Human Molecular Genetics Advance Access originally published online on March 27, 2008
Human Molecular Genetics 2008 17(13):2030-2038; doi:10.1093/hmg/ddn100
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Missense mutations in the forkhead domain of FOXL2 lead to subcellular mislocalization, protein aggregation and impaired transactivation
1 Center for Medical Genetics 2 Department of Ophthalmology, Ghent University Hospital, 9000 Ghent, Belgium 3 INSERM U567, Team 21, Genetics and Development Department 4 CNRS UMR8104, Institut Cochin, 24 rue du Faubourg St-Jacques, 75014 Paris, France 5 Université Paris Descartes, Faculté de Médecine Cochin-Port-Royal, 24 rue du Faubourg St-Jacques, 75014 Paris, France 6 Université Denis Diderot, Paris VII, 75014 Paris, France 7 Institute of Medical Genetics, Charité – Universitätsmedizin Berlin, Berlin, Germany
* To whom correspondence should be addressed at: Center for Medical Genetics, Ghent University Hospital, De Pintelaan 185, B-9000 Ghent, Belgium. Tel: +32 93325186; Fax: +32 93324970; Email: elfride.debaere{at}ugent.be
Received February 20, 2008; Accepted March 25, 2008
Mutations of the FOXL2 gene have been shown to cause blepharophimosis syndrome (BPES), characterized by an eyelid malformation associated with premature ovarian failure or not. Recently, polyalanine expansions and truncating FOXL2 mutations have been shown to lead to protein mislocalization, aggregation and altered transactivation. Here, we study the molecular consequences of 17 naturally occurring FOXL2 missense mutations. Most of them map to the conserved DNA-binding forkhead domain (FHD). The subcellular localization and aggregation pattern of the mutant FOXL2 proteins in COS-7 cells was variable and ranged from a diffuse nuclear distribution like the wild-type to extensive nuclear aggregation often in combination with cytoplasmic mislocalization and aggregation. We also studied the transactivation capacity of the mutants in FOXL2 expressing granulosa-like cells (KGN). Several mutants led to a loss-of-function, while others are suspected to induce a dominant negative effect. Interestingly, one mutant that is located outside the FHD (S217F), appeared to be hypermorphic and had no effect on intracellular protein distribution. This mutation gives rise to a mild BPES phenotype. In general, missense mutations located in the FHD lead to classical BPES and cannot be correlated with expression of the ovarian phenotype. However, a potential predictive value of localization and transactivation assays in the making of genotype–phenotype correlations is proposed. This is the first study to demonstrate that a significant number of missense mutations in the FHD of FOXL2 lead to mislocalization, protein aggregation and altered transactivation, and to provide insights into the pathogenesis associated with missense mutations of FOXL2 in human disease.
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.