Heterozygous kit mutants with little or no apparent anemia exhibit large defects in overall hematopoietic stem cell function.
OBJECTIVE
The evolutionarily conserved Kit receptor is vital for function of hematopoietic stem cells (HSC). Kit(W-41) (W-41) and Kit(W-42) (W-42) are single residue changes in the KIT intracellular phosphotransferase domain, while Kit(W-v) (W-v) is a single residue change in the ATP binding domain. This study tests how each mutation affects HSC function.


METHODS
Cells in mutant and C57BL/6J(+/+) blood and marrow were compared. Overall HSC function was measured by competitive repopulation. Functions of specific progenitor populations were tested with stage-specific competitive repopulation and standard colony-forming unit assays.


RESULTS
Bone marrow cells from these Kit mutants are severely defective at reconstituting peripheral blood lineages and bone marrow of irradiated recipients, when compared to +/+ control marrow. These defects increased with time. Marrow from W-41/+ and W-v/+ functions similarly but better than marrow from W-41/W-41 and W-42/+, to repopulate the erythroid and lymphoid lineages. Long-term (LT) and short-term (ST) HSC from W-v/+, W-41/W-41, and W-42/+ are more defective at reconstituting bone marrow than LT- and ST-HSC from W-41/+ and +/+. Common myeloid progenitor (CMP) cells from W-42/+ and W-41/W-41 are more defective at producing spleen colonies than CMP from W-v/+ and W-41/+.


CONCLUSIONS
Heterozygous Kit mutants with little or no apparent anemia exhibit surprisingly large defects in overall HSC function. Multiplying the fractional defects in LT-HSC, ST-HSC, and CMP can account for overall effects of W-v/+, but does not completely account for the defects observed with W-41/+, W-42/+, and W-41/W-41.
Sharma
Yashoda
Y
The Jackson Laboratory, Bar Harbor, ME 04609, USA.
Astle
Clinton M
CM
Harrison
David E
DE
D000740:Anemia / Q000235:genetics* / Q000276:immunology*; D000818:Animals; D001792:Blood Platelets / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology / Q000528:radiation effects; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D019070:Cell Lineage / Q000276:immunology / Q000528:radiation effects; D003114:Colony-Forming Units Assay / Q000379:methods; D005260:Female; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000276:immunology*; D006579:Heterozygote; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009154:Mutation; D023461:Myeloid Progenitor Cells / Q000276:immunology; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000276:immunology
D019009:Proto-Oncogene Proteins c-kit