Characterization of cultured mast cells derived from Ws/Ws mast cell-
deficient rats with a small deletion at tyrosine kinase domain of c-kit
H Tei, T Kasugai, T Tsujimura, S Adachi, T Furitsu, K Tohya, M Kimura, KM Zsebo, GF Newlands and HR Miller
Department of Pathology, Osaka University Medical School, Suita, Japan.
The Ws mutant allele of rats represents a 12-base deletion at the tyrosine
kinase domain of the c-kit gene. Although homozygous Ws/Ws rats were
deficient in both connective tissue-type mast cells (CTMC) and mucosal-type
mast cells (MMC), mast cells did develop when bone marrow cells of Ws/Ws
rats were cultured in the presence of concanavalin A-stimulated spleen cell
conditioned medium (ConA-SCM). Although the proliferative response of rat
cultured mast cells (RCMC) derived from Ws/Ws rats to ConA-SCM was
comparable to that of RCMC derived from control normal (+/+) rats, the
proliferative response of Ws/Ws RCMC to rat recombinant stem cell factor
(rrSCF; a ligand for the c-kit receptor tyrosine kinase) was much lower
than that of +/+ RCMC. However, a slight c-kit kinase activity was
detectable in Ws/Ws RCMC, and the proliferation of Ws/Ws RCMC was
accelerated when rrSCF was added to ConA-SCM. Because CTMC contain rat mast
cell protease-I (RMCP- I) and MMC contain RMCP-II, the phenotype of +/+ and
Ws/Ws RCMC in various culture conditions was evaluated by
immunohistochemistry of RMCPs. Both +/+ and Ws/Ws RCMC showed the MMC-like
phenotype (RMCP-I- /II+) when they were cultured with ConA-SCM alone. Most
+/+ RCMC and about half of Ws/Ws RCMC acquired a novel protease
(RMCP-I+/II+) phenotype when they were cultured with rrSCF alone. However,
because the number of Ws/Ws RCMC dropped to one-tenth in the medium
containing rrSCF alone, the absolute number of Ws/Ws RCMC with the
RMCP-I+/II+ phenotype did not increase significantly. The effect of rrSCF
in inducing the novel phenotype was suppressed when ConA-SCM was added to
rrSCF. In contrast, +/+ and Ws/Ws RCMC cocultured with +/+ fibroblasts
showed the RMCP-I+/II+ phenotype even in the presence of ConA-SCM.
Moreover, a fibroblast cell line derived from SI/SI mouse embryos that did
not produce SCF did not support the survival of both +/+ and Ws/Ws RCMC but
did induce the RMCP-I+/II+ phenotype in about half of +/+ and Ws/Ws RCMC
when their survival was supported by the addition of ConA- SCM. The normal
signal transduction through the c-kit receptor did not appear to be
prerequisite for the acquisition of the RMCP-I+/II+ phenotype.
Volume 83,
Issue 4,
pp. 916-925,
02/15/1994
Copyright © 1994 by The American Society of Hematology