Molecular genetics of Digeorge syndrome and related disorders

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Patients with several congenital anomaly syndrome, such as DiGeorge syndrome, conotruncal anomaly face syndrome, commonly have a deletion at 22q11. The acronym CATCH22 is now used for such syndromes, for they are thought to consist a contiguous gene syndrome. Although several cDNA have been mapped in this deletion, it is unknown whether they play roles in development of the syndrome. In order to localize the CATCH22 critical region, the refined deletion map of the 100 patients have been constructed using many genomic clones scattered in the deletion. As a result, patients were devided into three types of deletion ; common large deletion, proximal deletion, and distal deletioon. We identified two critical regions in the common deletion, which will provide important information for identification of the disease-causing gene. The phenotype-genotype correlation showed that CATCH22 is not a contiguous gene syndrome. Most patients have the common large deletion, suggesting that there lies characteristic repetitive sequences which easily cause the deletion. We also localized the the boundary of the common large deletion, which would be a help for analysis of the deletion breakpoint.