Cone cGMP-gated channel mutations and clinical findings in patients with achromatopsia, macular degeneration, and other hereditary cone diseases.
Unrelated patients with achromatopsia, macular degeneration with onset under age 50 years, cone degeneration or dysfunction, cone-rod degeneration, or macular malfunction were screened for mutations in the three genes known to be associated with achromatopsia: the GNAT2 gene encoding the alpha subunit of cone transducin and the CNGA3 and CNGB3 genes encoding the alpha and beta subunits of the cone cGMP-gated cation channel. We found no examples of patients with GNAT2 mutations. Out of 36 achromats, 12 (33%) had mutations in CNGA3 (13 different mutations including five novel mutations) and 12 (33%) had mutations in CNGB3 (six different mutations including four novel mutations). All achromats with CNG mutations had residual, presumably cone function as determined by computer-averaged 30-Hz electroretinograms (ERGs). There was considerable variability in acuity and color vision, with most patients having acuities of 20/200-20/400 and complete absence of color perception, and others having acuities of 20/25-20/40 and some color vision. Two pseudodominant achromatopsia cases were uncovered, both with CNGA3 mutations, including one family in which some compound heterozygotes with achromatopsia mutations were clinically unaffected. We found two novel CNGB3 changes in three patients with juvenile macular degeneration, a phenotype not previously associated with mutations in the cone channel subunits. These patients had subnormal acuity (20/30-20/60), normal to subnormal color vision, and normal to subnormal full-field cone ERG amplitudes. Our results indicate that some patients with channel protein mutations retain residual foveal cone function. Based on our findings, CNGB3 should be considered as a candidate gene to be evaluated in patients with forms of cone dysfunction, including macular degeneration.
Nishiguchi
Koji M
KM
Ocular Molecular Genetics Institute and the Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA.
Sandberg
Michael A
MA
Gorji
Nasim
N
Berson
Eliot L
EL
Dryja
Thaddeus P
TP
D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D018389:Codon, Nonsense; D003117:Color Vision Defects / Q000235:genetics* / Q000503:physiopathology; D016384:Consensus Sequence; D054815:Cyclic Nucleotide-Gated Cation Channels; D004252:DNA Mutational Analysis; D004596:Electroretinography; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D020962:Heterotrimeric GTP-Binding Proteins / Q000235:genetics; D006801:Humans; D007473:Ion Channels / Q000235:genetics* / Q000502:physiology; D008268:Macular Degeneration / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D017354:Point Mutation; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology; D012162:Retinal Degeneration / Q000235:genetics* / Q000503:physiopathology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015293:Transducin
C415904:CNGB3 protein, human; D018389:Codon, Nonsense; D054815:Cyclic Nucleotide-Gated Cation Channels; C034809:GNAT1 protein, human; D007473:Ion Channels; D020962:Heterotrimeric GTP-Binding Proteins; D015293:Transducin