Purpose: To identify the locus responsible for rge (retinopathyglobe enlarged) in chickens and further characterise the rgephenotype.Methods: A colony of chickens carrying the rge mutation wasrederived from a single heterozygous animal of the original line. Theeyes of blind, heterozygous and normal birds were subjected toophthalmic, morphometric and histopathological examination to confirmand extend published observations. DNA samples were obtained andsubjected to a whole genome linkage search.Results: From 138 classified backcross progeny, 56 birds were blindand 82 sighted. Heterozygous birds were indistinguishable from wildtype, but homozygotes had sluggish or unresponsive pupils, posteriorsub-capsular lens opacities and an atrophic pecten. The fundus appearednormal with no significant pigmentary disturbance, but axial length andeye weight were increased. Pathology revealed focal retinal lesions.Linkage analysis placed the rge locus in a small region of chickenchromosome 1.Conclusions: rge is a severe recessive retinal dystrophy inchickens, with associated globe enlargement. Linkage mapping hashighlighted chicken chromosome 1 in a region most probably homologous tohuman chromosomes 7q31-35, 21q21 or 22q12-21. Candidate disease lociinclude RP10 (IMPDH1) and uncharacterised Ushers (USH1E) andglaucoma (GLC1F) loci.
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