The use of pigment loci for detecting reverse mutations in somatic cells of mice

The retinal pigment epithelium (RPE) consists of a single layer of hexagonal cells, numbering about 10(5) in the 3-day mouse. Examination of the fixed and cleared RPE of mice homozygous for the unstable allele of pink-eye (pun), which shows a relatively high frequency of reversion to wild type, has revealed that the pigmented cells which result from such reversions (mainly arranged singly or in small clonal groups) can be detected with relative ease on the unpigmented RPE background. It is felt, therefore, that this system should provide a suitable way of studying somatic reversions induced by chemical agents in pink-eyed mutations of the mouse and other mammals.