A PHYSICAL MAP OF THE HUMAN APP GENE IN YACS

Several point mutations within exons 16 and 17 of the amyloid precurso r protein (APP) gene have been reported that are associated with Alzhe imer's disease in a small number of familial cases. To determine the s ize of the APP gene and the organization of the exons within human gen omic DNA, we have characterized 11 Yeast Artificial Chromosome (YAC) r ecombinants containing human APP gene sequences. The smallest YAC inse rt was 125 kb, and the largest was 1.4 Mb. The YACs were screened by p olymerase chain reaction amplification of APP exons to determine which of the 18 exons coding for APP770 were present. Four of the YACs (D11 0G1, D110G6, D110E9, and B 142F9) contain all 18 exons and at least pa rt of the promoter. Construction of an overlapping map of the gene wit h all of the YACs demonstrated that 3 of the 11 YACs were chimeric. Th e orientation and position of the coding sequence on the map was deter mined by probing digests of the YAC DNA with exon PCR products and the vector arms. The coding region of the APP gene spans approximately 40 0 kb of genomic DNA.