GUSB and mucopolysaccharidosis type 7: Many of the genes showing eQTL driven by variants in such regions are known to be involved in leukocyte biology; for example, the chemokine receptors CCR1 (ref. 63) and CCR3, or GUSB, a gene in which mutations cause mucopolysaccharidosis VII (ref. 64) in which recurrent respiratory infections are common.