Coordinated Control Of Connexin 26 And Connexin 30 At The Regulatory And Functional Level In The Inner Ear

摘要

Connexin 26 (C×26) and connexin 30 (C×30) are encoded by two genes (GJB2 and GJB6. respectively) that are found within 50 kb in the same complex deafness locus, DFNB1. Immunocytochemistry and quantitative PCR analysis of C×30 KO mouse cultures revealed that C×26 is downregulated at the protein level and at the mRNA level in nonsensory cells located between outer hair cells and the stria vascularis. To explore connexin coregulation, we manipulated gene expression using the bovine adeno-associated virus. Over-expression of C×30 in the C×30 KO mouse by transduction with bovine adeno-associated virus restored C×26 expression, permitted the formation of functional gap junction channels, and rescued propagating Ca~(2+) signals. Ablation of C×26 by transduction of C×26~(10×p/10×p) cultures with a Cre recombinase vector caused concurrent downregulation of C×30 and impaired intercellular communication. The coordinated regulation of C×26 and C×30 expression appears to occur as a result of signaling through PLC and the NF-kB pathway, because activation of IP_3-mediated Ca~(2+) responses by stimulation of P2Y receptors for 20 min with 20 nM ATP increased the levels of C×26 transcripts in C×30 KO cultures. This effect was inhibited by expressing a stable form of the IkB repressor protein that prevents activation/translocation of NF-kB. Thus, our data reveal a Ca~(2+)-dependent control in the expression of inner ear connexins implicated in hereditary deafness as well as insight into the hitherto unexplained observation that some deafness-associated DFNB1 alleles are characterized by hereditable reduction of both GJB2 and GJB6 expression.