Epithelium-Intrinsic MicroRNAs Contribute to Mucosal Immune Homeostasis by Promoting M-Cell Maturation
Epithelium-Intrinsic MicroRNAs Contribute to Mucosal Immune Homeostasis by Promoting M-Cell Maturation
Gaku Nakato 0 1 2 3
Koji Hase 0 1 2 3
Takao Sato 0 1 2 3
Shunsuke Kimura 0 1 2 3
Sayuri Sakakibara 0 1 2 3
Machiko Sugiyama 0 1 2 3
Yuuki Obata 0 1 2 3
Misaho Hanazato 0 1 2 3
Toshihiko Iwanaga 0 1 2 3
Hiroshi Ohno 0 1 2 3
0 1 Laboratory for Intestinal Ecosystem, RCAI, RIKEN Center for Integrative Medical Sciences (IMS-RCAI), Kanagawa, Japan, 2 Laboratory for Immunobiology, Graduate School of Medical Life Science, Yokohama City University , Kanagawa , Japan , 3 Division of Mucosal Barriology, International Research and Development Center for Mucosal Vaccines, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan , 4 PRESTO , Japan Science and Technology Agency, Tokyo, Japan, 5 Laboratory of Histology and Cytology, Graduate School of Medicine, Hokkaido University , Hokkaido , Japan , 6 Graduate School of Medical and Pharmaceutical Sciences, Chiba University , Chiba , Japan
1 Funding: The work was supported by the following: From The Japan Society for the Promotion of Science, Grant-in-Aid for Research Activity Start-up (G.N.) (Grant number: 22890238) , Grants-in-Aid for Young Scientists (B) (G.N.) (Grant number: 24790485) , Grants-in-Aid for Young Scientists (A) (K. H.) (Grant number: 22689017), Grants-in-Aid for Scientific Research (A) (H.O.) (Grant number: 24249029); From The Ministry of Education , Culture, Sports , Science and Technology of Japan , AMED-
2 Editor: Motoyuki Otsuka, The University of Tokyo , JAPAN
3 a Current address: Dermatology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America ¤b Current address: Division of Biochemistry, Faculty of Pharmacy, Keio University , Tokyo , Japan
M cells in the follicle-associated epithelium (FAE) of Peyer's patches (PPs) serve as a main portal for external antigens and function as a sentinel in mucosal immune responses. The scarcity of these cells has hampered identification of M cell-specific molecules. Recent efforts have begun to provide insight into antigen transcytosis and differentiation of M cells; however, the molecular mechanisms underlying these processes are not fully elucidated. Small non-coding RNAs including microRNA (miRNA) have been reported to regulate gene expression and control various biological processes such as cellular differentiation and function. To evaluate the expression of miRNAs in FAE, including M cells, we previously performed microarray analysis comparing intestinal villous epithelium (VE) and PP FAE. Here we confirmed FAE specific miRNA expression levels by quantitative PCR. To gain insight into miRNA function, we generated mice with intestinal epithelial cell-specific deletion of Dicer1 (DicerΔIEC) and analyzed intestinal phenotypes, including M-cell differentiation, morphology and function. DicerΔIEC mice had a marked decrease in M cells compared to control floxed Dicer mice, suggesting an essential role of miRNAs in maturation of these cells. Furthermore, transmission electron microscopic analysis revealed that depletion of miRNA caused the loss of endosomal structures in M cells. In addition, antigen uptake by M cells was impaired in DicerΔIEC mice. These results suggest that miRNAs play a significant
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
role in M cell differentiation and help secure mucosal immune homeostasis.
CREST, AMED, Grant-in-Aid For Scientific Research
on Priority Areas (K.H. and H.O.) (Grant number:
19041072); From The Japan Agency for Medical
Research and Development, Advanced Research
and Development Programs for Medical Innovation
(H.O.) (Grant number: 15gm0710009h0002);
Sasakawa Scientific Research Grant from the Japan
Science Society (G.N.) (Grant number:22-453); The
Sumitomo Foundation (K.H.) (Grant number:100737);
The Uehara Memorial Foundation (K.H.) (Grant
number:201120109); and Takeda Science
Foundation (H.O.) (http://www.takeda-sci.or.jp/).
