OBJECTIVETo test the frequency and pattern of rhodopsin (RHO) mutations in Chinese retinitis pigmentosa (RP) patients and to evaluate their effects in the pathogenesis of RP.

METHODSGenomic DNA was extracted from peripheral blood samples of 100 Hong Kong Chinese RP patients. Sequence variants of the entire coding exons of the RHO gene were tested using PCR, conformation sensitive gel electrophoresis and DNA sequencing.

RESULTSTotally six nucleotide changes were identified, among which three were silent mutations, two missense mutations and one deletion mutation. P347L was found in one RP proband and her three children who also had RP. P327(1 bp del) was novel and detected in a late-onset RP patient of 53 years. Her 26-year-old daughter, also carrying the identified mutation, had no RP phenotypes except for the mottled retinal pigment epithelium (RPE) revealed by fundal examination. Neither of the two mutations was detected in normal controls.

CONCLUSIONTwo patients had disease-causing mutations in the RHO gene, thus RHO mutations cause about 2.0% (95% confidence interval: 0.2%-7.0%) of all RP among Chinese in Hong Kong. A highly conserved C-terminal sequence QVS(A)PA was altered due to P347L and thereby resulting in an aberrant subcellular localization of rhodopsin. Loss of all six phosphorylatable residues at the C-terminus and the highly conserved C-terminal sequence QVS(A)PA may occur because of P327(1 bp del). To elucidate the predominant biochemical defects in such mutant, transgenic mice and transfected culture cells carrying P327(1 bp del) would be of greatest value.

Adolescent ; Adult ; Aged ; Child ; China ; DNA ; chemistry ; genetics ; DNA Mutational Analysis ; Female ; Gene Frequency ; Genetic Testing ; Humans ; Male ; Middle Aged ; Point Mutation ; Retinitis Pigmentosa ; genetics ; pathology ; prevention & control ; Rhodopsin ; genetics ; Sequence Deletion

OBJECTIVETo identify and evaluate mutations in the RP1 gene among Chinese patients with retinitis pigmentosa (RP).

METHODSLeukocyte DNA of 92 RP patients were collected in Hong Kong. Sequence changes of the entire coding region of the RP1 gene were examined using PCR, conformation sensitive gel electrophoresis and DNA sequencing.

RESULTSIn total, 1 nonsense mutation and 1 nonsense variant as well as 10 missense alterations were identified in the RP1 gene, among which, Arg677Ter was found in 1 RP patient and another nonsense variant, Arg1933Ter, was identified in 3 normal individuals and 1 patient with Stargardt's disease, suggesting its nonpathogenicity. Arg77Ter is expected to lead to large disruptions of the encoded protein.

CONCLUSIONSThe nonpathogenicity of Arg1933Ter indicates that the C-terminal 224 residues of RP1 protein may be not critical for RP1. The most C-terminal truncation previously reported was due to Tyr1053 (1-bp del) and occurred in RP patients. Thus RP can be caused by reduction in the level of the region of RP1 protein after codon 1052 but before 1933. To ascertain such a proposition, genotypes of more RP patients may reveal more RP causative mutations and more sequence alterations different than those of other ethnic groups.

Adolescent ; Adult ; Aged ; Child ; Codon, Nonsense ; DNA Mutational Analysis ; Eye Proteins ; genetics ; Female ; Humans ; Male ; Middle Aged ; Mutation, Missense ; Retinitis Pigmentosa ; genetics

OBJECTIVETo investigate the frequency and pattern of RP1 point mutations in Chinese retinitis pigmentosa (RP) patients and to examine their effects on the development of RP.

METHODSConformation sensitive gel electrophoresis (CSGE) and direct DNA sequencing were used to determine sequence alterations occurring in the entire coding region of the RP1 gene in 101 Chinese RP patients in Hong Kong.

RESULTSR677X was detected in one RP patient. A nonpathogenic nonsense mutation, R1933X, was identified in three normal individuals and one patient with Stargardt disease. The frequency of RP1 mutations among all RP patients in this study is 1/101. R677X is expected to lead to large disruptions of the encoded protein. Additionally, 10 more missense alterations in the RP1 gene were identified in the subjects of this study. Apart from M479I whose pathogenicity can not be determined currently, other sequence changes are just polymorphisms of the RP1 gene.

CONCLUSIONThe nonpathogenicity of R1933X indicates that the C-terminal 224 residues of RP1 protein may be not critical for RP1. Recently, a C-termnal truncating mutation, Y1053(1 bp del), was reported to occur in an RP patient. Thus RP can be caused by lack of the region of RP1 protein after codon 1052 but before 1933. To confirm such a proposition, a large genotyping study is necessary and is likely to reveal more RP causative mutations and uncover more sequence alterations different from those of other ethnic groups.

Adolescent ; Adult ; Aged ; Child ; China ; DNA ; chemistry ; genetics ; DNA Mutational Analysis ; Eye Proteins ; genetics ; Female ; Gene Frequency ; Genotype ; Humans ; Male ; Middle Aged ; Mutation ; Mutation, Missense ; Retinitis Pigmentosa ; genetics