FMR1 and ovarian dysfunction: While it was initially suggested that the toxic effect of the elevated levels of FMR1 mRNA could lead to a diminished ovarian reserve before birth (Conway et al., 1995), and indeed FMR1 is expressed in germ cells in the human foetal ovary (Rosario et al., 2016), it has since been proposed that ovarian dysfunction associated with premutation alleles could be considered a late age-of-onset disease, with mRNA toxic effects causing increased atresia of follicles throughout the lifetime (Sullivan et al., 2005).