Search

Purpose: This study was undertaken to investigate the causal mutations responsible for autosomal recessive congenital stationary night blindness (CSNB) in consanguineous Pakistani families., Methods: Two consanguineous families with multiple individuals manifesting symptoms of stationary night blindness were recruited. Affected individuals underwent a detailed ophthalmological examination, including fundus examination and electroretinography. Blood samples were collected and genomic DNA was extracted. Exclusion analyses were completed by genotyping closely spaced microsatellite markers, and two-point logarithm of odds (LOD) scores were calculated. All coding exons, along with the exon-intron boundaries of GRM6, were sequenced bidirectionally., Results: According to the medical history available to us, affected individuals in both families had experienced night blindness from the early years of their lives. Fundus photographs of affected individuals in both the families appeared normal, with no signs of attenuated arteries or bone spicule pigmentation. The scotopic electroretinogram (ERG) response were absent in all of the affected individuals, while the photopic measurements show reduced b-waves. During exclusion analyses, both families localized to a region on chromosome 5q that harbors GRM6, a gene previously associated with autosomal recessive CSNB. Bidirectional sequencing of GRM6 identified homozygous single base pair changes, specifically c.1336C>T (p.R446X) and c.2267G>A (p.G756D) in families PKRP170 and PKRP172, respectively., Conclusions: We identified a novel nonsense and a previously reported missense mutation in GRM6 that were responsible for autosomal recessive CSNB in patients of Pakistani decent.

Purpose: This study was conducted to localize and identify causal mutations associated with autosomal recessive retinitis pigmentosa (RP) in consanguineous familial cases of Pakistani origin., Methods: Ophthalmic examinations that included funduscopy and electroretinography (ERG) were performed to confirm the affectation status. Blood samples were collected from all participating individuals, and genomic DNA was extracted. A genome-wide scan was performed, and two-point logarithm of odds (LOD) scores were calculated. Sanger sequencing was performed to identify the causative variants. Subsequently, we performed whole exome sequencing to rule out the possibility of a second causal variant within the linkage interval. Sequence conservation was performed with alignment analyses of PDE6A orthologs, and in silico splicing analysis was completed with Human Splicing Finder version 2.4.1., Results: A large multigenerational consanguineous family diagnosed with early-onset RP was ascertained. An ophthalmic clinical examination consisting of fundus photography and electroretinography confirmed the diagnosis of RP. A genome-wide scan was performed, and suggestive two-point LOD scores were observed with markers on chromosome 5q. Haplotype analyses identified the region; however, the region did not segregate with the disease phenotype in the family. Subsequently, we performed a second genome-wide scan that excluded the entire genome except the chromosome 5q region harboring PDE6A. Next-generation whole exome sequencing identified a splice acceptor site mutation in intron 16: c.2028-1G>A, which was completely conserved in PDE6A orthologs and was absent in ethnically matched 350 control chromosomes, the 1000 Genomes database, and the NHLBI Exome Sequencing Project. Subsequently, we investigated our entire cohort of RP familial cases and identified a second family who harbored a splice acceptor site mutation in intron 10: c.1408-2A>G. In silico analysis suggested that these mutations will result in the elimination of wild-type splice acceptor sites that would result in either skipping of the respective exon or the creation of a new cryptic splice acceptor site; both possibilities would result in retinal photoreceptor cells that lack PDE6A wild-type protein., Conclusions: we report two splice acceptor site variations in PDE6A in consanguineous Pakistani families who manifested cardinal symptoms of RP. Taken together with our previously published work, our data suggest that mutations in PDE6A account for about 2% of the total genetic load of RP in our cohort and possibly in the Pakistani population as well.

