Construction of bac/cosmid contigs for the cat eye syndrome chromosome region (22q11)

Cat eye syndrome (CES) is caused by partial tetrasomy of the 22qll. The morphological anomalies in CES include coloboma of the eye and characteristic heart malformation (totally anomalous pulmonary venous return). Most (>90%) of the CES patient has a supernumerary bisatellited marker chromosome [22pter-qll::22ql 1-pter] consisting of two copies of the 22pter-qll region. We have constructed BAC/cosmid contigs of the CES chromosomal region to facilitate isolation of the disease-causing genes. As DNA resources, we used a CES region-specific cosmid library from the flowsorted marker chromosomes of a CES cell line (Minoshima et al., this meeting last year) and a BAC library from human total DNA (Asakawa et al., in this meeting). A number of STS's were established from cosmid clones and used to screen CEPH YAC library. Twenty YAC clones were identified and arrayed into a YAC contig. Thus, these YAC clones were used as probes to screen the CES cosmid library and BAC library, and 1,740 cosmids and 98 BAC clones were isolated. To construct BAC/cosmid contigs, the vectorette PCR method and finger printing have been applied. To date, 9 contigs consisting of 25 BAC clones and 24 cosmid clones have been constructed covering over 1.3 Mb. Genomic sequencing of one cosmid clone (36,226 bp) has been completed and other clones are in progress. The genomic sequence information is being used to identify the CES-causing genes.