Related Conditions
Most cases of 22q11.2 deletion syndrome are caused by the deletion of a small piece of chromosome 22. This region of the chromosome contains about 30 genes, including the TBX1 gene. In a small number of affected individuals without a chromosome 22 deletion, mutations in the TBX1 gene are thought to be responsible for the characteristic signs and symptoms of the syndrome. Of the three known mutations, two mutations change one amino acid (a building block of proteins) in the T-box 1 protein. The third mutation deletes a single amino acid from the protein. These mutations likely disrupt the ability of the T-box 1 protein to bind to DNA and regulate the activity of other genes.
Researchers believe that a loss of the TBX1 gene, due to either a mutation in the gene or a deletion of part of chromosome 22, is responsible for many of the features of 22q11.2 deletion syndrome. Specifically, a loss of the TBX1 gene is associated with heart defects, an opening in the roof of the mouth (a cleft palate), distinctive facial features, and low calcium levels, but does not appear to cause learning disabilities.
Read more about this topic: TBX1
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