Purpose: To localize and identify the gene and mutations causing autosomal recessive retinal dystrophy in two consanguineous Pakistani families., Methods: Consanguineous families from Pakistan were ascertained to be affected with autosomal recessive retinal degeneration. All affected individuals underwent thorough ophthalmologic examinations. Blood samples were collected, and genomic DNA was extracted using a salting out procedure. Genotyping was performed using microsatellite markers spaced at approximately 10 cM intervals. Two-point linkage analysis was performed with the lod score method. Direct DNA sequencing of amplified genomic DNA was performed for mutation screening of candidate genes., Results: Genome-wide linkage scans yielded a lod score of 3.05 at θ=0 for D17S1832 and 3.82 at θ=0 for D17S938, localizing the disease gene to a 12.22 cM (6.64 Mb) region flanked by D17S1828 and D17S1852 for family 61032 and family 61227, which contains aryl hydrocarbon receptor interacting protein-like 1 (AIPL1), a gene previously implicated in recessive Leber congenital amaurosis and autosomal dominant cone-rod dystrophy. Sequencing of AIPL1 showed a homozygous c.773G>C (p.Arg258Pro) sequence change in all affected individuals of family 61032 and a homozygous c.465G>T (p.(H93_Q155del)) change in all affected members of family 61227., Conclusions: The results strongly suggest that the c.773G>C (p.R258P) and c.465G>T (p.(H93_Q155del)) mutations in AIPL1 cause autosomal recessive retinal degeneration in these consanguineous Pakistani families.

Purpose: This study was designed to identify pathogenic mutations causing autosomal recessive retinitis pigmentosa (RP) in consanguineous Pakistani families., Methods: Two consanguineous families affected with autosomal recessive RP were identified from the Punjab Province of Pakistan. All affected individuals underwent a thorough ophthalmologic examination. Blood samples were collected, and genomic DNAs were extracted. Exclusion analysis was completed, and two-point LOD scores were calculated. Bidirectional sequencing of the β subunit of phosphodiesterase 6 (PDE6β) was completed., Results: During exclusion analyses both families localized to chromosome 4p, harboring PDE6β, a gene previously associated with autosomal recessive RP. Sequencing of PDE6β identified missense mutations: c.1655G>A (p.R552Q) and c.1160C>T (p.P387L) in families PKRP161 and PKRP183, respectively. Bioinformatic analyses suggested that both mutations are deleterious for the native three-dimensional structure of the PDE6β protein., Conclusions: These results strongly suggest that mutations in PDE6β are responsible for the disease phenotype in the consanguineous Pakistani families.

Purpose: To localize the disease interval for autosomal recessive congenital cataracts in a consanguineous Pakistani family., Methods: All affected individuals underwent detailed ophthalmologic examination. Blood samples were collected and genomic DNA was extracted. A genome-wide scan was performed with fluorescently-labeled microsatellite markers on genomic DNA from affected and unaffected family members and logarithm of odds (LOD) scores were calculated., Results: Clinical records and ophthalmological examinations suggested that affected individuals have bilateral congenital cataracts. Genome-wide linkage analysis localized the critical interval to chromosome 3q with a maximum LOD score of 3.87 at θ=0; with marker D3S3609. Haplotype analyses refined the critical interval to a 23.39 cM (18.01 Mb) interval on chromosome 3q, flanked by D3S1614 proximally and D3S1262, distally., Conclusions: Here, we report a new locus for autosomal recessive congenital cataract localized to chromosome 3q in a consanguineous Pakistani family.

Purpose: To investigate the genetic basis of Marinesco-Sjogren syndrome (MSS) in consanguineous Pakistani families., Methods: Two consanguineous Pakistani families with congenital cataract and muscular dystrophy were enrolled for this study. Detailed ophthalmic and systemic examination including slit lamp microscopy, electromyogram and computed tomography scans were performed to characterize the syndrome. Blood samples were collected from affected and unaffected individuals and a genome wide scan consisting of 382 polymorphic microsatellite markers was performed. Coding exons, exon-intron boundaries, 5' UTR, and 3' UTR of the candidate gene SIL1 residing in the linkage interval was sequenced bi-directionally., Results: Clinical examination of the affected members of families 60067 and 60078 revealed features of MSS. The linked interval at chromosome 5q31 harbors SIL1. Sequencing of SIL1 in family 60067 revealed a homozygous substitution; c1240C>T, leading to a premature substitution; p.Q414X. Similarly, sequencing of SIL1 in family 60078 identified a homozygous change; c.274C>T, leading to a non conservative substitution; p.R92W., Conclusion: In conclusion, our data report two novel missense mutations in two consanguineous Pakistani families affected with MSS.

