Quantitative gene expression

Gene expression profiling provides information on differential expression for thousands of genes at once. These differences may themselves be under genetic control, and sequence variations at some loci may exert local or regional influences affecting these same levels of expression. In the March 20 Nature, Eric Schadt and colleagues at the Merck Research Laboratories, West Point, Pennsylvania, US, demonstrate the existence of such loci in mouse, human, and maize, and identify a differential gene expression pattern in mice strongly associated with obesity (Nature, 422:297-302, March 20, 2003).

Friend et al. profiled expression of more than 23,000 genes in the third-generation offspring (F2) of two inbred strains of mice. Of these, more than 7000 showed a significant difference in expression level between the strains. They also sequenced 100 microsatellite markers evenly spaced across the murine chromosomes. Treating variations in expression levels as quantitative traits, and using...