Genetics of Quantitative Variation in Human Gene Expression

The extent of variation among individuals at the DNA sequence level has been well characterized. The goal of many genetic studies is to determine the consequences of these sequence variants, for both normal and disease phenotypes. We have extended the study of genome variation from the sequence to mRNA transcript level, with the goal of understanding natural variation in gene expression in humans. We began by measuring the quantitative differences in expression levels of genes among normal individuals and determining whether there is an inherited component to this variation. We found a set of genes whose expression levels are highly variable in lymphoblastoid cells prepared from white blood cells of normal individuals. For these genes, we observed that genetically related individuals tend to have more similar transcript levels than