Molecular understanding of the FMR1 premutation and fragile X-associated premature ovarian failure

CGG repeats expansion (55-200 units, premutation range) in the 5’UTR of FMR1 gene (Xq27.3) is associated with Fragile-X Tremor/ Ataxia Syndrome and Premature Ovarian Failure (POF). FMR1 premutation represents the most significant single gene variant associated with POF, however no studies are available to evaluate its pathogenic effect in the ovary context. As for FXTAS, an RNA-mediated toxic gain of function could be hypothesized for FX-POF. Human granulosa cell line were transfected with plasmid containing 76CGG repeat elements in the 5’-UTR of EGFP reporter under the control of CMV immediate early promoter (CMV-76CGG-EGFP), or with CMVEGFP as control. By RNA immunoprecipitation, the interaction of 76rCGG for rCGG-Repeat Binding Proteins (rCGG-RBPs), previously identified, was tested. 76rCGG solely immunoprecipitate with heat shock proteins, some hnRNPs and proteins involved in paraspeckles formation such as SFPQ and hnRNPM, suggesting that in vivo premutated FMR1 mRNA differs from the wild type in making RNA-protein complexes. In this regard in premutated granulosa cells a deregulation of structural components paraspeckles was observed suggesting an alteration of splicing. Furthermore an “heat shock like” response associated with a reduced cell viability in human ovary granulosa cells expressing expanded CGG mRNA was observed, indicating a toxic role of premutated mRNA itself in the ovaries. This work is supported by Telethon grant GGP009126.