What Causes Williams Syndrome?
Williams syndrome is caused by a missing segment of genetic material (DNA) in one of our chromosomes. Chromosomes come in pairs and humans have 23 pairs. We inherit one chromosome of each pair from our mother and the other from our father. Missing DNA is called a deletion.
Our genes are made of DNA, which is packaged into the chromosomes. Each gene has instructions for making a specific product our body needs to grow and function. When some of the instructions are missing, as in a deletion, this can cause medical concerns.
In Williams syndrome, the deletion occurs in a specific region or location on chromosome number 7, designated 7q11.23. This region is often referred to as the Williams-Beuren syndrome critical region (WBSCR) or the Williams syndrome critical region (WSCR). This region spans 26 to 28 different genes, and the loss of the DNA instructions for making these gene products causes the phenotype (or symptoms) associated with Williams syndrome.
Researchers are working to better understand the impact of each of the genes in this region. To date, one of the best understood genes associated with Williams syndrome is the ELN gene. This gene has instructions for a protein called elastin which gives connective tissue throughout the body its elastic and stretchy properties. Connective tissue supports and gives structure to other tissues and organs, including skin, joints and blood vessels. Having only one copy of this gene is felt to cause some of the signs and symptoms seen in someone with Williams syndrome.