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From the Department of Pathology,*
Osaka University
Medical School, Suita, Japan; and the Department of Oriental
Pharmacy,
College of Pharmacy, Wonkwang
University, Chonbuk, Republic of Korea
| Abstract |
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| Introduction |
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The protease expression phenotype is influenced not only by extracellular environmental factors16-19 but also by intracellular factors.20-22 As extracellular factors, effects of tissue environments and cytokines have been studied. Messenger RNA (mRNA) of mMCP-2 is expressed by mast cells in the mucosal layer of the stomach of (WB x C57BL6) F1 (hereafter called WBB6F1)-+/+ mice but not by mast cells in the muscle layer of the stomach.16 Addition of interleukin 9, interleukin 10, or transforming growth factor-ß1 significantly increased the mRNA expression of both mMCP-1 and -2 in cultured mast cells (CMCs).9,17,18 On the other hand, addition of stem cell factor increased the expression of mMCP-4 and -6 in CMCs.19
Transcription factors that are involved in the transactivation of mMCP genes are intracellular factors. The mi transcription factor (hereafter called MITF) is a member of the basic helix-loop-helix leucine zipper (bHLH-Zip) protein family and is encoded by the mi locus of mice.23,24 The MITF encoded by the mutant mi locus deletes one of four consecutive arginines in the basic domain.23,25,26 We showed that the mRNA expression of the mMCP-4, -5, and -6 was deficient in CMCs derived from C57BL/6 (B6)-mi/mi mice.20-22
Strain difference also affects the expression of mMCP genes. When considered as a whole mouse, the strain difference may be either an extracellular or intracellular factor. Amounts of secreted cytokines might be different among mouse strains. However, when protease expression phenotypes are compared among CMCs in the same culture condition, the strain difference may be an intracellular factor. Therefore, both the strain differences and transcription factors are considered to be intracellular factors that may affect the protease expression phenotype of CMCs.
We have studied the effect of MITF only in the B6 strain.20-22 The differences between B6-+/+ mice and B6-mi/mi mice have been examined. On the other hand, the expression of mMCP-2 and -4 genes was much higher in CMCs derived from WB-+/+ mice than in CMCs of B6-+/+ mice.16,27 The effect of MITF on the expression of mMCP-2 and -4 genes remained to be examined in the WB strain. In the present study, we crossed WB-+/+ mice to B6-mi/+ mice to obtain the mice that possessed the WB strain-derived mMCP-2 genes and the double gene dose of mutant mi allele. The expression of the WB strain-derived mMCP-2 gene was significantly lower in mice of mi/mi genotype than in mice of +/+ genotype. We also examined the expression of WB strain-derived mMCP-4 and -9 genes in mice of mi/mi genotype.
| Materials and Methods |
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WB-+/+ and B6-+/+ mice were raised in our laboratory. The original stock of B6-mi/+ mice was purchased from the Jackson Laboratory (Bar Harbor, ME) and maintained in our laboratory by consecutive back-crosses to our own inbred B6 colony (more than 19 generations at the time of the present experiment). We selected female and male B6-mi/+ mice by the presence of a white belly spot, and crossed together. The resulting B6-mi/mi mice were selected by their white coat color.28,29
The alleles of mMCP-2, -4, and -9 genes possessed by the B6 strain were described as P2B6, P4B6, and P9B6. And the alleles of mMCP-2, -4, and -9 genes of the WB strain were described as P2WB, P4WB, and P9WB. In the present experiment, mice of (P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, mi/mi) and control (P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, +/+) genotype were necessary. First, we crossed WB-(P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, +/+) mice with B6-(P2B6/P2B6, P4B6/P4B6, P9B6/P9B6, mi/+) mice. Then, we selected WBB6F1- (P2WB/P2B6, P4WB/PB6, P9WB/P9B6, mi/+) mice by the presence of a white belly spot. Then we back-crossed the F1 hybrid mice to WB-(P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, +/+) mice and obtained N2 mice. We selected N2 mice possessing the mutant mi allele (ie, N2-mi/+) by the presence of a remarkable white belly spot. We crossed together these N2-mi/+ mice, and finally selected mice of (P2B6/P2B6, P4B6/P4B6, P9B6/P9B6, mi/mi) (all white), (P2B6/P2B6, P4B6/P4B6, P9B6/P9B6, +/+) (all black), (P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, mi/mi) (all white), and (P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, +/+) (all black) by the coat color and the sequences of genomic DNAs of mMCP-2, -4, and -9.
