Project description:Microvilli are actin bundle-supported membrane protrusions essential for absorption, secretion, and sensation. Microvilli defects cause human diseases, including gastrointestinal disorders and inherited deafness; however, mechanisms controlling microvilli formation and organization remain unclear. Here, we study microvilli by vitrifying the C. elegans larvae and mouse intestinal tissues with high-pressure freezing, thinning them by cryo-focused ion beam milling, cryo-electron tomography, and sub-tomogram averaging. We show that hundreds of previously unrecognized stick-like structures, which we refer to as nanovilli, decorate the lateral surface of C. elegans and mouse microvilli. The C. elegans 37.5-nm long and 4.5-nm wide nanovilli are composed of the protocadherin family protein CDH-8. Loss of nanovilli slows down animal growth and increases the number of Y-shaped microvilli, intermediate structures when a microvillus splits from its tip and separates into two. Our results indicate that nanovilli space microvilli and suggest a microvilli division model through which microvilli assemble with striking uniformity.
Project description:Microvilli are actin-bundle-supported membrane protrusions essential for absorption, secretion, and sensation. Microvilli defects cause gastrointestinal disorders; however, mechanisms controlling microvilli formation and organization remain unresolved. Here, we study microvilli by vitrifying the Caenorhabditis elegans larvae and mouse intestinal tissues with high-pressure freezing, thinning them with cryo-focused ion-beam milling, followed by cryo-electron tomography and subtomogram averaging. We find that many radial nanometer bristles referred to as nanobristles project from the lateral surface of nematode and mouse microvilli. The C. elegans nanobristles are 37.5 nm long and 4.5 nm wide. Nanobristle formation requires a protocadherin family protein, CDH-8, in C. elegans. The loss of nanobristles in cdh-8 mutants slows down animal growth and ectopically increases the number of Y-shaped microvilli, the putative intermediate structures if microvilli split from tips. Our results reveal a potential role of nanobristles in separating microvilli and suggest that microvilli division may help generate nascent microvilli with uniformity.
Project description:This study aimed to investigate the highly-differentiated urothelial apical surface glycome. The functions of the mammalian urothelium, lining the majority of the urinary tract and providing a barrier against toxins in urine, are dependent on the correct differentiation of urothelial cells, relying on protein expression, modification and complex assembly to regulate the formation of multiple differentiated cell layers. Protein glycosylation, a poorly studied aspect of urothelial differentiation, contributes to the apical glycome and is implicated in the development of urothelial diseases. To enable surface glycome characterization, we have developed a method to collect the tissue apical surface N- and O-glycans. A simple, novel device using basic laboratory supplies was developed for enzymatic shaving of the luminal urothelial surface, with subsequent release and mass spectrometric analysis of apical surface O- and N-glycans; the first normal mammalian urothelial N-glycome to be defined. Trypsinization of superficial glycoproteins was tracked using immunolabelling of the apically-expressed uroplakin 3a protein to optimize enzymatic release, without compromising the integrity of the superficial urothelial layer. The approach developed for releasing apical tissue surface glycans allowed comparison with the N-glycome of total porcine urothelial cells, and thus identification of apical surface glycans as candidates implicated in urothelial barrier function.
Project description:Intestinal surface changes in size and function in response to environmental conditions, but what propels these alterations and what are the metabolic consequences is not clear. Here we show that in mice gut surface enlarges by increasing food amount rather than caloric intake, contributing to an increased absorptive function, and that it can be reversed by reducing daily food amount. Genetic- and environment-induced gut enlargement due to overeating is principally supported by upregulation of the intestinal lipid metabolism and transport. Intestinal knock-out, and pharmacological inhibition of PPARα supress intestinal crypt formation and shorten villi in the small intestine of mice and in human intestinal biopsies, respectively, and diminish post-prandial triglyceride transport and nutrient uptake. PPARα inhibition limits lipid absorption and restricts lipid droplet growth and PLIN2 levels, critical for the droplet formation. This improves lipid metabolism, reduces body adiposity and liver steatosis, suggesting an alternative target for treating obesity.
Project description:We have developed apical-out (AO)- endometrial organoids (EMO) that emulate the in vivo archtecture of endometrial epithelium. The AO-EMO exposes the apical surface of the epithelium. To explore the hormone responsiveness and spatial heterogeneity of AO-EMO, we conducted transcriptomic analysis.
Project description:Shuster SA, Li J, Chon U, Hu MC, Luginbuhl DJ, Udeshi ND, Carey DK, Takeo YH, Xu C, Mani D.R., Han S, Ting AY, Carr SA, Luo L.
Cell-surface proteins mediate cell-cell interactions throughout the lifetime of multicellular organisms, yet there are no general methods for profiling them in vertebrate tissues. Here, we present in-situ cell-surface proteome extraction by extracellular labeling (iPEEL) in mice, which enables cell-type-specific profiling of cell-surface proteomes in native tissues. Applying iPEEL to developing and mature cerebellar Purkinje cells revealed a differential enrichment in cell-surface proteins with post-translational processing and synaptic functions in the developing and mature proteomes, respectively. A proteome-instructed in vivo loss-of-function screen identified a critical role for Armadillo-like helical domain-containing protein 4 (Armh4) in Purkinje cell dendrite morphogenesis. Armh4 overexpression also disrupts dendrite morphogenesis; this effect requires its conserved cytoplasmic domain and is augmented by disruption of endocytosis. Our results highlight the utility of cell-surface proteomic profiling in native tissues in identifying regulators of cell-surface signaling events.
Project description:This project was done in collaboration with Dr. Richard Cummings to examine sialylation of CD44v6 and its role in clearance of neutrophils from inflamed intestinal epithelium. Specifically, we have employed a functional approach using membrane preparations from interferon gamma-stimulated intestinal epithelial cells to generate a monoclonal antibody, designated GM35, which blocks neutrophil transepithelial migration through the promotion of neutrophil adhesion at the apical surface of the intestinal epithelium. Protein biochemistry, sequencing, confocal microscopic analysis, and immunoprecipitation studies all identify the protein ligand for this antibody as CD44v6. However, selective inhibition of O- or N-linked glycosylation reveal that the antibody is specific for an O-linked glycotope and glycoarray analysis of the GM35 antibody by Core H of the Consortium for Functional Glycomics reveal that this antibody binds with high affinity and specificity to a carbohydrate epitope consistent in structure with sLeA. Inhibition of O-linked glycosylation attenuated both GM35 binding and its functional effects as did specific cleavage of sialic acid residues from the cell surface, using neuraminidase, although the functional effects of cleavage were smaller and harder to assess.