ORC1 and Meier-Gorlin syndrome: The Cyclin E-CDK2 kinase inhibitory activity is compromised by ORC1 Meier-Gorlin syndrome mutations that also alter the interaction between ORC1 and histone H4K20me2 (Hossain and Stillman, 2012; Kuo et al., 2012; Zhang et al., 2015; Bicknell et al., 2011b; Bicknell et al., 2011a; de Munnik et al., 2012).