Colon mucus segregates the intestinal microbiota from host tissues, but how it organizes to function throughout the colon is unclear. In mice, we found that colon mucus consists of two distinct ...O-glycosylated entities of Muc2: a major form produced by the proximal colon, which encapsulates the fecal material including the microbiota, and a minor form derived from the distal colon, which adheres to the major form. The microbiota directs its own encapsulation by inducing Muc2 production from proximal colon goblet cells. In turn, O-glycans on proximal colon-derived Muc2 modulate the structure and function of the microbiota as well as transcription in the colon mucosa. Our work shows how proximal colon control of mucin production is an important element in the regulation of host-microbiota symbiosis.
The liver has recently been identified as a major organ for destruction of desialylated platelets. However, the underlying mechanism remains unclear. Kupffer cells, which are professional phagocytic ...cells in the liver, comprise the largest population of resident tissue macrophages in the body. Kupffer cells express a C-type lectin receptor, CLEC4F, that recognizes desialylated glycans with an unclear in vivo role in mediating platelet destruction. In this study, we generated a CLEC4F-deficient mouse model (Clec4f
) and found that CLEC4F was specifically expressed by Kupffer cells. Using the Clec4f
mice and a newly generated platelet-specific reporter mouse line, we revealed a critical role for CLEC4F on Kupffer cells in mediating destruction of desialylated platelets in the liver in vivo. Platelet clearance experiments and ultrastructural analysis revealed that desialylated platelets were phagocytized predominantly by Kupffer cells in a CLEC4F-dependent manner in mice. Collectively, these findings identify CLEC4F as a Kupffer cell receptor important for the destruction of desialylated platelets induced by bacteria-derived neuraminidases, which provide new insights into the pathogenesis of thrombocytopenia in disease conditions such as sepsis.
Core 1-derived mucin-type O-glycans (O-glycans) are a major component of gastric mucus with an unclear role. To address this, we generated mice lacking gastric epithelial O-glycans (GEC C1galt1-/-). ...GEC C1galt1-/- mice exhibited spontaneous gastritis that progressed to adenocarcinoma with ∼80% penetrance by 1 yr. GEC C1galt1-/- gastric epithelium exhibited defective expression of a major mucus forming O-glycoprotein Muc5AC relative to WT controls, which was associated with impaired gastric acid homeostasis. Inflammation and tumorigenesis in GEC C1galt1-/- stomach were concurrent with activation of caspases 1 and 11 (Casp1/11)-dependent inflammasome. GEC C1galt1-/- mice genetically lacking Casp1/11 had reduced gastritis and gastric cancer progression. Notably, expression of Tn antigen, a truncated form of O-glycan, and CASP1 activation was associated with tumor progression in gastric cancer patients. These results reveal a critical role of O-glycosylation in gastric homeostasis and the protection of the gastric mucosa from Casp1-mediated gastric inflammation and cancer.
Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by defective intestinal barrier integrity toward the microbiota and epithelial damage. Double cortin-like kinase 1 ...(Dclk1), a marker of intestinal tuft cells, can regulate tissue regenerative responses, but its role in epithelial repair during bacterial-dependent chronic colitis is unclear. We addressed this question using our recently developed mouse model of spontaneous microbiota-dependent colitis induced by mucin-type O-glycan deficiency (DKO), which recapitulates most features of human UC. We generated DKO mice lacking intestinal epithelial Dclk1 (DKO;Dclk1
) and analyzed colitis onset and severity using clinical and histologic indices, immune responses by qPCR and immunostaining, and epithelial responses using proliferation markers and organoid culture. We found 3-4-week-old DKO;Dclk1
mice developed worsened spontaneous colitis characterized by reduced body weight, loose stool, severe colon thickening, epithelial lesions, and inflammatory cell infiltrates compared with DKO mice. The primary defect was an impaired epithelial proliferative response during inflammation. Dclk1 deficiency also reduced inflammation-induced proliferation and growth of colon organoids ex vivo. Mechanistically, Dclk1 expression was important for inflammation-induced Cox2 expression and prostaglandin E2 (PGE2) production in vivo, and PGE2 rescued proliferative defects in Dclk1-deficient colonic organoids. Although tuft cells were expanded in both DKO and DKO;Dclk1
relative to WT mice, loss of Dclk1 was associated with reduced tuft cell activation (i.e., proliferation) during inflammation. Similar results were found in DKO vs. DKO;Dclk1
mice at 3-6 months of age. Our results support that tuft cells, via Dclk1, are important responders to bacterial-induced colitis by enhancing epithelial repair responses, which in turn limits bacterial infiltration into the mucosa.
