Cholinergic regulation of circadian HSPC traffic. Overview of identified mechanisms, proteins, and cells that influence circadian trafficking (egress and homing) of HSPCs and leukocytes. ACh, acetylcholine; BMSC, BM mesenchymal stem/progenitor cell; Chrn, cholinergic nicotinic; CNS, central nervous system; E-sel, E-selectin; HSC, hematopoietic stem cell; NE, norepinephrine. See the visual abstract for the article by García-García et al that begins on page 224.