Search

Inherited retinal degenerations are a clinically and genetically heterogeneous group of blinding diseases characterized by progressive degeneration of the neuroretina and/or the retinal pigment epithelium. Currently, over 300 genes have been implicated in retinal degenerations (RetNet: https://sph.uth.edu/RetNet/). While mutations, or causative variants, in each of these genes are relatively rare, taken together they are a significant cause of blindness, especially in working-age individuals, which increases their economic and societal impact. Clinically, inherited retinal degenerations vary from retinitis pigmentosa and Leber congenital amaurosis, which are often manifest at birth and initially involve rod photoreceptors in the retinal periphery, to early-onset macular degeneration, which is a progressive degeneration affecting central vision (1). Inherited retinal degenerations can show autosomal-dominant, autosomal-recessive, and X-linked inheritance, as well as more complex or multifactorial inheritance patterns, especially for some of the later-onset progressive diseases. While mutations in the same gene usually show the same inheritance pattern, it is not uncommon for mutations in the same gene to cause two or more forms of retinal disease, complicating the nosology of this group of diseases (2). In addition, the presence of disease-associated alleles at one gene can affect the penetrance or expressivity of mutations at a second, resulting in complicated family histories and in some cases even digenic diallelic (3) or digenic triallelic (4) inheritance. In PNAS, Hanany et al. (5) address this intimidating set of related diseases by developing a system to identify disease alleles at each of the associated genes and, beyond that, to calculate the gene-specific carrier frequency and the prevalence of homozygosity for variants causing autosomal recessive retinal degenerations. While appearing somewhat mundane on the surface, this work actually has far-reaching implications for both the basic science of the retina and the clinical practice of ophthalmology. The genes associated with retinal degeneration and the changes … [↵][1]1To whom correspondence may be addressed. Email: hejtmancikj{at}nei.nih.gov. [1]: #xref-corresp-1-1

Cataract, the clinical correlate of opacity or light scattering in the eye lens, is usually caused by the presence of high-molecular-weight (HMW) protein aggregates or disruption of the lens microarchitecture. In general, genes involved in inherited cataracts reflect important processes and pathways in the lens including lens crystallins, connexins, growth factors, membrane proteins, intermediate filament proteins, and chaperones. Usually, mutations causing severe damage to proteins cause congenital cataracts, while milder variants increasing susceptibility to environmental insults are associated with age-related cataracts. These may have different pathogenic mechanisms: Congenital cataracts induce the unfolded protein response and apoptosis. By contrast, denatured crystallins in age-related cataracts are bound by α-crystallin and form light-scattering HMW aggregates. New therapeutic approaches to age-related cataracts use chemical chaperones to solubilize HMW aggregates, while attempts are being made to regenerate lenses using endogenous stem cells to treat congenital cataracts.

Congenital cataracts cause approximately one-third of blindness in infants worldwide. If untreated they can cause permanent blindness by interfering with the sharp focus of light onto the retina and thus fail to establish appropriate synaptic connections between the retina and the visual cortex. Between 8 and 30% (see later) of congenital cataracts are inherited, and our understanding of their genetic architecture is increasing. Delineating the relationship between the genes and mutations causing cataracts and their phenotypic presentation can help us to understand the biology of the lens and provide a framework for the clinical approach to diagnosis and treatment.

The RPE65 gene encodes a retinal pigment epithelium-specific isomerase that catalyzes the conversion of all-trans retinyl esters to 11-cis retinol, the activity of which affects the formation of visual pigment in photoreceptors. Mutations in RPE65 in inherited retinal dystrophies have been studied widely worldwide, especially now that gene therapy for patients with RPE65 mutations is available in the clinic. The aim of this study is to reveal the RPE65 mutation spectrum and frequency, the associated phenotypic characteristics, and potential genotype–phenotype correlations. In total, 201 mutations in RPE65 were identified in 479 patients from 353 families based on data reported in the literature. Mutations in 349 families caused autosomal recessive retinal degeneration, while a c.1430A>G (p.Asp477Gly) mutation in four families resulted in autosomal dominant retinal degeneration resembling retinitis pigmentosa, choroideremia, or vitelliform macular dystrophy with incomplete penetrance. Mutations identified in families with biallelic RPE65 mutations included missense (113/200 [56.5%]), frameshift indel (39/200 [19.5%]), splicing defect (24/200 [12.0%]), nonsense (19/200 [9.5%]), inframe indel (4/200 [2.0%]), and start loss (1/200 [0.5%]). A significant reduction in visual acuity was noticeable at 15 years of age and at 35 years of age, suggesting a critical window for treatment including gene therapy. Two major types of fundus changes were observed: (1) mild or obvious tapetoretinal degeneration, generalized or located mainly in the mid-peripheral retina; and (2) fundus albipunctatus-like retinopathy. Typical bone-spicule pigmentation was rarely seen in early childhood but may be observed after 35 years of age. A severe phenotype (Leber congenital amaurosis) is frequently associated with biallelic loss-of-function mutations, while milder phenotypes are more likely to be associated with one or two missense mutations. The overall information presented here should be useful as a reference guide in clinical practice, especially for clinical gene testing and enrollment in gene therapy.

Oxidative damage is one of the major contributors to retinal degenerative diseases such as age-related macular degeneration (AMD), while RPE mediated antioxidant defense plays an important role in preventing retinopathies. However, the regulatory mechanisms of antioxidant signaling in RPE cells are poorly understood. Here we show that transcription factor MITF regulates the antioxidant response in RPE cells, protecting the neural retina from oxidative damage. In the oxidative stress-induced retinal degeneration mouse model, retinal degeneration in Mitf+/- mice is significantly aggravated compared to WT mice. In contrast, overexpression of Mitf in Dct-Mitf transgenic mice and AAV mediated overexpression in RPE cells protect the neural retina against oxidative damage. Mechanistically, MITF both directly regulates the transcription of NRF2, a master regulator of antioxidant signaling, and promotes its nuclear translocation. Furthermore, specific overexpression of NRF2 in Mitf+/- RPE cells activates antioxidant signaling and partially protects the retina from oxidative damage. Taken together, our findings demonstrate the regulation of NRF2 by MITF in RPE cells and provide new insights into potential therapeutic approaches for prevention of oxidative damage diseases., Graphical abstract Image 1, Highlights • MITF haploinsufficiency exacerbates oxidative stress-induced retinal degeneration. • Specific overexpression of MITF in RPE cells protects retinas from oxidative damage in vivo. • MITF directly regulates the transcription and nuclear translocation of NRF2. • Partial rescue of retinal oxidative damage in Mitf ±mice by gene transfer mediated RPE cell specific expression of NRF2.

Peroxisomes, single-membrane intracellular organelles, play an important role in various metabolic pathways. The translocation of proteins from the cytosol to peroxisomes depends on peroxisome import receptor proteins and defects in peroxisome transport result in a wide spectrum of peroxisomal disorders. Here, we report a large consanguineous family with autosomal recessive congenital cataracts and developmental defects. Genome-wide linkage analysis localized the critical interval to chromosome 12p with a maximum two-point LOD score of 4.2 (θ = 0). Next-generation exome sequencing identified a novel homozygous missense variant (c.653 T > C; p.F218S) in peroxisomal biogenesis factor 5 (PEX5), a peroxisome import receptor protein. This missense mutation was confirmed by bidirectional Sanger sequencing. It segregated with the disease phenotype in the family and was absent in ethnically matched control chromosomes. The lens-specific knockout mice of Pex5 recapitulated the cataractous phenotype. In vitro import assays revealed a normal capacity of the mutant PEX5 to enter the peroxisomal Docking/Translocation Module (DTM) in the presence of peroxisome targeting signal 1 (PTS1) cargo protein, be monoubiquitinated and exported back into the cytosol. Importantly, the mutant PEX5 protein was unable to form a stable trimeric complex with peroxisomal biogenesis factor 7 (PEX7) and a peroxisome targeting signal 2 (PTS2) cargo protein and, therefore, failed to promote the import of PTS2 cargo proteins into peroxisomes. In conclusion, we report a novel missense mutation in PEX5 responsible for the defective import of PTS2 cargo proteins into peroxisomes resulting in congenital cataracts and developmental defects.

