Adenosine 3’, 5’-monophosphate cyclic (cAMP) is known to play important roles in mammalian sperm. It is involved in the acquisition and speed of motility as well as in the acrosomal exocytosis. cAMP regulates role sperm activities through protein phosphorylation dependent mechanisms involving PRKA, and through phosphorylation-independent events such as the activation of guanine nucleotide exchange factors like EPAC. Sperm intracellular cAMP levels depend on the opposing activity of adenylyl cyclases which generate cAMP, and on the activity of cyclic nucleotide phosphodiesterases (PDE) whose role is to degrade cAMP into 5’-AMP. The superfamily of PDE is subdivided into 11 families (PDE1 to 11), each of which being encoded by 1 to 4 genes. PDE families act exclusively on either cAMP or cGMP, or on both cAMP and cGMP although with different catabolic properties. PDE10, which is more effective on cAMP than cGMP, is one of the newest PDE that has been discovered for almost 15 years, and has been studied almost exclusively in the brain where it is associated with neurological disorders. Although high level of Pde10A gene expression is observed in the testis, there is no information on the isoforms expressed, on the presence of this enzyme this organ, nor on the cells, somatic or spermatogenic, that generate PDE10. The objective of this study was to identify the PDE10A isoforms expressed in the testis and germ cells, and to determine the presence and localization of PDE10A in mature spermatozoa. As a sub-objective, since Pde10A isoforms were reported strictly through analyses of bovine genomic sequence, we also wanted to determine the nucleotide and amino acid sequences by experimental evidence. We report that primary spermatocytes and spermatids express Pde10A variants X2 and X4. PDE10A variant X4 is also detected in mature spermatozoa.

Supported by the Natural Science and Engineering Research Council of Canada and L'Alliance Boviteq Inc.