Generating a mouse model for Velo-Cardio-Facial Syndrome (VCFS). R.S. Kucherlapati, S. Merscher, A. Puech, H. Sirotkin, B. Saint-Jore, A. Skoultchi. Dept Molecular Genetics, Albert Einstein Col Medicine, Bronx, NY.

   Velo-cardio-facial syndrome (VCFS) is a human developmental disorder that is characterized by heart defects, facial dysmorphology, cleft palate and learning disabilities. Most VCFS patients are hemizygous for a 3 Mb region on chromosome 22q11. Analysis of deletions in a large number of patients allowed the definition of a critical region that is 500 Kb in length. To fully understand the molecular mechanisms that lead to the complex phenotypes associated with VCFS, we generated mice that are hemizygous for a part of mouse chromosome 16 (MMU16) that has homology to human 22q11. The deletion spans a 500 Kb region and encompasses at least 12 genes. The deletion has the Idd gene as one of its boundaries and the Arvcf gene as its other boundary. To generate the deletion in mouse embryonic stem cells, a loxP site was introduced into each of Idd and Arvcf by gene targeting. We generated ES cells in which the two loxP sites were in cis or in trans. The cells were transfected with CAG-cre or CMV-cre and cells containing a deletion or deletion/duplication were selected using a new selectable system. A deletion of the same region was also obtained in vivo by mating mice carrying the Idd and Arvcf mutant alleles in cis with mice carrying a CMV- or Zp3-cre gene. Mice that are hemizygous for the deletion or that are partially trisomic are viable and appear normal. Mice that are homozygous for the deletion die during embryogenesis. The cause of this embryonic lethality and its relationship to VCFS associated phenotypes are being investigated.