This study was conducted to identify the genetic basis of retinal dystrophies in consanguineous Pakistani families. We recruited two families with retinitis pigmentosa (RP) displaying visual difficulties, including nyctalopia and constricted visual fields. Linkage analysis and Sanger sequencing resulted in the identification of a previously reported nonsense mutation, c.847C > T, in exon 5 of CERKL in one family and a novel four-base pair deletion in exon 4 of RP1, c.delAGAA4218_4221, leading to premature protein termination in the second family. Here, we report two RP-causing mutations extending the genetic heterogeneity of the disease.

βγ-Crystallins, having a uniquely stable two domain four Greek key structure, are crucial for transparency of the eye lens,. Mutations in lens crystallins have been proposed to cause cataract formation by a variety of mechanisms most of which involve destabilization of the protein fold. The underlying molecular mechanism for autosomal dominant zonular cataracts with sutural opacities in an Indian family caused by a c.215+1G>A splice mutation in the βA3/A1-crystallin gene CRYBA1 was elucidated using three transgenic mice models. This mutation causes a splice defect in which the mutant mRNA escapes nonsense mediated decay by skipping both exons 3 and 4. Skipping these exons results in an in-frame deletion of the mRNA and synthesis of an unstable p.Ile33_Ala119del mutant βA3/A1-crystallin protein. Transgenic expression of mutant βA3/A1-crystallin but not the wild type protein results in toxicity and abnormalities in the maturation and orientation of differentiating lens fibers in c.97_357del CRYBA1 transgenic mice, leading to a small spherical lens, cataract, and often lens capsule rupture. On a cellular level, the lenses accumulated p.Ile33_Ala119del βA3/A1-crystallin with resultant activation of the stress signaling pathway - unfolded protein response (UPR) and inhibition of normal protein synthesis, culminating in apoptosis. This highlights the mechanistic contrast between mild mutations that destabilize crystallins and other proteins, resulting in their being bound by the α-crystallins that buffer lens cells against damage by denatured proteins, and severely misfolded proteins that are not bound by α-crystallin but accumulate and have a direct toxic effect on lens cells, resulting in early onset cataracts.

Purpose To identify the molecular basis of inherited retinal degeneration (IRD) in a familial case of Pakistani origin using whole-exome sequencing.

Retinal dystrophies are a phenotypically and genetically complex group of conditions. Because of this complexity, it can be challenging in many families to determine the inheritance based on pedigree analysis alone. Clinical examinations were performed and blood samples were collected from a North American (M1186) and a consanguineous Pakistani (PKRD168) pedigree affected with two different retinal dystrophies (RD). Based on the structure of the pedigrees, inheritance patterns in the families were difficult to determine. In one family, linkage analysis was performed with markers on X-chromosome. In the second family, whole-exome sequencing (WES) was performed. Subsequent Sanger sequencing of genes of interest was performed. Linkage and haplotype analysis localized the disease interval to a 70 Mb region on the X chromosome that encompassed RP2 and RPGR in M1186 . The disease haplotype segregated with RD in all individuals except for an unaffected man (IV:3) and his affected son (V:1) in this pedigree. Subsequent analysis identified a novel RPGR mutation (p. Lys857Glu fs221X) in all affected members of M1186 except V:1. This information suggests that there is an unidentified second cause of retinitis pigmentosa (RP) within the family. A novel two-base-pair deletion (p. Tyr565Ter fsX) in CHM (choroideremia) was found to segregate with RD in PKRD168. This paper highlights the challenges of interpreting family history in families with RD and reports on the identification of novel mutations in two RD families.

Background Juvenile‐onset cataracts are known among the Hutterites of North America. Despite being identified over 30 years ago, this autosomal recessive condition has not been mapped, and the disease gene is unknown. Methods We performed whole exome sequencing of three Hutterite‐type cataract trios and follow‐up genotyping and mapping in four extended kindreds. Results Trio exomes enabled genome‐wide autozygosity mapping, which localized the disease gene to a 9.5‐Mb region on chromosome 6p. This region contained two candidate variants, LEMD2 c.T38G and MUC21 c.665delC. Extended pedigrees recruited for variant genotyping revealed multiple additional relatives with juvenile‐onset cataract, as well as six deceased relatives with both cataracts and sudden cardiac death. The candidate variants were genotyped in 84 family members, including 17 with cataracts; only the variant in LEMD2 cosegregated with cataracts (LOD = 9.62). SNP‐based fine mapping within the 9.5 Mb linked region supported this finding by refining the cataract locus to a 0.5‐ to 2.9‐Mb subregion (6p21.32‐p21.31) containing LEMD2 but not MUC21. LEMD2 is expressed in mouse and human lenses and encodes a LEM domain‐containing protein; the c.T38G missense mutation is predicted to mutate a highly conserved residue within this domain (p.Leu13Arg). Conclusion We performed a genetic and genomic study of Hutterite‐type cataract and found evidence for an association of this phenotype with sudden cardiac death. Using combined genetic and genomic approaches, we mapped cataracts to a small portion of chromosome 6 and propose that they result from a homozygous missense mutation in LEMD2.

The aim of this work is to identify the molecular cause of autosomal recessive early onset retinal degeneration in a consanguineous pedigree. Seventeen members of a four-generation Pakistani family were recruited and underwent a detailed ophthalmic examination. Exomes of four affected and two unaffected individuals were sequenced. Variants were filtered using exomeSuite to identify rare potentially pathogenic variants in genes expressed in the retina and/or brain and consistent with the pattern of inheritance. Effect of the variant observed in the gene Intraflagellar Transport Protein 43 (IFT43) was studied by heterologous expression in mIMCD3 and MDCK cells. Expression and sub-cellular localization of IFT43 in the retina and transiently transfected cells was examined by RT-PCR, western blot analysis, and immunohistochemistry. Affected members were diagnosed with early onset non-syndromic progressive retinal degeneration and the presence of bone spicules distributed throughout the retina at younger ages while the older affected members showed severe central choroidal atrophy. Whole-exome sequencing analysis identified a novel homozygous c.100 G > A change in IFT43 segregating with retinal degeneration and not present in ethnicity-matched controls. Immunostaining showed IFT43 localized in the photoreceptors, and to the tip of the cilia in transfected mIMCD3 and MDCK cells. The cilia in mIMCD3 and MDCK cells expressing mutant IFT43 were found to be significantly shorter (P

Mutations in RP2 and RPGR genes are responsible for the X-linked retinitis pigmentosa (XLRP). In this study, we analyzed the RP2 and RPGR gene mutations in five Han Chinese families with XLRP. An approximately 17Kb large deletion including the exon 4 and exon 5 of RP2 gene was found in an XLRP family. In addition, four frameshift mutations including three novel mutations of c.1059 + 1 G > T, c.2002dupC and c.2236_2237del CT, as well as a previously reported mutation of c.2899delG were detected in the RPGR gene in the other four families. Our study further expands the mutation spectrum of RP2 and RPGR, and will be helpful for further study molecular pathogenesis of XLRP.

[This corrects the article DOI: 10.1371/journal.pone.0137973.].

