Revisiting the pathogenic mechanism of the GJB1 5 ’ UTR c.-103C  & gt;  T mutation causing CMTX1

This study assessed the internal ribosomal entry site (IRES) activity previously reported for the ratGjb1 P2 5 ’ untranslated region (UTR). Using a bicistronic assay and transfecting RT4 Schwann cells, IRES activity of the humanGJB1 P2 5 ’ UTR was compared to theGJB1 P2 5 ’ UTR containing either the c.-103C >  T mutation or the non-pathogenic c.-102G >  A variant. No differences inGJB1 P2 5 ’ UTR IRES activity were observed between the negative control, the wild-type P2 5’ UTR, the c.-103C >  T 5’ UTR or the c.-102G >  A 5’ UTR, irrespective of theGJB1 intron being present (p = .429 with intron, andp = .865 without). A theoretical c.-131A >  G variant was predicted to result in the same RNA secondary structure as theGJB1 c.-103C  >  T P2 5’ UTR. However, no significant difference was observed between expression from the wild-typeGJB1 P2 5 ’ UTR and theGJB1 c.-131A  >  G variant (p = .688). Deletion of the conserved region surrounding the c.-103C >  T mutation (c.-108_-103del) resulted in significantly higher expression than the c.-103C >  T mutation alone (p = .019), suggesting that the conserved c.-108_-103 region was not essential for translation. The reporter assays in this study do not recapitulate the previously reportedGJB1 IRES activity and suggest an alternate pathogenic mechanism for the c.-103C  >  T CMTX1 non-coding mutation.
Source: Neurogenetics - Category: Genetics & Stem Cells Source Type: research