There is evidence that DNA methylation of X genes can vary according to the parental origin; a higher expression of the X gene toll-like receptor 7 (Tlr7) in XY mice with experimental autoimmune encephalomyelitis (a model system of multiple sclerosis) than XX littermates can only be explained by epigenetic modifications in the parental germ line (“parental imprinting”) [52]. The gene discussed is TLR7; the disease is experimental autoimmune encephalomyelitis.