Sequence of Genomic DNAs
Genomic DNAs were obtained from tail tip with the conventional phenol extraction method. Each genomic DNA was amplified in 25 µl of polymerase chain reaction (PCR) mixture containing 0.125 U of Taq DNA polymerase (Takara Shuzou, Kyoto, Japan) and 12.5 pmol each of sense (5'-GCCTATCTGAAGTTCACCAC-3', nucleotides +628 to +647, +1 is the transcription initiation site) and antisense (5'-ATGGCAAGTTGGCACTCTAC-3', nucleotides +988 to +1007)12 primers for the mMCP-2 gene, sense (GGAGACTCTGGAGGACCTCT-3', nucleotides +2209 to +2228) and antisense (5'-ACAGGGAACAGTCCATCATC-3', nucleotides +2526 to +2545)4 primers for the mMCP-4 gene, and sense (5'-GCTAACTTGACTTCTGCTGTGG-3', nucleotides +1617 to +1638) and antisense (5'-GGGTTATTAGAAGAGCTCTGGC-3', nucleotides +2445 to +2466)11 primers for the mMCP-9 gene by 28 cycles of denaturation at 94°C (30 seconds), annealing at 55°C (30 seconds), and synthesis at 72°C (1 minute). Three nucleotides in this portion (nucleotides +628 to +728) of mMCP-2 cDNA were different between WB and B6 strains. Six nucleotides in this portion (nucleotides +2209 to +2545) of mMCP-4 cDNA were different between WB and B6 strains, and moreover the other 11 nucleotides were deleted in B6 strain. Three nucleotides in this portion (nucleotides +1617 to +2466) of mMCP-9 genomic DNA were different between WB and B6 strains. The PCR products were subcloned into the Bluescript KS (-) plasmids (pBS; Stratagene, La Jolla, CA) for further analysis. Nucleotide sequence was determined as described previously.30 Strain-dependent differences of cDNA sequences were compared using the DNASIS sequence analysis program (Hitachi Software Engineering Co., Ltd., Tokyo, Japan).
Cells
Pokeweed mitogen-stimulated spleen cell-conditioned medium
(PWM-SCM) was prepared according to the method described by Nakahata et
al.31
Mice were used at 2 to 3 weeks of age to obtain
CMCs. Mice were killed by decapitation after ether anesthesia and
spleens were removed. Spleen cells were cultured in
-minimal
essential medium (
-MEM; ICN Biochemicals, Costa Mesa, CA)
supplemented with 10% PWM-SCM and 10% fetal calf serum (FCS; Nippon
Bio-supp Center, Tokyo, Japan). Half of the medium was replaced every 7
days. More than 95% of cells were CMCs 4 weeks after the initiation of
the culture.32,33
The helper virus-free packaging
cell line (
2) was maintained in Dulbeccos modified Eagles medium
(DMEM, ICN Biomedicals) supplemented with 10% FCS.34
The
IC-2 cell line was provided by Dr. I. Yahara (Tokyo Metropolitan
Institute of Medical Science, Tokyo, Japan)35
and
maintained in
-MEM supplemented with 10% PWM-SCM and 10% FCS.
