The largest functional analysis of mouse genes to date is reported in a study published online this week in Nature Genetics. The study identifies previously unknown functions for a large number of genes and provides a strategy for future research aimed at learning the functions of all mouse genes.

Approximately one third of genes in the mouse genome have been linked to a physical trait, or phenotype. However, the kinds of phenotypes that are noticed usually depend on the specific interests of the researcher.

Steve Brown and colleagues from 18 institutes in eight countries carried out a pilot project to analyze the full range of phenotypes for known mutations of 320 mouse genes. For each mutant mouse, the authors made 413 measurements ranging from body weight to metabolic and behavioral traits. The authors identified phenotypes associated with 159 out of 179 genes that previously had no known function. For example, a mutation of one such gene, Elmod1, which is expressed in the brain but has no known function, was found to be associated with reduced fasting blood sugar, lower body weight, and behavioral defects such as reduced startle response and increased activity.