Multicenter genetic study of retinitis pigmentosa in Japan: I. Genetic heterogeneity in typical retinitis pigmentosa

A nationwide, multicenter study of typical retinitis pigmentosa (RP) was carried out in collaboration with 18 hospitals throughout Japan to obtain current information for genetic counseling. We analyzed the genetic heterogeneity of RP based on the parental consanguinity of 434 probands registered during a 6-month period in 1990. A gradual decline in the frequency of consanguineous marriage was recognized among the normal parents of RP patients. The relative frequencies of inheritance patterns were estimated as: autosomal recessive, 25.2%; autosomal dominant, 16.9%; X-linked, 1.6%; and simplex, 56.3%. A comparison of these results with previous reports in Japan revealed a decline in the relative frequency of autosomal recessive cases and an increase in simplex cases. This suggests a decrease in the incidence of autosomal recessive retinitis pigmentosa in Japan, as well as the necessity for exhaustive investigations aimed at identifying inheritance patterns for RP patients seeking genetic counseling.     

Prevalence of retinitis pigmentosa and allied disorders in Denmark. III. Hereditary pattern.

A national epidemiological study revealed 1301 prevalent cases of retinitis pigmentosa (RP) in the Danish population on January 1, 1988. The corresponding number of 974 families were analyzed with respect to Mendelian inheritance groups. Thirty families, comprising 6.9% of the prevalent RP-cases, were categorized with an autosomal dominant inheritance pattern. In 187 families, 22.6% of RP-cases, autosomal recessive heredity was encountered. X-linked heredity was found in 45 families, 10.8% of the RP-cases. Simplex RP-cases comprised 562 persons (43.2% of RP-cases). About a fourth of the non-systemic X-linked cases were females. Half of these had an age at onset after 30 years, but a third had their first RP-symptoms before age 18 years. A representative fraction of parents to non-systemic autosomal dominant, autosomal recessive, X-linked, and simplex cases were evaluated concerning their age at the time they had their first affected child. Mothers of the male simplex cases were of statistically significant higher age than mothers of the other inheritance groups. This may imply a high rate of new mutations among simplex cases, especially on the X-chromosome.     

A genetic analysis of retinitis pigmentosa.

Genetic analysis of 457 patients with retinitis pigmentosa (RP) included categorisation of families by recognised mendelian pattern of inheritance and formal segregation analysis of all informative sibships. Of the 368 probands a surprisingly high 18% (68) had significant congenital loss of hearing and were diagnosed as having Usher syndrome. The RP probands were categorised as: 21.7% autosomal dominant, 9.0% X-linked, 16.0% autosomal recessive, 3.3% genetic type uncertain, and 50.0% simplex. Segregation analysis reflected this high proportion of simplex cases, accounting for reduced penetrance in dominant families; only 20% remain classified as sporadic (possibly nongenetic). In the matings between normal persons estimates of the segregation ratio also indicate lower values than expected. Unlike in RP sibship, segregation in the Usher syndrome is consistent with the hypothesis of recessive inheritance. Therefore RP with significant hearing loss segregates as expected, while even if a proband is classified as a dominant or recessive the recurrence risk for the RP phenotype may be below mendelian expectation.     

视网膜色素变性1基因在常染色体显性遗传视网膜色素变性家系中的突变分析

目的:研究常染色体显性遗传视网膜色素变性(autosomal dominant retinitis pigmentosa,ADRP)家系中视网膜色素变性1(retinitis pigmentosa-1,RP1)基因的突变特征及其在RP发病机制中的作用。方法:运用聚合酶链反应和直接测序方法,对6个ADRP家系的47例成员和50例对照者进行了RP1基因全编码区和邻近剪切位点的内含子区域序列突变的筛选与检测。运用单因素分析、多因素Logistic回归分析研究RP1基因点突变在RP发病中的作用。结果:ADRP家系成员和对照组RP1基因第4外显子上检测出2个变异位点。在1691和1725密码子存在杂合的两种类型的密码子(S1691P,Ser-Pro,TCT→CCT;Q1725Q,Gln-Gln,CAA→CAG)。ADRP家系成员中Ser-1691-Pro及Gln-1725-Gln位点突变率显著高于正常对照组(χ2=11.202,P<0.05)。结论:RP1基因Ser-1691-Pro及Gln-1725-Gln位点多态性可增高RP的危险性,具有潜在的致病性,考虑为ADRP家系的易感基因。     

