Other novel menopause loci implicate: the evolutionarily conserved maternal-effect gene ZAR1, which encodes an oocyte-specific protein that is critical for oocyte-to-embryo transition21; H1FX, which encodes a member of the histone H1 family; and RAD21, a gene involved in chromatid cohesion during mitosis and the repair of DNA double-strand breaks, and mutated in two children with Cornelia de Lange syndrome-4, a complex disorder with cellular characteristics of decreased chromatid separation, increased aneuploidy and defective DNA repair22. This evidence concerns the gene ZAR1 and Cornelia de Lange syndrome.