Isolation and identification of proteins from swine sperm chromatin and nuclear matrix

The aim of this study was to perform a proteomic analysis to isolate and identify proteins from the swine sperm nuclear matrix to contribute to a database of swine sperm nuclear proteins. We used pre-chilled diluted semen from seven boars (19 to 24 week-old) from the commercial line Landrace x Large White x Pietran. The semen was processed to separate the sperm heads and extract the chromatin and nuclear matrix for protein quantification and analysis by mass spectrometry, by LTQ Orbitrap ELITE mass spectrometer (Thermo-Finnigan) coupled to a nanoflow chromatography system (LC-MS/MS). We identified 222 different proteins in the sample; a total of 159 (71.6%) were previously described as present in the somatic or sperm nuclei of other species, 41 (18.5%) did not have a previously reported nuclear presence and 22 (9.9%) had not been characterized. The most abundant family of proteins corresponded to ribosomal (13.1%), followed by cytoskeleton (12.2%), uncharacterized (9.9%), histones (5.4%), proteasome subunits (3.6%) and heat shock (1.8%). The other proteins clustered in other families accounted for 54% of the total proteins. The protein isolation of the nuclear matrix of the swine spermatozoa was satisfactory, thus demonstrating that the protocol used was efficient. Several proteins were identified and described. However, it was not possible to identify some protein structures. Therefore, this study helps to establish a starting point for future proteomic studies comparing fertile and sub-fertile animals.