Sequence of mMCP-2, -4, and -9 cDNAs
Five micrograms of total RNA obtained from WB-+/+ CMCs or B6-+/+ CMCs were reverse-transcribed in 20 µl of the reaction mixture containing 20 U of avian myeloblastosis virus reverse transcriptase (Boehringer Mannheim GmbH Biochemica, Mannheim, Germany) and random hexamer. One µl of each reaction product was amplified in 25 µl of PCR mixture containing 0.125 U of Taq DNA polymerase and 12.5 pmol each of sense (5'-AGAAGCTCACCAAGGCCTCA-3', nucleotides +1 to +20) and antisense (5'-GCAAGAGGTTAGGTCTTTATTG-3', nucleotides +2490 to +2511)12 primers for the mMCP-2 gene, sense (5'-AGAATCTCTCTCCAAGCTGTGACCG-3', nucleotides +1 to +25) and antisense (5'-GGAGGTTAGGTCTTTACTGAGGTGCA-3', nucleotides +2548 to +2573)4,36 primers for the mMCP-4 gene, and sense (5'-AAAATCTCTCTCCAGACTGCGA-3', nucleotides +1 to +22) and antisense (5'-AAGACTCTGATGCACGCAGGTCA-3', nucleotides +2219 to +2241)11 primers for the mMCP-9 gene by 30 cycles of denaturation at 94°C (30 seconds), annealing at 57°C (30 seconds), and synthesis at 72°C (1 minute). Inserts were subcloned into the plasmid pBS for further analysis. Nucleotide sequence was determined as described previously.30
Northern Blot Analysis
Thirty micrograms of total RNA from CMCs were prepared by
the lithium chloride-urea method.37
Northern blot analysis
was performed using mMCP-2,3,12
-4,4
-5,5
-6,6
-9,11
and
ß-actin38
cDNAs labeled with
-[32P]dCTP (DuPont/NEN Research Products,
Boston, MA) by random oligonucleotide priming as probes. After
hybridization at 42°C, blots were washed to a final stringency of
0.2x standard saline citrate (1x standard saline citrate is 150
mmol/L NaCl and 15 mmol/L trisodium citrate, pH 7.4) at 50°C and
subjected to autoradiography.
Construction of Retrovirus Vector and Its Infection
Plasmid pBS containing the whole coding region of +-MITF or
mi-MITF (pBS-+-MITF and pBS-mi-MITF,
respectively) had been constructed in our laboratory.39,40
A retroviral vector, pM5Gneo,41
a derivative of
myeloproliferative sarcoma virus vector, was a kind gift from Dr. W.
Ostertag (Universität Hamburg, Hamburg, Germany). The purified
SmaI-HincII fragment from pBS-+-MITF or
pBS-mi-MITF was introduced into the blunted EcoRI
site of pM5Gneo. The resulting pM5Gneo-+-MITF and
pM5Gneo-mi-MITF were transfected into the packaging cell
line (
2)34
by the calcium phosphate precipitation
method,42
and neomycin-resistant
2 cell clones were
selected by culturing in DMEM supplemented with 10% FCS and G418 (0.8
mg/ml; Life Technologies, Inc., Grand Island, NY). For gene transfer,
spleen cells obtained from mi/mi mice were incubated on an
irradiated (30 Gy) subconfluent monolayer of virus-producing
2 cells
for 72 hours in
-MEM supplemented with 10% PWM-SCM and 10% FCS.
Neomycin resistant CMCs were obtained by continuing the culture in
-MEM containing 10% PWM-SCM, 10% FCS, and G418 (0.8 mg/ml) for 4
weeks.
Construction of Reporter Plasmids
The luciferase gene subcloned into pSP72 (pSPLuc)43 was generously provided by Dr. K. Nakajima (Osaka City University Medical School, Osaka, Japan). To construct reporter plasmids, a DNA fragment containing a promoter region and the first exon (noncoding region) of the mMCP-2 gene (nucleotides -1311 to +21)12 and mMCP-9 gene (nucleotides -1191 to +10)11 obtained from genomic DNA of B6-+/+ mouse were cloned into the upstream region of the luciferase gene in pSPLuc. The deletion of the mMCP-2 or -9 promoter was done by using the appropriate restriction enzyme. The mutations were introduced by PCR with mismatched primers. Deleted or mutated products were verified by sequencing.
