Pathogenetic role of the deafness-related M34T mutation of Cx26.
Mutations in the GJB2 gene, which encodes the gap junction protein connexin26 (Cx26), are the major cause of genetic non-syndromic hearing loss. The role of the allelic variant M34T in causing hereditary deafness remains controversial. By combining genetic, clinical, biochemical, electrophysiological and structural modeling studies, we have re-assessed the pathogenetic role of the M34T mutation. Genetic and audiological data indicate that the majority of heterozygous carriers and all five compound heterozygotes exhibited an impaired auditory function. Functional expression in transiently transfected HeLa cells showed that, although M34T was correctly synthesized and targeted to the plasma membrane, it inefficiently formed intercellular channels that displayed an abnormal electrical behavior and retained only 11% of the unitary conductance of the wild-type protein (HCx26wt). Moreover, M34T channels failed to support the intercellular diffusion of Lucifer Yellow and the spreading of mechanically induced intercellular Ca2+ waves. When co-expressed together with HCx26wt, M34T exerted dominant-negative effects on cell-cell coupling. Our findings are consistent with a structural model, predicting that the mutation leads to a constriction of the channel pore. These data support the view that M34T is a pathological variant of Cx26 associated with hearing impairment.
Bicego
Massimiliano
M
Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, University of Trieste, and Servizio di Genetica Medica, IRCCS-Ospedale Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy.
Beltramello
Martina
M
Melchionda
Salvatore
S
Carella
Massimo
M
Piazza
Valeria
V
Zelante
Leopoldo
L
Bukauskas
Feliksas F
FF
Arslan
Edoardo
E
Cama
Elona
E
Pantano
Sergio
S
Bruzzone
Roberto
R
D'Andrea
Paola
P
Mammano
Fabio
F
D000293:Adolescent; D000328:Adult; D000368:Aged; D019943:Amino Acid Substitution; D001298:Audiology; D020013:Calcium Signaling; D002648:Child; D002675:Child, Preschool; D004396:Coloring Agents / Q000737:chemistry / Q000493:pharmacokinetics; D000072259:Connexin 26; D017630:Connexins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003638:Deafness / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006367:HeLa Cells; D006801:Humans; D015640:Ion Channel Gating; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D014162:Transfection
D004396:Coloring Agents; D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26