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The RCS rat presents an autosomal recessive retinal pigment epithelium dystrophy characterized by the outer segments of photoreceptors being phagocytosis-deficient. A systematic genetic study allowed us to restrict the interval containing the rdylocus to that between the markers D3Mit13 and D3Rat256. We report the chromosomal localization of the rat c-mergene in the cytogenetic bands 3q35-36, based on genetic analysis and radiation hybrid mapping. Using a systematic biocomputing analysis, we identified two strong related candidate genes encoding protein tyrosine kinase receptors of the AXLsubfamily. The comparison of their expression patterns in human and mice tissues suggested that the c-mergene was the best gene to screen for mutations. RCS rdy− and RCS rdy+ cDNAs were sequenced. The RCS rdy− cDNAs carried a significant deletion in the 5′ part of the coding sequence of the c-mergene resulting in a shortened aberrant transcript encoding a 20 amino acid peptide. The c-mergene contains characteristic motifs of neural cell adhesion. A ligand of the c-merreceptor, Gas6, exhibits antiapoptotic properties.