Purpose: Two consanguineous Pakistani families with autosomal recessive primary congenital glaucoma were recruited to identify the disease locus., Methods: Ophthalmic examinations including slit lamp biomicroscopy and applanation tonometry were employed to classify the phenotype. Blood samples were collected and genomic DNA was extracted. A genome wide scan was performed on both families with 382 polymorphic microsatellite markers. Two point LOD scores were calculated, and haplotypes were constructed to define the disease interval., Results: Clinical records and ophthalmic examinations suggest that affected individuals in families PKGL005 and PKGL025 have primary congenital glaucoma. Maximum two-point LOD scores of 5.88 with D14S61 at theta=0 and 6.19 with D14S43 at theta=0 were obtained for families PKGL005 and PKGL025, respectively. Haplotype analysis defined the disease locus as spanning a 6.56 cM (~4.2 Mb) genetic interval flanked by D14S289 proximally and D14S85 distally., Conclusions: Linkage analysis localizes autosomal recessive primary congenital glaucoma to chromosome 14q24.2-24.3 in consanguineous Pakistani families.

Purpose: To identify the disease locus for autosomal recessive congenital cataracts in two consanguineous Pakistani families., Methods: Two Pakistani families were ascertained, ophthalmologic examination including slit lamp biomicroscopy was performed on all members, blood samples were collected and DNA was extracted. A genome-wide scan was performed using 382 polymorphic microsatellite markers on genomic DNA from affected and unaffected family members. Two-point logarithm of odds (LOD) scores were calculated using the LINKAGE program package., Results: All the affected individuals of family PKCC009 show bilateral membranous cataract, whereas the affected individuals of family PKCC039 show bilateral posterior sub-capsular cataract. Other ocular abnormalities include corneal opacities, microcornea and nystagmus in the affected individuals of PKCC009. Maximum two point LOD scores were obtained with D1S186 (4.14 at theta = 0), D1S432 (4.01 at theta = 0), D1S2892 (4.11 at theta = 0), and D1S2797 (4.07 at theta = 0) for family PKCC009 and with D1S496 (4.73 at theta = 0), D1S2892 (4.34 at theta = 0), D1S3721 (4.83 at theta = 0), and D1S2797 (4.32 at theta = 0) for family PKCC039. The common linked region, 20.76 cM (20.80 Mb), is flanked by markers D1S2729 and D1S2890 and co-segregates with the disease in both families, placing the disease locus on chromosome 1p34.3-p32.2., Conclusions: Linkage analysis of autosomal recessive cataracts in two consanguineous Pakistani families localizes a novel locus for autosomal recessive congenital cataract on chromosome 1p.

Purpose: To localize and identify the gene and mutations causing autosomal recessive retinitis pigmentosa (RP) in consanguineous Pakistani families., Methods: Families were ascertained and patients underwent complete ophthalmological examinations. Blood samples were collected and DNA was extracted. A genome-wide scan was performed using 382 polymorphic microsatellite markers on genomic DNA from affected and unaffected family members, and lod scores were calculated., Results: A genome-wide scan of 50 families gave a lod score of 7.4172 with D5S2015 using HOMOG1. RP in all 4 linked families mapped to a 13.85 cM (14.87 Mb) region on chromosome 5q31-33 flanked by D5S2090 and D5S422. This region harbors the PDE6A gene, which is known to cause autosomal recessive RP. Sequencing of PDE6A showed a homozygous single base pair change; c.889C->T, single base pair insertion; c.2218-2219insT, and single base pair substitution in the splice acceptor site; IVS10-2A->G in each of three families. In the fourth family linked to this region, no disease-causing mutation was identified in the PDE6A gene., Conclusions: These results provide strong evidence that mutations in PDE6A result in recessive RP in three consanguineous Pakistani families. Although a fourth family was linked to markers in the 5q31-33 interval, no mutation was identified in PDE6A.

