Non-bullous ichthyosiform erythroderma associated with retinitis pigmentosa

Non-bullous ichthyosiform erythroderma (NBIE) is an autosomal recessive condition characterized by generalized erythema and scaling. Two brothers with NBIE and retinitis pigmentosa are reported. One of them also had a marfanoid habitus, thoracic kyphosis, and arachnodactyly, and was heterozygous for alpha 1 antitrypsin deficiency. A third brother had skin involvement, but normal vision. Retinitis pigmentosa has been described in association with NBIE as part of Rud syndrome, which is no longer considered a separate entity. Major diagnostic features of Rud syndrome, such as hypogonadism, mental retardation, and epilepsy were absent in this family. The association of NBIE with retinitis pigmentosa in this family seems distinct from any previously described, currently recognized syndrome.     

Schizophrenia and mental retardation associated in a pedigree with retinitis pigmentosa and sensorineural deafness

A family is presented with multiple cases of mild mental retardation, schizophrenia and other functional psychoses, progressive hearing loss, and retinitis pigmentosa (RP). It closely resembles a previously reported Finnish family. We suggest that the phenotypes are not associated in this family by chance, but define a novel syndrome which may be caused by a mutant allele at a single genetic locus. © 1994 Wiley-Liss, Inc.     

SCAPER‐associated nonsyndromic autosomal recessive retinitis pigmentosa

Mutations in the gene SCAPER (S ‐phase C yclinA A ssociated P rotein residing in the E ndoplasmic R eticulum) have recently been identified as causing syndromic autosomal recessive retinitis pigmentosa with the extraocular manifestations of intellectual disability and attention‐deficit/hyperactivity disorder. We present the case of an 11‐year‐old boy that presented to our clinic with the complaint of decreased night vision. Clinical presentation, family history, and diagnostic imaging were congruent with the diagnosis of autosomal recessive retinitis pigmentosa. Genetic testing of the patient and both parents via whole‐exome sequencing revealed the homozygous mutation c.2023‐2A>G in SCAPER. Unique to our patient's presentation is the absence of intellectual disability and attention‐deficit/hyperactivity disorder, suggesting that SCAPER‐associated retinitis pigmentosa can also present without systemic manifestations.     

先天性大疱性鱼鳞病样红皮病基因突变检测

目的 研究1例先天性大疱性鱼鳞病样红皮病散发患者的基因突变情况,探讨基因型与表现型的相关性.方法 应用聚合酶链反应扩增KRT1和KRT10基因的热点突变区,通过DNA直接测序的方法,对先天性大疱性鱼鳞病样红皮病患者、家系中的正常成员和50名无亲缘关系的正常个体的KRT1和KRT10基因进行突变检测.结果 在患者KRT10基因的第1外显子上发现了1个错义突变(467G→A),导致角蛋白10(KRT10)1A区的精氨酸由组氨酸替代(R156H),而家系正常成员和无亲缘关系的50名正常对照中均未发现该突变.结论 KRT10基因第1外显子突变(467G→A)在该例先天性大疱性鱼鳞病样红皮病患病的分子机制中发挥重要作用.     

Variant haploinsufficiency and phenotypic non‐penetrance in PRPF31‐associated retinitis pigmentosa

Retinitis pigmentosa (RP) is a genetically heterogenous group of inherited disorders, characterized by death of the retinal photoreceptor cells, leading to progressive visual impairment. One form of RP is caused by mutations in the ubiquitously expressed splicing factor, PRPF31, this form being known as RP11. An intriguing feature of RP11 is the presence of non‐penetrance, which has been observed in the majority of PRPF31 mutation‐carrying families. In contrast to variable expressivity, which is highly pervasive, true non‐penetrance is a very rare phenomenon in Mendelian disorders. In this article, the molecular mechanisms underlying phenotypic non‐penetrance in RP11 are explored. It is an elegant example of how our understanding of monogenic disorders has evolved from studying only the disease gene, to considering a mutation on the genetic background of the individual – the logical evolution in this genomic era.     

