Clustered Gene Expression Changes Flank Targeted Gene Loci in Knockout Mice

BACKGROUND: Gene expression profiling using microarrays is a powerful technology widely used to study regulatory networks. Profiling of mRNA levels in mutant organisms has the potential to identify genes regulated by the mutated protein. METHODOLOGY/PRINCIPLE FINDINGS: Using tissues from multiple lines of knockout mice we have examined genome-wide changes in gene expression. We report that a significant proportion of changed genes were found near the targeted gene. CONCLUSIONS/SIGNIFICANCE: The apparent clustering of these genes was explained by the presence of flanking DNA from the parental ES cell. We provide recommendations for the analysis and reporting of microarray data from knockout mice