Correlation between Goldmann perimetry and maximal electroretinogram response in retinitis pigmentosa

To evaluate the relationship between Goldmann perimetry and maximal electroretinographic responses in patients with retinitis pigmentosa, analyses were performed on 220 affected subjects and separately on two subgroups with autosomal dominant (n = 35) and autosomal recessive (n = 29) inheritance. Electroretinograms were recorded averaging 100 iterations elicited with a 20-lux/s, 0.5-Hz white flash ganzfeld stimulation. The peripheral isopters of the visual fields were delimited with I4e, IIIe and V4e targets, measured on conventional perimetry charts with a light pen and expressed in square centimeters. Unlike most previously published reports, this investigation showed a definite correlation (p = 0.0001) between maximal electroretinographic response amplitude and visual field areas. This correlation was more evident for I4e and IIIe isopters (r = 0.89 and 0.87, respectively) than for V4e isopter (r = 0.69). This phenomenon appears to be related to distortion occurring on standard isometric charts and to spatial summation effects in the peripheral field. Such correlations held for both the autosomal dominant and autosomal recessive subgroups. It appears that, if enough accuracy is provided, maximal electroretinographic responses and Goldmann visual fields are both good measures of the remaining functioning retina in nonsyndromic retinitis pigmentosa, irrespective of inheritance models and dystrophic patterns.Abbreviations ADRP autosomal dominant retinitis pigmentosa - ARRP autosomal recessive retinitis pigmentosa - RP retinitis pigmentosa - VF visual field     

Evaluation of RLBP1 in 50 autosomal recessive retinitis pigmentosa and 4 retinitis punctata albescens Spanish families

Defects in retinal vitamin A metabolism or in genes expressed in the retinal pigment epithelium (RPE) are related to nonsyndromic retinitis pigmentosa (RP). The RLBP1 gene encodes the cellular retinaldehyde-binding protein which, in the RPE and Müller cells of the retina, is thought to play a role in retinoid metabolism and visual pigment regeneration. We describe a study of the involvement of the RLBP1 gene in 50 autosomal recessive retinitis pigmentosa (ARRP) and four retinitis punctata albescens Spanish families. Cosegregation and homozygosity studies using an intragenic polymorphism and three close markers (D15S116, D15S127, and D15S130) ruled out RLBP1 as the cause of ARRP in 26 pedigrees. In the remaining families, SSCP analysis of the coding region and sequencing of the abnormal migrating bands did not detect any disease-causing mutation. These results indicate that mutations in the RLBP1 gene are not responsible for the ARRP or retinitis punctata albescens in this set of Spanish families. We did, however, identify two frequent polymorphisms (3'UTR + 167 G > T, T: 0.23 and G: 0.77; IVS6 + 20 T > C, T: 0.36 and C: 0.64), a silent substitution (S218S), and a rare variant (5'UTR-101 G > A).     

常染色体显性视网膜色素变性家系的基因连锁定位和候选基因的序列分析

目的对一常染色体显性视网膜色素变性（RP）家系进行致病基因的连锁定位，并对候选基因进行序列分析。方法在家系中进行全基因组扫描以确定与疾病连锁的染色体区域，对该区域附近的候选基因进行直接序列分析。结果此家系致病基因的最小可能区域（MCR）被定位于19号染色体微卫星标记D19S246和D19S601之间不到5厘摩（cM）的区域。对该区域附近的候选基因进行直接序列分析的结果并未发现致病性基因突变。结论CRX（锥杆细胞同源基因）和PRPF3l基因是该家系的非致病性基因，在19号染色体上可能存在导致常染色体显性视网膜色素变性（adRP）的新的致病基因。     

视网膜色素变性遗传致病基因peripherin/RDS的突变筛选

目的 了解中国视网膜色素变性患者（RP）中peripherin/RDS基因的突变谱及突变率。方法 应用聚合酶链-异源双链-单链构象多态性（PCR-SSCP）及DNA序列分析技术对收集的15个常染色体显性遗传视网膜色谱变性家系和55例散发视网膜色素变性患者peripherin/RDS基因的第一，第二外显子进行检测。结果 15个家系及55例散发患者未检测到peripherin/RDS基因突变。结论 本研究所检测的视网膜色素变性患者与RDS基因无关，显示视网膜色素变性的遗传异质性。     

