermatozoa and the intraluminal compartment of the epididymis govern complex modifications of sperm macromolecular composition that are necessary for sperm maturation. There is increasing interest in extracellular microvesicles that modulate cell-cell interactions in many physiological systems: such vesicles are found in the intraluminal compartment of the epididymis are called epididymosomes. We have shown that the epididymosome protein composition varies along the epididymis, and that a subset of these proteins isselectively transferred to the male gamete. These proteins are targeted to different sperm sub-compartments and are proposed to be involved in both the acquisition of fertilizing ability and forward motility properties. More recently, we used a bovine model to show that different subpopulations of epididymosomes are present in the fluid of a given epididymal segment. One of these subpopulations is proposed to be involved in the transfer of specific proteins by a membrane fusion process mediated by tetraspanin complexes, whereas another population of epididymosomes is involved in a mechanism that protects epididymal sperm against degenerating ones.(AU)
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