There's really only two pieces of jargon you need to know to follow this story, and those are the two classes of genetic variants that alter the expression levels of genes: cis and trans variants. To put it simply, cis variants are those that are found close to a gene, and trans variants are those that act on a gene's expression levels but are found far away in the genome (typically on another chromosome).

The ominous message from this paper is this: by examining the effects of genetic ancestry on local gene expression levels in samples from African-Americans, the study provides the first solid estimate of the proportion of the variance in gene expression that is determined by cis-acting variants - and suggests that this proportion is low (around 12%). In other words, this paper suggests that ~88% of the variants altering the expression of a gene are trans variants found far from that gene.