Mutations in the gene coding for guanylate cyclase-activating protein 2 (<Emphasis Type="Italic">GUCA1B</Emphasis> gene) in patients with autosomal dominant retinal dystrophies

Background We investigated mutations in the gene coding for guanylate-cyclase activating protein 2 (GCAP2), also known as GUCA1B gene, in Japanese patients with retinitis pigmentosa (RP) and tried to identify phenotypic characteristics associated with mutations in the gene.Subjects and methods Genomic DNA samples from 63 unrelated patients with autosomal dominant retinitis pigmentosa (ADRP) and 33 patients with autosomal recessive retinitis pigmentosa (ARRP) were screened by single-strand conformational polymorphism analysis followed by direct sequencing. Clinical features associated with a mutation were demonstrated by visual acuity, visual field testing, fundus photography, and electroretinography.Results A novel transitional mutation converting GGA to AGA at codon 157 (G157R) was identified. This mutation has been found in three index patients from three independent families. Phenotypic examination of seven members of the three families revealed that this mutation was associated with RP with or without macular involvement in five members, macular degeneration in one member, and asymptomatic normal phenotype in one member. In addition, previously unknown polymorphic changes including V29V, Y57Y, T87I, and L180L were identified.Conclusions A racial difference exists in the spectrum of mutations and/or polymorphisms in the GCAP 2 gene between British and Japanese populations. Our findings suggest that the mutation in the GCAP 2 gene can cause one form of autosomal dominant retinal dystrophy, with variable phenotypic expression and incomplete penetrance.     

Genetic features of retinitis pigmentosa in Turkey

Sixty-two cases with retinitis pigmentosa from 42 index families were investigated to reveal the genetic features of the disease in Turkey. There were 42 propositi of whom 5 had a systemic syndrome associated with retinitis pigmentosa. Of the remaining 37 cases the condition was autosomal recessive in 21 (56.8%), sporadic in 12 (32.4%), autosomal dominant in 3 (8.1%) and X-linked recessive in one (2.7%). Sporadic cases may be more frequent as many hereditary cases are not brought to medical attention in rural families. Male preponderance among sporadic cases may indicate that there may be more X-linked cases. Nine out of 21 cases initially classified as sporadic displayed parental consanguinity and they were included as having autosomal recessive trait. Large families with autosomal recessive inheritance may prove valuable in linkage analysis and in defining future gene abnormalities.     

CRB1 mutations may result in retinitis pigmentosa without para-arteriolar RPE preservation

Purpose: To report a new phenotype in retinitis pigmenotosa (RP) patients with CRB1 mutations at the RP12 locus. Patients: Thirty-seven patients from two Pakistani families with severe retinitis pigmentosa. Methods: Samples were screened with single-strand conformation polymorphism analysis followed by DNA sequencing of the coding sequence of the CRB1 gene. Results: Two novel CRB1 mutations were discovered. No patients had evidence of preservation of the para-arteriolar retinal pigment epithelium (PPRPE) that has been previously reported in all cases of RP associated with CRB1 mutations. Conclusions: Patients with severe autosomal recessive (or simplex) RP who lack the finding of PPRPE should not be excluded from molecular analysis of CRB1 purely because they lack the clinical feature of PPRPE. This report illustrates that RP at the RP12 locus is not clinically uniform. The absence of PPRPE cannot be used to exclude CRB1 as a potential molecular explanation for RP.     

Analysis of genes coding for S-antigen, interstitial retinol binding protein, and the alpha-subunit of cone transducin in patients with retinitis pigmentosa

We screened 526 unrelated patients with autosomal dominant, autosomal recessive, or simplex retinitis pigmentosa for evidence of mutations of the genes encoding S-antigen (S-Ag), interstitial retinol binding protein (IRBP), and the alpha-subunit of cone-specific transducin. Restriction fragment length polymorphisms (RFLPs) were identified at each of these loci. Within each set of patients with a particular genetic type of retinitis pigmentosa, RFLP alleles at each of these loci showed no departure from Hardy-Weinberg equilibrium. No gene deletions or rearrangements could be detected in any patient. Furthermore, in each of six pedigrees (one autosomal dominant, one autosomal recessive, three Usher's syndrome type I, and one Laurence-Moon-Bardet-Biedl syndrome) there was no co-segregation of the disease with alleles determined by RFLPs at the locus for S-antigen. At the IRBP locus, lack of co-segregation was seen in one autosomal dominant, two autosomal recessive, and three Usher's syndrome type I pedigrees. Finally, one pedigree with autosomal recessive retinitis pigmentosa showed no co-segregation of the disease with alleles at the locus for the alpha-subunit of the cone-specific transducin. These data support the idea that the genes coding for S-Ag, IRBP, and the alpha-subunit of the cone-specific transducin do not play an etiologic role in the families with retinitis pigmentosa so far studied.     