Competing Interests: The authors have declared
that no competing interests exist.
The gastrointestinal tract is the site for digestion and absorption of nutrients, but at the
same time it is exposed to foreign antigens including enormous numbers of commensal
microorganisms as wells as pathogens. To protect from these foreign antigens, the
gastrointestinal tract is equipped with a specialized gut-associated lymphoid tissue (GALT) as well as
a variety of non-immunologic barriers, including gastric acid, pancreatic juice, bile,
glycocalyx, a mucus layer, intercellular junctional complexes (e.g., tight junctions and adherens
junctions), and rapid cell turnover [
]. The mucosal surface is also protected by secretory
antibody, especially immunoglobulin A, as well as antimicrobial peptides secreted from
Paneth cells and enterocytes. In addition, GALT serves as the leading edge of an
immunological barrier. GALT, comprised of Peyer’s patches (PPs), isolated lymphoid follicles, appendix
and colonic patches is the main inductive site for mucosal immune responses . Luminal
surfaces of PPs are covered by the follicle-associated epithelium (FAE), which contains
relatively limited numbers of goblet cells and enteroendocrine cells but harbors a unique subset
of epithelial cells, membranous or microfold cells (M cells) [
]. Unlike the villus epithelium
(VE), the FAE is specially designed to promote contact with luminal antigens to induce
mucosal immune responses. For example, there are limited numbers of goblet cells in FAE
and a thinner mucus layer compared to the VE region [
]. It has also been reported that FAE
enterocytes lack polymeric Ig receptors for the local transport and secretion of secretory IgA
]. In addition, antimicrobial peptide-producing Paneth cells are not present in the FAE
]. These features provide easier access to FAE by luminal particulate antigens such
as bacteria and viruses. By contrast, the VE consists primarily of enterocytes, with scattered
goblet cells and occasional enteroendocrine cells. The main function of the VE is the
digestion and absorption of nutrients. Thus, the cellular composition and function of FAE and
VE are quite different; however, the mechanisms that differentially regulate FAE and VE
differentiation remain unknown.
M cells are specialized epithelial cells located in the FAE [
] that continuously sample and
transport luminal antigens to the underlying GALT. The antigens are then captured by
immature dendritic cells (DCs) residing in the subepithelial dome region beneath the FAE. The
antigen-primed DCs undergo maturation and migrate to the T-cell area of GALT to present
antigens to T cells, leading to activation of antigen-specific B cells and ultimately the
production of IgA antibodies by lamina propria plasma cells [
]. Accumulated studies have begun to
provide insight into antigen transcytosis and differentiation of M cells [
]; however, the
molecular mechanisms underlying these processes are not fully elucidated.
MicroRNAs (miRNA) are ~19–25 nucleotide non-coding RNA molecules that regulate
gene expression via repression of target mRNA. Binding of miRNAs to the 3' untranslated
region of target mRNAs leads to translation inhibition or mRNA degradation [
substantial number of studies have shown that miRNAs regulate many biological processes including
cell or tissue development timing, differentiation and growth control [
]. The miRNAs are
transcribed by RNA polymerase II as primary transcripts that are later processed by the RNase
III-type endonuclease called Dicer into mature miRNAs. However, the complete loss of Dicer
leads to embryonic lethality in mice [
], making its many functions difficult to study. To
elucidate the importance of miRNAs in a particular tissue development or cell differentiation
process, many groups have therefore used tissue or cell type-specific recombination approaches to
deplete the Dicer1 gene[
]. Expression profiles and functions of miRNAs in intestinal
epithelium have been examined in jejunal and colonic mucosa , but those in FAE remain
unknown. We generated intestinal epithelium-specific Dicer1 deletion mice and investigated
the role of miRNA in this tissue, focusing on the FAE. Here we report that miRNAs in FAE
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contribute to M-cell differentiation and that loss of miRNAs leads to impaired antigen
transcytosis function via depletion of endosomes.
