chromatin mark (54), is among our candidate genes. Remarkably, hematopoietic stem cells in the bone marrow of adult mice lacking Ezh2 fail to properly undergo lymphopoiesis (55), suggesting that variation in the basal level of expression of this chromatin modifier could potentially influence lymphocyte counts. PcG targets are known to be tissue-specific (56; in fact, mouse embryonic stem cells lacking Ezh2 give rise to a different phenotype), and so further studies of variation in regulatory targets of the PcG would be most valuable. For example, ChIP-seq across a panel of induced pluripotent stem cells from asthmatics and healthy controls could potentially identify differential targets influencing lymphocyte counts and even asthma susceptibility.
