One copy of 22q11.2, a large segment of chromosome 22 that includes many genes, is missing in 1 of every 4,000 individuals. This non-inherited genetic abnormality results in several physical abnormalities, most of which can be repaired surgically early in life. But the most pernicious deficits are cognitive, including severe learning disabilities and a high risk for mental illness. Maria Karayiorgou and colleagues at Columbia University have studied the neurobiology of this deletion for several years. Armed with an exciting new technology that allows researchers to produce neurons from a simple skin biopsy, they plan to embark on studies in which skin samples from individuals carrying this deletion and their healthy control siblings will be made into brain cells and then studied at a level of unprecedented resolution. These studies will afford a view into the brain that was not previously possible. The researchers have also created a mouse model carrying the equivalent of the human 22q11.2 deletion, and are planning to study neurons from this mouse model. These two methods should allow the researchers to draw firm conclusions about the changes in neuronsí activity and structure and in synapses - the junction between neurons - that result from the 22q11.2 deletion. The results could help explain the cognitive deficits and learning disabilities seen in children carrying this devastating deletion. The use of genetic mouse models may also help elucidate the neural circuit malfunctions that underlie schizophrenia and similar diseases, such as autism.