The National Eye Institute (NEI) of the United States, the Centre for Excellence in Molecular Biology (CEMB), and Allama Iqbal Medical College in Lahore, Pakistan collaborate in an ongoing international genetic collaboration to identify the genes and mutations responsible for retinitis pigmentosa and congenital cataracts in the Pakistani population. To date, we have recruited a total of 115 consanguineous families with autosomal recessive congenital cataract (arCC) and 138 consanguineous families with autosomal recessive retinal dystrophy (arRD). After undergoing linkage analysis and sequencing of candidate genes in identified linked regions, unmapped families were subjected to homozygosity exclusion mapping by screening closely flanking microsatellite markers at known candidate gene/loci, followed by Sanger sequencing of the nearby candidate gene if homozygosity was present. Analysis of these families has resulted in identification of disease loci or genes causing disease in 42 families with arCC and 96 families with (RD), including novel disease-causing genes in 5 of these families. Since selection of both families and candidate loci was unbiased, this approach allowed an accurate estimate of the contributions of various genes to arCC and arRD in Pakistan. The causative genes remain unidentified in about 2/3 arCC families and 1/3 of arRD families in our study, making next-generation sequencing an ideal method for identification of new genes.

PurposeTo investigate the genetic basis of autosomal recessive congenital cataracts (arCC) in a large consanguineous Pakistani family.MethodsAll participating members of family, PKCC074 underwent an ophthalmic examination. Slit-lamp photographs were ascertained for affected individuals that have not been operated for the removal of the cataractous lens. A small aliquot of the blood sample was collected from all participating individuals and genomic DNAs were extracted. A genome-wide scan was performed with polymorphic short tandem repeat (STR) markers and the logarithm of odds (LOD) scores were calculated. All coding exons and exon-intron boundaries of HSF4 were sequenced and expression of Hsf4 in mouse ocular lens was investigated. The C-terminal FLAG-tagged wild-type and mutant HSF4b constructs were prepared to examine the nuclear localization pattern of the mutant protein.ResultsThe ophthalmological examinations suggested that nuclear cataracts are present in affected individuals. Genome-wide linkage analyses localized the critical interval to a 10.95 cM (14.17 Mb) interval on chromosome 16q with a maximum two-point LOD score of 4.51 at θ = 0. Sanger sequencing identified a novel missense mutation: c.433G>C (p.Ala145Pro) that segregated with the disease phenotype in the family and was not present in ethnically matched controls. Real-time PCR analysis identified the expression of HSF4 in mouse lens as early as embryonic day 15 with a steady level of expression thereafter. The immunofluorescence tracking confirmed that both wild-type and mutant HSF4 (p.Ala145Pro) proteins localized to the nucleus.ConclusionHere, we report a novel missense mutation in HSF4 associated with arCC in a familial case of Pakistani descent.

Congenital cataracts (CCs), responsible for about one-third of blindness in infants, are a major cause of vision loss in children worldwide. Autosomal-recessive congenital cataracts (arCC) form a clinically diverse and genetically heterogeneous group of disorders of the crystalline lens. To identify the genetic cause of arCC in consanguineous Pakistani families, we performed genome-wide linkage analysis and fine mapping and identified linkage to 3p21-p22 with a summed LOD score of 33.42. Mutations in the gene encoding FYVE and coiled-coil domain containing 1 (FYCO1), a PI(3)P-binding protein family member that is associated with the exterior of autophagosomes and mediates microtubule plus-end-directed vesicle transport, were identified in 12 Pakistani families and one Arab Israeli family in which arCC had previously been mapped to the overlapping CATC2 region. Nine different mutations were identified, including c.3755 delC (p.Ala1252AspfsX71), c.3858_3862dupGGAAT (p.Leu1288TrpfsX37), c.1045 C>T (p.Gln349X), c.2206C>T (p.Gln736X), c.2761C>T (p.Arg921X), c.2830C>T (p.Arg944X), c.3150+1 G>T, c.4127T>C (p.Leu1376Pro), and c.1546C>T (p.Gln516X). Fyco1 is expressed in the mouse embryonic and adult lens and peaks at P12d. Expressed mutant proteins p.Leu1288TrpfsX37 and p.Gln736X are truncated on immunoblots. Wild-type and p.L1376P FYCO1, the only missense mutant identified, migrate at the expected molecular mass. Both wild-type and p. Leu1376Pro FYCO1 proteins expressed in human lens epithelial cells partially colocalize to microtubules and are found adjacent to Golgi, but they primarily colocalize to autophagosomes. Thus, FYCO1 is involved in lens development and transparency in humans, and mutations in this gene are one of the most common causes of arCC in the Pakistani population.

Purpose: To describe clinical and functional features of a patient with Bietti crystalline dystrophy and atypical electroretinogram responses. Methods: The patient underwent a thorough medical anamnesis, genetic counseling, peripheral blood draw for CYP4V2 gene analysis and electron microscopy, and a complete ophthalmological assessment including optical coherence tomography, indocyanine green angiography, microperimetry, full-field electroretinogram and multifocal electroretinogram. Results: The most striking features of the retina were deposits of yellowish-white glistening crystals and focal lobular areas of choriocapillary atrophy at the posterior pole and midperiphery. The full-field electroretinogram was normal and the multifocal electroretinogram showed extinguished central recordings. Mutation analysis revealed a homozygous c. 332T>C p.I111T mutation in exon 3 of the CYP4V2 gene. Typical cytoplasmic inclusions containing crystalline-like structure and large degenerative lysosomes were seen on electron microscopy of peripheral leukocytes. Conclusion: Here we describe a patient with Bietti crystalline dystrophy with a CYP4V2 gene mutation and typical leukocyte inclusions who showed the classical retinal lesions but had a normal electroretinogram. This suggests the existence of less severe forms of BCD related to relatively mild CYP4V2 mutations.

Background Retinitis pigmentosa (RP) is one of the most common ophthalmic disorders affecting one in approximately 5000 people worldwide. A nuclear family was recruited from the Punjab province of Pakistan to study the genetic basis of autosomal recessive RP. Methods All affected individuals underwent a thorough ophthalmic examination and the disease was characterised based upon results for fundus photographs and electroretinogram recordings. Genomic DNA was extracted from peripheral leucocytes. Exclusion studies were performed with short tandem repeat (STR) markers flanking reported autosomal recessive RP loci. Haplotypes were constructed and results were statistically evaluated. Results The results of exclusion analyses suggested that family PKRP173 was linked to chromosome 2q harbouring mer tyrosine kinase protooncogene ( MERTK ), a gene previously associated with autosomal recessive RP. Additional STR markers refined the critical interval and placed it in a 13.4 cM (17 Mb) region flanked by D2S293 proximally and D2S347 distally. Significant logarithm of odds (LOD) scores of 3.2, 3.25 and 3.18 at θ=0 were obtained with markers D2S1896, D2S2269 and D2S160. Sequencing of the coding exons of MERTK identified a mutation, c.718G→T in exon 4, which results in a premature termination of p.E240X that segregates with the disease phenotype in the family. Conclusion Our results strongly suggest that the nonsense mutation in MERTK , leading to premature termination of the protein, is responsible for RP phenotype in the affected individuals of the Pakistani family.

Objective To identify a disease locus for autosomal recessive retinitis pigmentosa in a consanguineous Pakistani family. Design Prospective linkage study. Methods Blood samples were collected and genomic DNA was extracted. A genome-wide scan was performed using 382 polymorphic microsatellite markers on genomic DNA from 4 affected and 5 unaffected family members, and logarithm of odds scores were calculated. Results A maximum 2-point logarithm of odds score of 3.14 at θ = 0 was obtained for marker D2S165 during the genome-wide scan. Fine mapping markers identified a 20.92-cM (19.98-Mb) interval flanked by D2S149 and D2S367 that cosegregates with the disease phenotype. Haplotype analyses further refined the critical interval, distal to D2S220 in a 12.31-cM (13.35-Mb) region that does not harbor any genes that previously have been associated with retinitis pigmentosa. Conclusions Linkage analysis identified a new locus for autosomal recessive retinitis pigmentosa that maps to chromosome 2p22.3-p24.1 in a consanguineous Pakistani family.

