Human Molecular Genetics Advance Access originally published online on June 10, 2009
Human Molecular Genetics 2009 18(17):3324-3333; doi:10.1093/hmg/ddp273
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Towards a functional classification of pathogenic FOXL2 mutations using transactivation reporter systems
1 UMR7592-CNRS, Institut Jacques Monod 75013, Paris, France 2 Université Denis Diderot, Paris VII, 75013 Paris, France 3 Université Paris-Sud, Paris XI, 91400 Orsay, France 4 Equipe de Statistique Appliquée, ESPCI Paris Tech, 75005 Paris, France
* To whom correspondence should be addressed at: Institut Jacques Monod, bâtiment Buffon,15 rue Hélène Brion, 75205 Paris Cedex 13, France. Tel: +33 144412301; Fax: +33 144412302; Email: reiner.veitia{at}inserm.fr
Received April 27, 2009; Accepted June 6, 2009
Mutations of FOXL2 are responsible for the Blepharophimosis–Ptotsis–Epicantus-inversus Syndrome (BPES), involving complex eyelid malformations often associated with premature ovarian failure (POF). Loss-of-function mutations are expected to lead to BPES associated with POF, whereas hypomorphic mutations would lead to BPES without ovarian dysfunction. However, multiple exceptions to the genotype–phenotype correlation have been described and missense mutations in the forkhead domain can lead to either type of BPES. This renders almost impossible the prediction of a POF condition from a given genotype. Moreover, no clear-cut correlation between nuclear and/or cytoplasmic aggregation or cytoplasmic retention of mutant FOXL2 forms and the BPES type has been established thus far. Here, we dissect the molecular and functional effects of 10 FOXL2 mutants, known to induce BPES associated with POF or not. We found a correlation between the transcriptional activity of FOXL2 variants on two different reporter promoters and the type of BPES. We used this functional classification framework to explore the behavior of 18 missense mutations leading to BPES of unknown type. The reporters used enabled us to assess the risk of POF associated with these mutations. Moreover, we document a previously overlooked correlation between subcellular mislocalization and aggregation of mutant FOXL2 and the type of BPES, known or predicted using our reporter assays. Thus, intranuclear aggregation and cytoplasmic mislocalization of mutant FOXL2 may be considered as loose predictors of ovarian dysfunction. The functional classification tool described here is a first step towards circumventing the lack of a clear-cut genotype–phenotype correlation in BPES.