Expression of CXCR4b and SDF1a in zebrafish larvae. (A) Reverse transcription–polymerase chain reaction of csf1r (macrophage marker), mpo (neutrophil marker), eflα (loading control), CXCR4a, and CXCR4b from MPO:Dendra2 high (hi) and low (lo) populations. WKM indicates whole kidney marrow from adult wild-type fish. (B-C) Whole-mount in situ hybridization of SDF1a expression in 2 dpf larvae, lateral view. Note SDF1a expression in the head (B) and CHT (C arrowheads). P indicates pronephric duct; cht, caudal hematopoietic tissue. (D) Whole-mount Sudan Black staining to visualize neutrophils in 2 dpf larvae, lateral view. Note neutrophil accumulation in areas of SDF1a expression in the head (box) and CHT (arrowheads). Bar = 200 μm (B-D).