What are the genetic changes related to Rubinstein-Taybi syndrome ?
Mutations in the CREBBP gene are responsible for some cases of Rubinstein-Taybi syndrome. The CREBBP gene provides instructions for making a protein that helps control the activity of many other genes. This protein, called CREB binding protein, plays an important role in regulating cell growth and division and is essential for normal fetal development. If one copy of the CREBBP gene is deleted or mutated, cells make only half of the normal amount of CREB binding protein. Although a reduction in the amount of this protein disrupts normal development before and after birth, researchers have not determined how it leads to the specific signs and symptoms of Rubinstein-Taybi syndrome.  Mutations in the EP300 gene cause a small percentage of cases of Rubinstein-Taybi syndrome. Like the CREBBP gene, this gene provides instructions for making a protein that helps control the activity of other genes. It also appears to be important for development before and after birth. EP300 mutations inactivate one copy of the gene in each cell, which interferes with normal development and causes the typical features of Rubinstein-Taybi syndrome. The signs and symptoms of this disorder in people with EP300 mutations are similar to those with mutations in the CREBBP gene; however, studies suggest that EP300 mutations may be associated with milder skeletal changes in the hands and feet.  Some cases of severe Rubinstein-Taybi syndrome have resulted from a deletion of genetic material from the short (p) arm of chromosome 16. Several genes, including the CREBBP gene, are missing as a result of this deletion. Researchers believe that the loss of multiple genes in this region probably accounts for the serious complications associated with severe Rubinstein-Taybi syndrome.  About half of people with Rubinstein-Taybi syndrome do not have an identified mutation in the CREBBP or EP300 gene or a deletion in chromosome 16. The cause of the condition is unknown in these cases. Researchers predict that mutations in other genes are also responsible for the disorder.