The release of the HapMap data in 2003 and the availability of immortalized cell lines from HapMap participants initiated a new era of research investigating how SNPs affect how genes are expressed at the mRNA level. In 2005, two landmark publications evaluated how SNPs affect overall transcription in immortalized cell line samples collected from unrelated individuals [1,2]. Since those initial publications, the work has advanced with additional studies using more sophisticated microarrays, larger more diverse sample sets, and with studies of heritability of transcript and exon-level expression [3–6].
