一个X-连锁视网膜色素变性中国家系的RPGR基因的新突变

目的 对中国人X-连锁视网膜色素变性一家系进行分子遗传学检测，报告RPGR基因突变。方法 首先对该家系X染色体进行致病基因的连锁分析，然后用单链构象多态性技术和直接DNA测序方法进行基因突变分析。结果 连锁分析在多态性微卫星遗传标记DXSS012和DXS8025产生正的Lod值分别为2．41（Zmax=2．40，θ=0）和1．26。进一步单倍型分析确定该家系致病基因位于Xp21．1，与RP3连锁。用RPGR基因突变分析，在外显子ORF15＋483－484发现GA缺失，引起阅读框架的改变，该基因缺失突变在家系中共分离。结论 报告了中国人X-连锁视网膜色素变性RPGR基因外显子ORF15＋483-484的GA缺失突变，丰富了中国人RPGR基闪突变谱，为今后研究X-连锁视网膜色素变性的基因奠定基础。     

Analysis of RPGR in a South African family with X-linked retinitis pigmentosa: research and diagnostic implications

Analysis of exon ORF15 of the RPGR gene has revealed a novel mutation in a South African family with X-linked retinitis pigmentosa (XLRP), which has implications for the rest of the family in terms of pre-symptomatic testing. The ability to test for this mutation will be beneficial for the accurate determination of carrier status in female relatives who may have been unaware of their risk before this study was performed. This work also highlights the need to be aware of the ramifications of mutation testing in what may appear to be small families. This is the first report of an RPGR ORF15 mutation in a South African family of mixed ancestry.     

Novel mutations of the RPGR gene in RP3 families

X-linked retinitis pigmentosa is a severe retinal degeneration characterized by night blindness and visual field constriction, leading to complete blindness within the third decade of life. Mutations in the RPGR gene (retinitis pigmentosa GTPase regulator), located on Xp21.1 in the RP3 region, have been associated with an RP phenotype. Further to our previous mutation screening of RPGR in families segregating with the RP3 locus, we have expanded this study to include other 8 RP3 pedigrees. Here we report the results of this expanded study and the identification of five mutations in RPGR, four of which are novel (IVS6+5 G>A, 950-951delAA, 963 T>C, EX8del) and one of which occurs in the donor splice site of intron 1 (IVS1+1 G>A). These findings bring the proportion of "RP3 genotypes" with a mutation in this gene to 27% (10/37). Hum Mutat 15:386, 2000.     

A non-ancestral RPGR missense mutation in families with either recessive or semi-dominant X-linked retinitis pigmentosa

Most X-linked diseases show a recessive pattern of inheritance in which female carriers are unaffected. In X-linked retinitis pigmentosa (XLRP), however, both recessive and semi-dominant inheritance patterns have been reported. We identified an Israeli family with semi-dominant XLRP due to a missense mutation (p.G275S) in the RPGR gene. The mutation was previously reported in two Danish families with recessive XLRP. Obligate carriers from the two Danish families had no visual complaints and normal to slightly reduced retinal function, while those from the Israeli family suffered from high myopia, low visual acuity, constricted visual fields, and severely reduced electroretinogram (ERG) amplitudes. The disease-related RPGR haplotype of the Israeli family was found to be different from the one found in the two Danish families, indicating that the mutation arose twice independently on different X-chromosome backgrounds. A series of genetic analyses excluded skewed X-inactivation pattern, chromosomal abnormalities, distorted RPGR expression level, and mutations in candidate genes as the cause for the differences in disease severity of female carriers. To the best of our knowledge, this is the first detailed analysis of an identical mutation causing either a recessive or a semi-dominant X-linked pattern of disease in different families. Our results indicate that an additional gene (or genes), linked to RPGR, modulate disease expression in severely affected carriers. These may be related to the high myopia concomitantly found in affected carriers from the Israeli family.     

Two novel mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in X-linked retinitis pigmentosa (RP3). Mutations in brief no. 172. Online

Recently a new gene called RPGR (retinitis pigmentosa GTPase regulator) was isolated in Xp21.1 and found to be mutated in patients with RP3 type X-linked retinitis pigmentosa. Two new mutations, the first a single base pair deletion and the other a two base pairs deletion, have been found in one Spanish and one Italian family.     