Multicenter genetic study of retinitis pigmentosa in Japan: II. Prevalence of autosomal recessive retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of genetically heterogeneous diseases with autosomal recessive (AR), autosomal dominant, and X-linked modes of inheritance. Autosomal recessive retinitis pigmentosa (ARRP) is the most common form in Japan. A genetic analysis was done to determine the prevalence of ARRP indirectly, to provide an estimation of changing trends in the overall prevalence of RP. Data on the frequency of consanguinity and marriage year of normal parents of 59 ARRP patients were obtained from a nationwide multicenter survey of typical retinitis pigmentosa conducted in 1990. The gene frequency of ARRP was 0.01145 (Dahlberg's formula). In 1990, the number of young symptomatic ARRP patients decreased, while the number of patients aged 40 years and older increased. The total number of symptomatic ARRP patients in 1990 was nearly 21% higher than in 1970. Despite a dramatic decline in consanguinity in recent decades in Japan, the number of ARRP patients has increased. This increase is attributed to greater longevity and overall population growth. Our results suggest that the total number of RP patients has not decreased, and may even have increased.     

A survey of hereditary aspects of pigmentary retinal dystrophies

A study of 707 cases of retinitis pigmentosa and choroideraemia presenting over 12 years were classified according to their modes of inheritance-439 autosomal recessive (62%), 193 autosomal dominant (27%), 75 X-linked (10.7%). The patients with autosomal recessive transmission included 58 Usher syndrome, 12 Laurence-Moon-Bardet-Biedl syndrome and 33 Leber's congenital amaurosis. Another 37 had an early onset with macular degeneration and 31 were of late onset with pericentral dystrophy. Forty two were offspring of consanguineous parents. Of 193 individuals (78 families) with autosomal dominant inheritance, 20% had night blindness from early childhood. With X-linked transmission, 33 males and 31 female carriers comprised the retinitis pigmentosa group and eight males and three carrier females, choroideraemia. Almost all this X-linked group were of British ancestry. Of patients originating from the Mediterranean area, 94% had autosomal recessive disease.     

A survey of hereditary aspects of pigmentary retinal dystrophies

A study of 707 cases of retinitis pigmentosa and choroideraemia presenting over 12 years were classified according to their modes of inheritance--439 autosomal recessive (62%), 193 autosomal dominant (27%), 75 X-linked (10.7%). The patients with autosomal recessive transmission included 58 Usher syndrome, 12 Laurence-Moon-Bardet-Biedl syndrome and 33 Leber's congenital amaurosis. Another 37 had an early onset with macular degeneration and 31 were of late onset with pericentral dystrophy. Forty two were offspring of consanguineous parents. Of 193 individuals (78 families) with autosomal dominant inheritance, 20% had night blindness from early childhood. With X-linked transmission, 33 males and 31 female carriers comprised the retinitis pigmentosa group and eight males and three carrier females, choroideraemia. Almost all this X-linked group were of British ancestry. Of patients originating from the Mediterranean area, 94% had autosomal recessive disease.     

Molecular analysis of RIM1 in autosomal recessive Retinitis pigmentosa

Retinitis pigmentosa (RP) is a frequent retinal dystrophy characterized by a progressive loss of photoreceptors along with retinal degeneration. RIM1, encoding a presynaptic protein involved in the glutamate neurotransmission, is the responsible gene for autosomal dominant cone-rod dystrophy CORD7, whose locus overlaps partially with a locus of autosomal recessive RP (arRP), RP25. Given the genetic heterogeneity that features RP, it is plausible that mutations in RIM1 are also implicated in the disease in arRP families genetically linked to the CORD7 region. To test our hypothesis we analysed the complete RIM1 gene in 8 arRP families by DNA sequencing. Even though the absence of pathogenic mutations suggests that RIM1 is notinvolved in arRP, a role for this gene in other inherited forms of RP as well as other retinal dystrophies needs to be elucidated.     

