Loss of function mutations in PAK3 contribute to non-syndromic X-linked intellectual disability (NS-XLID) by affecting dendritic spine density and morphology. Linkage analysis in a three-generation family with affected males showing intellectual disability, agenesis of corpus callosum, cerebellar hypoplasia, microcephaly and ichthyosis, revealed a candidate disease locus in Xq21.33q24 encompassing over 280 genes. Subsequent to sequencing all coding exons of the X chromosome, we identified a single novel variant within the linkage region, affecting a conserved codon of PAK3. Biochemical studies showed that, similar to previous NS-XLID-associated lesions, the predicted amino acid substitution (Lys389Asn) abolished the kinase activity of PAK3. In addition, the introduced residue conferred a dominant negative function to the protein that drives the syndromic phenotype. Using a combination of in vitro and in vivo studies in zebrafish embryos we show that PAK3N389 escapes its physiologic degradation and is able to perturb MAPK signaling via an uncontrolled kinase-independent function, which in turn leads to alterations of cerebral and craniofacial structures in vivo. Our data expand the spectrum of phenotypes associated with PAK3 mutations, characterize a novel mechanism resulting in a dual molecular effect of the same mutation with a complex PAK3 functional deregulation, and provide evidence for a direct functional impact of aberrant PAK3 function on MAPK signaling.

A mutation in PAK3 with a dual molecular effect deregulates the RAS/MAPK pathway and drives an X-linked syndromic phenotype.

MAGINI, PAMELA;TURCHETTI, DANIELA;CENACCHI, GIOVANNA;NERI, IRIA;Cordelli DM;BERGAMASCHI, ROSALBA;GASPARRE, GIUSEPPE;MAZZANTI, LAURA;PATRIZI, ANNALISA;FRANZONI, EMILIO;SERI, MARCO
2014

Abstract

Loss of function mutations in PAK3 contribute to non-syndromic X-linked intellectual disability (NS-XLID) by affecting dendritic spine density and morphology. Linkage analysis in a three-generation family with affected males showing intellectual disability, agenesis of corpus callosum, cerebellar hypoplasia, microcephaly and ichthyosis, revealed a candidate disease locus in Xq21.33q24 encompassing over 280 genes. Subsequent to sequencing all coding exons of the X chromosome, we identified a single novel variant within the linkage region, affecting a conserved codon of PAK3. Biochemical studies showed that, similar to previous NS-XLID-associated lesions, the predicted amino acid substitution (Lys389Asn) abolished the kinase activity of PAK3. In addition, the introduced residue conferred a dominant negative function to the protein that drives the syndromic phenotype. Using a combination of in vitro and in vivo studies in zebrafish embryos we show that PAK3N389 escapes its physiologic degradation and is able to perturb MAPK signaling via an uncontrolled kinase-independent function, which in turn leads to alterations of cerebral and craniofacial structures in vivo. Our data expand the spectrum of phenotypes associated with PAK3 mutations, characterize a novel mechanism resulting in a dual molecular effect of the same mutation with a complex PAK3 functional deregulation, and provide evidence for a direct functional impact of aberrant PAK3 function on MAPK signaling.
Magini P;Pippucci T;Tsai IC;Coppola S;Stellacci E;Bartoletti-Stella A;Turchetti D;Graziano C;Cenacchi G;Neri I;Cordelli DM;Marchiani V;Bergamaschi R;Gasparre G;Neri G;Mazzanti L;Patrizi A;Franzoni E;Romeo G;Bordo D;Tartaglia M;Katsanis N;Seri M
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/237483
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