Project description:Background; MUC2 mucin produced by intestinal goblet cells is the major component of the intestinal mucus barrier. MUC2 homo-oligomerizes intracellularly into large secreted polymers which give mucus its viscous properties. The inflammatory bowel disease (IBD) ulcerative colitis is characterized by depleted goblet cells and a reduced mucus layer, whereas goblet cells and the mucus layer are increased in the other major inflammatory bowel disease, Crohnâs disease. Methods and Findings; By murine N-ethyl-N-nitrosourea-mutagenesis we identified two distinct non-complementing missense mutations in Muc2 exons encoding N- and C-terminal homo-oligomerization domains causing an ulcerative colitis-like phenotype. Both strains developed mild spontaneous distal intestinal inflammation, chronic diarrhea, rectal bleeding and prolapse, increased susceptibility to acute and chronic colitis induced by a luminal toxin, aberrant Muc2 biosynthesis, smaller goblet cell thecae (less stored mucin) and a diminished mucus barrier. Enhanced local production of IL-1beta, TNF-alpha and IFN-gamma was seen in the distal colon. The number of leukocytes within mesenteric lymph nodes was increased five-fold and leukocytes cultured in vitro produced both Th1 and Th2 cytokines (IFN-gamma, TNF-alpha and IL-13). Intestinal permeability was increased and the luminal bacterial flora were more heavily coated with immunoglobulin as occurs in IBD. This pathology was accompanied by accumulation of the Muc2 precursor and ultrastructural and biochemical evidence of endoplasmic reticulum (ER) stress in goblet cells, activation of the unfolded protein response, and altered intestinal expression of genes involved in ER stress, inflammation, apoptosis and wound repair. Expression of mutated Muc2 oligomerization domains in vitro demonstrated that aberrant Muc2 oligomerization underlies the ER stress. These models show that mutations in Muc2 oligomerization domains can lead to aberrant assembly of the Muc2 complex leading to ER stress, a depleted mucus barrier and intestinal inflammation. In ulcerative colitis we demonstrate similar accumulation of non-glycosylated MUC2 precursor in goblet cells together with ultrastructural and biochemical evidence of ER stress even in non-inflamed intestinal tissue. Conclusions; The observations that mucin misfolding and ER stress lead directly to intestinal inflammation and that ER stress and goblet cell pathology occur in ulcerative colitis suggest that ER stress-related mucin depletion could be a fundamental component of the pathogenesis of colitis. Experiment Overall Design: 3 individual mice from the Eeyore, Winnie or Wild-type strains were compared as groups. An Affymetrix ID was compared between groups if the ID was Present within two of the three mice within each grouping. IDs were compared by calculating the log2 of Group One average signal divided by Group 2 average signal.
Project description:Background MUC2 mucin produced by intestinal goblet cells is the major component of the intestinal mucus barrier. MUC2 homo-oligomerizes intracellularly into large secreted polymers which give mucus its viscous properties. The inflammatory bowel disease (IBD) ulcerative colitis is characterized by depleted goblet cells and a reduced mucus layer, whereas goblet cells and the mucus layer are increased in the other major inflammatory bowel disease, Crohn’s disease. Methods and Findings By murine N-ethyl-N-nitrosourea-mutagenesis we identified two distinct non-complementing missense mutations in Muc2 exons encoding N- and C-terminal homo-oligomerization domains causing an ulcerative colitis-like phenotype. Both strains developed mild spontaneous distal intestinal inflammation, chronic diarrhea, rectal bleeding and prolapse, increased susceptibility to acute and chronic colitis induced by a luminal toxin, aberrant Muc2 biosynthesis, smaller goblet cell thecae (less stored mucin) and a diminished mucus barrier. Enhanced local production of IL-1beta, TNF-alpha and IFN-gamma was seen in the distal colon. The number of leukocytes within mesenteric lymph nodes was increased five-fold and leukocytes cultured in vitro produced both Th1 and Th2 cytokines (IFN-gamma, TNF-alpha and IL-13). Intestinal permeability was increased and the luminal bacterial flora were more heavily coated with immunoglobulin as occurs in IBD. This pathology was accompanied by accumulation of the Muc2 precursor and ultrastructural and biochemical evidence of endoplasmic reticulum (ER) stress in goblet cells, activation of the unfolded protein response, and altered intestinal expression of genes involved in ER stress, inflammation, apoptosis and wound repair. Expression of mutated Muc2 oligomerization domains in vitro demonstrated that aberrant Muc2 oligomerization underlies the ER stress. These models show that mutations in Muc2 oligomerization domains can lead to aberrant assembly of the Muc2 complex leading to ER stress, a depleted mucus barrier and intestinal inflammation. In ulcerative colitis we demonstrate similar accumulation of non-glycosylated MUC2 precursor in goblet cells together with ultrastructural and biochemical evidence of ER stress even in non-inflamed intestinal tissue. Conclusions The observations that mucin misfolding and ER stress lead directly to intestinal inflammation and that ER stress and goblet cell pathology occur in ulcerative colitis suggest that ER stress-related mucin depletion could be a fundamental component of the pathogenesis of colitis. Keywords: Single gene, multiple mutant comparison
