paternal allele [65, 93, 94]; however, the antisense transcript shows biallelic expression in the adrenal and testes [65]. Consistent with allele-specific expression, the paternal antisense promoter is associated with acetylated histone and histone-3 Lys4 methylation, while the maternal promoter lacks histone acetylation and carries histone-3 Lys9 methylation [87]. Furthermore, studies in mice have shown that the maternal methylation at the antisense promoter is present even in the oocytes and, therefore, represents a germ-line imprint mark [95].
