Science Snippet: Isolating Mutations in Multifactorial Genetic Diseases

A gene is made up of a specific sequence of a 20-letter coding alphabet. A mutation results when the sequence becomes altered, and the gene fails to make the proper protein (enzyme). If this enzyme is critical to cell function, a disease state can result. Some diseases result from a mutation (change) in a single gene, (e.g. cystic fibrosis, sickle cell anemia, Huntington’s Disease, etc.). However, most disease states are “multifactorial genetic diseases,” which means that the disease is caused by multiple genes. Recent studies on schizophrenia show that the disease is caused by about eight genetically distinct groups, each of which contributes to specific symptoms associated with the disorder. Scientists arrived at this conclusion after studying the genetic influences in more than 4,000 people with schizophrenia and then matching these against the genes of 3,800 healthy individuals. Almost 700,000 different genes were analyzed and it was found that certain individual genes, by themselves, have only a weak correlation with the disorder. However, when a cluster of such genes interacts with other clusters, the risk for schizophrenia is greatly enhanced. A total of eight gene clusters appear to play a role in producing schizophrenic behavior. For example, interaction between several clusters may result in hallucinations. Another set of clusters may be responsible for speech or hearing voices. These studies give pause to investigators trying to discover a single gene that leads to schizophrenia. It is not that simple. (Cloninger, R.C., in the Journal of Psychiatry, Sept. 25, 2014)