An international collaboration will delve into why patients with chromosome 22q11.2 deletion syndrome have an elevated risk of schizophrenia and other psychiatric illnesses. Genetics experts from The Children’s Hospital of Philadelphia are among the top leaders of this major collaboration, which aims to discover the genes implicated in the syndrome and to shed light on the biological causes of mental illness in the general population.
Found in approximately 1 in 4,000 live births, 22q11.2 deletion syndrome (22q11.2 DS) involves birth defects and developmental and behavioral differences. Caused by the absence of a DNA sequence on the long arm of chromosome 22, the syndrome carries many possible signs and symptoms that may affect the heart, palate, the immune and endocrine systems, and the kidneys. Some patients may have seizures, hearing loss, scoliosis, or feeding and swallowing problems.
In addition, many children with 22q11.2 DS have developmental delays, including learning disabilities and delays in language emergence, or may have an autism spectrum disorder, attention-deficit hyperactivity disorder, anxiety or obsessive-compulsive disorder. As they enter adolescence or young adulthood, approximately 25 to 30 percent of patients are at risk of developing schizophrenia, which represents a much higher rate than the one percent rate found in the general population.
Donna McDonald-McGinn, MS, CGC, program director of the 22q and You Center at CHOP, is the co-director of the International Consortium on Brain and Behavior in 22q11.2 Deletion Syndrome, which has just received a $12 million, four-year grant from the National Institute of Mental Health, part of the National Institutes of Health. The consortium brings together caregivers and scientists from 22 clinical centers and five genotyping sites throughout the world.
The consortium’s research tools will include whole-genome sequencing to uncover genetic variation among patients with chromosome 22q11.2 DS. Children’s Hospital, which has a long-standing research and clinical program focused on this condition, has evaluated more than 1,200 patients, making it the world’s largest center of its kind.
Two genetics researchers with global prominence in studying this diagnosis, Beverly S. Emanuel, Ph.D., and Elaine Zackai, M.D., are co-investigators at CHOP’s site in the Brain and Behavior Consortium. Among many other accomplishments, in 1995 both scientists were on the team that created an early genetic map of chromosome 22, setting the stage for it to become the first chromosome sequenced in the Human Genome Project.
While focusing on the genetic roots of psychiatric disorders in 22q11.2 DS, the consortium leaders expect to identify biological pathways leading to schizophrenia in the broader population, with the hope that such data may inform novel, more effective treatments.
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