A novel missense mutation in ACTG1 causes dominant deafness in a Norwegian DFNA20/26 family, but ACTG1 mutations are not frequent among families with hereditary hearing impairment.
The gamma-actin gene (ACTG1) encodes a major cytoskeletal protein of the sensory hair cells of the cochlea. Recently, mutations in ACTG1 were found to cause autosomal dominant, progressive, sensorineural hearing impairment linked to the DFNA20/26 locus on chromosome 17q25.3 in four American families and in one Dutch family. We report here the linkage of autosomal dominant, progressive, sensorineural hearing impairment in a large Norwegian family to the DFNA20/26 locus. Sequencing of ACTG1 identified a novel missense mutation (c.1109T>C; p.V370A) segregating with the hearing loss. Functional analysis in yeast showed that the p.V370A mutation restricts cell growth at elevated temperature or under hyperosmolar stress. Molecular modelling suggested that the p.V370A mutation modestly alters a site for protein-protein interaction in gamma-actin and thereby modestly alters gamma-actin-based cytoskeletal structures. Nineteen Norwegian and Danish families with autosomal, dominant hearing impairment were analyzed for mutations in ACTG1 by sequencing, but no disease-associated mutations were identified. Finally, a long-term follow-up of the hearing loss progression associated with the p.V370A mutation in ACTG1 is provided. The present study expands our understanding of the genotype-phenotype relationship of this deafness gene and provides a sensitive and simple functional assay for missense mutations in this gene, which may assist future molecular diagnosis of autosomal-dominant hearing impairment. Finally, the present results do not indicate that mutations in ACTG1 are a frequent cause of autosomal-dominant postlingual sensorineural hearing impairment in Norway nor Denmark.
Rendtorff
Nanna D
ND
Department of Medical Biochemistry and Genetics, Wilhelm Johannsen Centre for Functional Genomics, University of Copenhagen, Copenhagen, Denmark.
Zhu
Mei
M
Fagerheim
Toril
T
Antal
Torben L
TL
Jones
MaryPat
M
Teslovich
Tanya M
TM
Gillanders
Elizabeth M
EM
Barmada
Michael
M
Teig
Erik
E
Trent
Jeffrey M
JM
Friderici
Karen H
KH
Stephan
Dietrich A
DA
Tranebjaerg
Lisbeth
L
D000199:Actins / Q000235:genetics*; D004252:DNA Mutational Analysis; D005500:Follow-Up Studies; D005799:Genes, Dominant; D006319:Hearing Loss, Sensorineural / Q000235:genetics*; D020125:Mutation, Missense / Q000235:genetics*; D009664:Norway; D010375:Pedigree; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development
D000199:Actins