Purpose: The purpose of this paper is to map the locus for a variant form of Oguchi disease in a Pakistani family and to identify the causative mutation., Methods: Family 61029 was ascertained in the Punjab province of Pakistan. It includes three 13- to 19-year-old patients with night blindness and 12 unaffected family members. A complete ophthalmological examination including fundus photography and electroretinography (ERG) was performed on each family member. A genome-wide scan was performed using microsatellite markers at about 10 cM intervals, and two-point lod scores were calculated. Polymerase chain reaction (PCR) cycle dideoxynucleotide sequencing was used to screen candidate genes inside the linked region for mutations and to delineate the deletion. Multiplex PCR and long template PCR were used to detect deletions and to define the size of deletions. Evaluation of fundus changes and ERG, lod score estimation, and identification of a mutation in the GRK1 gene were carried out., Results: All patients had night blindness since early childhood. Irregular coarse pigmentation was observed in the peripheral retina of each patient. The fundus appearance before and after 4 h of dark adaptation was similar except that the peripheral retinal pigmentary changes were slightly less evident after extended dark adaptation. Minimal or no rod function with normal cone function on ERG recordings were detected in all three affected members. The rod showed slow recovery to nearly normal amplitude after 4 h in the dark ERG in one individual but not in two other patients. A genome-wide scan showed linkage only to D13S285. Fine mapping defined a region from D13S1315 to 13qter, with a lod score of 2.89 at theta=0 shown by D13S285 and 2.90 at theta=0 by the D13S261-D13S285-D13S1295-D13S293 haplotype. Analysis of the GRK1 gene, which is included in this interval, identified a c.827+623_883del mutation. This intragenic deletion cosegregates with the disease in the family and is only homozygous in affected individuals. This mutation was not detected in 96 controls., Conclusions: The retinal disease in the family reported here has several features differing from typical Oguchi disease, including an atypical Mizuo-Nakamura phenomenon and a non-recordable rod ERG even after 4 h of dark adaptation. Normal visual acuity, normal caliber of retinal blood vessels, and normal cone response on ERG recording suggest retinal dysfunction rather than degeneration (i.e., a variant form of Oguchi disease but unlikely to be retinitis pigmentosa). The disease in the Pakistani family localizes to 13q34 and is caused by a novel deletion including Exon 3 of the GRK1 gene.

Purpose: To map the locus for autosomal recessive retinitis pigmentosa in a large Pakistani family and to determine the causative mutation., Methods: A large family with multiple individuals affected by autosomal recessive retinitis pigmentosa was ascertained in the Punjab province of Pakistan as part of an ongoing project between the CEMB, Lahore, Pakistan and the NEI to identify genetic causes of eye diseases. After initial analysis of previously identified autosomal recessive retinitis pigmentosa loci, a genome wide scan was performed using microsatellite markers at about 10 cM intervals. Two point lod scores were calculated and haplotypes were analyzed in order to define disease locus. Bidirectional dideoxynucleotide sequencing was used to screen for mutations in candidate genes., Results: In the genome wide scan, autosomal recessive retinitis pigmentosa in this Pakistani family showed linkage to an 11.7 cM region of chromosome 4p12 between D4S405 and D4S1592 with a maximum lod score of 2.90 with D4S405 at theta;=0.01 Sequence analysis of CNGA1 identified a 2 bp deletion in exon 8: c.626_627delTA resulting in a frameshift, p.Ser209fsX26 in the translated protein. This mutation results in deletion of the COOH terminal 482 of 690 total amino acids in CNGA1 and their replacement by 25 novel amino acids before a premature termination. The mutation is found in a homozygous state in all 7 affected individuals and was heterozygous in all 15 unaffected family members examined. The mutant allele of CNGA1 itself shows linkage to the disease with maximum lod score of 4.43 at theta;=0., Conclusions: The autosomal recessive retinitis pigmentosa in this family is caused by a mutation in CNGA1 gene. To our knowledge, this is the first report in which both linkage analysis and identification of a mutation support CNGA1 as a cause for autosomal recessive retinitis pigmentosa.