The gene networks underlying closure of the optic fissure during vertebrate eye development are poorly understood. Here, we profile global gene expression during optic fissure closure using laser capture microdissected (LCM) tissue from the margins of the fissure. From these data, we identify a unique role for the C 2 H 2 zinc finger proteins Nlz1 and Nlz2 in normal fissure closure. Gene knockdown of nlz1 and/or nlz2 in zebrafish leads to a failure of the optic fissure to close, a phenotype which closely resembles that seen in human uveal coloboma. We also identify misregulation of pax2 in the developing eye of morphant fish, suggesting that Nlz1 and Nlz2 act upstream of the Pax2 pathway in directing proper closure of the optic fissure.

Uveitis is a complex multifactorial autoimmune disease of the eye characterized by inflammation of the uvea and retina, degeneration of the retina, and blindness in genetically predisposed patients. Using the rat model of experimental autoimmune uveitis (EAU), we previously identified three quantitative trait loci (QTL) associated with EAU on rat chromosomes 4, 12, and 10 (Eau1, Eau2, and Eau3). The primary goal of the current study is to delineate additional non-MHC chromosomal regions that control susceptibility to EAU, and to identify any QTLs that overlap with the QTLs of other autoimmune diseases. Using a set of informative microsatellite markers and F2 generations of resistant and susceptible MHC class II-matched rat strains (F344 and LEW), we have identified several new significant or suggestive QTLs on rat chromosomes 2, 3, 7, 10, and 19 that control susceptibility to EAU. A protective allele was identified in the susceptible LEW strain in the Eau5 locus at D7Wox18, and epistatic interactions between QTLs were found to influence the severity of disease. The newly identified regions (Eau4 through Eau9) colocalize with the genetic determinants of other autoimmune disease models, and to disease-regulating syntenic regions identified in autoimmune patients on human chromosomes 4q21-31, 5q31-33, 16q22-24, 17p11-q12, 20q11-13, and 22q12-13. Our results suggest that uveitis shares some of the pathogenic mechanisms associated with other autoimmune diseases, and lends support to the “common gene, common pathway” hypothesis for autoimmune disorders.

Mutation in the PROM1 gene previously has been identified in one family with retinal degeneration for which neither ERG recordings nor detailed information about visual impairment is available. A large family with multiple individuals affected by retinal degeneration was ascertained in the Punjab province of Pakistan. 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. Rod and cone responses on ERG recordings were extinguished in patient's teens. A genome-wide scan mapped the disease to a 34.7 cM region of chromosome 4p14-p16 between D4S1599 and D4S405. A maximum lod score of 3.96 with D4S403 and D4S391 is seen at theta = 0. Sequence analysis of PROM1 located in the linkage interval identified a c.1726CT homozygous transition in exon 15: resulting in p.Gln576X in the translated protein. This mutation is found in a homozygous state in all six affected individuals and was heterozygous in five of the six unaffected family members examined. The mutation was not detected in 192 chromosomes of unrelated control individuals of the same ethnicity and from the same region. This delineates the phenotypic characteristics of retinopathy caused by mutations in PROM1.

Background Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is a rare autosomal dominant disease. Mutations in the forkhead box L2 (FOXL2) gene cause two types of BPES distinguished by the presence (type I) and absence (type II) of premature ovarian failure (POF). The purpose of this study was to identify possible mutations in FOXL2 in two Chinese families with BPES. Methods Two large autosomal dominant Chinese BPES families were enrolled in this study. Genomic DNA was obtained from the leukocytes in peripheral venous blood. Four overlapping sets of primers were used to amplify the entire coding region and nearby intron sequences of the FOXL2 gene for mutations detection using polymerase chain reaction (PCR) and sequencing analyses. The sequencing results were analyzed using DNAstar software. Results All patients of the two families demonstrated typical features of BPES type II, including small palpebral fissures, ptosis, telecanthus, and epicanthus inversus without female infertility (POF). A novel FOXL2 heterozygous indel mutation c.675_690delinsT, including a 16-bp deletion and a 1-bp(T) insertion (p.Ala226_Ala230del), which would result in deletion of 5 alanine residues of a poly-alanine (poly-Ala) tract in the protein, was identified in all affected members of family A. A novel heterozygous missense mutation (c.223C > T, p.Leu75Phe) was identified in family B. Conclusions Two novel FOXL2 mutations were identified in Chinese families with BPES. Our results expand the spectrum of FOXL2 mutations and provide additional structure-function insights into the FOXL2 protein.

PURPOSE:To define the molecular basis of retinal degeneration in consanguineous Pakistani pedigrees with early onset retinal degeneration. METHODS:A cohort of 277 individuals representing 26 pedigrees from the Punjab province of Pakistan was analyzed. Exomes were captured with commercial kits and sequenced on an Illumina HiSeq 2500. Candidate variants were identified using standard tools and analyzed using exomeSuite to detect all potentially pathogenic changes in genes implicated in retinal degeneration. Segregation analysis was performed by dideoxy sequencing and novel variants were additionally investigated for their presence in ethnicity-matched controls. RESULTS:We identified a total of nine causal mutations, including six novel variants in RPE65, LCA5, USH2A, CNGB1, FAM161A, CERKL and GUCY2D as the underlying cause of inherited retinal degenerations in 13 of 26 pedigrees. In addition to the causal variants, a total of 200 variants each observed in five or more unrelated pedigrees investigated in this study that were absent from the dbSNP, HapMap, 1000 Genomes, NHLBI ESP6500, and ExAC databases were identified, suggesting that they are common in, and unique to the Pakistani population. CONCLUSIONS:We identified causal mutations associated with retinal degeneration in nearly half of the pedigrees investigated in this study through next generation whole exome sequencing. All novel variants detected in this study through exome sequencing have been cataloged providing a reference database of variants common in, and unique to the Pakistani population.

Purpose This study was initiated to identify causal mutations responsible for autosomal recessive congenital cataracts in consanguineous familial cases. Methods Affected individuals underwent a detailed ophthalmological and clinical examination, and slit-lamp photographs were ascertained for affected individuals who have not yet been operated for the removal of the cataractous lens. Blood samples were obtained, and genomic DNA was extracted from white blood cells. A genome-wide scan was completed with short tandem repeat (STR) markers, and the logarithm of odds (LOD) scores were calculated. Protein coding exons of CRYAB were sequenced, bi-directionally. Evolutionary conservation was investigated by aligning CRYAB orthologues, and the expression of Cryab in embryonic and postnatal mice lens was investigated with TaqMan probe. Results The clinical and ophthalmological examinations suggested that all affected individuals had nuclear cataracts. Genome-wide linkage analysis suggested a potential region on chromosome 11q23 harboring CRYAB. DNA sequencing identified a missense variation: c.34C>T (p.R12C) in CRYAB that segregated with the disease phenotype in the family. Subsequent interrogation of our entire cohort of familial cases identified a second familial case localized to chromosome 11q23 harboring a c.31C>T (p.R11C) mutation. In silico analyses suggested that the mutations identified in familial cases, p.R11C and p.R12C will not be tolerated by the three-dimensional structure of CRYAB. Real-time PCR analysis identified the expression of Cryab in mouse lens as early as embryonic day 15 (E15) that increased significantly until postnatal day 6 (P6) with steady level of expression thereafter. Conclusion Here, we report two novel missense mutations, p.R11C and p.R12C, in CRYAB associated with autosomal recessive congenital nuclear cataracts.

