SGCE and myoclonus-dystonia syndrome: In this imprinted region, only two paternally expressed genes, PEG10 and SGCE, exist together with other maternally expressed genes (Ono et al., 2003) and loss-of-function mutations on SGCE are reported to cause myoclonus dystonia syndrome, which is characterized by bilateral, alcohol-sensitive myoclonic jerks mainly affecting the arms and axial muscles (Zimprich et al., 2001), suggesting that retrovirus-derived PEG10 may be causative gene in placental dysplasia.