Transient Assay
The expression vector containing the ß-galactosidase gene was used as an internal control. Because IC-2 cells expressed effector gene by themselves,22 the reporter and the expression vector containing the ß-galactosidase gene were added to cell suspension (1 x 107) in 0.7 ml phosphate-buffered saline, mixed gently, and incubated on ice for 10 minutes. For gene transfer, cells were electroporated by a single pulse (975 microfarads at 350 V) from a Gene Pulser II (Bio-Rad Laboratories, Richmond, CA). After incubation on ice for 10 minutes, the cells were suspended in 10 ml of complete culture medium. IC-2 cells were harvested 8 hours after transfection. Cells were lysed with 0.1 mol/L potassium phosphate buffer (pH 7.4) containing 1% Triton X-100 (Sigma, St Louis, MO). Extracts were then used to assay luciferase activity with luminometer model LB96P (Berthold, Wildbad, Germany) and ß-galactosidase activity. Luciferase activity was normalized by ß-galactosidase activity and total protein concentration according to the method described by Yasumoto et al.44
Electrophoretic Gel Mobility Shift Assay (EGMSA)
The production and purification of
glutathione-S-transferase (GST) -+-MITF and
GST-mi-MITF fusion proteins were described
previously.39,40
Oligonucleotides were labeled with
-[32P]dCTP by filling 5'-overhangs, and were
used as probes for EGMSA. DNA binding assays were performed in a 20
µl reaction mixture containing 10 mmol/L Tris-HCl (pH 8.0), 1 mmol/L
ethylenediaminetetraacetic acid, 75 mmol/L KCl, 1 mmol/L
dithiothreitol, 4% Ficoll type 400, 50 ng poly (dI-dC), 25 ng of the
labeled DNA probe, and 3.5 µg of GST-+-MITF or GST-mi-MITF
fusion protein. After incubation at room temperature for 15 minutes,
the reaction mixture was subjected to electrophoresis at 14 V/cm at
4°C on a 5% polyacrylamide gel in 0.25x TBE buffer (1x TBE is 90
mmol/L Tris-HCl, 64.6 mmol/L boric acid, and 2.5 mmol/L
ethylenediaminetetraacetic acid, pH 8.3). The polyacrylamide gels were
dried on Whatman 3MM chromatography paper (Whatman, Maidstone, UK) and
subjected to autoradiography. Competitive DNA binding assays were
performed as described above, except that the unlabeled competitive DNA
was added to the reaction mixture before addition of GST-+-MITF fusion
protein.
Semiquantitative Reverse Transcriptase (RT) Modification of PCR
Various amounts of total RNA (5.0, 0.5, and 0.05 µg) obtained from CMCs derived from WB-+/+ or B6-+/+ mice were reverse-transcribed in 20 µl of the reaction mixture containing 20 U of avian myeloblastosis virus reverse transcriptase and random hexamer. One µl of each reaction product was amplified in 25 µl of PCR mixture containing 0.125 U of Taq DNA polymerase and 12.5 pmol each of sense (5'-CTGATCTGGTGAATCGGATC-3', nucleotides +1051 to +1070)23 and antisense (5'-TCCTGAAGAAGAGAGGGAGC-3', nucleotides +1422 to +1441)23 primers for MITF gene by 28 cycles of 30 seconds of denaturation at 94°C, 30 seconds of annealing at 55°C, and 1 minute of synthesis at 72°C. Ten µl of the PCR products was electrophoresed in 1.0% agarose gel containing ethidium bromide.
| Results |
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Low Expression of mMCP-2 and -9 Genes in B6-mi/mi Mice
We already reported that the expression of the mMCP-4, -5, and -6
was significantly higher in CMCs derived from B6-+/+ mice than those
derived from B6-mi/mi mice.20-22
In the
present experiment, the mRNA expression of mMCP-2 and -9 genes was
compared between B6-+/+ CMCs and B6-mi/mi CMCs. The mRNA
expression of mMCP-2 and -9 was significantly higher in B6-+/+ CMCs
than in B6-mi/mi CMCs (Figure 1)
.