In prospective memory (PM) research, a common finding is that people are slower to perform an ongoing task with concurrent PM demands than to perform the same task alone. This slowing, referred to as ...costs, has been seen as reflecting the processes underlying successful PM. Historically, costs have been interpreted as evidence that attentional capacity is being devoted toward detecting PM targets and maintaining the intention in working memory; in other words, the claim is that participants are monitoring. A new account, termed delay theory, instead suggests that costs indicate a strategic speed/accuracy adjustment in favor of accuracy, allowing more time for PM-related information to reach its own threshold. Taking a meta-analytic approach, we first review studies in the PM literature that have reported ongoing task performance, both with and without a concurrent PM task, identifying key factors suitable for the meta-analysis. Next, we analyze the data of these studies, using our factors as moderators in a series of metaregressions, to determine their impact on the presence or magnitude of PM-related costs. Finally, we interpret the results of the meta-analysis from both monitoring and delay perspectives in an effort to better understand the nature of costs and what they reflect about the underlying cognitive processes involved in PM.
Public Significance Statement
This meta-analysis supports general findings in prospective memory (memory for to-be-performed intentions) that retrieval can be accomplished by two different routes. Provided that cues are processed in the focus of attention, retrieval can be relatively automatic and does not require any behavioral adjustment. However, if cues do not grab one's attention, extra processing (rehearsal or delay) is necessary for successful prospective memory.
Most platelet membrane proteins are modified by mucin-type core 1-derived glycans (O-glycans). However, the biological importance of O-glycans in platelet clearance is unclear. Here, we generated ...mice with a hematopoietic cell-specific loss of O-glycans (HC C1galt1
−/−). These mice lack O-glycans on platelets and exhibit reduced peripheral platelet numbers. Platelets from HC C1galt1
−/− mice show reduced levels of α-2,3-linked sialic acids and increased accumulation in the liver relative to wild-type platelets. The preferential accumulation of HC C1galt1
−/− platelets in the liver was reduced in mice lacking the hepatic asialoglycoprotein receptor Ashwell–Morell receptor (AMR). However, we found that Kupffer cells are the primary cells phagocytosing HC C1galt1
−/− platelets in the liver. Our results demonstrate that hepatic AMR promotes preferential adherence to and phagocytosis of desialylated and/or HC C1galt1
−/− platelets by the Kupffer cell through its C-type lectin receptor CLEC4F. These findings provide insights into an essential role for core 1 O-glycosylation of platelets in their clearance in the liver.
Mucin-type O-linked oligosaccharides (O-glycans) are primary components of the intestinal mucins that form the mucus gel layer overlying the gut epithelium. Impaired expression of intestinal ...O-glycans has been observed in patients with ulcerative colitis (UC), but its role in the etiology of this disease is unknown. Here, we report that mice with intestinal epithelial cell-specific deficiency of core 1-derived O-glycans, the predominant form of O-glycans, developed spontaneous colitis that resembled human UC, including massive myeloid infiltrates and crypt abscesses. The colitis manifested in these mice was also characterized by TNF-producing myeloid infiltrates in colon mucosa in the absence of lymphocytes, supporting an essential role for myeloid cells in colitis initiation. Furthermore, induced deletion of intestinal core 1-derived O-glycans caused spontaneous colitis in adult mice. These data indicate a causal role for the loss of core 1-derived O-glycans in colitis. Finally, we detected a biosynthetic intermediate typically exposed in the absence of core 1 O-glycan, Tn antigen, in the colon epithelium of a subset of UC patients. Somatic mutations in the X-linked gene that encodes core 1 β1,3-galactosyltransferase-specific chaperone 1 (C1GALT1C1, also known as Cosmc), which is essential for core 1 O-glycosylation, were found in Tn-positive epithelia. These data suggest what we believe to be a new molecular mechanism for the pathogenesis of UC.
ASXL2 is an ETP family protein that interacts with PPARγ. We find that ASXL2−/− mice are insulin resistant, lipodystrophic, and fail to respond to a high-fat diet. Consistent with genetic variation ...at the ASXL2 locus and human bone mineral density, ASXL2−/− mice are also severely osteopetrotic because of failed osteoclast differentiation attended by normal bone formation. ASXL2 regulates the osteoclast via two distinct signaling pathways. It induces osteoclast formation in a PPARγ/c-Fos-dependent manner and is required for RANK ligand- and thiazolidinedione-induced bone resorption independent of PGC-1β. ASXL2 also promotes osteoclast mitochondrial biogenesis in a process mediated by PGC-1β but independent of c-Fos. Thus, ASXL2 is a master regulator of skeletal, lipid, and glucose homeostasis.