Project description:Intestinal epithelia are protected by a layer of mucin secreted by goblet cells against mechanical and chemical injuries, potent causes of inflammation, and the most abundant secreted intestinal mucin is encoded by the Muc2 gene. Genetic deletion of Muc2 causes intestinal inflammation in early stage and tumors after 3 months. The underlying mechanisms are not clear, but epigenetic alterations, particularly, up- and down-regulated microRNAs are involved in the malignant transformation from colitis to cancer. We used miRNA array to profile the differential expression of the miRNAs in Muc2-/- mouse colonic epithelial lin comparison with those in wild-type mice. Total RNA were extracted from mouse colonic epithelial cells and Muc2-/- and +/+, and the RNA were hybridized on Affymetrix miRNA microarray to determine the alterations of miRNAs during colitis development and its malignant transformation from colitis to cancer. To the end, we found miRNA were differential expressed in the Muc2-/- mice, among them 20 miRNAs were significantly downregulated and 71 miRNAs were significantly upregulated in Muc2-/- mice, in comparison with Muc2+/+ mice (change fold >2 or <0.5; T<0.01, p value< 0.05, q value< 0.05).
Project description:Intestinal epithelia are protected by a layer of mucin secreted by goblet cells against mechanical and chemical injuries, potent causes of inflammation, and the most abundant secreted intestinal mucin is encoded by the Muc2 gene. Genetic deletion of Muc2 causes intestinal inflammation in early stage and tumors after 3 months. The underlying mechanisms are not clear, but epigenetic alterations, particularly, up- and down-regulated microRNAs are involved in the malignant transformation from colitis to cancer. We used miRNA array to profile the differential expression of the miRNAs in Muc2-/- mouse colonic epithelial lin comparison with those in wild-type mice.
Project description:Protein disulfide isomerases (PDIs) aid protein folding and assembly by catalyzing formation and shuffling of cysteine disulfide bonds in the endoplasmic reticulum (ER). Many members of the PDI family are expressed in mammals but the roles of specific PDIs in vivo are poorly understood. A recent homology-based search for additional PDI family members identified anterior gradient homolog 2 (AGR2), a protein originally presumed to be secreted by intestinal epithelial cells, but the function of AGR2 has been obscure. Here we show that AGR2 is expressed in the ER of secretory cells and is essential for in vivo production of intestinal mucin, a large cysteine-rich glycoprotein that forms the protective mucus gel lining the intestine. A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, consistent with a direct role for AGR2 in mucin processing. Despite a complete absence of intestinal mucin, mice lacking AGR2 appeared healthy but were highly susceptible to dextran sodium sulfate-induced experimental colitis, indicating a critical role for AGR2 in protection from environmental insults. We conclude that AGR2 is a unique member of the PDI family that has a specialized and non-redundant role in intestinal mucus production. Keywords: small intestine and colon gene expression profiles for Agr2-/- and littermate control mice
Project description:Protein disulfide isomerases (PDIs) aid protein folding and assembly by catalyzing formation and shuffling of cysteine disulfide bonds in the endoplasmic reticulum (ER). Many members of the PDI family are expressed in mammals but the roles of specific PDIs in vivo are poorly understood. A recent homology-based search for additional PDI family members identified anterior gradient homolog 2 (AGR2), a protein originally presumed to be secreted by intestinal epithelial cells, but the function of AGR2 has been obscure. Here we show that AGR2 is expressed in the ER of secretory cells and is essential for in vivo production of intestinal mucin, a large cysteine-rich glycoprotein that forms the protective mucus gel lining the intestine. A cysteine residue within the AGR2 thioredoxin-like domain forms mixed disulfide bonds with MUC2, consistent with a direct role for AGR2 in mucin processing. Despite a complete absence of intestinal mucin, mice lacking AGR2 appeared healthy but were highly susceptible to dextran sodium sulfate-induced experimental colitis, indicating a critical role for AGR2 in protection from environmental insults. We conclude that AGR2 is a unique member of the PDI family that has a specialized and non-redundant role in intestinal mucus production. Keywords: small intestine and colon gene expression profiles for Agr2-/- and littermate control mice DNA miocroarrays were used to analyze small intenstine and colon mRNA expression of AGR2 KO and littermate control mice. The experiment incorporated a 1 color design and used Agilent arrays that contained roughly 44,00 60mer probes that provide complete coverage of the mouse genome. 