MOLECULAR ASPECTS OF VELO-CARDIO-FACIAL SYNDROME

The goal of this project grant application is to understand the molecular basis of vole-cardio-facial syndrome (VCFS). This human syndrome has an incidence that is grater than 1 in 5,000 live births and is characterized by defects involving several organ and tissue systems. The children have cleft palate, pharyngeal insufficiency, cardiac and conotruncal abnormalities that result from thymic asplasia and hypoparathyroidism. As the children grow, they exhibit learning disabilities and older individuals develop psychiatric illness. Because several of the affected organs are derived from neural crest and from the pharyngeal pouches, it was postulated that at least some of the phenotypes are the result of a developmental field defect. A large proportion of VCFS patients have an interstitial deletion of chromosome 22 suggests that haploinsufficiency of one or more genes in the deleted region causes the disorder. To understand the molecular basis of this disorder, we constructed a high resolution physical map of the 22q11 region in the form of overlapping yeast artificial chromosomes and bacterial clones, mapped highly polymorphic markers and used them to de3fine a commonly deleted or a "critical" region. Twenty genes that fall in the critical region have been identified by us and others. During the past two years, we have defined the mechanism for deletions in these patients, examined the expression patterns of several genes and generated mice with mutations in a number of genes. We now proposed to extend these studies. In Project 1, we will examine the precise DNA sequences that undergo germline rearrangement that lead to deletions and will seek cis elements that might make the chromosomes prone to rearrangement. We will also isolate cDNAs in the region common deleted in VCFS patients and conduct genotype-phenotype correlations. In Project 2, we propose a new method to examine changes in patterns of gene expression in embryos from several knockout mice we generated and others that are VCFS phenocopies. We expect that these studies will lead to identification of genes whose haploinsufficiency leads to phenotypes associated with VCFS. In Project 3, we propose to produce mice withy mutations in mutations in Ufd11 and Tbx, two genes that are candidates for VCFS phenotypes. We also propose to produce and analyze deletions in mice that correspond to those seen in human patients. Such mice may provide models for VCFS, leading to a detailed understanding of the molecular basis of VCFS.