Novel 2336-2337delCT mutation in RP1 gene in a Japanese family with autosomal dominant retinitis pigmentosa

PURPOSE: To determine the frequency and kinds of mutations in the RP1 gene, and to characterize the clinical features of a Japanese family with autosomal dominant retinitis pigmentosa (ADRP) with a novel 2336 to 2337delCT mutation in the RP1 gene. DESIGN: Case reports and results of DNA analysis. METHODS: Mutational screening by direct sequencing was performed on 96 unrelated patients with ADRP. The clinical features were determined by complete ophthalmologic examinations. RESULTS: A novel 2336 to 2337delCT mutation in the RP1 gene was identified in two patients from a Japanese family with ADRP. In addition, three families with ADRP carried a previously reported nonpathogenic Arg1933X mutation. The ophthalmic findings with a 2336 to 2337delCT mutation were similar to those of typical retinitis pigmentosa with rapid progression after age 40 years. CONCLUSIONS: The most common Arg677X mutation in the white population was not found in the Japanese population; instead a novel mutation was found.     

Whole-exome sequencing identifies novel mutations in genes responsible for retinitis pigmentosa in 2 nonconsanguineous Chinese families

AIM: To detect the pathogenetic mutations responsible for nonsyndromic autosomal recessive retinitis pigmentosa (RP) in 2 nonconsanguineous Chinese families. METHODS: The clinical data, including detailed medical history, best corrected visual acuity (BCVA), slit-lamp biomicroscope examination, fundus photography, optical coherence tomography, static perimetry, and full field electroretinogram, were collected from the members of 2 nonconsanguineous Chinese families preliminarily diagnosed with RP. Genomic DNA was extracted from the probands and other available family members; whole-exome sequencing was conducted with the DNA samples provided by the probands, and all mutations detected by whole-exome sequencing were verified using Sanger sequencing in the probands and the other available family members. The verified novel mutations were further sequenced in 192 ethnicity matched healthy controls. RESULTS: The patients from the 2 families exhibited the typical symptoms of RP, including night blindness and progressive constriction of the visual field, and the fundus examinations showed attenuated retinal arterioles, peripheral bone spicule pigment deposits, and waxy optic discs. Whole-exome sequencing revealed a novel nonsense mutation in FAM161A (c.943A>T, p.Lys315*) and compound heterozygous mutations in RP1L1 (c.56C>A, p.Pro19His; c.5470C>T, p.Gln1824*). The nonsense c.5470C>T, p.Gln1824* mutation was novel. All mutations were verified by Sanger sequencing. The mutation p.Lys315* in FAM161A co-segregated with the phenotype, and all the nonsense mutations were absent from the ethnicity matched healthy controls and all available databases. CONCLUSION: We identify 2 novel mutations in genes responsible for autosomal recessive RP, and the mutation in FAM161A is reported for the first time in a Chinese population. Our result not only enriches the knowledge of the mutation frequency and spectrum in the genes responsible for nonsyndromic RP but also provides a new target for future gene therapy.     

Analysis of rhodopsin gene in patients with retinitis pigmentosa using allele-specific polymerase chain reaction.

Point mutations within the rhodopsin gene have been found recently in some patients with autosomal dominant retinitis pigmentosa (ADRP). Currently, four types of point mutations at codons 23, 58 and 347 have been identified. The purposes of this study were to establish simple methods for screening patients with retinitis pigmentosa (RP) to detect these point mutations, and to apply these methods to determine if these mutations are found in Japanese patients with RP. Utilizing the polymerase chain reaction (PCR), a one-step method was developed to detect point mutations at codon 23. This method was then applied to screen genomic DNAs from 30 patients with various types of RP, including ADRP, autosomal recessive RP, simplex RP, Leber's congenital amaurosis or Usher's syndrome. Subsequently, point mutations at codons 58 and 347 were detected by restriction enzyme digestion (Dde I or Msp I) of exons 1 and 5 amplified by PCR. To date, no mutations have been found in codons 23 and 58 in Japanese patients. By using the allele-specific PCR, however, two patients from one pedigree of ADRP were confirmed to have a C-to-T transition at the second nucleotide of codon 347, which results in the substitution of leucine for proline. Our findings indicated the availability of this simple method for detecting these point mutations.