Neanthes japonica (Iznka) fibrinolytic enzyme reduced cerebral infarction, cerebral edema and increased antioxidation in rat models of focal cerebral ischemia

X-linked retinitis pigmentosa (XLRP) is the most severe type of retinitis pigmentosa (RP), with patients consistently showing early onset and rapid deterioration. Obtaining a genetic diagnosis for a family with XLRP is important for counseling purposes. In this study, we aimed to identify disease-causing mutations in two unrelated XLRP families. Genetic analysis was performed on two unrelated XLRP families. Genomic DNA was extracted from peripheral blood or amniotic fluid samples. The coding regions and intron/exon boundaries of the Retinitis Pigmentosa GTPase Regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. A clinically unaffected pregnant female and the four month old fetus were found to have a hemizygous 2 base pair deletion (g.ORF15+484_485delAA) in the exon ORF15 of RPGR gene. In another XLRP family, a nonsense mutation (g.ORF15+810G>T) was identified. Neither mutation has been reported previously. Both are predicted to cause premature termination of the protein. In conclusion, we identified a micro-deletion through prenatal genetic diagnosis and another novel nonsense mutation in RPGR-ORF15. Identifying a disease-causing mutation facilitated early diagnosis and genetic counseling for the patients. Discovery of novel mutations also broadens knowledge of XLRP and the spectrum of its pathogenic genotypes.     

The retinitis pigmentosa GTPase regulator (RPGR) interacts with novel transport-like proteins in the outer segments of rod photoreceptors

Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene cause X-linked retinitis pigmentosa type 3 (RP3), a severe, progressive and degenerative retinal dystrophy eventually leading to complete blindness. RPGR is ubiquitously expressed, yet mutations in the RPGR gene lead to a retina-restricted phenotype. To date, all RP3 associated missense mutations that have been identified are located in the RCC1-homologous domain (RHD) of RPGR. To investigate the molecular pathogenesis of RP3, we screened retinal yeast two-hybrid libraries with the RHD of RPGR. We identified several alternatively spliced gene products, some with retina-restricted expression, that interact specifically with RPGR in vivo and in vitro. Thus, these proteins were named RPGR-interacting protein 1 (RPGRIP1) isoforms. They contain a C-terminal RPGR-interacting domain and stretches of variable coiled-coil domains homologous to proteins involved in vesicular trafficking. The interaction between RPGR and RPGRIP1 isoforms was impaired in vivo by RP3-associated mutations in RPGR. Moreover, RPGR and RPGRIP1 co-localize in the outer segment of rod photoreceptors, which is in full agreement with the retinitis pigmentosa phenotype observed in RP3 patients. The localization of RPGRIP1 at 14q11 makes it a strong candidate gene for RP16. These results provide a clue for the retina-specific pathogenesis in RP3, and hint towards the involvement of RPGR and RPGRIP1 in mediating vesicular transport-associated processes.     

Five novel RPGR mutations in families with X-linked retinitis pigmentosa

X-linked forms of retinitis pigmentosa (XLRP) are among the most severe because of their early onset, often leading to significant visual impairment before the fourth decade. RP3, genetically localized at Xp21.1, accounts for 70% of XLRP in different populations. The RPGR (Retinitis Pigmentosa GTPase Regulator) gene that was isolated from the RP3 region is mutated in 20% of North American families with XLRP. From mutation analysis of 27 independent XLRP families, we have identified five novel RPGR mutations in 5 of the families (160delA, 789 A>T, IVS8+1 G>C, 1147insT and 1366 G>A). One of these mutations was detected in a family from Chile. Hum Mutat 17:151, 2001.     

Somatic and gonadal mosaicism in X-linked retinitis pigmentosa

The g.ORF15 + 652-653delAG mutation in the RPGR gene is the most frequent mutation in X-linked retinitis pigmentosa (XLRP). The objective of this study was to investigate the possibility of mosaicism in an XLRP family. Eight subjects in the RP family were recruited. Blood samples were collected for DNA extraction. Haplotype analysis and mutational screening on the RPGR gene were performed. Additionally, samples of hair follicles and buccal cells from the mother of the proband were acquired for DNA extraction and molecular analysis. Phenotype was characterized with routine ophthalmic examination, Goldmann perimetry, electroretinography, and color fundus photography. A g.ORF15 + 652-653delAG mutation was identified in second- and third-generation patients/carriers. A first-generation female, who was considered to be an obligate carrier, demonstrated a normal phenotype as well as a normal genotype in lymphocytic DNA, indicating the gonadal mosaicism; however, a heterozygous AG-deletion at nucleotide 652 and 653 was identified in the genomic DNA of hair follicles, hair shaft, and buccal cells, indicating that the mutation is somatic. In conclusion, we reported on a family in which an asymptomatic woman with somatic-gonadal mosaicism for a RPGR gene mutation transmitted the mutation to an asymptomatic daughter and to a son with XLRP. Gonadal mosaicism may be responsible for a proportion of multiplex or simplex RP families, in which more than 50% of all cases of RP are found. (c) 2007 Wiley-Liss, Inc.     

