Color Vision Pathway Follows the Expansion Repeats in SCA7

Abstract

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by gene ataxin7 mutation with a polymorphic CAG repeat tract that falls in first axon. The gene which encodes ataxin7 normally contains a ten CAG repeat tract starting a codon 30, in affected patients the CAG repeat tract expands from 37 to 250 triplets, decreasing the transcription of an antisense non-coding RNA. Clinically SCA7 is characterized by progressive cerebellar ataxia, slow saccadic eye movements and progressive blindness. SCA7 neurotoxicity can be showed by the cone-rod dystrophy which follows in the generations the CAG repeats expansions in the affected patients. As retinal disease progresses in SCA7, the photoreceptors cells do become involved, and then loss of central visual acuity proceeds to complete blindness. The presence in the long run of the altered cone function, allows SCA7 to be classified as a cone dystrophy type of retinal degeneration [1]. Considering the X-linked inheritance of color vision deficiency, fixed sampling of only males, that compensation’s phenomenon in the heterozygous females [2], which can hid a real acquired color vision deficiency. The acquired color vision deficiency is real in the males where the anomaly has not hidden, and due to this reason we suggest sampling only male patients when color vision has studied both in neurological and metabolic diseases [3].