It is well know that the nuclei of spermatogenic cells experience one of the most extremely marked chromatin changes known in cells.At the end of spermatogenesis,the histones are removed in many species and the DNA is condensed by the highly positively charged protamines forming highly compact nucleoprotamine complexes.1-3 In the human mature sperm cell,the nucleoprotamine complexes condense most of the DNA,while 5％-15％ of the DNA remains associated to nucleosomes.4,5 For many years,it was thought that the only function of the sperm cell was to transmit the patemal genomic DNA into the next generation.1 This idea started to change with the discovery of sex-specific imprinting of genes mediated through DNA methylation differences set during gametogenesis,and epigenetically transmitted to the next generation.