A novel mutation of RPGR gene in an X-linked Chinese family with retinitis pigmentosa

PurposeTo localize and identify the gene and mutations causing an X-linked Chinese family with retinitis pigmentosa.MethodsAn XLRP Chinese family was ascertained and patients underwent ophthalmological examinations. Blood samples were collected and genomic DNA was extracted. Linkage scan was performed on genomic DNA from affected and unaffected family members using microsatellite markers flanking 17 known autosomal dominant loci and markers covering the entire X chromosome. Mutation screening of RPGR gene was carried out by direct DNA sequence analysis.ResultsA genome wide scan yielded a lod score of 2.7 at θ = 0 with DXS1068 and 3.29 at θ = 0 with DXS993. This region harbors the RPGR gene. Direct DNA sequence analysis reveals one base pair deletion, gORF15 + 556delA, in all affected individuals. The deletion results in the frameshift change of RPGR gene and produces a truncated protein.ConclusionsWe identified a novel mutation, gORF15 + 556delA (p.Lys184fs), in a Han Chinese family with retinitis pigmentosa. This mutation expands the mutation spectrum of RPGR and helps to study molecular pathogenesis of RP further.     

RPGR mutation analysis and disease: an update

Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene are the most common single cause of retinitis pigmentosa, accounting for up to 15 to 20% of cases in Caucasians. A total of 240 different RPGR mutations have been reported, including 24 novel ones in this work, which are associated with X-linked retinitis pigmentosa (XLRP) (95%), cone, cone-rod dystrophy, or atrophic macular atrophy (3%), and syndromal retinal dystrophies with ciliary dyskinesia and hearing loss (2%). All disease-causing mutations occur in one or more RPGR isoforms containing the carboxyl-terminal exon open reading frame 15 (ORF15), which are widely expressed but show their highest expression in the connecting cilia of rod and cone photoreceptors. Of reported RPGR mutations, 55% occur in a glutamic acid-rich domain within exon ORF15, which accounts for only 31% of the protein. RPGR forms complexes with a variety of other proteins and appears to have a role in microtubular organization and transport between photoreceptor inner and outer segments.     

Sequence variation within the RPGR gene: evidence for a founder complex allele

In our study of sequence variation within the RPGR gene associated with X-linked retinitis pigmentosa, we and others have observed a high rate of new mutation within this gene, as all reported mutations are unique or uncommon. In this article we report the identification in a single family of a complex allele of 7 sequence variants in linkage disequilibrium, of which four result in amino-acid alterations (Arg425Lys, DGlu, Thr533Met and Gly566Glu). This complex allele was initially found in a family with XLRP. However, further study revealed an estimated prevalence of 4.3% (15/344 chromosomes) with this complex allele in the European population indicating the non-pathogenic nature of this allele and, along with previously reported polymorphisms, further supporting a high level of human protein diversity for RPGR. This common complex allele may have been established in the population as a founder effect. Complete gene sequencing identified a potential pathogenic sequence variant in the family described (IVS6+5G>A). This study emphasises the need to create a more complete picture of the allelic variation within a gene, suggests cautious interpretation of a phenotypic association with variant sequences, and highlights the potential problems associated with interpreting genetic studies for diagnostic purposes.     

Three novel mutations of the RPGR gene exon ORF15 in three Japanese families with X-linked retinitis pigmentosa.

We describe three new mutations in a recently identified exon, ORF15, of the retinitis pigmentosa GTPase regulator gene (RPGR) in three unrelated Japanese families (Families 1-3) with X-linked retinitis pigmentosa (XLRP). The affected males had typical retinitis pigmentosa (RP), whereas the obligate carrier females showed a wide clinical spectrum, ranging from minor symptoms to severe visual disability. Some carrier females in Families 1 and 2 showed typical RP, most carriers manifested high myopia and astigmatism, and their corrected visual acuity was insufficient. They showed an impairment of cone function following the rod dysfunction and accompanied by refractive errors. Microsatellite analysis of Family 1 revealed that the RP in the family was linked to the RP3 locus. Although one patient in the family had no mutation in the previously published exons 1-19 including exon 15a, he had a single-nucleotide insertion in exon ORF15 (g.ORF15 + 753-754 insG). Likewise, patients in Families 2 and 3 had two-base insertion/deletion in the exon, i.e., g.ORF15 + 833-834delGG and g.ORF15 + 861-862insGG, respectively. These insertional/deletional mutations observed in the three families are all different and new, and are predicted to lead to a frameshift, resulting in a truncated protein. These findings may support the previous hypothesis that RPGR-ORF15 is a mutational hot spot.     

