Objective

To identify pathogenic mutations responsible for autosomal recessive retinitis pigmentosa in 5 consanguineous Pakistani families.

Methods

Affected individuals in the families underwent a detailed ophthalmological examination that consisted of fundus photography and electroretinography. Blood samples were collected from all participating family members, and genomic DNA was extracted. A genome-wide linkage scan was performed, followed by exclusion analyses among our cohort of nuclear consanguineous families with microsatellite markers spanning the TULP1 locus on chromosome 6p. Two-point logarithm of odds scores were calculated, and all coding exons of TULP1 were sequenced bidirectionally.

Results

The results of ophthalmological examinations among affected individuals in these 5 families were suggestive of retinitis pigmentosa. The genome-wide linkage scan localized the disease interval to chromosome 6p, harboring TULP1 in 1 of 5 families, and sequential analyses identified a single base pair substitution in TULP1 that results in threonine to alanine substitution (p.T380A). Subsequently, we investigated our entire cohort of families with autosomal recessive retinitis pigmentosa and identified 4 additional families with linkage to chromosome 6p, all of them harboring a single base pair substitution in TULP1 that results in lysine to arginine substitution (p.K489R). Results of single-nucleotide polymorphism haplotype analyses were suggestive of a common founder in these 4 families.

Conclusion

Pathogenic mutations in TULP1 are responsible for the autosomal recessive retinitis pigmentosa phenotype in these consanguineous Pakistani families, with a single ancestral mutation in TULP1 causing the disease phenotype in 4 of 5 families.

Clinical Relevance

Clinical and molecular characterization of pathogenic mutations in TULP1 will increase our understanding of retinitis pigmentosa at a molecular level.

Objective

To identify disease-causing mutations in two consanguineous Pakistani families with fundus albipunctatus.

Methods

Affected individuals in both families underwent a thorough clinical examination including funduscopy and electroretinography. Blood samples were collected from all participating members and genomic DNA was extracted. Exclusion analysis was completed with microsatellite short tandem repeat markers that span all reported loci for fundus albipunctatus. Two-point logarithm of odds (LOD) scores were calculated, and coding exons and exon–intron boundaries of RLBP1 were sequenced bi-directionally.

Results

The ophthalmic examination of affected patients in both families was consistent with fundus albipunctatus. The alleles of markers on chromosome 15q flanking RLBP1 segregated with the disease phenotype in both families and linkage was further confirmed by two-point LOD scores. Bi-directional sequencing of RLBP1 identified a nonsense mutation (R156X) and a missense mutation (G116R) that segregated with the disease phenotype in their respective families.

Conclusions

These results strongly suggest that mutations in RLBP1 are responsible for fundus albipunctatus in the affected individuals of these consanguineous Pakistani families.

Congenital stationary night blindness is characterized by impaired night vision, decreased visual acuity, nystagmus, myopia, and strabismus. A genome-wide linkage scan was completed that localized the critical interval to the short arm of chromosome 3 and sequencing identified a novel missense mutation in GNAT1.

Purpose.

Congenital stationary night blindness is a nonprogressive retinal disorder manifesting as impaired night vision and is generally associated with other ocular symptoms, such as nystagmus, myopia, and strabismus. This study was conducted to further investigate the genetic basis of CSNB in a consanguineous Pakistani family.

Methods.

A consanguineous family with multiple individuals manifesting cardinal symptoms of congenital stationary night blindness was ascertained. All family members underwent detailed ophthalmic examination, including fundus photographic examination and electroretinography. Blood samples were collected and genomic DNA was extracted. Exclusion and genome-wide linkage analyses were completed and two-point LOD scores were calculated. Bidirectional sequencing of GNAT1 was completed, and quantitative expression of Gnat1 transcript levels were investigated in ocular tissues at different postnatal intervals.

Results.

The results of ophthalmic examinations were suggestive of early-onset stationary night blindness with no extraocular anomalies. The genome-wide scan localized the critical interval to chromosome 3, region p22.1-p14.3, with maximum two-point LOD scores of 3.09 at θ = 0, flanked by markers D3S3522 and D3S1289. Subsequently, a missense mutation in GNAT1, p.D129G, was identified, which segregated within the family, consistent with an autosomal recessive mode of inheritance, and was not present in 192 ethnically matched control chromosomes. Expression analysis suggested that Gnat1 is expressed at approximately postnatal day (P)7 and is predominantly expressed in the retina.

Conclusions.

