Abstract
Abstract: :
Purpose: A knockout mouse model showed that, out of the two G–protein variants expressed in the ON bipolar retinal cells (Gαo1 and Gαo2), only Gαo1 is required to produce electroretinogram (ERG) b–waves, which is comprised in large part by the massed response of ON bipolar retinal cells. (Dhingra et al., J Neurosci 22:4878–4884, 2002) Because patients with congenital stationary night blindness (CSNB) have ERGs with severely reduced b–waves, we set out to screen this phenotype for mutations in the Gαo1 splice variant of the Gαo protein. Methods: Leukocyte DNA samples from 26 unrelated CSNB patients were evaluated by direct sequencing for mutations in the two coding exons of Gαo1 at the 3’ end that differ from those of Gαo2 as well as in the exon and flanking intron upstream of this region. Results: With 22 of 26 patients screened so far, no mutations have been found. We did identify a short variable tandem repeat (AC) beginning at IVS8+45. Alleles containing 14, 15, 16, or 20 repeats of the dinucleotide AC were seen in our patient population. It is unlikely that alleles at this microstaellite polymorphism are associated with the retinal disease, as it is located in the intron. Conclusions: At the present time, no mutations have been detected in the coding exons unique to the Gαo1 splice variant.
Keywords: bipolar cells • candidate gene analysis