Materials and Methods
BALB/cA and C57BL/6 mice were purchased from CLEA Japan. Dicer1 flox mice (DicerF/F)
were purchased from The Jackson laboratory and were backcrossed onto the C57BL/6
background. To generate intestinal epithelial cell-specific Dicer1 knockout (DicerΔIEC) mice, we
crossed Dicer1 flox mice with villin-cre transgenic mice. DicerΔIEC and control DicerF/F
littermates were maintained under specific pathogen-free conditions. Mice are sacrificed by cervical
dislocation. Animal experiments were approved by the Animal Research Committees of
RIKEN and Yokohama City University [(Permit Numbers Kei 24–005 (RIKEN) and T11-001
(Yokohama City University)].
Preparation FAE and VE for quantitative PCR
PPs were harvested from mice using curved scissors and flushed out the luminal contents with
Hank’s balanced salt solution (HBSS). PPs were soaked in HBSS containing 30 mM EDTA for
20 min at 4°C. Epithelial cell sheets were peeled off from PPs, and FAE and VE were dissected
by using 26G needles under stereomicroscopic monitoring ([
]) to obtain epithelium sheets
of FAE and VE ([
]). To count and calculate follicle numbers and surface area, PPs
incubated with 3% acetic acid for 15 min at room temperature were analyzed using a SZX16
stereoscopic microscope (Olympus). Follicle surface area was calculated using DP2-BSW (Olympus).
Quantitative PCR of miRNA
Total RNA including the small RNA fraction was extracted from murine FAE and VE using a
mirVana kit (Ambion) and was reverse transcribed with a Taqman MicroRNA Reverse
Transcription Kit (Applied Biosystems). Quantitative PCR was performed to quantify miRNA
expression levels using the TaqMan Universal PCR Master Mix II w/ UNG (Applied
Biosystems) and the Thermal Cycler Dice Real Time System (TAKARA). Values were normalized
relative to the small nucleolar RNA Sno202. Specific primer sets were purchased from Applied
Quantitative PCR of mRNA
Total RNA was extracted from murine FAE and VE using a mirVana kit (Ambion) and was
reverse-transcribed using ReverTra Ace-α (TOYOBO). Quantitative PCR was performed to
quantify mRNA expression levels using the SYBR Premix Ex Taq and the Thermal Cycler Dice
Real Time System (TAKARA). Values were normalized to Gapdh. Specific primer pairs for
each gene are listed in Table 1.
Hematoxylin and Eosin (H&E) stain
Paraffin embedded tissue sections were deparaffinized and rehydrated. Then, sections were
stained with hematoxylin and eosin.
Whole mount immunostaining
PPs were excised from the small intestine, fixed with Cytofix/Cytoperm (BD Biosciences) for
1 hour at 4°C and then incubated with 10 μg/ml anti-CD16/32 monoclonal antibody (93;
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eBioscience) / 0.1% saponin / 0.2% BSA in phosphate buffered saline (PBS) to block
non-specific Fc binding. The whole mount specimens were then stained overnight at 4°C with 1 μg/ml
Alexa Fluor 488-conjugated anti-mouse GP2 (2F11C3; MBL) and 1 U/ml Alexa Fluor
555-conjugated Phalloidin (Molecular probes). The specimens were analyzed with a DM-IRE2 confocal
laser scanning microscope and Leica confocal software (Leica Microsystems). To count M cells
number, FAE sheet were peeled off from PPs as describe above. Then, FAE sheets were fixed
with Cytofix/Cytoperm (BD Biosciences) for 1 hour at 4°C and incubated with 10 μg/ml
antiCD16/32 monoclonal antibody (93; eBioscience) / 0.1% saponin / 0.2% BSA in phosphate
buffered saline (PBS) to block non-specific Fc binding. The whole mount specimens were then
stained overnight at 4°C with 1 μg/ml Alexa Fluor 488-conjugated anti-mouse GP2 (2F11C3;
MBL). The specimens were analyzed with a BX51 fluorescence microscope (Olympus). M cell
count and FAE area measurement were examined using ImageJ software.
