Abstract 795 Mechanisms in Hereditary Disease Platform, Tuesday, 5/4

Van der Woude syndrome (VWS) is the most common form of syndromic cleft lip and palate and accounts for about 2% of all cleft lip and palate cases. Distinguishing characteristics include cleft lip with or without cleft palate, isolated cleft palate, bilateral lip pits, hypodontia, normal intelligence, and an autosomal dominant mode of transmission with a high degree of penetrance. The VWS locus has been mapped to a 1.6cM region of chromosome 1q32 by linkage analysis and the discovery of a microdeletion around D1S205. One 850 kb YAC, yCEPH785B2, contains both flanking markers, D1S491 and D1S205, and encompasses the microdeletion. Human bacterial artificial chromosome (BAC) clones have been isolated from the critical region by screening of the Research Genetics human BAC library with STSs across the critical region. A complete contig has been constructed containing 14 BACs ranging from 90 to 300 kb in size. The minimum tiling path of 4 BACs suggest that the maximum size of the critical region is 610kb. The BAC contig and STSs generated across this region have been used in a large scale sequencing project which has generated over 670,000 bp of sequence to the region of interest. Genes identified within the critical region include 11-beta-hydroxysteroid dehydrogenase, laminin B3, G0S2, camodulin dependent protein kinase, interferon regulatory factor 6, and a yeast open reading frame which have been excluded by mutational analysis. Eleven previously underscribed candidate genes have been located by BLAST homology searches against both the non-redundant and EST Genbank databases, and by using various gene recognition programs. SSCP analysis of affected family members has uncovered another family with a microdeletion and resulting loss of heterozygosity. This microdeletion has similar boundaries at the centromeric and telomeric sides. Currently, mutation analysis is being done on a candidate gene which is transected by both microdeletions. In conclusion, the mechanism of VWS due to haploinsufficiency is supported by our studies and microdeletions are not uncommon. Sequencing of this entire contig is near completion. The analysis of high throughput sequence will greatly facilitate the identification of the VWS gene and give way to mutational analysis, association studies, and the development animal models.