Methylation Status of Imprinted Genes and Repetitive Elements in Sperm DNA from Infertile Males

er in sperm samples leading to pregnancy and live-birth than in those that did not. Sperm samples leading to abor-tions showed significantly lower ALU methylation levels than those leading to the birth of a baby. Copyright © 2011 S. Karger AG, Basel Gametogenesis is a highly complex process that in-volves dramatic epigenetic changes [Reik et al., 2001; Haaf, 2006]. In the mammalian germline, genome-wide demethylation erases essentially all methylation patterns in primordial germ cells around the time when the cells enter the gonadal ridge to ensure an equivalent epigenetic state in germ cells of both sexes [Hajkova et al., 2002]. Parent-specific methylation patterns according to the sex of the germline are then established during germ-cell dif-ferentiation. In the male germline, remethylation is initi-ated after prenatal mitotic arrest and completed postna-tally during pachytene [Marchal et al., 2004; Oakes et al., 2007]. Experimental demethylation of male germ cells in neonatal and adult mice interfered with spermatogenesis and pregnancy outcome, indicating the biological sig-nificance of germ-cell methylation [Raman and Narayan, 1995; Kelly et al., 2003]. A number of recent studies re-ported epigenetic abnormalities, mostly aberrant meth