Scanning electron microscopy
PPs were excised and fixed for 2.5 hours with 2.5% glutaraldehyde in 0.1 M phosphate buffer
(pH7.4). The tissues were completely dehydrated in a graded ethanol series. Specimens were
coated with a gold layer using a sputter coater MSP-1S (Shinku Device) and observed by SEM
Transmission electron microscopy
PPs and VE were excised and fixed for 48 hours with 2.5% glutaraldehyde in 0.1 M phosphate
buffer (pH7.4). The tissues were cut into 1–2 mm pieces, immersed for an additional 4 hours in
the same fixative, postfixed for 1.5 hours with 1% OsO4 dissolved in distilled water, dehydrated
in a graded series of ethanol, and embedded in Epon. Ultrathin sections were cut on an
ultramicrotome and stained with uranyl acetate and lead citrate for observation under an electron
microscope (H7100, Hitachi).
Evaluation of bead uptake
8- to 10-week-old DiecrF/F or DicerΔIEC mice (four mice per group) were inoculated by gavage
with 1 x 1011 FluoSpheres (Invitrogen). After 4 hours, PPs were dissected and incubated at
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25°C in sterile PBS. Prepared frozen sections were examined using a BX51 fluorescence
microscope (Olympus) and beads in PP follicles were counted manually.
Evaluation of oral infection
8- to 10-week-old DiecrF/F or DicerΔIEC mice (five mice per group) were inoculated
intragastrically by gavage with 0.2 ml of 0.1 M sodium bicarbonate to neutralize gastric acid. Mice were
then inoculated intragastrically by gavage with 1 x 108 CFU of Yersinia enterocolitica
(ATCC27729). After 24 hours, three PPs from the ileal end were dissected and incubated at
25°C in sterile PBS containing 20 μg/ml gentamicin for 30 minutes, homogenized in sterile PBS
and plated on Yersinia Selective Agar base (OXID) with Yersinia selective supplement (OXID)
to determine CFU.
Statistical analysis was performed with the Mann-Whitney U test. Differences were considered
as significant at P < 0.05.
Different miRNA expression profiles in FAE and VE
To examine the miRNA expression profile in FAE, we have previously dissected FAE and VE
surrounding the FAE of PPs [
] and compared their miRNA expression profiles by
microarray analysis. We identified 43 miRNAs up-regulated at least two-fold in FAE compared with
VE and 9 miRNAs down-regulated in FAE by at least two-fold . The expression levels of
the 43 miRNAs upregulated in FAE were further examined in C57BL/6 and BALB/cA mice by
quantitative PCR (q-PCR). Only 5 miRNAs were commonly up-regulated at least two-fold in
FAE compared with VE in both strains (Fig 1 and data not shown). We therefore reasoned that
these five miRNAs are likely involved in FAE-specific translational regulation.
