Abstract
Abstract: :
Purpose:To evaluate the coding sequences of the ABCA4 gene in a cohort of patients with cone-rod dystrophy Methods:Thirty-six unrelated probands with the clinical diagnosis of cone-rod dystrophy were identified by reviewing the medical records of a single clinician (GAF). All patients had central vision loss and electroretinographic evidence of significant cone and rod dysfunction. After informed consent was obtained, blood samples were drawn and used to prepare genomic DNA. The entire coding sequence of the ABCA4 gene of each patient was then screened for sequence variations using single-strand conformational polymorphism analysis (SSCP) followed by automated DNA sequencing. Results:Thirteen of the probands (36%) were found to have a plausible disease-causing mutation on at least one allele. These thirteen patients each exhibited one of two ophthalmoscopically distinct phenotypes. Ten patients exhibited diffuse degenerative changes with both hypopigmentation and pigment clumping. Four of these patients harbored an Ala1038Val change, which is the second most common ABCA4 variant observed in patients with Stargardt disease. The three patients with the less common phenotype exhibited very minimal fundus changes. Two of these patients harbored a Leu1201Arg variation. The most common ABCA4 change seen in Stargardt patients, Gly1961Glu, was not observed at all in this cohort of patients with cone-rod dystrophy. Conclusion:As originally recognized by Maugeri and colleagues, variations in the ABCA4 gene are a common cause of cone-rod dystrophy. The Gly1961Glu variant seems less likely to cause this phenotype than Ala1038Val.
Keywords: 562 retinal degenerations: hereditary • 476 molecular biology