视网膜色素变性患者中视网膜色素变性1基因点突变的研究

目的 研究中国视网膜色素变性（retinitis pigmentosa，RP)患者RP1基因的突变频率、特征及其在RP发病机理中所起的作用。方法 运用构象敏感凝胶电泳（conformation sensitive gel electrophoresis,CSGE)和DNA直接测序方法对101例香港地区RP患者的RP1基因全编码区进行突变的筛选与检测。结果 101例RP患者中检出1例患者携带常见的RP1致病突变－R677X，另外在3名正常个体及1例Stargardt患者中检出非致病的无义突变－R1933X。RP1基因在所有RP患者中的突变检出率为1／101。突变最终导致RP1蛋白严重截短。此外，在本研究人群中还发现10个错义突变，除M479I的病理意义未确定之外，其余均系RP1基因的多态现象。结论 R1933X无致病意义，提示羧基端224个氨基酸的区域可能为RP1蛋白非功能区，结合最近发现的RP1羧基端的移码突变－Y1053（1bp del)的病理意义，推测RP1蛋白中相应片段（密码子1052－1933）的缺失会导致RP的发生。为证实这种推测，大范围的RP1基因分型工作是有必要的，并且可同时发现更多的RP致病突变以及不同于其他种族人群的RP1基因多态变化。     

Dominant Leber congenital amaurosis,cone‐rod degeneration,and retinitis pigmentosa caused by mutant versions of the transcription factor CRX

We summarize 18 mutations in the human CRX gene that have been associated with Leber congenital amaurosis (congenital retinal blindness), cone‐rod degeneration, or retinitis pigmentosa. Except for one obviously null allele not definitely associated with a phenotype (a frameshift in codon 9), all CRX mutations appear to be completely penetrant and cause disease in heterozygotes. These dominant alleles fall into two categories. In one group are missense mutations and short, in‐frame deletions; in the second group are frameshift mutations, all of which are in the last exon. All of these dominant mutations are likely to produce stable mRNA that is translated. Mutations in the missense group preferentially affect the conserved homeobox (codons 39–98), and all frameshift mutations leave the homeodomain intact but alter the OTX motif encoded by codons 284–295 at the carboxy terminus. We could not uncover any correlation between type of disease (congenital amaurosis vs. cone‐rod degeneration or retinitis pigmentosa) and the type of mutation (missense vs. frameshift). Four of the 18 mutations (～20%) were de novo mutations, and all of these were found in isolate cases of Leber congenital amaurosis. Dominant CRX mutations have not been associated with mental retardation or developmental delay that has sometimes been found in Leber congenital amaurosis caused by other genes. Implications regarding potential future therapies are discussed. Hum Mutat 18:488–498, 2001. © 2001 Wiley‐Liss, Inc.     

WDR19: An ancient,retrograde, intraflagellar ciliary protein is mutated in autosomal recessive retinitis pigmentosa and in Senior‐Loken syndrome

Autosomal recessive retinitis pigmentosa (arRP) is a clinically and genetically heterogeneous retinal disease that causes blindness. Our purpose was to identify the causal gene, describe the phenotype and delineate the mutation spectrum in a consanguineous Quebec arRP family. We performed Arrayed Primer Extension (APEX) technology to exclude ∼500 arRP mutations in ∼20 genes. Homozygosity mapping [single nucleotide polymorphism (SNP) genotyping] identified 10 novel significant homozygous regions. We performed next generation sequencing and whole exome capture. Sanger sequencing provided cosegregation. We screened another 150 retinitis pigmentosa (RP) and 200 patients with Senior‐Løken Syndrome (SLS). We identified a novel missense mutation in WDR19, c.2129T>C which lead to a p.Leu710Ser. We found the same mutation in a second Quebec arRP family. Interestingly, two of seven affected members of the original family developed ‘sub‐clinical’ renal cysts. We hypothesized that more severe WDR19 mutations may lead to severe ciliopathies and found seven WDR19 mutations in five SLS families. We identified a new gene for both arRP and SLS. WDR19 is a ciliary protein associated with the intraflagellar transport machinery. We are currently investigating the full extent of the mutation spectrum. Our findings are crucial in expanding the understanding of childhood blindness and identifying new genes.     