miRNAs in FAE contribute to M-cell maturation
To elucidate the functions of miRNAs in intestinal epithelium, including FAE, we generated
mice lacking mature miRNAs in intestinal epithelium by crossing floxed Dicer mice to
villincre mice. Both DicerΔIEC FAE and VE displayed approximately 85–95% reduction of Dicer1
mRNA expression levels compared with DicerF/F (S1 Fig) DicerΔIEC mice showed decreased
number of goblet cells and increased number of apoptotic cells in the crypt region. In addition,
the number of Paneth and enteroendocrine cells was similar in both mice. These phenotypes
are consistent with previous reports [
]. On the other hands, villous length and PPs structure
in DicerΔIEC were similar to DicerF/F (Fig 2A and 2B). Total number of PPs and follicles
remained unchanged in DicerΔIEC mice (Fig 2C, S2A and S2B Fig). By contrast, the surface
area of FAE in DicerΔIEC was less than that of control floxed Dicer (DicerF/F) mice (Fig 2C, S2A
and S2B Fig). In addition, whole mount immunostaining revealed that the density of M cells in
FAE was decreased by more than half in DicerΔIEC compared to DicerF/F mice (Fig 2D and 2E,
Recent studies suggests that maturing M cells can be classified into distinct differentiation
stages based on the expression of M-cell markers (Fig 3A and [
]), therefore, we next
examined their expression by q-PCR. The mRNA levels of SpiB, Ccl9 and Gp2 were
significantly decreased in DicerΔIEC FAE compared to DicerF/F; however, expression of the earliest
known M-cell marker Marcksl1 was the same in both mice (Fig 3B). We also examined the
morphology of M cells by electron microscopy. Scanning electron micrographs of FAE showed
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Fig 1. miRNA expression profiles in intestinal epithelium. Q-PCR analysis was performed for miRNA
expression in FAE and VE. The relative levels of each miRNA relative to the small nucleolar RNA Sno202 are
shown. Values are mean ± SE of three samples from different mice. *P<0.05.
a decrease in the number of cells with the typical M-cell morphology, i.e. organized microvilli
on the apical surface, in DicerΔIEC FAE (Fig 4A). To understand in more detail the M-cell
morphology, we also performed transmission electron microscopic (TEM) analysis, confirming the
loss of organized microvilli (Fig 4B). On the other hand, morphology of microvilli in DicerΔIEC
VE was similar to that in DicerF/F (Fig 4B). These results are consistent with whole mount
immunostaining. Taken together, these results indicate that miRNAs in FAE are important for
Fig 2. Total number of M cells in Peyer’s patches is decreased in DicerΔIEC mice. (A) H&E staining of
small intestines VE region of DicerΔIEC and DicerF/F. (B) H&E staining in PPs of DicerΔIEC and DicerF/F. (C)
The total number of follicles and surface area in DicerΔIEC and DicerF/F. Data are means± SE (n = 3).
*P < 0.05. (D) Whole mount immunostaining of PPs with anti-GP2 (red) and F-actin (green) analyzed using a
confocal microscope. Scale bars: 100 μm (E) M cell number/mm2 in FAE of each mouse strain. Data are
means and SE. *P < 0.05.
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Fig 3. FAE miRNAs involved in M cell maturation. (A) Flowchart of M cell maturation. (B) Q-PCR analysis
was performed for Marcksl1, SpiB, Ccl9 and Gp2 mRNA expression in DicerΔIEC FAE and DicerF/F FAE. The
relative expression levels of each gene to Gapdh are shown. Values represent the mean ± SD of three
samples from different mice. *P < 0.05 **P < 0.01.
Impaired antigen uptake by DicerΔIEC M cells
Many endocytic/endosomal structures were observed by TEM in the DicerF/F M cells, whereas
these structures were nearly absent in the DicerΔIEC M cells (Fig 4B and 4C), suggesting that
endocytic activity is impaired in DicerΔIEC M cells.
To verify this point, we inoculated mice with fluorescent beads via the oral route. The beads
were easily detected in the subepithelial dome region of DicerF/F PPs, whereas very few were
observed in DicerΔIEC PPs (Fig 5A and 5B). We further investigated the impaired antigen
uptake by M cells in the PPs of DicerΔIEC mice by examining the translocation of orally
administered Yersinia enterocolitica and found that it was markedly reduced in DicerΔIEC compared
to DicerF/F mice (Fig 5C). Taken together, our results indicate that FAE miRNA is important
for both morphological and functional maturation of M cells.