Item does not contain fulltext OBJECTIVE: To determine the refractive error in patients with autosomal recessive retinitis pigmentosa (arRP) caused by RP1 mutations and to compare it with that of other genetic subtypes of RP. METHODS: Twenty-six individuals had arRP with RP1 mutations, 25 had autosomal dominant RP (adRP) with RP1 mutation, 8 and 33 had X-linked RP (xlRP) with RP2 and RPGR mutations, respectively, 198 and 93 had Usher syndrome and arRP without RP1 mutations, respectively. The median of the spherical equivalent (SE) and the IQR (Q25-Q75) was determined and multiple comparisons were performed. RESULTS: arRP patients with RP1 mutations had SE median at -4.0 dioptres (D) OD (Ocula Dextra); -3.88 D OS (Ocula Sinistra), whereas arRP patients without RP1 mutations (-0.50 D OD; -0.75 D OS) and Usher syndrome patients (-0.50 D OD; -0.38 D OS) were significantly less myopic (p

Purpose To identify the genes causing autosomal recessive retinal dystrophy in Indian families and to characterize the associated phenotypes. Design Experimental and observational. Methods Families with autosomal recessive nonsyndromic retinal dystrophies were recruited. Complete ophthalmic evaluation, including visual acuity, visual fields, fundus examinations, and electroretinography, was performed on all members. Genotyping of 14 families for two or more microsatellite markers flanking each of 21 different genes causing retinal dystrophy was done by standard methods to screen for the presence of homozygosity by descent. Mutational screening of the ABCA4 gene was carried out on 18 members (five affected) of two families by amplification and direct automated sequencing of exons and flanking sequences. Sequence alterations identified were tested for cosegregation with disease in the families and for presence in 100 unrelated normal controls. Results Two of 14 families showed homozygosity shared by affected individuals for markers flanking the ABCA4 locus. A homozygous nonsense mutation in the ABCA4 gene of Arg2030Stop was found in one family and a homozygous single base deletion leading to frameshift at Arg409 was found in the second family. Both of these mutations were found to cosegregate with disease. Five affected individuals from the two families had early-onset visual loss, diminished rod and cone electroretinographic responses, and widespread atrophy of the retinal pigment epithelium. Conclusion Homozygous null mutations in ABCA4 produced a severe widespread retinal degeneration that showed marked central retinal involvement.

A severe form of autosomal recessive retinitis pigmentosa (arRP) was identified in a large Pakistani family ascertained in the Punjab province of Pakistan. All affected individuals in the family had night blindness in early childhood, early complete loss of useful vision, and typical RP fundus changes plus macular degeneration. After exclusion of known arRP loci, a genome-wide scan was performed using microsatellite markers at about 10 cM intervals and calculating two-point lod scores. PCR cycle dideoxynucleotide sequencing was used to sequence candidate genes inside the linked region for mutations. RP in this family shows linkage to markers in a 10.5 cM (8.9 Mbp) region of chromosome 1p13.3-p21.2 between D1S2896 and D1S457. D1S485 yields the highest lod score of 6.54 at theta=0. Sequencing the exons and intron-exon boundaries of five candidate genes and six ESTs in this region, OLFM3, GNAI3, LOC126987, FLJ25070, DKFZp586G0123, AV729694, BU662869, BU656110, BU171991, BQ953690, and CA397743, did not identify any causative mutations. This novel locus lies approximately 4.9 cM (7.1 Mbp) from ABCA4, which is excluded from the linked region. Identification and study of this gene may help to elucidate the phenotypic diversity of arRP mapping to this region.

Usher syndrome type I (USH1), the most severe form of this syndrome, is characterized by profound congenital sensorineural deafness, vestibular dysfunction, and retinitis pigmentosa. At least seven USH1 loci, USH1A-G, have been mapped to the chromosome regions 14q32, 11q13.5, 11p15, 10q21-q22, 21q21, 10q21-q22, and 17q24-25, respectively. Mutations in five genes, including MYO7A, USH1C, CDH23, PCDH15 and SANS, have been shown to be the cause of Usher syndrome type 1B, type 1C, type 1D, type 1F and type 1G, respectively. In the present study, we carried out a systematic mutation screening of these genes in USH1 patients from USA and from UK. We identified a total of 27 different mutations; of these, 19 are novel, including nine missense, two nonsense, four deletions, one insertion and three splicing defects. Approximatelly 35–39% of the observed mutations involved the USH1B and USH1D genes, followed by 11% for USH1F and 7% for USH1C in non-Acadian alleles and 7% for USH1G. Two of the 12 MYO7A mutations, R666X and IVS40-1G>T accounted for 38% of the mutations at that locus. A 193delC mutation accounted for 26% of CDH23 (USH1D) mutations, confirming its high frequency. The most common PCDH15 (USH1F) mutation in this study, 5601-5603delAAC, accounts for 33% of mutant alleles. Interestingly, a novel SANS mutation, W38X, was observed only in the USA cohort. The present study suggests that mutations in MYO7A and CDH23 are the two major components of causes for USH1, while PCDH15, USH1C, and SANS are less frequent causes.

Advances in molecular biological and genetic technology have greatly accelerated elucidation of the genetic contribution to age-related cataract. Epidemiological studies have documented tendencies for cataracts to occur more frequently in relatives of cataract patients than in the general population, genetic studies have demonstrated contributory roles of some specific genes in age related cataract in small populations, and molecular studies have shown changes in expression of specific genes in cataractous lenses. Together, these studies are beginning to provide a conceptual framework for understanding age-related cataracts.

Bietti crystalline corneoretinal dystrophy (BCD) is an autosomal recessive retinal dystrophy characterized by multiple glistening intraretinal crystals scattered over the fundus, a characteristic degeneration of the retina, and sclerosis of the choroidal vessels, ultimately resulting in progressive night blindness and constriction of the visual field. The BCD region of chromosome 4q35.1 was refined to an interval flanked centromerically by D4S2924 by linkage and haplotype analysis; mutations were found in the novel CYP450 family member CYP4V2 in 23 of 25 unrelated patients with BCD tested. The CYP4V2 gene, transcribed from 11 exons spanning 19 kb, is expressed widely. Homology to other CYP450 proteins suggests that CYP4V2 may have a role in fatty acid and steroid metabolism, consistent with biochemical studies of patients with BCD.

Rare germ-line mutations in the coding regions of the human EPHA2 gene (EPHA2) have been associated with inherited forms of pediatric cataract, whereas, frequent, non-coding, single nucleotide variants (SNVs) have been associated with age-related cataract. Here we sought to determine if germ-line EPHA2 coding SNVs were associated with age-related cataract in a case-control DNA panel (> 50 years) and if somatic EPHA2 coding SNVs were associated with lens aging and/or cataract in a post-mortem lens DNA panel (> 48 years). Micro-fluidic PCR amplification followed by targeted amplicon (exon) next-generation (deep) sequencing of EPHA2 (17-exons) afforded high read-depth coverage (1000x) for > 82% of reads in the cataract case-control panel (161 cases, 64 controls) and > 70% of reads in the post-mortem lens panel (35 clear lens pairs, 22 cataract lens pairs). Novel and reference (known) missense SNVs in EPHA2 that were predicted in silico to be functionally damaging were found in both cases and controls from the age-related cataract panel at variant allele frequencies (VAFs) consistent with germ-line transmission (VAF > 20%). Similarly, both novel and reference missense SNVs in EPHA2 were found in the post-mortem lens panel at VAFs consistent with a somatic origin (VAF > 3%). The majority of SNVs found in the cataract case-control panel and post-mortem lens panel were transitions and many occurred at di-pyrimidine sites that are susceptible to ultraviolet (UV) radiation induced mutation. These data suggest that novel germ-line (blood) and somatic (lens) coding SNVs in EPHA2 that are predicted to be functionally deleterious occur in adults over 50 years of age. However, both types of EPHA2 coding variants were present at comparable levels in individuals with or without age-related cataract making simple genotype-phenotype correlations inconclusive.

