Fig. 7.
Schematic model of the regulation of granulopoiesis and neutrophil functions by VD3 in zebrafish. ① In adult zebrafish, the gene expression of csf3b and the neutrophil markers were enhanced in the intestine of the fish fed with VD3-containing diet, compared to those fed with non-VD3 diet. ② The gene expression of csf3b and neutrophil abundance in the intestine of adult zebrafish with a cyp2r1 mutant were reduced. Interestingly, microbiota is involved in VD-mediated granulopoiesis in adult zebrafish. ③ Addition of exogenous VD3 promoted granulopoiesis in zebrafish larvae. However, VD-regulated neutrophil generation independent of the microbiota during early development. ④ VD3 treatment significantly decreased bacterial counts and mortality in zebrafish larvae infected with E. tarda in a neutrophil-dependent manner. ⑤ VD3 augmented the gene expression of IL-8 and neutrophil recruitment to the site of caudal fin amputation. csf3b, colony-stimulating factor 3b; VD3, vitamin D3; E. tarda, Edwardsiella tarda.