title: Identification and in silico analysis of 14 novel GJB1, MPZ and PMP22 gene mutations.
abstract: Duplication within the chromosome 17p11.2 (CMT1Adup), peripheral myelin protein 22 (PMP22), myelin protein zero (MPZ) and gap junction beta1-protein (GJB1) gene mutations are frequent causes of the Charcot-Marie-Tooth disease (CMT). A large number of mutations in these genes are listed in databases. Sequence variants identified in patients are frequently reported as mutations without further evaluation. We analyzed 250 consecutively recruited unrelated Austrian CMT patients for CMT1Adup by microsatellite marker typing, real-time PCR or MLPA, and found 79 duplications (31.6%). The coding regions of the PMP22, MPZ and GJB1 genes were analyzed by direct sequencing in the remaining patients; 28 patients showed mutations, 14 of which were novel. We scored the pathogenicity of novel missense mutations by segregation studies and by their exclusion in control samples. Our comprehensive literature study found that up to 60% of the reported mutations in these genes had not been evaluated regarding their pathogenicity, and the PANTHER bioinformatics tool was used to score novel and published missense variants. The PANTHER program scored known polymorphisms as such, but scored approximately 82-88% only of the published and novel mutations as most likely deleterious. Mutations associated with axonal CMT were less likely to be classified as deleterious, and the PMP22 S72L mutation repeatedly associated with severe CMT was classified as a polymorphism using default parameters. Our data suggest that this in silico analysis tool could be useful for assessing the functional impact of DNA variations only as a complementary approach. The CMT1Adup, GJB1, MPZ and PMP22 mutation frequencies were in the range of those described in other CMT patient collectives with different ethnical backgrounds.
authors.affiliation: Division of Clinical Genetics, Innsbruck Medical University, Innsbruck, Austria.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Miltenberger-Miltenyi
authors.forename: Thomas
authors.initials: T
authors.lastname: Schwarzbraun
authors.forename: Wolfgang N
authors.initials: WN
authors.lastname: Löscher
authors.forename: Julia
authors.initials: J
authors.lastname: Wanschitz
authors.forename: Christian
authors.initials: C
authors.lastname: Windpassinger
authors.forename: Hans-Christoph
authors.initials: HC
authors.lastname: Duba
authors.forename: Rainer
authors.initials: R
authors.lastname: Seidl
authors.forename: Gerhard
authors.initials: G
authors.lastname: Albrecht
authors.forename: Helga
authors.initials: H
authors.lastname: Weirich-Schwaiger
authors.forename: Heinz
authors.initials: H
authors.lastname: Zoller
authors.forename: Gerd
authors.initials: G
authors.lastname: Utermann
authors.forename: Michaela
authors.initials: M
authors.lastname: Auer-Grumbach
authors.forename: Andreas R
authors.initials: AR
authors.lastname: Janecke
mesh_terms: D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D001317:Austria; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics / Q000473:pathology; D019295:Computational Biology / Q000379:methods*; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D018993:Myelin P0 Protein / Q000235:genetics*; D009185:Myelin Proteins / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D000097002:Gap Junction beta-1 Protein
chemical_list: D017630:Connexins; D018993:Myelin P0 Protein; D009185:Myelin Proteins; D000097002:Gap Junction beta-1 Protein; C073687:PMP22 protein, human