The Sperm Specific Protein Proakap4 as an Innovative Marker to Evaluate Sperm Quality and Fertility

As classical methods for semen analyses (i.e. motility, concentration, morphology, etc.) remains unsatisfactory in determining fertility outcomes in livestock animals, new methods based on proteomic markers have been recently introduced to analyze sperm quality in breeding centers. This review focuses on a sperm macromolecule, called proAKAP4 that have been successfully introduced as a pertinent indicator of sperm quality and fertility in mammals. Albeit absence or weak expression of AKAP4 have been described over the years as being related to sperm dysfunctions with motility impairments, proAKAP4 was under investigated up to recently due to the lack of reliable tools. Sandwich ELISA kits known as 4MID® kits have recently reached the artificial insemination markets and brought new highlights about the proAKAP4 master role in reproduction. Structurally, proAKAP4 must be processed to release the mature AKAP4, that is essential to coordinate major transduction signals regulating sperm motility and fertility. ProAKAP4 amount as quantified in ejaculated spermatozoa reflect the ability of spermatozoa to keep active and functional up to the site of fertilization. Any modification of proAKAP4 expression during spermatogenesis or modification of its metabolism will have consequence on sperm motility, sperm capacitation and fertility. Consolidated data from field studies have shown correlation between proAKAP4 expression with fertility and prolificity. We will review here literature data on proAKAP4 involvement in spermatozoa functions and results in animal fertility. The translation of fundamental discoveries around proAKAP4 sperm protein marker to a functional tool such as 4MID® kits will be beneficial in breeding industries and veterinarian practices.