Histological changes caused by the rc mutation in chickens

The rc gene represents a recessive mutation in chickens, known to cause retinal degeneration and blindness, as well as abnormal sarcolemmal membranes of cardiac myocytes associated with reduced choline transport. In this study, the visceral organs from ''old'' (aged 12 months) and ''young'' (aged 5 months) homozygous blind (rc/rc), heterozygous (Rc(+)/rc) and normal (Rc(+)/Rc(+)) chickens were examined histologically to investigate whether the primary effect of the mutation was on cellular structure. Homozygous birds showed enlarged thyroids with acidophilic colloids in enlarged and often ruptured follicles, macrovesicular lipid accumulation in the liver, increased numbers of nuclei in the myocardial fibres, hypertrophy of the lobular structure of the medullary portion of the thymus, cloudy swelling of the tubular epithelium of the kidney and slow maturation (in young birds) and degeneration (in old birds) of the gonads. All lesions, except for those of the thymus, Mere more severe in old than in young birds. Some heterozygous chickens were mildly affected and none of the normal (Rc(+)/Rc(+)) birds exhibited these abnormalities.