By analyzing blood samples from that single family two parents and four adult children they found that the mother, who has schizophrenia, her two children with schizophrenia, and her child with major depression all had the mutant version of NPAS3. The NPAS3 gene provides instructions for the production of a protein that contains 933 amino acids. The altered gene led to a single flaw: a valine was switched to an isoleucine. Nucifora says it is not yet known how this single mutation affects the function or structure of NPAS3. A possible hint comes from the finding of other investigators that a change from valine to isoleucine in a protein known as APP is linked to Alzheimer's disease.
Nucifora cautions that, by itself, finding a mutation in a single family with mental illness doesn't establish the altered gene as the cause of the illness. Nucifora and his colleagues therefore set out to determine whether the mutation plays any role in the function of NPAS3, which serves as a master switch in cells, controlling the fate of many other genes involved in brain development and metabolism.
To do that, Nucifora and his colleagues grew neurons with either normal or mutated copies of NPAS3 in a dish, and found that the healthy neurons grew nice long extensions, a process that typically allows them to make good connections with other cells and is therefore critical for brain function. In neurons with the mutated gene, the extensions were abnormally short.
Other genes believed to be involved in mental illness also have been found to disrupt the growth of longer neuronal e
|Contact: Stephanie Desmon|
Johns Hopkins Medicine