Preliminary studies of FMRP expression during rat follicular development.

FERDER IANINA, SUNDBLAD VICTORIA, ABRAMOVICH DALHIA, CHIAUZZI VIOLETA, PARBORELL FERNANDA, CHARREAU EDUARDO, TESONE MARTA, DAIN LILIANA

Baeza, España

Workshop; Workshop "Fragile X-related syndromes: from molecular to clinical approach"; 2007

Premature Ovarian Failure (POF) is characterized by the cesation of gonadal function before 40 years of age, hypoestrogenism, elevated gonadotrophin serum levels, and different stages of follicular atresia. POF is a very heterogeneous syndrome with multicausal pathogenesis affecting 1% of women in reproductive age. Due to frequent inheritance in families, it was suggested that POF may be a genetic disorder. Indeed, specific genetic alterations or mutations are already identified in some genes as responsible for cases of POF, in more than 90 % of patients the aetiology of the disease is still unknown. Previous reports, however, indicate an incidence close to 4% of FMR1-premutation carriers among POF patients. Moreover, close to 20% of the permutated mothers of Fragile-X childs develop POF. Even though the underlying molecular mechanism is not yet understood, it was suggested that premutation might be related to the disease. The product of FMR-1 gene, FMRP, associates with polyribosomes in an RNA-dependent manner through messenger ribonucleoprotein particles and it can suppress translation both in vitro and in vivo,linking FMRP to the microRNA pathway. Though FMRP is expressed in a wide range of tissues including the ovary, its function in this gonad has not been elucidated, nor its expression during follicular development. The aim of our study was to analyse expression of FMRP in different stages of follicular development. Expression of the protein was assessed by Western-blot in a ribosomal-enriched fraction from different isolated follicles, or by the aid of Immunohistochemistry in paraffin-embedded tissue. Ovaries were removed from female Sprague-Dawley prepuberal rats (18 days-old) or from 23 days-old rats that were injected subcutaneously with diethylstilbestrol (DES: 1 mg/rat daily for three days) to stimulate the development of early antral follicles. Alternatively, 23 days-old rats were injected with PMSG (25 UI/rat) to stimulate the development of preovulatory follicles. In each experiment, 4 to 24 ovaries were used, and all experiments were repeated at least two times. Western blot and Immunohistochemical analyses showed that prepuberal ovaries do not express FMRP, while expression of the protein was observed in ovaries from DES or PMSG treated rats. On the other hand, FMRP was expressed in granulosa cells only in preovulatory follicles. In earlier follicular stages, expression of FMRP was confined to theca or stromal cells. In addition, expression of FMRP was also  observed in the corpus-luteum. Our results might indicate a differential expression of FMRP during follicular development.