Association of non‐syndromic macrocephaly with autism

Harlequin ichthyosis, (MIM 242500), is a rare, autosomal recessive skin disorder due to an inborn error of epidermal keratinization. The gene for this condition has not been localized. We present a case of HI in which there was a de novo deletion of chromosome 18q: the karyotype was 46, XY, del(18)(q21.3). We postulate that the gene for HI may lie at, or distal to 18q21.3 and that the deletion observed in this case may have unmasked this autosomal recessive disorder. © 2001 Wiley‐Liss, Inc.     

Next generation sequencing of pooled samples reveals new SNRNP200 mutations associated with retinitis pigmentosa

The gene SNRNP200 is composed of 45 exons and encodes a protein essential for pre-mRNA splicing, the 200 kDa helicase hBrr2. Two mutations in SNRNP200 have recently been associated with autosomal dominant retinitis pigmentosa (adRP), a retinal degenerative disease, in two families from China. In this work we analyzed the entire 35-Kb SNRNP200 genomic region in a cohort of 96 unrelated North American patients with adRP. To complete this large-scale sequencing project, we performed ultra high-throughput sequencing of pooled, untagged PCR products. We then validated the detected DNA changes by Sanger sequencing of individual samples from this cohort and from an additional one of 95 patients. One of the two previously known mutations (p.S1087L) was identified in 3 patients, while 4 new missense changes (p.R681C, p.R681H, p.V683L, p.Y689C) affecting highly conserved codons were identified in 6 unrelated individuals, indicating that the prevalence of SNRNP200-associated adRP is relatively high. We also took advantage of this research to evaluate the pool-and-sequence method, especially with respect to the generation of false positive and negative results. We conclude that, although this strategy can be adopted for rapid discovery of new disease-associated variants, it still requires extensive validation to be used in routine DNA screenings.     

A single‐base substitution within an intronic repetitive element causes dominant retinitis pigmentosa with reduced penetrance

We report the study of a large American family displaying autosomal dominant retinitis pigmentosa with reduced penetrance, a form of hereditary retinal degeneration. Although the inheritance pattern and previous linkage mapping pointed to the involvement of the PRPF31 gene, extensive screening of all its exons and their boundaries failed in the past to reveal any mutation. In this work, we sequenced the entire PRPF31 genomic region by both the classical Sanger method and ultrahigh throughput (UHT) sequencing. Among the many variants identified, a single‐base substitution (c.1374+654C>G) located deep within intron 13 and inside a repetitive DNA element was common to all patients and obligate asymptomatic carriers. This change created a new splice donor site leading to the synthesis of two mutant PRPF31 isoforms, degraded by nonsense‐mediated mRNA decay. As a consequence, amounts of PRPF31 mRNA derived from the mutant allele were very reduced, with no evidence of mutant proteins being synthesized. Our results indicate that c.1374+654C>G causes retinitis pigmentosa via haploinsufficiency, similar to the vast majority of PRPF31 mutations described so far. We discuss the potential of UHT sequencing technologies in mutation screening and the continued identification of pathogenic splicing mutations buried deep within intronic regions. Hum Mutat 30:1–8, 2009. © 2009 Wiley‐Liss, Inc.     

