HCRTR2 and cyclic hematopoiesis: To date, targeted genes have been investigated, including the calcium voltage-gated channel subunit alpha1 A (CACNA1A) [8], three nitric oxide synthase (NOS) genes [9], the period circadian regulator 3 (PER3) [10] and the hypocretin receptor 2 (HCRTR2) [11], and none showed evidence of involvement in CH.