These data suggest that a homozygous missense mutation in GNAT1 is associated with autosomal recessive stationary night blindness.

Many proteins necessary for sound transduction have been discovered through positional cloning of genes that cause deafness1–3. In this study, we report that mutations of LRTOMT are associated with profound non-syndromic hearing loss at the DFNB63 locus on human chromosome 11q13.3-q13.4. LRTOMT has two alternative reading frames and encodes two different proteins, LRTOMT1 and LRTOMT2, that are detected by Western blot analyses. LRTOMT2 is a putative methyltransferase. During evolution, novel transcripts can arise through partial or complete coalescence of genes4. We provide evidence that in the primate lineage LRTOMT evolved from the fusion of two neighboring ancestral genes, which exist as separate genes (Lrrc51and Tomt) in rodents.

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.

Objective

To investigate the genetic basis and molecular characteristics of the isolated form of ectopia lentis.

Methods

We ascertained a consanguineous Pakistani family with multiple individuals with ectopia lentis. All affected as well as unaffected members with isolated ectopia lentis underwent detailed ophthalmologic and medical examination. Blood samples were collected and DNA was extracted. A genome-wide scan was completed with 382 polymorphic microsatellite markers, and logarithm of odds (LOD) scores were calculated.

Results

Maximum 2-point LOD scores of 5.68 and 2.88 at θ=0 were obtained for markers D8S285 and D8S260, respectively, during the genome-wide scan. Additional microsatellite markers refined the disease locus to a 16.96-cM (14.07-Mb) interval flanked by D8S1737 proximally and D8S1117 distally.

Conclusions

We report on a new locus for nonsyndromic autosomal recessive ectopia lentis on chromosome 8q11.23-q13.2 in a consanguineous Pakistani family.

Clinical Relevance

Identification of genetic loci and genes involved in ectopia lentis will enhance our understanding of the disease at a molecular level, leading to better genetic counseling and family screening and possible future development of better treatment.

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.

A +57C>T substitution in the microRNA miR-184 causes an autosomal dominant syndrome of endothelial dystrophy, iris hypoplasia, congenital cataract, and stromal thinning (EDICT).

Purpose.

To investigate the cause of the syndrome characterized by endothelial dystrophy, iris hypoplasia, congenital cataract, and stromal thinning (EDICT).

Methods.

Previously a multigenerational family was reported that comprised 10 individuals affected by syndromal anterior segment dysgenesis. Blood samples were re-collected from eight affected and two unaffected individuals, and genomic DNA was extracted. A total of 24 candidate genes and 4 microRNAs residing within the critical interval were sequenced bidirectionally. In silico analyses were performed to examine the effect of the causal variant on the stability of the pre-microRNA structure.

Results.

Bidirectional sequencing identified the single-base substitution +57C>T in miR-184. This variation segregated with the disease phenotype and was absent in the 1000 Genomes project, 1130 control chromosomes, and 28 nonhuman vertebrates.

Conclusions.

The single-base-pair substitution in the seed region of miR-184 is responsible for the disease phenotype observed in EDICT syndrome.

The authors describe the screening of 55 families of European, Tunisian, and Arab descent for mutations in 15 BBS and 5 additional ciliopathy genes. The spectrum of mutations is described with a discussion of possible third-allele effects.

Purpose.

Bardet-Biedl syndrome (BBS) is genetically heterogeneous with 15 BBS genes currently identified, accounting for approximately 70% of cases. The aim of our study was to define further the spectrum of BBS mutations in a cohort of 44 European-derived American, 8 Tunisian, 1 Arabic, and 2 Pakistani families (55 families in total) with BBS.

Methods.

A total of 142 exons of the first 12 BBS-causing genes were screened by dideoxy sequencing. Cases in which no mutations were found were then screened for BBS13, BBS14, BBS15, RPGRIP1L, CC2D2A, NPHP3, TMEM67, and INPP5E.

Results.

Forty-three mutations, including 8 frameshift mutations, 10 nonsense mutations, 4 splice site mutations, 1 deletion, and 20 potentially or probably pathogenic missense variations, were identified in 46 of the 55 families studied (84%). Of these, 21 (2 frameshift mutations, 4 nonsense mutations, 4 splice site mutations, 1 deletion, and 10 missense variations) were novel. The molecular genetic findings raised the possibility of triallelic inheritance in 7 Caucasian families, 1 Arabian family, and 1 Tunisian patient. No mutations were detected for BBS4, BBS11, BBS13, BBS14, BBS15, RPGRIP1L, CC2D2A, NPHP3, TMEM67, or INPP5E.

