Studies of Multiple Endocrine Neoplasia Type 2A Syndrome: Linkage Analyses and Comparison of Constitutional and Tumor Genotypes

Linkage analyses were carried out in nine Japanese kindreds with multiple endocrine neoplasia type 2A (MEN-2A) using polymorphic classical markers and DNA markers. We excluded close linkage of the MEN-2A gene (MEN2A) locus with Gm, JK, PGMl, and a DNA segment, D20S5, which is assigned to band 12 of the short arm of chromosome 20 (20p12.2). Assuming that MEN2A is recessive at the cellular level as in retinoblastoma (RB) and Wilms\u27 tumor (WT). comparison of constitutional and tumor genotypes may be useful in the search for the MEN2A locus. When DNA samples from 12 patients with medullary thyroid carcinoma (MTC) were compared with 15 polymorphic DNA markers including two assigned to chromosome 20, the results were negative. Both the negative linkage data and the failure to find loss of heterozygosity in MTC with chromosome 20 probes suggest that MEN2A may not be at 20p12.2, which was previously suggested as the site of an inherited chromosomal deletion in MEN-2A