title: A missense mutation within the fork-head domain of the forkhead box G1 Gene (FOXG1) affects its nuclear localization.
abstract: The forkhead box G1 (FOXG1)gene has recently been associated with the congenital variant of Rett syndrome, and so far 17 mutations have been reported. We screened the coding region in 150 patients affected by postnatal microcephaly, and identified two mutations: the c.326C>T (p.P109L) substitution inherited from the healthy father; and the de novo c.730C>T transition, which induces the p.R244C mutation within the DNA-binding forkhead domain. This latter mutation is carried by an 8-year-old girl, who presented a phenotype reminiscent of the congenital variant of Rett syndrome. Immunofluorescence analysis of the wild-type protein revealed a homogeneous nuclear staining excluding the nucleoli, while the p.R244C mutant showed abnormal nuclear foci in a large proportion of cells, suggesting that its mislocalization may reduce and/or impair target recognition. Interestingly, this missense mutation results in a mislocalization of FoxG1 to specific nuclear foci referred to as nuclear speckles, and affects the cyclin-dependent kinase inhibitor p21 CDKN1A expression. Because CDKL5, which is involved in the early-onset variant of Rett syndrome, is also located in these speckles, we suggest that disregulation of the dynamic behaviour of nuclear speckles may functionally link these two proteins, which are both involved in atypical forms of Rett syndrome.
authors.affiliation: Inserm, U1016, Paris, France.
authors.forename: Tangui
authors.initials: T
authors.lastname: Le Guen
authors.forename: Yann
authors.initials: Y
authors.lastname: Fichou
authors.forename: Juliette
authors.initials: J
authors.lastname: Nectoux
authors.forename: Nadia
authors.initials: N
authors.lastname: Bahi-Buisson
authors.forename: François
authors.initials: F
authors.lastname: Rivier
authors.forename: Nathalie
authors.initials: N
authors.lastname: Boddaert
authors.forename: Bertrand
authors.initials: B
authors.lastname: Diebold
authors.forename: Delphine
authors.initials: D
authors.lastname: Héron
authors.forename: Jamel
authors.initials: J
authors.lastname: Chelly
authors.forename: Thierry
authors.initials: T
authors.lastname: Bienvenu
mesh_terms: D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D002648:Child; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D005260:Female; D051858:Forkhead Transcription Factors / Q000032:analysis / Q000235:genetics*; D006801:Humans; D007223:Infant; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D015518:Rett Syndrome / Q000235:genetics; D016415:Sequence Alignment
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C090173:FOXG1 protein, human; D051858:Forkhead Transcription Factors; D009419:Nerve Tissue Proteins; D017346:Protein Serine-Threonine Kinases; C114482:CDKL5 protein, human