Van Buchem disease decoded( d the SOST coding sequence for associat...)

Recently, however, a large 52-kilobase deletion was identified at a significant distance approximately 35 kilobases from the SOST gene in humans. This deletion, although associated perfectly with Van Buchem disease, removed a large non-protein-coding region; thus, its function, if any, in the development of the disease remained unclear.

The current study, which was led by Dr. Loots, was designed to rigorously investigate the underlying molecular mechanism by which this non-coding sequence might ultimately give rise to Van Buchem disease. Her team included researchers from Lawrence Berkeley National Laboratory (Berkeley, CA), the Novartis Institutes for BioMedical Research (Basel, Switzerland), and the DOE Joint Genome Institute (Walnut Creek, CA).

Dr. Loots and her colleagues engineered a human bacterial artificial chromosome (BAC) and generated transgenic mice with and without the 52 kilobases of DNA that are absent in Van Buchem patients. Although SOST was expressed normally in the early mouse embryo from both lines, SOST was dramatically downregulated in adult mice carrying the deletion, when compared to wild-type transgenic mice. These results provided strong evidence that the lack of SOST expression in humans homozygous for the 52-kilobase deletion is caused by a regulatory element most likely an enhancer that is located within the 52-kilobase region and that functions in a bone- and age-specific manner.

The team then utilized comparative sequence analyses and transient transfection assays to identify the actual enhancer sequence within the 52-kilobase deletion region that is responsible for SOST regulation. They aligned 140-kilobases of the human SOST region with the orthologous mouse sequence and identified seven evolutionarily conserved regions (ECRs). The seven ECRs were subjected to in vitro transient t
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Contact: Maria A. Smit
smit@cshl.edu
516-422-4013
Cold Spring Harbor Laboratory
16-Jun-2005