Spinocerebellar ataxia type 7 (SCA7) shows a cone-rod dystrophy phenotype.
Experimental Eye Research. 2002-06-01; 74(6): 737-745
DOI: 10.1006/exer.2002.1169
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1. Exp Eye Res. 2002 Jun;74(6):737-45.
Spinocerebellar ataxia type 7 (SCA7) shows a cone-rod dystrophy phenotype.
Aleman TS(1), Cideciyan AV, Volpe NJ, Stevanin G, Brice A, Jacobson SG.
Author information:
(1)Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania,
Philadelphia, PA 19104, USA.
Autosomal dominant spinocerebellar ataxia 7 is associated with retinal
degeneration. SCA7, the causative gene, encodes ataxin-7, a ubiquitous 892 amino
acid protein of variable sub-cellular localization, and the disease is due to
expansion of an unstable CAG repeat in the coding region of the gene. Recent
increases in understanding of the mechanisms ofSCA7 -related retinopathy from in
vitro and murine model studies prompted us to perform a detailed study of the
retinal phenotype of affected members of a family with SCA7 mutation (45-47 CAG
repeats). There was a spectrum of severity from mild to severe dysfunction. Early
functional abnormalities were at both photoreceptor and post-receptoral levels.
When cone and rod photoreceptor dysfunction was present, it was approximately
equal. Regional retinal dysfunction was evident: there was more dysfunction
centrally than peripherally with least effect in the midperiphery. In vivo
cross-sectional retinal images with optical coherence tomography showed an early
disease stage of altered foveal lamination (abnormal area of low reflectivity
splitting the outer retina-choroidal complex) accompanied in the parafovea by
reduced retinal thickness. Later disease stages showed foveal and parafoveal
retinal thinning. The phenotype in this family with SCA7 is that of a cone-rod
dystrophy. These observations increase interest in a recent hypothesis that
ataxin-7 may interfere with the function of CRX (cone-rod homeobox), a
transcription factor regulating photoreceptor genes and a cause of a cone-rod
dystrophy phenotype in man.
DOI: 10.1006/exer.2002.1169
PMID: 12126946 [Indexed for MEDLINE]