Cloning of the human homologue of the murine flt3 ligand: a growth factor for early hematopoietic progenitor cells

Abstract

Using a fragment of the murine flt3 ligand as a probe, we have succeeded in cloning a human flt3 ligand from a human T-cell lambda gt10 cDNA library. The human and murine ligands are 72% identical at the amino acid level. Analysis of multiple cDNA clones shows that alternative splicing of the human flt3 mRNA can occur at a number of positions. A recombinant soluble form of the human flt3 ligand stimulates the proliferation and colony formation of a subpopulation of human bone marrow cells that are CD34+ and are enriched for primitive hematopoietic cells. In addition, the human flt3 ligand also stimulates the proliferation of cells expressing murine flt3 receptors. Northern blot analysis shows widespread expression of flt3 ligand mRNA transcripts in human tissues.

Reconstitution of human haematopoiesis in non‐obese diabetic/severe combined immunodeficient mice by clonal cells expanded from single CD34+CD38– cells expressing Flk2/Flt3

“…Although most of myelocytic progenitors expressed Flk2/Flt3, erythroid progenitors contained both CD34 + Flk2/Flt3 + and CD34 + Flk2/Flt3cell fractions. This result was consistent with the previous reports that FL alone or in synergy with other cytokines stimulates mylocytic progenitors (Lyman et al, 1994;McKenna et al, 1995;Rusten et al, 1996;Lyman & Jacobsen, 1998), and our study showing that FL synergizes with IL-6/sIL-6R to support the growth of erythroid progenitors, although the activity was weaker than that of SCF , indicating that Flk2/Flt3 signal as well as c-Kit signal functions in the development of myelocytic and erythroid progenitors. Furthermore, haematopoietic multipotential progenitors were also present in the CD34 + Flk2/Flt3 + and CD34 + Flk2/Flt3cell fractions.…”

“…Flk2/Flt3 belongs to the tyrosine kinase receptor superfamily as well as c-Fms and c-Kit, which act as the receptors for macrophage colony-stimulating factor (M-CSF) and stem cell factor (SCF), respectively, was identified, and a cDNA encoding human Flk2/Flt3 was cloned from a CD34 + haematopoietic stem/progenitor cell-enriched library (Rosnet et al, 1993;Small et al, 1994). The ligand for Flk2/Flt3 (FL), which was subsequently identified using the receptor, has been shown to stimulate human haematopoiesis (Lyman et al, 1994;Lyman & Jacobsen, 1998). FL alone or in synergy with other cytokines, such as interleukin (IL) 3 and granulocyte-macrophage colony-stimulating factor (GM-CSF), supports the growth of human myelocytic progenitors (Lyman et al, 1994;McKenna et al, 1995;Rusten et al, 1996;Lyman & Jacobsen, 1998).…”

Flt3L induces the ex‐vivo amplification of umbilical cord blood committed progenitors and early stem cells in short‐term cultures

“…Our data are consistent with previous results showing the potent co-stimulating effect of¯t3L both on BM (Lyman et al, 1994;McKenna et al, 1995;Rusten et al, 1996;Petzer et al, 1996) and CB CD34 cells Takahira et al, 1996;Piacibello et al, 1997). In our study the addition of¯t3L signi®cantly increased cell proliferation inducing an output of nucleated cells 2-fold higher than in cultures lacking this cytokine.…”

Quantitation and characterization of human megakaryocyte colony‐forming cells using a standardized serum‐free agarose assay

“…Confirmatory evidence for this in vivo is provided by the demonstrated persistence of some megakaryocytopoiesis in mice with homozygous inactivation of either the TPO gene (de Sauvage et al, 1995) or its receptor, the product of c-mpl (Gurney et al, 1994). FL is another recently described cytokine that has been shown to have stimulatory activity on primitive haemopoietic progenitors, particularly in combination with other growth factors such as IL-3 (Lyman et al, 1994;Petzer et al, 1996). In the present studies, no action of FL either alone or in combination with TPO, IL-3 or SF was seen on CFC-Mk, non-Mk or mixed lineage progenitors in serumfree agarose assays of light density bone marrow cells.…”

“…Various cytokines which had previously been reported to have Mk-colony stimulating activity (before thrombopoietin (TPO) was available) were used to develop a growth factor cocktail which supported maximal growth of Mk colonies (Bruno et al, 1988Ishibashi et al, 1989;Teramura et al, 1988;Williams et al, 1990). Subsequently, the effect on Mk colony growth of both TPO and flt-3 ligand alone and in combination with other cytokines was evaluated in this assay (Bartley et al, 1994;Debili et al, 1995;Kaushansky et al, 1994;Lyman et al, 1994).…”