Purpose To identify the genetic origins of autosomal recessive congenital cataracts (arCC) in the Pakistani population. Methods Based on the hypothesis that most arCC patients in consanguineous families in the Punjab areas of Pakistan should be homozygous for causative mutations, affected individuals were screened for homozygosity of nearby highly informative microsatellite markers and then screened for pathogenic mutations by DNA sequencing. A total of 83 unmapped consanguineous families were screened for mutations in 33 known candidate genes. Results Patients in 32 arCC families were homozygous for markers near at least 1 of the 33 known CC genes. Sequencing the included genes revealed homozygous cosegregating sequence changes in 10 families, 2 of which had the same variation. These included five missense, one nonsense, two frame shift, and one splice site mutations, eight of which were novel, in EPHA2, FOXE3, FYCO1, TDRD7, MIP, GALK1, and CRYBA4. Conclusions The above results confirm the usefulness of homozygosity mapping for identifying genetic defects underlying autosomal recessive disorders in consanguineous families. In our ongoing study of arCC in Pakistan, including 83 arCC families that underwent homozygosity mapping, 3 mapped using genome-wide linkage analysis in unpublished data, and 30 previously reported families, mutations were detected in approximately 37.1% (43/116) of all families studied, suggesting that additional genes might be responsible in the remaining families. The most commonly mutated gene was FYCO1 (14%), followed by CRYBB3 (5.2%), GALK1 (3.5%), and EPHA2 (2.6%). This provides the first comprehensive description of the genetic architecture of arCC in the Pakistani population.

Lens opacities or cataract(s) represent a universally important cause of visual impairment and blindness. Typically, cataract is acquired with aging as a complex disorder involving environmental and genetic risk factors. Cataract may also be inherited with an early onset either in association with other ocular and/or systemic abnormalities or as an isolated lens phenotype. Here we briefly review recent advances in gene discovery for inherited and age-related forms of cataract that are providing new insights into lens development and aging.

Congenital cataracts are one of the leading causes of visual impairment and blindness in children, and genetic factors play an important role in their development. This study aimed to identify the genetic defects associated with autosomal dominant congenital progressive punctate cataracts in a Chinese family and to explore the potential pathogenesis. Detailed family history and clinical data were recorded, and all the family members' blood samples were collected for DNA extraction. Linkage analysis was performed by microsatellite markers that are associated with punctate cataracts, and logarithm (base 10) of odds (LOD) scores were calculated using the LINKAGE program. Positive two-point LOD scores were obtained at markers D12S1622 (Zmax = 2.71 at θ = 0.0), D12S1724 (Zmax = 2.71 at θ = 0.0), and D12S90 (Zmax = 2.71 at θ = 0.0), which flank the major intrinsic protein of lens fiber (MIP) gene on chromosomal region 12q13. Direct sequencing of the encoding region of the MIP gene revealed a novel mutation (G>D) in exon 4 at nucleotide 644, which caused a substitution of glycine to aspartic acid at codon 215 (p.G215D) for the MIP protein. The mutation cosegregated with all patients with congenital progressive punctate cataracts, but it was absent in the healthy members. Bioinformatics analysis predicted that the mutation affects the function of the MIP protein. The wild type (WT) and G215D mutant of MIP were transfected with green fluorescent protein (GFP) into Hela cells separately, and it was found that the G215D mutant was aberrantly located in the cytoplasm instead of in the plasma membrane. In summary, our study presented genetic and functional evidence linking the new MIP mutation of G215D to autosomal dominant congenital cataracts, which adds to the list of MIP mutations linked to congenital progressive punctate cataracts.

Mutations underlying hereditary cataracts in two families impair the function of an enzyme that synthesizes the lens molecule lanosterol. The finding may lead to non-surgical prevention and treatment of cataracts. See Letter p.607

PURPOSE: To study the phenotypic variability in patients inheriting the disease gene for malattia leventinese (dominant macular drusen) and refine the localization of the gene. METHODS: A family with dominant radial drusen was ascertained and studied with clinical examination and DNA linkage analysis. Inheritance of the disease gene was determined by DNA analysis and used to document the variability in phenotypic expression. RESULTS: Fifty family members were studied with fundus photography and genotyping. Linkage analysis showed that the disease in this family was linked to chromosome 2p16-21 with a maximum lod score of 3.72 at D2S2153. An affected patient with obligate recombinations allowed refinement of the disease interval to a 6.2-cM region between D2S2227 and D2S378. The phenotype of older affected patients varied from severe geographic atrophy or subretinal fibrosis to a single druse adjacent to the optic disk. Small and medium-sized, nonradial, and soft macular drusen seen in four older individuals in the family were not specifically associated with the disease haplotype. CONCLUSIONS: Refinement of the localization of the gene for malattia leventinese will facilitate its positional cloning. Genotypic documentation of the variable expression of the disease shows that a single, large, subretinal druse adjacent to the optic disk is consistent with inheritance of the disease gene. Soft macular drusen in low abundance were not specifically associated with inheritance of the disease gene. These results will facilitate the genetic counseling of patients with malattia leventinese. It is unknown what proportion of age-related macular degeneration arises from mutations in disease genes for dominant drusen.

The Usher syndromes (USH) are a group of autosomal recessive diseases characterized by progressive pigmentary retinopathy and sensorineural hearing loss. Five USH genes have been mapped and at least one additional gene is known to exist. By homozygosity mapping in a consanguineous family, a sixth USH gene has been localized. Clinical findings in the four affected children are consistent with established diagnostic criteria for Ush1. Linkage to known USH loci was excluded, and using two genomic DNA pools, one from the affected children and the other from the parents, 161 polymorphic markers evenly spaced across the autosomal human genome were screened. The location of the Ush1D gene was defined by the only region showing homozygosity by descent in the affected siblings, a 15 cM interval on chromosome 10q bounded by D10S529 and D10S573.

Purpose This study was performed to investigate the genetic determinants of autosomal recessive congenital cataracts in large consanguineous families. Methods Affected individuals underwent a detailed ophthalmological examination and slit-lamp photographs of the cataractous lenses were obtained. An aliquot of blood was collected from all participating family members and genomic DNA was extracted from white blood cells. Initially, a genome-wide scan was performed with genomic DNAs of family PKCC025 followed by exclusion analysis of our familial cohort of congenital cataracts. Protein-coding exons of CRYBB1, CRYBB2, CRYBB3, and CRYBA4 were sequenced bidirectionally. A haplotype was constructed with SNPs flanking the causal mutation for affected individuals in all four families, while the probability that the four familial cases have a common founder was estimated using EM and CHM-based algorithms. The expression of Crybb3 in the developing murine lens was investigated using TaqMan assays. Results The clinical and ophthalmological examinations suggested that all affected individuals had nuclear cataracts. Genome-wide linkage analysis localized the causal phenotype in family PKCC025 to chromosome 22q with statistically significant two-point logarithm of odds (LOD) scores. Subsequently, we localized three additional families, PKCC063, PKCC131, and PKCC168 to chromosome 22q. Bidirectional Sanger sequencing identified a missense variation: c.493G>C (p.Gly165Arg) in CRYBB3 that segregated with the disease phenotype in all four familial cases. This variation was not found in ethnically matched control chromosomes, the NHLBI exome variant server, or the 1000 Genomes or dbSNP databases. Interestingly, all four families harbor a unique disease haplotype that strongly suggests a common founder of the causal mutation (p

