Linkage testing using Affymetrix 6.0 SNP Arrays mapped the disease locus in 
TCD-G, an Irish family with autosomal dominant retinitis pigmentosa (adRP), to 
an 8.8 Mb region on 1p31. Of 50 known genes in the region, 11 candidates, 
including RPE65 and PDE4B, were sequenced using di-deoxy capillary 
electrophoresis. Simultaneously, a subset of family members was analyzed using 
Agilent SureSelect All Exome capture, followed by sequencing on an Illumina 
GAIIx platform. Candidate gene and exome sequencing resulted in the 
identification of an Asp477Gly mutation in exon 13 of the RPE65 gene tracking 
with the disease in TCD-G. All coding exons of genes not sequenced to sufficient 
depth by next generation sequencing were sequenced by di-deoxy sequencing. No 
other potential disease-causing variants were found to segregate with disease in 
TCD-G. The Asp477Gly mutation was not present in Irish controls, but was found 
in a second Irish family provisionally diagnosed with choroideremia, bringing 
the combined maximum two-point LOD score to 5.3. Mutations in RPE65 are a known 
cause of recessive Leber congenital amaurosis (LCA) and recessive RP, but no 
dominant mutations have been reported. Protein modeling suggests that the 
Asp477Gly mutation may destabilize protein folding, and mutant RPE65 protein 
migrates marginally faster on SDS-PAGE, compared with wild type. Gene therapy 
for LCA patients with RPE65 mutations has shown great promise, raising the 
possibility of related therapies for dominant-acting mutations in this gene.