Close localization of the genes for GM-CSF and IL3 in human genome.

Colony-stimulation factors (CSFs), a family of glycoprotein growth factors, have been shown to support clonal proliferation of hematopoietic progenitor cells in vitro [1]. Macrophage-CSF (MCSF or CSF -1) [2] and granulocyte-CSF (G-CSF) [3] stimulate cells committed to the macrophage and granulocyte lineages respectively, whereas granulocytemacrophage-CSF (GM-CSF) and interleukin-3 (IL3 or multi-CSF) are capable of stimulating proliferation and differentiation of progenitors along multiple pathways. Successful cloning of cDNA and genomic copies of mouse and human genes for IL3 [3, 4] and GM-CSF [5, 6], as well as for M-CSF and G-CSF, have had a great impact on the analysis of biological properties of those molecules in vivo and in vitro [7, 8]. The GM-CSF and IL3 genes have been mapped to human chromosome 5 at bands q23-31 [9, 10], a region that is frequently deleted in patients with myeloid disorders [del(5q)] [11]. Several other growth factors and growth-factor receptors in particular, the CSF -1 gene and proto-oncogene FMS, coding a protein possibly identical to the receptor for CSF-l are also located within this region of chromosome 5 [12]. There is a possibility that a family of genes responsible for regulation of cell growth during hematopoiesis is located within the limited segment of chromosome 5 [9]. Precise mapping of this region is essential to