Genome sweep finds two new diabetes genes.

Using a powerful gene-mapping technique, researchers report homing in on the location of two new genes that underlie type I diabetes. People with this form of diabetes generally require daily injections of the hormone insulin in order to survive.

Rather than hunting laboriously for a single gene associated with diabetes, a British research team headed by John A. Todd of the University of Oxford in England relied on a method that allows simultaneous analysis of all 46 human chromosomes. At a genetics meeting in Bar Harbor, Maine, in July, Todd reported that their genomewide sweep had revealed 18 different chromosome regions linked to type I diabetes (SN: 8/6/94, p.85). He also said the group had confirmed the importance of the IDDM1 gene in this form of diabetes, an autoimmune disorder.

In the Sept. 8 NATURE, Todd's team further refines the emerging picture of this complex disorder, which is caused by the interaction of many genes and environmental factors. In a study of families with at least one afflicted member, the researchers found a region on the long arm of chromosome 11 and another on the long arm of chromosome 6 that are associated with type I diabetes. The scientists believe that the DNA sections of those chromosomes house two new genes for type I diabetes. In addition, they found confirmatory evidence that a third gene for type I diabetes resides on the long arm of chromosome 18.

Using more conventional gene-mapping methods, another research group also implicates the same chromosome 11 site in type I diabetes. This largely French team describes its results in the same issue of NATURE.

Because there may be scores of genes in each suspect DNA region, scientists now must identify and sequence the actual genes contributing to type I diabetes, notes Oxford's Simon T. Bennett, a coauthor of the first NATURE report. Once they have homed in on the genes, researchers can investigate their function. For example, the gene on chromosome 6 may play a role in the destruction of the pancreatic islet cells that manufacture insulin, he notes. Such pancreatic damage is a hallmark of type I diabetes.

One day, scientists may use such information to find children at high risk of developing type I diabetes, a disease that often strikes at an early age. Armed with better information about what causes this sugar-processing disorder, researchers hope eventually to fashion a therapy to prevent it, Bennett adds.