Zebrafish Kit ligands cooperate with erythropoietin to promote erythroid cell expansion

Abstract

Key points:• Kit signaling contributes to erythroid cell development and is conserved from fish to man • Ex vivo expansion and self-renewal of zebrafish erythroid progenitors requires addition of recombinant Kitlga AbstractKit ligand (Kitlg) is pleiotropic cytokine with a prominent role in vertebrate erythropoiesis. Although the role of Kitlg in this process has not yet been reported in Danio rerio (zebrafish), in the present study, we show that its function is evolutionary conserved. Zebrafish possess two copies of Kitlg genes (Kitlga and Kitlgb) due to whole genome duplication. To determine the role of each ligand in zebrafish, we performed a series of ex vivo and in vivo gain-and loss-of-function experiments. First, we tested the biological activity of recombinant Kitlg proteins in suspension culture from zebrafish whole kidney marrow and we demonstrate that Kitlga is necessary for expansion of erythroid progenitors ex vivo. To further address the role of kitlga and kitlgb in hematopoietic development in vivo, we performed gain-of-function experiments in zebrafish embryos, showing that both ligands cooperate with erythropoietin (Epo) to promote erythroid cell expansion. Finally, using the kita mutant (kita b5/b5 or sparse), we show that Kita receptor is crucial for Kitlga/b cooperation with Epo in erythroid cells. In summary, using optimized suspension culture conditions with recombinant cytokines (Epo, Kitlga), we are reporting for the first time ex vivo suspension cultures of zebrafish hematopoietic progenitor cells, which can serve as an indispensable tool to study normal and aberrant hematopoiesis in zebrafish. Furthermore, we conclude that although partial functional diversification of Kit ligands has been described in other processes, in erythroid development, both paralogs play a similar role and their function is evolutionary conserved.

Application of haematology parameters for health management in fish farms

“…EPO can promote the proliferation of erythrocytes, induce differentiation, maintain normal osmotic pressure inside and outside the membrane, and stimulate multidirectional progenitor cells, megakaryocyte progenitor cells and granuloprogenitor cells to some extent. 142,143 Lymphocytes are the basis of animal immunity. The structure of lymphocytes has not changed much during species evolution.…”

“…Studies have shown that EPO mainly acts on erythroid progenitor cells, presumably through the action of genetic deblocking factors that determine haemoglobin synthesis. EPO can promote the proliferation of erythrocytes, induce differentiation, maintain normal osmotic pressure inside and outside the membrane, and stimulate multidirectional progenitor cells, megakaryocyte progenitor cells and granuloprogenitor cells to some extent 142,143 …”