Tight linkage of the ret proto-oncogene with the multiple endocrine neoplasia type 2A locus

The ret proto-oncogene has been mapped to 10q11.2 near the MEN2A locus by in situ hybridization. We carried out a linkage study of Japanese multiple endocrine neoplasia type 2A (MEN2A) families using a cosmid clone containing the ret proto-oncogene as probe. Two polymorphic alleles (A1 and A2) could be detected by digesting DNA with EcoRI: allele A1 was detected as a 10 kb fragment and A2 as 5.4 and 4.6 kb fragments. Of 11 Japanese MEN2A families analysed, four were informative, and the maximum lod score was 4.23 at a recombination fraction of 0.00. This result suggests the ret proto-oncogene to be close to the MEN2A gene and therefore possibly to be a useful DNA marker for cloning the latter.