We compared the anterior segment characteristics of congenital cataract (CC) patients with lens opacities in different locations and proposed a modified, simple CC category system.Cataractous eyes of CC patients were classified into four groups based on the locations of lens opacities shown in slit-lamp examinations and by a 3-dimensional anterior segment imaging system as follows: total, anterior, interior, and posterior cataracts. The mean keratometry value, corneal astigmatism (CA), central corneal thickness (CCT), and anterior chamber depth (ACD) of eyes in different groups were compared.We included a total of 428 CC patients. Half of the patients with an anterior cataract had the complication of a pupillary residual membrane. Among the patients with posterior lentiglobus cataracts, 90.38% had unilateral involvement. Patients with total, anterior, or interior cataracts had larger keratometry values than those with either posterior cataracts or clear lens. Congenital cataract patients had greater CA and CCT values than those with a clear lens. The largest CA was presented in patients with anterior cataracts, and the value decreased gradually with more posterior locations of lens opacities. Eyes with total and anterior cataracts had smaller ACDs, and eyes with interior and posterior cataracts had greater ACDs than eyes with a clear lens.Cataractous eyes in CC patients with lens opacities in different locations presented distinct anterior segment characteristics. The modified CC category system, based on the relationships among the locations of lens opacities and anterior segment characteristics, may be beneficial for CC diagnosis and treatment.

To determine whether mutations in different Bardet-Biedl syndrome (BBS) genes result in different ocular phenotypes.Thirty-seven patients from 31 families were enrolled who met the clinical criteria for BBS and for whom a BBS mutation had been identified. Seventeen patients harbored mutations in BBS1, 10 in BBS10, and 10 in other genes (BBS2, BBS3, BBS5, BBS7, and BBS12). All the patients underwent ocular examination; 36 patients had computerized full-field electroretinograms (ERGs).Visual acuity was significantly better in BBS1 patients than in patients with other BBS mutations (P=.01), and a larger proportion of BBS1 patients had good (≥20/50) visual acuity (P=.01). The ERG amplitudes were significantly higher in BBS1 patients than in patients with other BBS mutations in response to 0.5-Hz and 30-Hz flashes (P.001 for both). All the BBS1 patients harbored at least 1 missense mutation compared with only 45% of patients with mutations in other BBS genes (P.001); the rest harbored only null alleles. However, multivariate analysis demonstrated that visual acuity or ERG amplitude did not depend on the type of mutation present (missense or null) when controlling for BBS gene. Prevalences of bone spicule pigmentation and cataract were comparable in BBS subtypes.Patients with BBS1 mutations had a milder phenotype than did patients with mutations in other BBS genes. Clinically, this manifested as significantly better visual acuity and larger ERG amplitudes.These phenotypic differences can help guide genetic testing and genetic counseling for patients with this syndrome.

Purpose: While intrafamilial morphologic heterogeneity of autosomal dominant congenital cataracts has been well established, interocular variation in individual patients of described pedigrees is small. The authors describe a seven-generation family with 48 of 138 individuals known to be affected with autosomal dominant congenital cataracts of the pulverulent type. Affected patients exhibit a seemingly random expression of either unilateral or bilateral lens opacities. Methods: Ophthalmic and medical histories were obtained, complete ophthalmologic examinations were performed, blood samples were drawn, and transformed lymphoblastoid lines were established on 53 patients. Eighty-five members of the family were unable to be examined. Results: Twenty-eight of the 53 individuals examined had congenital cataracts. Of these patients, 19 eyes (8 right eyes and 11 left eyes) were unilateral and 9 were bilateral. The clinically unaffected eye in patients with unilateral cataracts showed no evidence of lenticular opacity under detailed slit-lamp examination. Severity of the cataracts included a subtle unilateral zonular cataract with 20/20 visual acuity, bilateral inner fetal nuclear pulverulent opacities with 20/16 visual acuity in both eyes, and dense unilateral and bilateral nuclear cataracts requiring early surgical removal. Incorporating the historic data on patients who were not examined, we found 48 affected members (28 unilateral, 17 bilateral, 3 obligate carriers who were not examined). Conclusions: Hereditary cataracts typically are symmetric in affected individuals. The authors describe a large pedigree with the apparently random expression of an autosomal dominant gene as either unilateral or bilateral cataract. To their knowledge, this is the first such family described in the literature. Currently, work is under way to determine if the causative gene is linked to previously defined cataract loci on chromosomes 1, 2, or 16.

Bardet-Biedl syndrome (BBS; MIM 209900) is a genetically heterogeneous autosomal recessive disorder characterized by progressive retinal degeneration, truncal obesity, cognitive impairment, polydactyly, hypogonadism, and renal anomalies.1–6 Among the nonconsanguineous populations of Northern Europe and America, the prevalence ranges from 1 in 100,000 in North America7 to 1 in 160,000 in Switzerland.8 BBS incidence increases within populations of high consanguinity or those that are geographically isolated.4,9,10 To date, 15 genes (BBS112, Meckel syndrome 1 [MKS1, BBS13], centrosomal protein 290 kDa/nephronophthisis 6 [CEP290/NPHP6, BBS14], and C2ORF86 [BBS15]) have been implicated in BBS.11,12 Mutations in these genes account only for approximately 70% of BBS patients, suggesting that there are additional genes to be found for BBS.13BBS1 and BBS10 are major pathogenic genes in European populations, each accounting for at least 20% of cases in most series.14,15 However, most other genes are rare contributors. For example, there is only a single documented family with mutations in each of BBS11 (TRIM32), BBS13 (MKS1), BBS14 (CEP290), and BBS15 (C2ORF86).12,16,17 A number of recent publications have expanded the spectrum of known BBS mutations,18–21 and suggested that mutations in some genes, including BBS13 and TMEM67/MKS3, can modify the expression of BBS phenotypes in patients who have mutations in other genes. BBS is also characterized by profound interfamilial and intrafamilial clinical variability, which is possibly explained in part by the presence of second-site modifiers. In some families, three mutated alleles in two BBS genes have been implicated (triallelic inheritance). BBS1, BBS2, BBS3, BBS4, BBS5, BBS6, BBS7, BBS8, and BBS10 have been implicated in triallelic inheritance of BBS,22–25 but the specific contribution of each allele is difficult to ascertain. Moreover, it has been suggested that there might be a connection between triallelism and the phenotypic severity of the disease.26 However, some studies have not identified a complex inheritance mode in this syndrome.27,28 In this study, we analyzed 55 families for known BBS genes (BBS1-BBS15) and identified 43 mutations in 46 families, 21 of which are novel. We also identified 7 Caucasian, 1 Arabic, and 1 Tunisian family in whom the molecular genetic findings raised the possibility of triallelic inheritance involving BBS1, BBS2, BBS3, BBS6, BBS7, BBS8, BBS9, BBS10, or BBS12. Although some sequence variations were identified in additional genes, no homozygous potential mutations were identified in previously unidentified BBS genes.