Conclusions.

This mutational analysis extends the spectrum of known BBS mutations. Identification of 21 novel mutations highlights the genetic heterogeneity of this disorder. Differences in European and Tunisian patients, including the high frequency of the M390R mutation in Europeans, emphasize the population specificity of BBS mutations with potential diagnostic implications. The existence of some BBS cases without mutations in any currently identified BBS genes suggests further genetic heterogeneity.

Purpose

Mutation of the autophagy gene FYVE (named after the four cysteine-rich proteins: Fab 1 [yeast orthologue of PIKfyve], YOTB, Vac 1 [vesicle transport protein], and EEA1) and coiled coil containing 1 (fyco1) causes human cataract suggesting a role for autophagy in lens function. Here, we analyzed the range and spatial expression patterns of lens autophagy genes and we evaluated whether autophagy could be induced in lens cells exposed to stress.

Methods

Autophagy gene expression levels and their spatial distribution patterns were evaluated between microdissected human lens epithelium and fibers at the mRNA and protein levels by microarray data analysis, real-time PCR and western blot analysis. Selected autophagy protein spatial expression patterns were also examined in newborn mouse lenses by immunohistochemistry. The autophagosomal content of cultured human lens epithelial cells was determined by counting the number of microtubule-associated protein 1 light chain 3B (LC3B)-positive puncta in cells cultured in the presence or absence of serum.

Results

A total of 42 autophagy genes were detected as being expressed by human lens epithelium and fibers. The autophagosomal markers LC3B and FYCO1 were detected throughout the newborn mouse lens. Consistently, the autophagy active form of LC3B (LC3B II) was detected in microdissected human lens fibers. An increased number of LC3B-positive puncta was detected in cultured lens cells upon serum starvation suggesting induction of autophagy in lens cells under stress conditions.

Conclusions

The data provide evidence that autophagy is an important component for the function of lens epithelial and fiber cells. The data are consistent with the notion that disruption of lens autophagy through mutation or inactivation of specific autophagy proteins could lead to loss of lens resistance to stress and/or loss of lens differentiation resulting in cataract formation.

Homozygous mutations in the sodium-bicarbonate transporter SLC4A11 cause two early onset corneal dystrophies: congenital hereditary endothelial dystrophy (CHED) and Harboyan syndrome. More recently, four sporadic patients with late onset Fuchs corneal dystrophy (FCD), a common age-related disorder, were also reported to harbor heterozygous mutations at this locus. We therefore tested the hypothesis that SLC4A11 contributes to FCD and asked whether mutations in SLC4A11 are responsible for familial cases of late onset FCD. We sequenced SLC4A11 in 192 sporadic and small nuclear late-onset FCD families and found seven heterozygous missense novel variations that were absent from ethnically matched controls. Familial data available for one of these mutations showed segregation under a dominant model in a three-generational family. In silico analyses suggested that most of these substitutions are intolerant, while biochemical studies of the mutant protein indicated that these alleles impact the localization and/or post-translational modification of the protein. These results suggest that heterozygous in SLC4A11 are modest contributors to the pathogenesis of adult FCD, suggesting a causality continuum between FCD and CHED. Taken together with a recent model between FCD and yet another early onset corneal dystrophy, PPCD, our data suggest a shared pathomechanism and genetic overlap across several corneal dystrophies.

The authors report the first independent replication of rs613872, an intronic SNP of TCF4 associated with late-onset Fuchs corneal dystrophy.

Purpose.

Fuchs corneal dystrophy (FCD) is an autosomal dominant disease of the corneal endothelium with variable penetrance and expressivity. Recently, rs613872, an intronic variation of TCF4 associated with late-onset FCD, was reported. The present study was undertaken to examine this association in our cohort of FCD patients, to assess the significance of this finding, and to investigate the candidacy of TCF4 in the context of the mapped FCD2 locus.

Methods.

The authors recruited 170 patients with late-onset FCD and 180 age-matched controls. Blood samples were collected, and genomic DNA was extracted. A panel of nine SNPs spanning the entire TCF4 locus was genotyped both on this cohort and on three previously reported FCD2-linked families. The association of an individual SNP with late-onset FCD was evaluated with the Fisher exact test, and the coding exons and exon-intron boundaries of TCF4 were sequenced in 96 affected persons.

