title: Murine hematopoietic stem cells and multipotent progenitors express truncated intracellular form of c-kit receptor.
abstract: The c-kit receptor plays a vital role in self-renewal and differentiation of hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs). We have discovered that besides c-kit, the murine multipotent HSC/MPP-like cell line EML expresses the transcript and protein for a truncated intracellular form of c-kit receptor, called tr-kit. Notably, the tr-kit transcript and protein levels were down-regulated during cytokine-induced differentiation of the HSC/MPP-like cell line EML into myeloerythroid lineages. These findings prompted us to analyze tr-kit expression in purified murine fetal liver and bone marrow cell populations containing long-term repopulating (LTR) HSCs, short-term repopulating (STR) HSCs, MPPs, lineage-committed progenitors, and immature blood cells. Remarkably, these studies have revealed that in contrast to more widespread expression of c-kit, tr-kit is transcribed solely in cell populations enriched for LTR-HSCs, STR-HSCs, and MPPs. On the other hand, cell populations in which HSCs and MPPs are either present at a much lower frequency or are absent altogether, cells representing more advanced stages of differentiation into lymphoid and myeloid lineages do not express tr-kit. The observation that tr-kit is co-expressed with c-kit only in more primitive HSC- and MPP-enriched cell populations raises an exciting possibility that tr-kit functions either as a new component of the stem cell factor (SCF)/c-kit pathway or is involved in a novel signaling pathway, present exclusively in HSC and MPPs. Taken together, these findings necessitate functional characterization of tr-kit and analysis of its potential role in the self-renewal, proliferation, and/or differentiation of HSC and multipotent progenitors.
authors.affiliation: Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Zayas
authors.forename: Danislav S
authors.initials: DS
authors.lastname: Spassov
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Nachtman
authors.forename: Roland
authors.initials: R
authors.lastname: Jurecic
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage; D049109:Cell Proliferation; D002478:Cells, Cultured; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D008969:Molecular Sequence Data; D039902:Multipotent Stem Cells / Q000378:metabolism* / Q000502:physiology; D010446:Peptide Fragments / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D017434:Protein Structure, Tertiary; D019009:Proto-Oncogene Proteins c-kit / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid
chemical_list: D010446:Peptide Fragments; D019009:Proto-Oncogene Proteins c-kit