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To examine the involvement of +-MITF in the expression of the
mMCP-2 and -9 genes, we introduced cDNA encoding +-MITF or
mi-MITF to CMCs of B6-mi/mi mouse origin.
Overexpression of either +-MITF or mi-MITF was confirmed in
the B6-mi/mi CMCs. The poor mRNA expression of the mMCP-2
and -9 genes was normalized in the B6-mi/mi CMCs
overexpressing +-MITF but not in the B6-mi/mi CMCs
overexpressing mi-MITF (Figure 2)
.
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MITF is a member of bHLH-Zip protein family transcription factors
and may recognize and bind various CANNTG motifs (any nucleotides are
possible at position N).45
The mMCP-2 promoter starting
from nucleotides -1311 have three CANNTG motifs, CAAGTG (nucleotides
-1304 to -1299), CACATG (nucleotides -377 to -372), and CATATG
(nucleotides -316 to -311). We introduced the luciferase gene under
the control of various mMCP-2 promoters into the IC-2 mast cell line
that expressed +-MITF.22
Luciferase activity was enhanced
after introduction of the reporter plasmid starting from either
nucleotide -1311 or nucleotide -379 (Figure 3)
. Then, the deleted reporter plasmid
containing the mMCP-2 promoter starting from nucleotide -364 or
nucleotide -310 was constructed and introduced into IC-2 cells. In
either case, the luciferase activity was not enhanced (Figure 3)
. We
mutated either the CACATG motif (nucleotides -377 to -372) to
CTCAAG or the CATATG (nucleotides -316 to
-311) motif to CTTAAG in the reporter plasmid
starting from nucleotide -379. The luciferase activity was not
enhanced when the CACATG motif (nucleotides -377 to -372) was mutated
(Figure 3)
. On the other hand, the luciferase activity remained to be
enhanced when the CATATG motif (nucleotides -316 to -311) was mutated
(Figure 3)
. The luciferase activity was not enhanced either when both
CACATG (nucleotides -377 to -372) and CATATG (nucleotides -316 to
-311) motifs were mutated (Figure 3)
. Only the CACATG motif of the
mMCP-2 promoter seemed to play a role for the enhancement of the mMCP-2
gene expression.
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We examined the interaction of +-MITF with 5'-upstream region of
the mMCP-9 gene. The mMCP-9 promoter starting from nucleotide -1132
have five CANNTG motifs, CACATG (nucleotides -1099 to -1094), CATTTG
(nucleotides -1054 to -1049), CAGCTG (nucleotides -782 to -777),
CATATG (nucleotides -556 to -551) and CATATG (nucleotides -381 to
-376). The reporter plasmid that contained the luciferase gene under
the control of the mMCP-9 promoter starting from nucleotides -1132,
-787, -390, -364 was constructed. We introduced the luciferase gene
under the control of the mMCP-9 promoter into IC-2 cells. Luciferase
activity was enhanced when we used the reporter plasmid containing the
mMCP-9 promoter starting from nucleotides -1132, -787, and -390
(Figure 5)
. In contrast, the luciferase
activity was not enhanced when we used the reporter plasmid starting
from nucleotide -364. Transcription activity of the mMCP-9 promoter
starting from nucleotide -390 was abolished when the CATATG motif
(nucleotides -381 to -376) was mutated.
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Expression of mMCP-2, -4, and -9 Genes in WB-+/+ Mice
We have reported that the expression of mMCP-2 was much higher in
CMCs derived from WB-+/+ mice than in CMCs derived from B6-+/+ mice,
whereas the expression of mMCP-6 was comparable between CMCs derived
from WB-+/+ mice and CMCs derived from B6-+/+ mice. As shown in Figure 7
, the expression of mMCP-2, -4, and -9
genes was higher in CMCs of WB-+/+ mice than in CMCs of B6-+/+ mice,
whereas the expression of mMCP-5 and -6 was comparable between WB-+/+
and B6-+/+ CMCs.