Results.

The risk allele G of rs613872 is associated significantly with late-onset FCD (odds ratio, 4.2; P = 4.28 × 10−15) and was present in male and female affected persons without any sex bias, replicating recent findings, though the authors found no apparent correlation with the severity of the disease phenotype. Moreover, the risk allele did not cosegregate with the disease phenotype in any of the three FCD2-linked families. The authors did not identify any pathogenic variants in the coding region of TCF4.

Conclusions.

The authors report the first independent replication of rs613872 conferring risk of late-onset FCD. Their data suggest that this risk factor is likely independent of the FCD2 locus, whose causality remains unknown.

Fuchs corneal dystrophy (FCD) is a common ocular disorder that affects approximately 4% of the United States population over the age of 40. This study examines the age-severity relationship in families with late-onset FCD through the use of retroillumination photography.

Purpose.

Fuchs corneal dystrophy (FCD) is a progressive disorder of the corneal endothelium and is pathologically defined by the presence of guttae, which are excrescences of the Descemet membrane. The present study was undertaken to investigate the age-severity relationship of the FCD2-linked disease phenotype using retroillumination photography and to compare it with the characteristics of FCD1.

Methods.

Two large families with multiple affected members were recruited. Exclusion analyses of the known late-onset FCD loci were completed with closely spaced STR markers, whereas genes associated with early- and late-onset FCD were investigated by bidirectional sequencing. Haplotypes were constructed, and two-point LOD scores were calculated. To document age-severity relationships, retroillumination photographs were acquired from members of both families.

Results.

Parametric linkage and haplotype analysis mapped both families to FCD2 with significant two-point LOD scores. A total of 70,249 guttae were counted in 14 persons from both families. A significant increase in guttae density in the inferotemporal region (P = 0.016) was observed, a pattern similarly observed in a family linked to FCD1. Similarly, FCD2-linked families display an exponential trend in severity with age, as was observed in a family linked to FCD1. Finally, comparison of FCD1 and FCD2 exponential models suggested that the FCD1 phenotype is significantly more severe (P = 0.01).

Conclusions.

A combination of genetic mapping and retroillumination photography was used to quantify the severity of the disease phenotype associated with FCD2 and to compare it to the disease characteristics of FCD1. These data suggest that this approach might have sufficient resolution to discriminate between discrete genetic FCD backgrounds, which will potentially aid in patient management.

Fuchs endothelial corneal dystrophy (FECD) is a common, late-onset disorder of the corneal endothelium. Although progress has been made in understanding the genetic basis of FECD by studying large families in which the phenotype is transmitted in an autosomal dominant fashion, a recently reported genome-wide association study identified common alleles at a locus on chromosome 18 near TCF4 which confer susceptibility to FECD. Here, we report the findings of our independent validation study for TCF4 using the largest FECD dataset to date (450 FECD cases and 340 normal controls). Logistic regression with sex as a covariate was performed for three genetic models: dominant (DOM), additive (ADD), and recessive (REC). We found significant association with rs613872, the target marker reported by Baratz et al.(2010), for all three genetic models (DOM: P = 9.33×10−35; ADD: P = 7.48×10−30; REC: P = 5.27×10−6). To strengthen the association study, we also conducted a genome-wide linkage scan on 64 multiplex families, composed primarily of affected sibling pairs (ASPs), using both parametric and non-parametric two-point and multipoint analyses. The most significant linkage region localizes to chromosome 18 from 69.94cM to 85.29cM, with a peak multipoint HLOD = 2.5 at rs1145315 (75.58cM) under the DOM model, mapping 1.5 Mb proximal to rs613872. In summary, our study presents evidence to support the role of the intronic TCF4 single nucleotide polymorphism rs613872 in late-onset FECD through both association and linkage studies.

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 identify the disease locus for autosomal recessive congenital cataract in a consanguineous Pakistani family.

Methods

All affected individuals underwent detailed ophthalmologic and medical examination. Blood samples were collected and DNA was extracted. A genome-wide scan was performed with polymorphic microsatellite markers on genomic DNA from affected and unaffected family members, and logarithm of odds (LOD) scores were calculated.

Results

The clinical records and ophthalmological examinations suggested that all affected individuals have nuclear cataracts. Maximum LOD scores of 5.01, 4.38, and 4.17 at θ=0 were obtained with markers D7630, D7S657, and D7S515, respectively. Fine mapping refined the critical interval and suggested that markers in a 27.78 cM (27.96 Mb) interval are flanked by markers D7S660 and D7S799, which co-segregate with the disease phenotype in family PKCC108.