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•ASXL2-null mice are osteopetrotic, lipodystrophic, and insulin resistant•Attenuated osteoclastogenesis in ASXL2 KO mice reflects failure of PPARγ activation•c-Fos and PGC1β differentially regulate osteoclast formation and function•ASXL2 independently regulates skeletal and metabolic homeostasis
ASXL2 regulates glucose homeostasis, adipogenesis, and osteoclast differentiation by activating PPARγ. Izawa et al. find that ASXL2-deficient mice are insulin resistant, lipodystrophic, and osteopetrotic. ASXL2 promotes osteoclast formation in a Fos-dependent manner independent of PGC-1β. ASXL2 enhances osteoclast mitochondrial biogenesis in a process mediated by PGC-1β but independent of c-Fos.
Background & Aims Core 1– and core 3–derived mucin-type O-linked oligosaccharides (O-glycans) are major components of the colonic mucus layer. Defective forms of colonic O-glycans, such as Tn ...antigen, frequently are observed in patients with ulcerative colitis and colorectal cancer, but it is not clear if they contribute to pathogenesis. We investigated whether and how impaired O-glycosylation contributes to the development of colitis-associated colorectal cancer using mice lacking intestinal core 1– and core 3–derived O -glycans. Methods We generated mice that lack the core 1– and core 3–derived intestinal O-glycans (DKO mice) and analyzed them, along with mice that lack the intestinal epithelial core 1 O-glycans (IEC C1galt1 - /- mice) or mice that lack core 3 O-glycans (C3 Gnt-/- mice). Intestinal tissues were collected at different time points and analyzed for levels of mucin and Tn antigen, development of colitis, and tumor formation using imaging, quantitative polymerase chain reaction, immunoblot, and enzyme-linked immunosorbent assay techniques. We also used cellular and genetic approaches, as well as intestinal microbiota depletion, to identify inflammatory mediators and pathways that contribute to disease in DKO and wild-type littermates (controls). Results Intestinal tissues from DKO mice contained higher levels of Tn antigen and had more severe spontaneous chronic colitis than tissues from intestinal epithelial cell (IEC) C1galt1 - /- mice, whereas spontaneous colitis was absent in C3GnT - /- and control mice. IEC C1galt1 - /- mice and DKO mice developed spontaneous colorectal tumors, although the onset of tumors in the DKO mice occurred earlier (age, 8–9 mo) than that in IEC C1galt1 -/- mice (approximately age 12 months). Antibiotic depletion of the microbiota did not cause loss of Tn antigen but did reduce the development of colitis and cancer formation in DKO mice. Colon tissues from DKO mice, but not control mice, contained active forms of caspase 1 and increased caspase 11, which were reduced after antibiotic administration. Supernatants from colon tissues of DKO mice contained increased levels of interleukin-1β and interleukin-18, compared with those from control mice. Disruption of the caspase 1 and caspase 11 genes in DKO mice (DKO/ Casp 1/11 - /- mice) decreased the development of colitis, characterized by reduced colonic thickening, hyperplasia, and inflammatory infiltrate, compared with DKO mice. Conclusions Impaired expression of O-glycans causes colonic mucus barrier breach and subsequent microbiota-mediated activation of caspase 1–dependent inflammasomes in colonic epithelial cells of mice. These processes could contribute to colitis-associated colon cancer in human beings.
Altered intestinal O-glycan expression has been observed in patients with ulcerative colitis and colorectal cancer, but the role of this alteration in the etiology of these diseases is unknown. ...O-glycans in mucin core proteins are the predominant components of the intestinal mucus, which comprises part of the intestinal mucosal barrier. Core 3-derived O-glycans, which are one of the major types of O-glycans, are primarily expressed in the colon. To investigate the biological function of core 3-derived O-glycans, we engineered mice lacking core 3 beta1,3-N-acetylglucosaminyltransferase (C3GnT), an enzyme predicted to be important in the synthesis of core 3-derived O-glycans. Disruption of the C3GnT gene eliminated core 3-derived O-glycans. C3GnT-deficient mice displayed a discrete, colon-specific reduction in Muc2 protein and increased permeability of the intestinal barrier. Moreover, these mice were highly susceptible to experimental triggers of colitis and colorectal adenocarcinoma. These data reveal a requirement for core 3-derived O-glycans in resistance to colonic disease.
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