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The poor expression of mMCP-7 mRNA in the B6 strain was attributed to the presence of a stop codon.46 Truncated transcript was unstable. The nucleotide sequences of mMCP-2, -4, and -9 cDNAs of the B6 strain was compared to those of the WB strain.
The complete nucleotide sequence of the mMCP-2 cDNA of BALB/c strain
has been reported by Gurish et al.12
We sequenced the
mMCP-2 cDNA obtained from the CMCs of B6 strain and compared it to that
of the BALB/c strain. Two nucleotides (nucleotides +900 and +941) were
different (Figure 8)
, but those
nucleotide changes did not result in the alternation of amino acids.
Then we compared the nucleotide sequence of the mMCP-2 cDNA between
BALB/c and WB strains. Eleven nucleotides (nucleotides +229, +231,
+232, +353, +564, +612, +613, +659, +768, +900, and +941) were
different, but four of 11 nucleotide changes did not result in the
alternation of amino acids (Figure 8)
. The remaining seven nucleotide
changes caused five amino acid alternations: AAT codon at nucleotides
230 to 232 changed to AGA, leading to an alternation from Asn to Arg;
TAT codon at nucleotides 353 to 355 changed to AAT, leading to an
alternation from Try to Asn; AGT codon at nucleotides 563 to 565
changed to AAT, leading to an alternation from Ser to Asn; TCA codon at
nucleotides 611 to 613 changed to TTG, leading to an alternation from
Ser to Leu; AGT codon at nucleotides 659 to 661 changed to GGT, leading
to an alternation from Ser to Gly.
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We compared the nucleotide sequences of mMCP-2, -4, and -9 between B6
and WB strains. Nine nucleotide changes and the resulting five amino
acid alternations were found in the sequence of mMCP-2. Eleven
nucleotide changes and the resulting three amino acid alternations were
observed in mMCP-4, moreover deletion of 11 nucleotides were observed
in the mMCP-4 sequence of the B6 strain. There were no differences in
the sequence of mMCP-9 between B6 and WB strains. No particular stop
codons were found in mMCP-2, -4, and -9 sequences of B6 strain. In
fact, the size of the transcripts were comparable between B6 and WB
strains (Figures 8 and 9)
.
Xia et al47
reported that the mMCP-1, -2, and -4
transcripts have multiple UGXCCCC sequences in their 3'-UTRs. A
possibility has been raised that these sequences may be the
cis-acting elements that regulate the steady-state levels of
these transcripts.47
We found three UGXCCCC sequences in
the 3'-UTR of mMCP-2 in all BALB/c, B6, and WB strains (Figure 8)
. In
the 3'-UTR of mMCP-4, six UGXCCCC sequences were present in WB and
DBA/2 strains, but only three UGXCCCC sequences in B6 strain (Figure 9)
.
Effect of MITF
To examine the effect of MITF on the expression of the WB
strain-derived mMCP-2, -4, and -9 genes, we crossed
WB-(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, +/+) mice to
B6-(P2B6/P2B6,
P4B6/P4B6,
P9B6/P9B6, mi/+) mice,
and ultimately obtained mice of the following genotypes;
(P2B6/P2B6,
P4B6/P4B6,
P9B6/P9B6, +/+),
(P2B6/P2B6,
P4B6/P4B6,
P9B6/P9B6, mi/mi),
(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, +/+) and
(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, mi/mi). The
strain origin of mMCP-2 and -4 genes was confirmed by sequencing cDNAs
of mMCP-2 and -4 genes. Because there was no difference between the B6
and WB strain in the mMCP-9 cDNA, we confirmed the strain origin by
sequencing the genomic DNAs of mMCP-9 genes (nucleotides +1617 to
+2466). Because the expression of mMCP-5 and -6 genes was comparable
between CMCs of WB-+/+ mice and those of B6-+/+ mice, we did not
examine the strain origin of mMCP-5 and -6 genes. As already described,
the expression of mMCP-2, -4, -5, -6, and -9 genes was reduced in
B6-mi/mi mice when compared to B6-+/+ mice (Figure 1)
. The
reduction of the similar magnitude was observed in CMCs derived from
N2 x N2-(P2B6/P2B6,
P4B6/P4B6,
P9B6/P9B6, mi/mi) mice
(Figure 10)
. The expression of mMCP-2,
-4, -5, -6, and -9 genes was also comparable between WB-+/+ and N2
x N2-(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, +/+) mice (Figure 10)
.