12 arrays were hybridized and represent 8 small intestine samples ( 4 each KO and WT) and 4 colon samples (2 each KO and WT)
Project description:Missense mutations in transcription factor GATA1 underlie several distinct forms of anemia and thrombocytopenia. Clinical severity depends on the site and type of substitution, and distinct substiutions of the same residue produce disparate phenotypes. To investigate the effect of GATA1 missense mutations on erythroid differentiation we expressed conditionally activated wild type or mutant versions of GATA1 in GATA1-null G1E cells. We used gene expression microarrays to explore how GATA1 missense mutations affect erythroid transcription programs. GATA1-null G1E cells ectopically expressing conditionally activated versions of GATA1 (GATA1-ER, GATA1(R216Q)-ER, GATA1(R216W)-ER, GATA1(D218G)-ER, or GATA1(D218Y)-ER) were treated with estradiol for 24 hours to initiate erythroid differentiation. Total RNA from treated cells was extracted for Affymetrix microarray. All data were generated from three biological replicates. Transcript levels were compared in wild type vs. mutant lines.
Project description:Mucus has an important protective function and forms a barrier that minimizes the bacterial contact with the colonic epithelium. It is organized as a complex network with several specific proteins of which most are still poorly understood. Abundant proteins in intestinal mucus, in addition to the mucin MUC2, are CLCA1 and FCGBP. FCGBP is expressed in all intestinal goblet cells and secreted into the mucus. It is comprised of repeated von Willebrand Factor D (vWD) domain assemblies, of which most have a GDPH amino acid sequence. This sequence can be autocatalytically cleaved, as previously found in MUC2 and MUC5AC. We show that all vWD with a GDPH sequence are cleaved, and that these cleavages occur early during biosynthesis in the endoplasmic reticulum. All cleaved fragments remained connected by a disulfide bond within each vWD domain. The cleavage can generate a C-terminal reactive Asp-anhydride that could react with other molecules, such as MUC2, but this was not observed. Quantitative analyses by mass spectrometry showed that, in chaotropic solutions, FCGBP was mainly soluble whereas MUC2 was insoluble, and most of the secreted FCGBP was not covalently bound to MUC2. As its name indicates, FCGBP has been suggested to bind IgG, something that was not possible to reproduce in vitro using purified proteins. The function of FCGBP is still unknown, but our results suggest that the Asp-anhydrides do not contribute to covalent crosslinking in the mucin framework nor does FCGBP incorporate IgG in mucus.
Project description:Mucus has an important protective function and forms a barrier that minimizes the bacterial contact with the colonic epithelium. It is organized as a complex network with several specific proteins of which most are still poorly understood. Abundant proteins in intestinal mucus, in addition to the mucin MUC2, are CLCA1 and FCGBP. FCGBP is expressed in all intestinal goblet cells and secreted into the mucus. It is comprised of repeated von Willebrand Factor D (vWD) domain assemblies, of which most have a GDPH amino acid sequence. This sequence can be autocatalytically cleaved, as previously found in MUC2 and MUC5AC. We show that all vWD with a GDPH sequence are cleaved, and that these cleavages occur early during biosynthesis in the endoplasmic reticulum. All cleaved fragments remained connected by a disulfide bond within each vWD domain. The cleavage can generate a C-terminal reactive Asp-anhydride that could react with other molecules, such as MUC2, but this was not observed. Quantitative analyses by mass spectrometry showed that, in chaotropic solutions, FCGBP was mainly soluble whereas MUC2 was insoluble, and most of the secreted FCGBP was not covalently bound to MUC2. As its name indicates, FCGBP has been suggested to bind IgG, something that was not possible to reproduce in vitro using purified proteins. The function of FCGBP is still unknown, but our results suggest that the Asp-anhydrides do not contribute to covalent crosslinking in the mucin framework nor does FCGBP incorporate IgG in mucus.