To ensure efficient antigen uptake, the cellular composition and function of FAE differs
significantly from VE. Besides absorptive enterocytes, the VE is populated with scattered goblet cells
and enteroendocrine cells, while the FAE consists of very few goblet and enteroendocrine cells
and instead contains M cells [
]. We identified five miRNAs that are two-fold or more
upregulated in FAE compared to VE in C57BL/6 (Fig 1) and BALB/cA mice (data not shown), thus it
seemed likely that miRNAs may affect or regulate the cell distribution or function in FAE.
To test this possibility, we generated intestinal epithelium-specific Dicer-KO (DicerΔIEC)
mice. A similar strategy has been taken by others, who have reported that miRNAs are involved
in goblet-cell differentiation in the intestine [
], supporting the notion that this is a reliable
approach to examine the role of miRNAs in intestinal epithelial cells. The total number of PPs
as well as lymphoid follicles remained unchanged, but the size of the FAE in DicerΔIEC mice
was smaller than in DicerF/F mice (Fig 2C). In addition, the total number of immune cells in
PPs also decreased in DicerΔIEC mice (data not shown). Chemokines specifically expressed by
the FAE are thought to be important for recruitment of immune cells to PPs [
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Fig 4. Morphology of M cells in DicerΔIEC. Electron micrographs of DicerF/F and DicerΔIEC PP. (A) Surface
of FAE by scanning electron microscopy. Arrowheads indicate M cells. Scale bars: 10 μm (B) Transmission
electron micrographs of an M cell in FAE and enterocyte in VE. Scale bars: 1.8 μm (C) High magnification
image of (B). Arrow indicate the endosomes in M cell. Scale bars: 500 nm.
example, CXCL16 expressed by the FAE plays a critical role in the recruitment and retention of
T cells in the subepithelial dome , while CCL20 derived from FAE is important for
migration of CCR6hiCD11cint B cells [
]. Furthermore, CCL20 is also a crucial chemokine for M-cell
differentiation and/or maintenance, since mice lacking CCR6, the sole receptor for CCL20, had
a reduction in M cells [
]. Of note, Ccl20 and Cxcl16 mRNA was decreased in DicerΔIEC
FAE compared to DicerF/F (data not shown). Collectively, the phenotype of DicerΔIEC PPs
described in this study may at least partly reflect the dysregulated expression of these
chemokines by intestinal epithelial miRNAs.
DicerΔIEC mice had a prominent decrease in the number of mature M cells (Fig 2D and 2E,
S3 Fig). The M-cell reduction was confirmed by electron microscopy (Fig 4A). Concomitantly,
one of the main functions of M cells, mucosal antigen transcytosis, was impaired in DicerΔIEC
mice PP, as measured by uptake of beads and by bacterial translocation (Fig 5A, 5B and 5C). In
addition, the small number of M cells remaining in DicerΔIEC FAE lack endocytic/endosomal
structures normally observed (Fig 4B and 4C). These results indicate that FAE miRNAs are
important for differentiation and/or maturation of functional M cells.
In this study, we identified five miRNAs that were up-regulated at least two-fold in FAE
compared with VE in both C57BL/6 and BALB/cA mice (Fig 1). Among them, two miRNAs,
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Fig 5. Impaired antigen uptake by DicerΔIEC M cells. (A) DicerΔIEC and DicerF/F mice were inoculated by
gavage with 1 x 1011 FluoSpheres. After 4 hours, frozen sections were prepared to examine translocated
beads in PPs. Scale bars: 100 μm (B) Count data of beads taken up in PP each mouse strain. Data are
expressed as the mean ± SE of four different samples for each group. **P < 0.01. (C) DicerΔIEC and DicerF/F
mice were inoculated intragastrically by gavage with 1 x 108 CFU of Yersinia enterocolitica. After 24 hours,
the bacterial translocation to Peyer’s patches was examined by plating PP homogenates. Data are
expressed as the mean ± SE of five different mice/each group. *P < 0.05.
