A transcription map of the DiGeorge and velo-cardio-facial syndrome minimal critical region on 22q11.

The majority of patients with DiGeorge syndrome (DGS) and velo-cardio-facial syndrome (VCFS) have a microdeletion of 22q11. Using translocation breakpoints and fluorescence in situ hybridization analysis (FISH), the minimal DiGeorge critical region (MDGCR) has been narrowed to 250 kb in the vicinity of D22S75 (N25). The construction of a detailed transcription map covering the MDGCR is an essential first step toward the identification of genes important to the etiology of DGS/VCFS, two complex disorders. We have identified a minimum of 11 transcription units encoded in the MDGCR using a combination of methods including cDNA selection, RT-PCR, RACE and genomic sequencing. This approach is somewhat unique and may serve as a model for gene identification. Of the 11 transcripts, one is the previously reported DGCR2/IDD/LAN gene, and three revealed a high level of similarity to mammalian genes: a Mus musculus serine/threonine kinase, a rat tricarboxylate transport protein and a bovine clathrin heavy chain. The remaining transcripts do not demonstrate any significant homology to genes of known function. The identification of these transcription units in the MDGCR will facilitate their further characterization and help elucidate their role in the etiology of DGS/VCFS.