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Abdul Hameed, Shagufta Khaliq, Muhammad Ismail, Khalid Anwar, S. Qasim Mehdi, David Bessant, Annette M. Payne, Shomi S. Bhattacharya; A New Locus for Autosomal Recessive RP (RP29) Mapping to Chromosome 4q32-q34 in a Pakistani Family. Invest. Ophthalmol. Vis. Sci. 2001;42(7):1436-1438.
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purpose. To map the disease locus in a six-generation, consanguineous Pakistani
family with autosomal recessive retinitis pigmentosa (arRP). All
affected individuals had pigmentary retinopathy associated with
symptoms of night blindness and the loss of peripheral visual fields by
the age of 20 years, loss of central vision between the ages of 25 and
30 years, and complete blindness between the ages of 40 and 50 years.
methods. Genomic DNA from family members was typed for alleles at known
polymorphic genetic markers using polymerase chain reaction. Alleles
were assigned to individuals, which allowed calculation of LOD scores
using the programs Cyrillic (http://www.cyrillicsoftware.com)
and MLINK (Cherwell Scientific Publishing Ltd., Oxford, UK). The genes
for membrane glycoprotein (M6a) and chloride
channel 3 (CLCN3) were analyzed by direct sequencing for
results. A new locus for arRP (RP29) has been mapped to
chromosome 4q32-q34. A maximum two-point LOD score of 3.76 was obtained
for the marker D4S415, with no recombination. Two recombination events
in the pedigree positioned this locus to a region flanked by markers
D4S621 and D4S2417. A putative region of homozygosity by
descent was observed between the loci D4S3035 and D4S2417,
giving a probable disease interval of 4.6 cM. Mutation screening of two
candidate genes, M6a and CLCN3, revealed
no disease-associated mutations.
conclusions. The results suggest that the arRP phenotype maps to a new locus and is
due to a mutated gene within the 4q32-q34 chromosomal
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