ABSTRACT: A greater understanding of the proteins involved in reproduction can benefit animal production. New advances in proteomics are having a major impact on our understanding of how spermatozoa acquire their capacity for fertilization [1]. Sperm proteomics aims at the identification of the proteins that compose the sperm cell and the study of their function [2]. The sperm cell is one of the most highly differentiated cells and is composed of a head with a highly compacted chromatin structure and a large flagellum with midpiece that contains the required machinery for movement and therefore to deliver the paternal genetic and epigenetic content to the oocyte [3]. By being so highly differentiated, spermatozoa are advantageous cells to study proteomics of specific compartments such as the membrane, which basically is the area of major importance for its role in interacting with the surroundings and the oocyte [4]. The fusion of a sperm and an oocyte is a sophisticated process that must be preceded by suitable changes in the sperm's membrane composition [5]. Recent studies of spermatozoa from the proteomic point of view have allowed the identification of different proteins in spermatozoa that are responsible for the regulation of normal/defective sperm functions [6]. While several techniques are available in proteomics, LC-MS based analysis of complex protein/peptide mixtures has turned out to be a mainstream analytical technique for quantitative proteomics [7]. Using this method, detailed proteomic data are now available for human [8], macaque [9,10], mouse [11], rat [12], bull [13-15], stallion [16], fruit fly [17], Caenorhabditis elegans [18], carp [19], rainbow trout [20], mussel [21], ram [22], honeybee [23] and rooster [24] sperm membrane proteins. Rabbit (Oryctolagus cuniculus) is an important mammalian species worldwide, being at the same time of commercial interest and a research model animal. European rabbit meat production is approximately 500 thousand tons, corresponding to a 30% share of world production [25]. Besides, rabbits account for the seventh highest number of animals slaughtered per year in the European Union-27, with 347,603 × 1000 head in 2014 [26]. In a previous work, we identified and quantified rabbit seminal plasma proteins between two different genotypes [27], concluding the clear effect of genotype in the abundance of certain seminal plasma proteins. However, it is unknown at present whether these differences also exist at sperm proteome level. Therefore, the aim of the present study was to characterise rabbit sperm membrane proteins through NanoLC-MS/MS analysis focusing on the influence of the genetic origin.
Luz Valero 
