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Ameet Shah, Naushin H. Waseem, Shomi S. Bhattacharya, David F. Garway-Heath; Mutation Screening of GPNMB In 96 Patients With Pigment Dispersion Syndrome. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2419.
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Mutations in the Gpnmb gene are responsible for iris pigment dispersion (IPD), a feature of pigmentary glaucoma as seen in DBA/2J mice. GPNMB is a transmembrane glycoprotein located at 7p13 in humans, which shows homology to the pmel17 precursor, a melanocyte-specific protein. Anderson et al. (2002) sequenced the GPNMB coding region from 8 affected individuals in 4 families with autosomal dominant pigment dispersion and detected no mutations. We have screened a panel of 96 unrelated patients with pigment dispersion syndrome for mutations in GPNMB coding regions.
96 patients examined by one investigator (AS) meeting diagnostic criteria for pigment dispersion syndrome were phenotyped, consented and bled. DNA was extracted from peripheral blood lymphocytes. All eleven exons of GPNMB were amplified and sequenced on a 3730 DNA Analyzer. The results were analysed using Sequence Analysis 5.2 and Sequencher 4.1.4.
One patient was found to have a missense change in exon 6 of GPNMB. This change results in a proline to leucine substitution at codon 325 and was not present in 182 caucasian control samples. The amino acid change is in a region which is evolutionarily conserved in mice and macaques but not in chickens. The significance of this change is therefore unclear.
We have identified a missense change in GPNMB in 1 out of 96 PDS patients. As GPNMB shows homology to the pmel17 precursor, a melanocyte-specific protein, the possibility of a causative GPNMB mutation may support a role for dysregulation of melanocyte processing in the pathogenesis of PDS.
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