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1.  Nonsense mutation in MERTK causes autosomal recessive retinitis pigmentosa in a consanguineous Pakistani family 
The British Journal of Ophthalmology  2010;94(8):1094-1099.
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.
doi:10.1136/bjo.2009.171892
PMCID: PMC3393880  PMID: 20538656
2.  Mutations in the β-subunit of rod phosphodiesterase identified in consanguineous Pakistani families with autosomal recessive retinitis pigmentosa 
Molecular Vision  2011;17:1373-1380.
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.
PMCID: PMC3108895  PMID: 21655355
3.  Identification of two new mutations in the GPR98 and the PDE6B genes segregating in a Tunisian family 
Autosomal recessive retinitis pigmentosa (ARRP) is a genetically heterogeneous disorder. ARRP could be associated with extraocular manifestations that define specific syndromes such as Usher syndrome (USH) characterized by retinal degeneration and congenital hearing loss (HL). The USH type II (USH2) associates RP and mild-to-moderate HL with preserved vestibular function. At least three genes USH2A, the very large G-protein-coupled receptor, GPR98, and DFNB31 are responsible for USH2 syndrome. Here, we report on the segregation of non-syndromic ARRP and USH2 syndrome in a consanguineous Tunisian family, which was previously used to define USH2B locus. With regard to the co-occurrence of these two different pathologies, clinical and genetic reanalysis of the extended family showed (i) phenotypic heterogeneity within USH2 patients and (ii) excluded linkage to USH2B locus. Indeed, linkage analysis disclosed the cosegregation of the USH2 phenotype with the USH2C locus markers, D5S428 and D5S618, whereas the ARRP perfectly segregates with PDE6B flanking markers D4S3360 and D4S2930. Molecular analysis revealed two new missense mutations, p.Y6044C and p.W807R, occurring in GPR98 and PDE6B genes, respectively. In conclusion, our results show that the USH2B locus at chromosome 3p23–24.2 does not exist, and we therefore withdraw this locus designation. The combination of molecular findings for GPR98 and PDE6B genes enable us to explain the phenotypic heterogeneity and particularly the severe ocular affection first observed in one USH2 patient. This report presents an illustration of how consanguinity could increase familial clustering of multiple hereditary diseases within the same family.
doi:10.1038/ejhg.2008.167
PMCID: PMC2986209  PMID: 18854872
Usher syndrome type II; mutation; GPR98; PDE6B; USH2B family; consanguinity

Results 1-3 (3)