Non‐classic cystic fibrosis associated with D1152H CFTR mutation

Burgel P‐R, Fajac I, Hubert D, Grenet D, Stremler N, Roussey M, Siret D, Languepin J, Mely L, Fanton A, Labbé A, Domblides P, Vic P, Dagorne M, Reynaud‐Gaubert M, Counil F, Varaigne F, Bienvenu T, Bellis G, Dusser D. Non‐classic cystic fibrosis associated with D1152H CFTR mutation. Background: Limited knowledge exists on phenotypes associated with the D1152H cystic fibrosis transmembrane conductance regulator (CFTR) mutation. Methods: Subjects with a D1152H allele in trans with another CFTR mutation were identified using the French Cystic Fibrosis Registry. Phenotypic characteristics were compared with those of pancreatic insufficient (PI) and pancreatic sufficient (PS) cystic fibrosis (CF) subjects in the Registry (CF cohort). Results: Forty‐two subjects with D1152H alleles were identified. Features leading to diagnosis included chronic sinopulmonary disease (n = 25), congenital absence of the vas deferens (n = 11), systematic neonatal screening (n = 4), and genetic counseling (n = 2). Median age at diagnosis was 33 [interquartile range (IQR, 24–41)] years in D1152H subjects. Median sweat chloride concentrations were 43.5 (39–63) mmol/l in D1152H subjects and were markedly lower than in PI and PS CF subjects (p < 0.05). Bronchiectasis was present in 67% of D1152H subjects, but Pseudomonas aeruginosa colonization and pancreatic insufficiency were present in <30% of subjects. Estimated rates of decline in forced expiratory volume in 1 s (FEV₁) were lower in D1152H subjects vs PI CF subjects (p < 0.05). None of the D1152H subjects identified since 1999 had died or required lung transplantation. Conclusions: When present in trans with a CF‐causing mutation, D1152H causes significant pulmonary disease, but all subjects had prolonged survival.     

PRPF mutations are associated with generalized defects in spliceosome formation and pre-mRNA splicing in patients with retinitis pigmentosa

Proteins PRPF31, PRPF3 and PRPF8 (RP-PRPFs) are ubiquitously expressed components of the spliceosome, a macromolecular complex that processes nearly all pre-mRNAs. Although these spliceosomal proteins are conserved in eukaryotes and are essential for survival, heterozygous mutations in human RP-PRPF genes lead to retinitis pigmentosa, a hereditary disease restricted to the eye. Using cells from patients with 10 different mutations, we show that all clinically relevant RP-PRPF defects affect the stoichiometry of spliceosomal small nuclear RNAs (snRNAs), the protein composition of tri-small nuclear ribonucleoproteins and the kinetics of spliceosome assembly. These mutations cause inefficient splicing in vitro and affect constitutive splicing ex-vivo by impairing the removal of at least 9% of endogenously expressed introns. Alternative splicing choices are also affected when RP-PRPF defects are present. Furthermore, we show that the steady-state levels of snRNAs and processed pre-mRNAs are highest in the retina, indicating a particularly elevated splicing activity. Our results suggest a role for PRPFs defects in the etiology of PRPF-linked retinitis pigmentosa, which appears to be a truly systemic splicing disease. Although these mutations cause widespread and important splicing defects, they are likely tolerated by the majority of human tissues but are critical for retinal cell survival.     

A heterozygous mutation in RPGR associated with X‐linked retinitis pigmentosa in a patient with Turner syndrome mosaicism (45,X/46,XX)

Turner syndrome with retinitis pigmentosa (RP) is rare, with only three cases reported based on clinical examination alone. We summarized the 4‐year follow‐up and molecular findings in a 28‐year‐old patient with Turner syndrome and the typical features of short stature and neck webbing, who also had X‐linked RP. Her main complaints were night blindness and progressive loss of vision since the age of 9 years. Ophthalmologic examination, optical coherent tomographic imaging, and visual electrophysiology tests showed classic manifestations of RP. The karyotype of peripheral blood showed mosaicism (45,X [72%]/46,XX[28%]). A novel heterozygous frameshift mutation (c.2403_2406delAGAG, p.T801fsX812) in the RP GTPase regulator (RPGR) gene was detected using next generation sequencing and validated by Sanger sequencing. We believe that this is the first report of X‐linked RP in a patient with Turner syndrome associated with mosaicism, and an RPGR heterozygous mutation. We hypothesize that X‐linked RP in this woman is not related to Turner syndrome, but may be a manifestation of the lack of a normal paternal X chromosome with intact but mutated RPGR.     

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. © 2001 Wiley‐Liss, Inc.