Severe manifestations in carrier females in X linked retinitis pigmentosa.

Retinitis pigmentosa (RP) is a group of progressive hereditary disorders of the retina in which various modes of inheritance have been described. Here, we report on X linked RP in nine families with constant and severe expression in carrier females. In our series, however, the phenotype was milder and delayed in carrier females compared to hemizygous males. This form of X linked RP could be regarded therefore as partially dominant. The disease gene maps to chromosome Xp2.1 in the genetic interval encompassing the RP3 locus (Zmax=13.71 at the DXS1100 locus). Single strand conformation polymorphism and direct sequence analysis of the retinitis pigmentosa GTPase regulator (RPGR) gene, which accounts for RP3, failed to detect any mutation in our families. Future advances in the identification of X linked RP genes will hopefully help to elucidate the molecular basis of this X linked dominant RP.     

Mapping of X-linked progressive retinal atrophy (XLPRA), the canine homolog of retinitis pigmentosa 3 (RP3)

X-linked progressive retinal atrophy (XLPRA) in the Siberian husky dog is a naturally occurring X-linked retinopathy closely resembling X-linked retinitis pigmentosa (XLRP) in humans. In affected males, initial degeneration of rods is followed by cone degeneration and complete retinal atrophy; carrier females have random patches of rod degeneration consistent with random X chromosome inactivation. By typing the XLPRA pedigree with five intragenic markers [dystrophin, retinitis pigmentosa GTPase regulator ( RPGR ), tissue inhibitor of metalloproteinases 1, androgen receptor and factor IX], we established a linkage map of the canine X chromosome, and confirmed that the order of these five genes is identical to that on the human X. XLPRA was tightly linked to an intragenic RPGR polymorphism (LOD 11.7, zero recombination), thus confirming locus homology with RP3. We cloned the full-length canine RPGR cDNA and three additional splice variants. No disease-causing mutation was found in the RPGR-coding sequence of the four splice variants characterized, a finding similar to approximately 80% of human XLRP patients whose disease maps to the RP3 locus. In addition, there were no significant differences in the proportional expression of each splice variant in normal and pre-degenerate XLPRA-affected retina. Expression of all RPGR splice variants increased later in the disease, when retinas were undergoing active degeneration. The results provide further evidence of cross-species retention of a complex splicing pattern in the 3' portion of RPGR, the functional significance of which is unknown. In addition, the possibility of another disease locus in the RP3 region is supported.     

常染色体显性遗传视网膜色素变性家系的基因筛查

目的：确定一个常染色体显性遗传视网膜色素变性(autosomal dominant retinitis pigmentosa,ADRP）家系的致病基因及其突变位点和类型。方法：应用聚合酶链反应－单链构象多态性结合DNA测序技术，对来自同一家系的4例RP患者及4名正常人外周血DNA进行分子遗传学分析，筛查3个候选基因共8个外显子。结果：来自同一家系的4例RP患者均发现有视紫红质基因（rhodopsin,RHO)第1外显子第52密码子存在TTC→TAC的点突变（Phe52Tyr），而4名正常人未发现这种突变。结论：在这个中国ADRP大家系中，发现RHO基因的致病突变，表明ADRP存在明显遗传异质性。     

Genetic and prenatal diagnosis of a retinitis pigmentosa pedigreeCSCD

Objective To explore the genetic etiology of a pedigree affected with hereditary retinitis pigmentosa. Methods High-throughput DNA sequencing was used to analyze the sequences of 173 genes associated with hereditary eye diseases in the proband. Suspected mutation was verified with PCR amplification and Sanger sequencing. Results The proband was found to have carried a c. 570-571 ins GAAGATGCTGT insertional mutation in the RP2 gene located on the X chromosome. All female carriers of the pedigree were heterozygous, while all affected males were hemizygous for the same mutation. Conclusion The inheritance pattern of this retinitis pigmentosa pedigree was X-linked recessive. The c. 570-571 ins GAAGATGCTGT insertional mutation of the RP2 gene probably underlies the disease. © 2018 West China University of Medical Sciences. All rights reserved.