Background Diabetic retinopathy (DR) is classically defined as a microvasculopathy that primarily affects the small blood vessels of the inner retina as a complication of diabetes mellitus (DM).It is a multifactorial disease with a strong genetic component. The aim of this study is to investigate the association of a set of nine candidate genes with the development of diabetic retinopathy in a South Indian cohort who have type 2 diabetes mellitus (T2DM). Methods Seven candidate genes (RAGE, PEDF, AKR1B1, EPO, HTRA1, ICAM and HFE) were chosen based on reported association with DR in the literature. Two more, CFH and ARMS2, were chosen based on their roles in biological pathways previously implicated in DR. Fourteen single nucleotide polymorphisms (SNPs) and one dinucleotide repeat polymorphism, previously reported to show association with DR or other related diseases, were genotyped in 345 DR and 356 diabetic patients without retinopathy (DNR). The genes which showed positive association in this screening set were tested further in additional sets of 100 DR and 90 DNR additional patients from the Aravind Eye Hospital. Those which showed association in the secondary screen were subjected to a combined analysis with the 100 DR and 100 DNR subjects previously recruited and genotyped through the Sankara Nethralaya Hospital, India. Genotypes were evaluated using a combination of direct sequencing, TaqMan SNP genotyping, RFLP analysis, and SNaPshot PCR assays. Chi-square and Fisher exact tests were used to analyze the genotype and allele frequencies. Results Among the nine loci (15 polymorphisms) screened, SNP rs2070600 (G82S) in the RAGE gene, showed significant association with DR (allelic P = 0.016, dominant model P = 0.012), compared to DNR. SNP rs2070600 further showed significant association with DR in the confirmation cohort (P = 0.035, dominant model P = 0.032). Combining the two cohorts gave an allelic P < 0.003 and dominant P = 0.0013). Combined analysis with the Sankara Nethralaya cohort gave an allelic P = 0.0003 and dominant P = 0.00011 with an OR = 0.49 (0.34 - 0.70) for the minor allele. In HTRA1, rs11200638 (G>A), showed marginal significance with DR (P = 0.055) while rs10490924 in LOC387715 gave a P = 0.07. No statistical significance was observed for SNPs in the other 7 genes studied. Conclusions This study confirms significant association of one polymorphism only (rs2070600 in RAGE) with DR in an Indian population which had T2DM.

Retinitis pigmentosa (RP) is a phenotypically and genetically heterogeneous group of inherited retinal degenerations characterized clinically by night blindness, progressive constriction of the visual fields, and loss of vision, and pathologically by progressive loss of rod and then cone photoreceptors. Autosomal-recessive RP (arRP) in a consanguineous Pakistani family previously linked to chromosome 2p22.3-p24.1 is shown to result from a homozygous missense mutation (c.1015T>C [p.C339R]) in ZNF513, encoding a presumptive transcription factor. znf513 is expressed in the retina, especially in the outer nuclear layer, inner nuclear layer, and photoreceptors. Knockdown of znf513 in zebrafish reduces eye size, retinal thickness, and expression of rod and cone opsins and causes specific loss of photoreceptors. These effects are rescued by coinjection with wild-type (WT) but not p.C339R-znf513 mRNA. Both normal and p.C339R mutant ZNF513 proteins expressed in COS-7 cells localize to the nucleus. ChIP analysis shows that only the wild-type but not the mutant ZNF513 binds to the Pax6, Sp4, Arr3, Irbp, and photoreceptor opsin promoters. These results suggest that the ZNF513 p.C339R mutation is responsible for RP in this family and that ZNF513 plays a key role in the regulation of photoreceptor-specific genes in retinal development and photoreceptor maintenance.

The most common cause of ectopia lentis is trauma to the eye, but familial simple ectopia lentis without any systemic abnormality has been described.1,2 Ectopia lentis may occur because of flawed zonule formation.3 Mutations of the fibrillin genes are the bases of Marfan and Beal syndromes, both of which may include ectopia lentis. The most common ocular problems associated with isolated forms of ectopia lentis are myopia, astigmatism, and anisometropia, the severity of which depends on the extent of dislocation of the lens. The most common cause of ectopia lentis is trauma to the eye, but heritable forms also exist.2 Although rare, familial simple ectopia lentis unassociated with any systemic abnormality has been described. It is most often inherited as an autosomal dominant disorder, but autosomal recessive inheritance has also been reported.4–7 Mutations in the fibrillin 1 gene (FBN1 [OMIM 134797]) have been associated with ectopia lentis, both in an autosomal dominant as well as autosomal recessive fashion.8–12 Recently, mutations in thrombospondin repeat–containing 1 (AD-AMTSL4 [OMIM 610113]) were associated with the simple form of ectopia lentis13; ADAMTSL4 belongs to a large superfamily of proteins, ADAMTS-like protein 4 precursor (thrombospondin repeat–containing protein 1), that are involved in various biological processes, including connective tissue organization, coagulation, and cell migration.14 We report a consanguineous family with 7 affected members ascertained from the Punjab province of Pakistan. All affected family members examined have had dislocated lenses. Clinical physical examination showed no signs of cardiac abnormalities or skeletal features associated with syndromes including ectopia lentis. A genome-wide linkage scan was performed and linkage analysis provided evidence of a new locus for autosomal recessive simple ectopia lentis on chromosome 8q11.23-q13.2.

We appreciate the letter by Liu et al. (1) and commend them on their work (1). We are encouraged that they have confirmed association of primary open-angle glaucoma (POAG) with rs12994401, although it is to the opposite allele from that seen in the Barbados population (2). These results, in addition to the presence of a monogenic POAG locus in this region, provide substantive confirmation of a locus for POAG (3). The inverse association of risk alleles between African Americans is not completely surprising given the high degree of genetic diversity in African and African-derived populations (4) and previously described divergent levels and patterns of linkage disequilibrium (LD) in African subpopulations (5). The situation becomes even more complex when migration patterns to the Caribbean islands are considered (6). We agree with the conclusion by Liu et al. (1) that rs12994401 most likely represents a tagging SNP that is in linkage disequilibrium with a yet unidentified causative SNP in this region.

Tissue-specific alternative splicing is an important mechanism for providing spatiotemporal protein diversity. Here we show that an in-frame splice mutation in BBS8, one of the genes involved in pleiotropic Bardet-Biedl syndrome (BBS), is sufficient to cause nonsyndromic retinitis pigmentosa (RP). A genome-wide scan of a consanguineous RP pedigree mapped the trait to a 5.6 Mb region; subsequent systematic sequencing of candidate transcripts identified a homozygous splice-site mutation in a previously unknown BBS8 exon. The allele segregated with the disorder, was absent from controls, was completely invariant across evolution, and was predicted to lead to the elimination of a 10 amino acid sequence from the protein. Subsequent studies showed the exon to be expressed exclusively in the retina and enriched significantly in the photoreceptor layer. Importantly, we found this exon to represent the major BBS8 mRNA species in the mammalian photoreceptor, suggesting that the encoded 10 amino acids play a pivotal role in the function of BBS8 in this organ. Understanding the role of this additional sequence might therefore inform the mechanism of retinal degeneration in patients with syndromic BBS or other related ciliopathies.

The Usher syndromes (USH) are autosomal recessive diseases characterized by congenital sensorineural hearing loss and progressive pigmentary retinopathy. While relatively rare in the general population, collectively they account for approximately 6% of the congenitally deaf population. Usher syndrome type II (USH2) has been mapped to chromosome 1q (W. J. Kimberling, M. D. Weston, C. Moller, et al., 1990, Genomics 7: 245-249; R. A. Lewis, B. Otterud, D. Stauffer, et al., 1990, Genomics 7: 250-256), and one form of Usher syndrome type I (USH1) has been mapped to chromosome 14q (J. Kaplan, S. Gerber, D. Bonneau, J. Rozet, M. Briord, J. Dufier, A. Munnich, and J. Frezal, 1990. Cytogenet. Cell Genet. 58: 1988). These loci have been excluded as regions of USH genes in our data set, which is composed of 8 French-Acadian USH1 families and 11 British USH1 families. Both of these sets of families show linkage to loci on chromosome 11. Linkage analysis demonstrates locus heterogeneity between these sets of families, with the French-Acadian families showing linkage to D11S419 (Z = 4.20, theta = 0) and the British families showing linkage to D11S527 (Z = 6.03, theta = 0). Genetic heterogeneity of the data set was confirmed using HOMOG and the M test (log likelihood ratio > 10(5)). These results confirm the presence of two distinct USH1 loci on chromosome 11.