[Aberrant expression pattern of a novel mutation in connexin 26 gene resulting in autosomal recessive deafness].
OBJECTIVE
To report a novel deafness-causing mutation c.465T>A, p.Y155X in connexin 26 (CX26) (also called gap junction protein beta-2, GJB2), and perform functional analysis of the mutated protein p.Y155X in Hela cells to explore the underlying mechanism on deafness.


METHODS
Mutations in CX26 gene of the proband in an autosomal recessive inherited deafness family were tested by direct DNA sequencing method. Mutant p.Y155X, which was found in the deafness family, and wild type CX26 (wtCX26), were directionally subcloned into the pEGFP-N1 plasmid to construct the recombinant fusion protein expression vector of CX26 p.Y155X-EGFP and wtCX26-EGFP, followed by transfecting into HeLa cells. The expression of the mutated and wild type proteins was analyzed using Western blot analysis. The intracellular localization of proteins and the formation of gap junction-like plaques at plasma membrane were observed under confocal microscope. Gap junction coupling was tested by calcein-AM dye transfer experiment.


RESULTS
A novel nonsense mutation c.465T>A, p.Y155X in the CX26 gene was found in the autosomal recessive deafness family. The molecular weight of protein p.Y155X was smaller than that of wtCX26 in transiently expressed HeLa cells. The mutated protein failed to reach the cell surface to form gap junction plaques, and displayed cytoplasmic accumulation. Also, no calcein-AM dye was transferred from the donor cells to the recipient cells when both were transfected with CX26 p.Y155X. The wtCX26 protein localized at the cell membrane to form gap junction plaques with permeability to fluorescent dye calcein AM.


CONCLUSIONS
CX26 p.Y155X could not be targeted to the plasma membrane and there was no formation of gap junction channels between the adjacent cells. The mutation c.465T>A, p.Y155X in CX26 gene was responsible for the autosomal recessive hearing impairment in this family.
Yang
Zhong-chun
ZC
Department of Otolaryngology-Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, 410011 PR China.
Xiao
Zi-an
ZA
Xie
Ding-hua
DH
Xia
Kun
K
D000595:Amino Acid Sequence; D002648:Child; D018389:Codon, Nonsense / Q000235:genetics; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis; D003638:Deafness / Q000235:genetics*; D005260:Female; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010375:Pedigree; D017386:Sequence Homology, Amino Acid
D018389:Codon, Nonsense; D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26