When the expression of mMCP-2, -4, -5, -6, and -9 genes was compared
between N2 x
N2-(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, +/+) mice and N2 x
N2-(P2WB/P2WB,
P4WB/P4WB,
P9WB/P9WB, mi/mi) mice,
the expression of each protease gene was significantly greater in the
former mice than in the latter mice (Figure 10)
. When the magnitude of
reduction was compared among different proteases, it was greater in
mMCP-5 and -6 genes than in mMCP-2, -4, and -9 genes (Figure 10)
.
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| Discussion |
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All mMCP-2, -4, -5, and -9 are chymases.3-5,7,11 +-MITF directly bound CANNTG motifs in the promoter region of the mMCP-2, -4, and -9 genes and transactivated each gene,22 whereas the binding of +-MITF to the CANNTG motif in the promoter region of the mMCP-5 gene was not detectable.21 The +-MITF seemed to regulate the transactivation of the mMCP-5 gene indirectly. The regulation mechanism of mMCP-2, -4, and -9 genes seemed to be different from that of mMCP-5 gene.
The expression of mMCP-2, -4, and -9 genes was greater in CMCs of WB-+/+ mice than in those of B6-+/+ mice. This is consistent with the results of Eklund et al.27 The poor expression of mMCP-7 gene in the B6 mice is because of the presence of a stop codon. The resulting truncated transcript degraded quickly in CMCs.46 We compared the nucleotide sequences of mMCP-2, -4, and -9 cDNAs between WB and B6 strains, but no stop codons were observed in the sequences of mMCP-2, -4, and -9 cDNAs of B6 mice. The poor expression of mMCP-2, -4, and -9 genes was not considered to be because of the presence of stop codon in each cDNA of the B6 strain.
Multiple UGXCCCC sequences were found in the 3'UTR of mMCP-2 and -4 transcripts as reported by Xia et al.47 Three UGXCCCC sequences were observed in 3'UTR of mMCP-2 in both B6 and WB strains. Three UGXCCCC sequences were found in 3'UTR of B6 mMCP-4 whereas six sequences in 3'UTR of WB mMCP-4. The smaller number of UGXCCCC sequences in the B6 mMCP-4 may explain the poor expression of mMCP-4 gene in CMCs of B6 strain. However, the rank order in difference of the expression between WB and B6 strains was mMCP-2 > mMCP-4, the poor expression of the B6 strain was not completely explained by the possible effect of the repetitive sequences on the stability of ß-chymases.
The expression of mMCP-2, -4, and -9 genes was influenced by the strain difference between B6 and WB mice, but the expression of mMCP-5 and -6 genes was comparable between B6 and WB mice. Although mMCP-5 is a chymase as mMCP-2, -4, and -9, the regulation of mMCP-5 gene was similar to that of mMCP-6 gene encoding a tryptase rather than to that of mMCP-2, -4, and -9 genes. This is consistent with the result of Morii et al.21 All mMCP-2, -4, -9, and -5 genes were located on chromosome 14, but the regulation of mMCP-5 seemed to be unique among chymases.
