ABSTRACT
FMR1 is an X-linked gene that codes for an RNA binding protein. Expansion of a triplet
repeat within exon 1 of the gene causes the fragile X syndrome, which is characterized
by mental retardation and various physical anomalies. The triplet repeat in FMR1 can expand to varying degrees. Only the very large expansions in which there is concomitant
methylation of the gene cause the fragile X syndrome. Expansions of between 50 and
200 repeats are premutations. Although premutations were originally perceived to be
without phenotypic effect, there is now substantial evidence that female carriers
of premutations are at increased risk of having early menopause. The FMR1 premutation is also associated with a significant number of cases ascertained because
of idiopathic premature ovarian failure, particularly when ovarian failure is a familial
trait. The molecular mechanism to explain the association between ovarian failure
and premutations is unknown.
KEYWORD
premature ovarian failure - premutation