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A. A. Gibriel, R. J. Tate, H. M. Hammer, J. N. A. Tettey, N. J. Pyne, C. A. Converse; A Survey of GARP 2 in Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1660. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
GARP2, glutamic-acid-rich protein-2, is produced as a splice variant from the CNGCB gene in rods. Two conserved repeats, R2 and R3 (in exons 5 and 8) are of reported functional significance. Amino acid changes Thr82Ile and Arg86Gln (in exon 4) have been found in ARRP patients in an American study, but linkage to RP was not determined (Bharadwaj et al, ARVO abstract 3153, 1999). Therefore we screened for changes in these exons (4, 5 and 8) in 130 Scottish autosomal recessive or simplex RP patients.
Exons were amplified using fluorescent PCR primers. Fluorescent SSCP was performed on amplicons using CE and those differing from control DNA were sequenced. The study conformed to the Helsinki Declaration and was approved by the local ethics committee.
One RP patient (a Ghanaian) showed the previously reported homozygous change (CGG/CAG - Arg86Gln) in exon 4, so we tested DNA from 9 asymptomatic, unrelated West Africans. Three out of 4 of the Ghanaians showed the same polymorphism (2 heterozygous, one homozygous), while all 5 of the Nigerians were homozygous for this change. In addition, polymorphisms were found in exon 5 in both control and RP subjects, and one RP patient had an intron polymorphism at the 3`end of exon 8, not affecting the splice site.
We report that the amino acid change Arg86Gln in GARP2 seems not to be directly linked to RP but may be a polymorphism common to persons of West African descent. So far, no mutations in GARP2 showing linkage to RP have been found in our study, though the polymorphisms identified could be involved in multifactorial disease.
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