Involvement of transcription factor encoded by the mi locus in the expression of c-kit receptor tyrosine kinase in cultured mast cells of mice

Abstract

The mi locus of mice encodes a member of the basic-helix-loop-helix- leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF). Cultured mast cells of mi/mi genotype (mi/mi CMCs) did not normally respond to stem cell factor (SCF), a ligand for the c-kit receptor tyrosine kinase. The poor response of mi/mi CMCs to SCF was attributed to the deficient expression of c-kit both the mRNA and protein levels. The purpose of the present study is to investigate the effect of MITF on the transcription of the c-kit gene. First, we introduced cDNA encoding normal (+) MITF or mutant (mi) MITF into mi/mi CMCs using the retroviral vector. Overexpression of (+)-MITF but not mi- MITF normalized the expression of the c-kit and the poor response of mi/mi CMCs to SCF, indicating the involvement of (+)-MITF in the c-kit gene transactivation. Second, we analyzed the promoter of the c-kit gene. Three CANNTG motifs recognized by bHLH-Zip-type transcription factors were conserved between the mouse and human c-kit promoters. Among these three CANNTG motifs, only the CACCTG motif (nt -356 to - 351) was specifically bound by (+)-MITF. When the luciferase gene under the control of the c-kit promoter was contransfected into NIH/3T3 fibroblasts with cDNA encoding (+)-MITF or mi-MITF, the luciferase activity significantly increased only when (+)-MITF cDNA was cotransfected. The deletion of the promoter region containing the CACCTG motif or the mutation of the CACCTG to CTCCAG abolished the transactivation effect of (+)-MITF, indicating that (+)-MITF transactivated the c-kit gene through the CACCTG motif. When the luciferase gene under the control of the c-kit promoter was introduced into the FMA3 mastocytoma and FEC-P1 myeloid cell lines, remarkable luciferase activity was observed only in FMA3 cells. Thus, the involvement of (+)-MITF in the c-kit transactivation appeared to be specific to the mast cell lineage.

Identification of a novel nonsense mutation on the Pax3 gene in ENU-derived white belly spotting mice and its genetic interaction with c-Kit

“…Secondly, Pax3 regulates c-Kit expression via downstream genes, probably via transcription factor Mitf, SP1 or AP-2. It is well known that Mitf is activated by Pax3, and that Mitf regulates c-Kit expression in the mast cell lineage (Tsujimura et al, 1996). One would postulate that Pax3 regulates c-Kit expression by activating Mitf.…”

The controversial role of mast cells in fibrosis

“…For example, CADM1 and Kit cooperate and contribute to human lung MC survival and proliferation. 146 In addition, both CADM1 and Kit exist under the transcriptional control of micropthalmia transcription factor (MITF), 157,174 co-immunoprecipitate from HMC-1 cells, 146 and co-localize in human lung MCs at points of adhesion to human ASM cells, as determined by confocal imaging. 146…”

Impaired development of melanoblasts in the black‐eyed white Mitfmi‐bw mouse, a model for auditory–pigmentary disorders

“…The dosage-sensitive role of Mitf-M may account for the lack of melanoblasts in bw mouse embryos, based on the report for the self-regulation of the MITF gene . Moreover, MITF appears to be involved in the regulation of the KIT gene promoter (Tsujimura et al 1996). It is therefore tempting to speculate that the loss or the low level of Mitf-M expression may be associated with the decrease in transcription of Kit and ⁄ or Dct genes, which impairs melanoblast development in bw mice.…”