 It has also been found that calcium ions can act as chemotactic signals to HSCs via the G protein–coupled receptor (GPCR) calcium-sensing receptor (CaSR).CaSR knockout mice have shown hematopoietic cells in the circulation and spleen, but few in the bone marrow, indicating this receptor's importance in this particular niche.Conversely, stimulation of HSC CaSR via its agonist cinacalcet increases migration and engraftment of these cells in the bone marrow.