Expression of functional human CSF-1 receptors on mouse bone marrow erythroid progenitor cells

We have previously shown that a murine multipotent hematopoietic cell line could proliferate in response to CSF-1 after retroviral transfer of human CSF-1 receptor (CSF-1R) gene (c-fms) without loss of the erythroid differentiation potential. In the light of these data, we asked whether ectopic expression of human c-fms gene would lead to the conditional immortalization of murine hematopoietic progenitor cells. In the present studies, murine bone marrow cells were infected with recombinant retroviruses containing the human c-fms cDNA. We found that CSF-1 could exert a stimulatory activity on erythroid progenitors in the presence of Epo only when bone marrow cells had been previously infected with c-fms retroviruses. In addition, expression of human CSF-1R in murine Epo-dependent, v-src-immortalized cells resulted in CSF-1-dependent proliferation of these cells in the absence of Epo. These data show that human CSF-1R (i) can stimulate early bone marrow erythroid progenitors, (ii) might require additional signals provided by oncogenes or cytokine receptors to transduce a mitogenic signal into mouse bone marrow erythroid progenitors.