miR34a and miR365, might be involved in M-cell maturation. The miR34a is a member of the
miR-34 family, which is conserved from C. elegans to mammals. Recent studies have shown
that miR-34a regulates the notch signaling pathway [
], for example, miR-34a represses
Delta-like 1 (Dll1) [
] and miR34a down-regulation leads to increased Notch1 and Jag1
]. We showed in this study that the expression of M-cell marker genes such as
SpiB, Ccl9 and Gp2 was much less in DicerΔIEC mice than in DicerF/F mice (Fig 3B). The Ets
family transcription factor Spi-B plays a critical role in M-cell differentiation [
mice showed a phenotype similar to the Spib-knockout mice [
], which raises the possibility
that miRNAs regulate Spib expression. It has been reported that Dll1-induced Notch1 signaling
induces down-regulation of Spi-B in plasmacytoid DCs [
]. Taken together with our results, it
seems possible that miR34a also regulates Dll1, Jag1 and Notch1 in FAE and this might, in turn,
promote Spi-B expression required for M-cell maturation. Because miR34a was highly
expressed in FAE among miRNAs examined, we tried to generate miR34a null mice for the
examination of M cells development. However, miR34a heterozygous crossing could not give
rise to any miRNA34a null mice, The result may indicate that miRNA34a plays a crucial role in
murine embryonic development, and precludes the possibility for us to use these mice to study
the role miR34a in M-cell/FAE development.
During colonic epithelium maturation, miR365 has been reported to regulate Myb-related
protein B (MYBL2) expression, which is important in both cell cycle regulation and
differentiation in various biological processes [
]. Reduction of MYBL2 expression is important for
acquisition of full differentiation of colonic epithelial cell lines [
]. However Mybl2 mRNA
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expression was similar expression levels between DicerΔIEC FAE and DicerF/F (S4 Fig).
Therefore, the Mybl2 expression level controlled by miR365 may not involve in M-cell maturation.
Functions of the other three miRNAs, miR149, miR193 and miR466a-3p, have not been
previously examined in the intestinal epithelium in vitro or in vivo. Generation of individual or
multiple miRNA null or individual miRNA conditional knockout mice will help to further
understand the mechanisms of M-cell maturational regulation by these miRNAs.
In conclusion, our data suggest that intestinal epithelial miRNAs are critical for the
morphological and functional maturation of M cells. The appropriate regulation of gene expression
by intestinal epithelial miRNAs should contribute to the cell fate decision and/or maintenance
of cellular differentiation and functions in mucosal immune homeostasis.
S1 Fig. Dicer1 mRNA dramatically decrease DicerΔIEC epithelium. Q-PCR analysis was
performed for Dicer1 mRNA expression in FAE and VE in DicerΔIEC and DicerF/F. The relative
expression levels of each gene to Gapdh are shown. Values represent the mean ± SD of three
samples from different mice. P < 0.05.
S2 Fig. Compare follicle number between DicerΔIEC and DicerF/F. Stereomicroscopic images
of DicerF/F PPs (A) and DicerΔIEC PPs (B) after citric acid fixation. Asterisk showed individual
follicle. Solid line in (A) showed representative area of calculated follicle surface. Scale bars:
S3 Fig. GP2 positive M cell decreased in FAE. Whole mount immunostaining of isolated
epithelial sheet with anti-GP2 (Green) analyzed using BX51 fluorescence microscope (Olympus).
Solid line showed FAE region. Scale bars: 200 μm.
S4 Fig. Mybl2 levels was similar between DicerF/F FAE and DicerΔIEC FAE. Q-PCR analysis
was performed for Mybl2 mRNA expression in DicerΔIEC FAE and DicerF/F FAE. The relative
expression levels of each gene to Gapdh are shown. Values represent the mean ± SD of three
samples from different mice.
We would like to thank P. D. Burrows for critical review and English editing of the manuscript
and Y. Yamada for secretarial assistance.
Conceived and designed the experiments: GN KH HO. Performed the experiments: GN TS SK
SS MS YO MH TI. Analyzed the data: GN TS SK SS MS YO MH TI. Wrote the paper: GN HO.
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