Purpose:
To locate and identify the gene and mutation causing autosomal dominant retinitis pigmentosa(adRP) in a large Chinese adRP family, and to investigate the patients’ clinic features and the phenotype-genotype correlations.
Methods:
A large family with multiple generations and multiple individuals affected by retinitis pigmentosa was ascertained in the Anhui province of China. Blood samples were collected and DNA was extracted. Genome scan was performed by using 30 microsatellite markers chosen in the regions of 15 known genes of adRP, and two-point linkage analysis was performed. Direct sequencing was used to screen the mutation of RP. The patients were taken clinical examinations, including visual acuity, funduscopy and humphrey threshold perimetry, electroretinogram(ERG), Fundus fluorescein angiography(FFA) as well as optical coherence tomographic(OCT) assessment.
Results:
Two-point LOD scores were less than 1 with all markers tested except D3S1292(Zmax = 2.313, θ=0), this region(3q21-24) harbors RHO which is known to cause autosomal dominant retinitis pigmentosa. Sequencing of the coding exons of RHO showed missense mutation in exon 2, 512C>T(P171L). All affected individuals in the family are heterozygous for the mutation. The mutation was not detected in 100 unrelated control individuals. The phenotype of the patients with RHOmutation showed severe clinic featuring, early onset and rapid deterioration. The night blindness was found when patients were one or two years old. The visual acuity of all affected patients in the family was severely compromised beginning in early childhood. The retinal disease in this family is a severe form of retinitis pigmentosa (RP) accompanied by macular degeneration. Fundus changes advanced with age. Choriocapillaris atrophy and posterior RPE atrophy were obvious allowing visualization of the large choroidal vessels in patients over 40 years of age.
Conclusions:
This large severe adRP Chinese family was mapped to 3q21-24, associated with a mutation of RHO 512C>T, resulting in p. P171L in the translated protein. This RHO mutation 512C>T(p. P171L) causes the severe form of adRP, but the phenotypes of the RHO mutations usually causes the lighter forms of RP that’s reported before.
Keywords: retina • gene mapping • gene screening