1. An early nonsense mutation facilitates the expression of a short isoform of CNGA3 by alternative translation initiation
- Author
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Joachim Täger, Bernd Wissinger, David G. Birch, Peggy Reuter, Dianna K H Wheaton, and Susanne Kohl
- Subjects
0301 basic medicine ,Achromatopsia ,genetic structures ,Color Vision Defects ,Polymerase Chain Reaction ,genetics [Color Vision Defects] ,genetics [Peptide Chain Initiation, Translational] ,Mice ,0302 clinical medicine ,CNGA3 protein, human ,Protein Isoforms ,Peptide Chain Initiation, Translational ,medicine.diagnostic_test ,Immunohistochemistry ,Sensory Systems ,Cell biology ,Codon, Nonsense ,Retinal Cone Photoreceptor Cells ,Electrophoresis, Polyacrylamide Gel ,Visual phototransduction ,Gene isoform ,Retinal Disorder ,genetics [Protein Isoforms] ,Blotting, Western ,Nonsense mutation ,physiology [Gene Expression Regulation] ,Cyclic Nucleotide-Gated Cation Channels ,genetics [Cyclic Nucleotide-Gated Cation Channels] ,Biology ,Transfection ,Article ,Cell Line ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Eukaryotic translation ,Western blot ,medicine ,Animals ,Humans ,ddc:610 ,genetics [Codon, Nonsense] ,metabolism [Retinal Cone Photoreceptor Cells] ,medicine.disease ,Ophthalmology ,HEK293 Cells ,030104 developmental biology ,Gene Expression Regulation ,030221 ophthalmology & optometry ,metabolism [Color Vision Defects] ,sense organs ,metabolism [HEK293 Cells] ,Function (biology) - Abstract
The cyclic nucleotide-gated (CNG) channel - composed of CNGA3 and CNGB3 subunits - mediates the influx of cations in cone photoreceptors after light stimulation and thus is a key element in cone phototransduction. Mutations in CNGA3 and CNGB3 are associated with achromatopsia, a rare autosomal recessive retinal disorder. Here, we demonstrate that the presence of an early nonsense mutation in CNGA3 induces the usage of a downstream alternative translation initiation site giving rise to a short CNGA3 isoform. The expression of this short isoform was verified by Western blot analysis and DAB staining of HEK293 cells and cone photoreceptor-like 661W cells expressing CNGA3-GST fusion constructs. Functionality of the short isoform was confirmed by a cellular calcium influx assay. Furthermore, patients carrying an early nonsense mutation were analyzed for residual cone photoreceptor function in order to identify a potential role of the short isoform to modify the clinical outcome in achromatopsia patients. Yet the results suggest that the short isoform is not able to compensate for the loss of the long isoform leaving the biological role of this variant unclear. more...
- Published
- 2018
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