The deletion of part of one of the copies of chromosome 22 results in several developmental defects. The region concerned is called 22q11, and so the cluster of disorders caused by deletions in this region is called the deletion 22q11 syndrome, which includes DiGeorge syndrome, velocardiofacial syndrome and other disorders. Common findings include congenital heart disease, skull and facial anomalies, improper development of the thymus (leading to an immune deficiency), impaired parathyroid gland function (leading to calcium deficiency), mental retardation, and neuropsychiatric problems.

Ongoing research at the Baylor College of Medicine Mental Retardation Developmental Disabilities Research Center:

Further understanding of the disease
Almost twenty genes have so far been identified in the region that is missing in the deletion 22q11 syndrome. However, several fundamental questions still need to be answered: (1) Are symptoms caused by the loss of a single gene or multiple genes? (2) Are any of the genes in the 22q11 region that have been found so far involved in producing symptoms of the disorder? and (3) Which developmental pathways are disrupted in the deletion 22q11 syndrome?

To answer these questions, researchers at Baylor College of Medicine are using newly developed genetic engineering techniques to generate mouse models with chromosomal deletions that mimic the human mutations in the deletion 22q11 syndrome. By producing different mouse lines that have disruptions or deletions of single genes in the region, and then studying the effect of those mutations, it may be possible to discern the individual roles of those different genes in development.

As further evidence of what are critical genes in the region, mouse models that show appropriate symptoms can be supplied with one or more of the missing genes to see if the reintroduction of those genes modifies or corrects the original deficiency.

Making mouse models of the human deletion 22q11 syndrome will be a consequence of these experiments, and such mouse models can be studied further to investigate the developmental pathways that are affected in the disorder.

One mouse model of the human deletion 22q11 syndrome that is already available displays schizophrenia-related behavior and learning and memory impairments, as do many of the human patients. This suggests that there are one or more genes in the mouse deleted region that affect or control these behaviors, and that the equivalent gene is missing in the human syndrome. Researchers are seeking these genes.

Baylor investigators working on del22q11 syndrome:

Baylor MRDDRC projects associated with del22q11 syndrome:

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del22q11 syndrome resources:

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