A GENE FOR ULNAR-MAMMARY SYNDROME MAPS TO 12Q23-Q24.1

Ulnar-mammary syndrome (UMS) is an autosomal dominant disorder charact erized by posterior limb deficiencies or duplications, apocrine/mammar y gland hypoplasia and/or dysfunction, abnormal dentition, delayed pub erty and genital anomalies, We report the mapping of a gene causing UM S to chromosome 12q23-24.1. Linkage analysis generated a positive led score of 6.21 at theta = 0.00 with the marker D12S79, and recombinants bracket the UMS gene to a 21 cM region. This region contains a locus for Holt-Oram syndrome (HOS) suggesting that the genes for UMS and HOS may be allelic or closely linked. The identification of the gene caus ing UMS will be an important step toward understanding the molecular m echanisms that control limb and apocrine gland development.