Our observation that the regulation of mMCP-5 was different from that
of mMCP-2, -4, and -9 is consistent with the reported characteristics
of mMCP-5.48
mMCP-5 is the only mouse chymase which has a
close human homologue.49
Although
- and
ß-chymases are known in mammalian mast cells, human, baboon, and dog
mast cells contain only
-chymases.5,49-53
In contrast,
mast cells of mice, rat, and gerbils have been reported to contain
four, two, and one ß chymase-encoding genes,
respectively.50,53
All mMCP-2, -4, and -9 are
ß-chymases, and the transcriptional regulation of mMCP-2, -4, and -9
genes is highly similar.48,49
The transcriptional behavior
of the mMCP-5 gene may resemble to that of genes encoding other
-chymases.
We examined the effect of mutation of the mi locus on the expression of WB strain-derived mMCP-2, -4, and -9 genes. The expression of these genes was reduced in N2 x N2-(P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, mi/mi) mice when compared to that of N2 x N2-(P2WB/P2WB, P4WB/P4WB, P9WB/P9WB, +/+) mice. The mi mutation affected not only the B6 strain-derived mMCP-2, -4, and -9 genes but also the WB strain-derived counterparts. The expression level of MITF was comparable between CMCs of WB-+/+ mice and CMCs of B6-+/+ mice. Moreover, the CANNTG motifs in the promoter region of mMCP-2, -4, and -9 genes were not different between B6 and WB strains. Therefore, the interstrain difference in the expression of mMCP-2, -4, and -9 genes was not attributable to the interaction of MITF and each CANNTG motifs.
The rank order of the magnitude in the expression of mMCP-2 gene was
(P2WB/P2WB, +/+) >
(P2WB/P2WB,
mi/mi) >
(P2B6/P2B6, +/+) >
(P2B6/P2B6,
mi/mi). That of mMCP-4 gene was
(P4WB/P4WB, +/+) >
(P4WB/P4WB,
mi/mi)
(P4B6/P4B6, +/+) >
(P4B6/P4B6,
mi/mi). That of mMCP-9 gene was
(P9WB/P9WB, +/+) >
(P9WB/P9WB,
mi/mi)
(P9B6/P9B6, +/+) >
(P9B6/P9B6,
mi/mi). This suggested that the effect of the strain
difference of particular mMCP genes and the effect of mi
mutation were independent of each other, and that both effects were
additive on the expression of particular mMCP genes.
All genes encoding granzyme B, cathepsin G, mMCP-1, -2, -4, -5, and -9
are located on chromosome 14.12
It was suggested that
there may be a locus control region for the granzymes and another locus
control region for cathepsin G and the downstream
chymases.54,55
The expression of mMCP-2, -4, and -9 genes
was greater in CMCs of WB-+/+ mice than in CMCs of B6-+/+ mice. The
higher expression of these chymase genes in CMCs of WB-+/+ mice may be
driven by the locus control region for cathepsin G and the downstream
chymases. The rank order in difference of the expression between WB and
B6 strains was mMCP-2 > mMCP-9 > mMCP-4. It was reported
that mMCP-2 was mapped
30 kb downstream from the cathepsin G
gene.55
Because the effect of locus control region
activity is considered to be distance-dependent,56-58
the
rank order might reflect on the distance from the locus control region.
Reed et al59 examined whether the strain of mouse affected the mast cell development. Bone marrow cells taken from SWR and NIH mice produced large numbers of CMCs whereas those from C57BL/10 mice produced relatively few numbers of CMCs. The result suggested that development of mast cell was strain-dependent. We showed that the expression of mMCP genes was also strain-dependent. Studying the expression of mMCP genes seems to be a good model for clarifying the strain-dependent mast cell differentiation.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by grants from the Ministry of Education, Science and Culture, the Ministry of Health and Welfare, and the Organization for Pharmaceutical Safety and Research.
The sequences reported in this paper have been deposited in the GenBank database (accession nos. AY007568, AY007569, AY007570, AF302234, and AF302235).
Accepted for publication September 26, 2000.
| References |
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-chain genes on chromosome 14. Genomics 1990, 6:252-259[Medline]
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-chymase gene. J Immunol 1997, 159:4367-4375[Abstract]
- and ß-globin gene expression. Mol Cell Biol 1993, 13:4836-4843This article has been cited by other articles:
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