Conclusions

We have identified a new locus for autosomal recessive congenital cataract, localized to chromosome 7q21.11-q31.1 in a consanguineous Pakistani family.

Purpose

To investigate the genetic basis of autosomal recessive congenital cataracts in a consanguineous Pakistani family.

Methods

All affected individuals underwent a detailed ophthalmological and clinical examination. Blood samples were collected and genomic DNAs were extracted. A genome-wide scan was performed with polymorphic microsatellite markers. Logarithm of odds (LOD) scores were calculated, and Eph-receptor type-A2 (EPHA2), residing in the critical interval, was sequenced bidirectionally.

Results

The clinical and ophthalmological examinations suggested that all affected individuals have nuclear cataracts. Genome-wide linkage analyses localized the critical interval to a 20.78 cM (15.08 Mb) interval on chromosome 1p, with a maximum two-point LOD score of 5.21 at θ=0. Sequencing of EPHA2 residing in the critical interval identified a missense mutation: c.2353G>A, which results in an alanine to threonine substitution (p.A785T).

Conclusions

Here, we report for the first time a missense mutation in EPHA2 associated with autosomal recessive congenital cataracts.

Purpose

To identify the pathogenic mutations responsible for autosomal recessive congenital cataracts in consanguineous Pakistani families.

Methods

All affected individuals underwent detailed ophthalmologic and medical examination. Blood samples were collected and genomic DNA was extracted. A genome-wide scan was performed with polymorphic microsatellite markers on genomic DNA from affected and unaffected family members and logarithm of odds (LOD) scores were calculated. All coding exons of galactokinase (GALK1) were sequenced to identify pathogenic lesions.

Results

Clinical records and ophthalmological examinations suggested that affected individuals have nuclear cataracts. Linkage analysis localized the critical interval to chromosome 17q with a maximum LOD score of 5.54 at θ=0, with D17S785 in family PKCC030. Sequencing of GALK1, a gene present in the critical interval, identified a single base pair deletion: c.410delG, which results in a frame shift leading to a premature termination of GALK1: p.G137fsX27. Additionally, we identified a missense mutation: c.416T>C, in family PKCC055 that results in substitution of a leucine residue at position 139 with a proline residue: p.L139P, and is predicted to be deleterious to the native GALK1 structure.

Conclusions

Here, we report pathogenic mutations in GALK1 that are responsible for autosomal recessive congenital cataracts in 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 identify the disease locus for autosomal recessive congenital cataracts in a consanguineous Pakistani family.

Methods

All affected individuals underwent a detailed ophthalmologic examination. Blood samples were collected and genomic DNA was extracted. A genome-wide scan was completed with fluorescently-labeled microsatellite markers on genomic DNA from affected and unaffected family members. Logarithms of odds (LOD) scores were calculated under a fully penetrant autosomal recessive model of inheritance.

Results

Ophthalmic examination suggested that affected individuals have bilateral cataracts. Linkage analysis localized the critical interval to chromosome 8p with LOD scores of 3.19, and 3.08 at θ=0, obtained with markers D8S549 and D8S550, respectively. Haplotype analyses refined the critical interval to 37.92 cM (16.28 Mb) region, flanked by markers, D8S277 proximally and D8S1734 distally.

Conclusions

Here, we report a new locus for autosomal recessive congenital cataract mapped to chromosome 8p 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 θ=0 and 6.19 with D14S43 at θ=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-causing mutations in three consanguineous Pakistani families with multiple members affected by primary congenital glaucoma.

Methods

Blood samples were collected, and DNA was extracted. Linkage analysis for reported primary congenital glaucoma loci was performed using closely spaced polymorphic microsatellite markers on genomic DNA from affected and unaffected family members. All coding exons, the exon-intron boundaries, and the 5′ untranslated region of CYP1B1 were sequenced.

Results

The alleles of chromosome 2p markers segregate with the disease phenotype in all three families with positive LOD scores. The sequencing results identified three novel mutations (L177R, L487P, and D374E) and one previously reported mutation (E229K) in CYP1B1 that segregate with the disease phenotype in their respective families. None of these sequence variations were present in 96 ethnically matched control samples.

Conclusions

These results strongly suggest that missense mutations in CYP1B1 are most likely to be responsible for primary congenital glaucoma in these families.