High resolution dynamic mapping of the C. elegans intestinal brush border

The intestinal brush border is made of an array of microvilli that increases the membrane surface area for nutrient processing, absorption, and host defense. Studies on mammalian cultured epithelial cells uncovered some of the molecular players and physical constrains required to establish this apical specialized membrane. However, the building and maintenance of a brush border in vivo has not been investigated in detail yet. Here, we combined super-resolution imaging, transmission electron microscopy and genome editing in the developing nematode C. elegans to build a high-resolution and dynamic localization map of known and new brush border markers. Notably, we show that microvilli components are dynamically enriched at the apical membrane during microvilli outgrowth and maturation but become highly stable once microvilli are built. This new toolbox will be instrumental to understand the molecular processes of microvilli growth and maintenance in vivo as well as the effect of genetic perturbations, notably in the context of disorders affecting brush border integrity.

High resolution dynamic mapping of the C. elegans intestinal brush border

The intestinal brush border is made of an array of microvilli that increases the membrane surface area for nutrient processing, absorption, and host defence. Studies on mammalian cultured epithelial cells uncovered some of the molecular players, structural components and physical constrains required to establish this apical specialized membrane. However, the building and maintenance of a brush border in vivo has not been investigated in detail yet. Here, we combined super-resolution imaging, transmission electron microscopy and genome editing in the developing nematode C. elegans to build a high-resolution and dynamic localization map of known and new markers of the brush border. Notably, we show that microvilli components are dynamically enriched at the apical membrane during microvilli outgrowth and maturation but become highly stable when microvilli are built. This new mapping tool will be instrumental to understand the molecular processes of microvilli growth and maintenance in vivo as well as the effect of genetic perturbations, notably in the context of disorders affecting the brush border integrity.

Lactobacillus plantarum IS-20506 Probiotic Restores Galectin-4 and Myosin-1a Expressions in Duodenum, Jejunum and Ileum of Lipopolysaccharide-induced Rats

BACKGROUND: Galectin-4 and Myosin-1a are important proteins for normal intestinal brush border structure and composition. Damage of these proteins by inflammation may alter digestion, absorption and barrier function. Probiotic has been widely known in maintaining gut health. However, the molecular mechanism of Lactobacillus plantarum IS-2056 probiotic in repairing intestinal brush border is not well defined. Therefore, current study was conducted by investigating the Galectin-4 and Myosin-1a expressions in a rodent model.METHODS: Male Wistar rats were induced with/without lipopolysaccharide (LPS) and treated with/without L. plantarum IS-2056 probiotic. On the seventh day, duodenum, jejunum, and ileum were collected and analyzed with western blot and immunohistochemistry for Galectin-4 and Myosin-1a expressions.RESULTS: Rats administrated with L. plantarum IS-2056 probiotic showed significant increase of Galectin-4 and Myosin-1a expressions in duodenum, jejunum, and ileum compared to the control group (p<0.05). While in control group, Galectin-4 level tended to increase in more distal of intestinal segment and Myosin-1a level tended to decrease in more distal intestinal segment.CONCLUSION: L. plantarum IS-20506 probiotic may facilitate the repairment of damaged intestinal brush border as demonstrated by significant restoration of Galectin-4 and Myosin-1a expressions in duodenum, jejunum, and ileum of LPS-induced rats.KEYWORDS: Lactobacillus plantarum, IS-20506, probiotic, galectin-4, myosin-1a, duodenum, jejunum, ileum

In vitro Gastrointestinal Models for Prebiotic Carbohydrates: A Critical Review

Background: In the last decade, various consortia and companies have created standardized digestion protocols and gastrointestinal simulators, such as the protocol proposed by the INFOGEST Consortium, the simulator SHIME, the simulator simgi®, the TIM, etc. Most of them claim to simulate the entire human gastrointestinal tract. However, few results have been reported on the use of these systems with potential prebiotic carbohydrates. Methods: This critical review addresses the existing data on the analysis of prebiotic carbohydrates by different in vitro gastrointestinal simulators, the lack of parameters that could affect the results, and recommendations for their enhancement. Results: According to the reviewed data, there is a lack of a realistic approximation of the small intestinal conditions, mainly because of the absence of hydrolytic conditions, such as the presence of small intestinal brush border carbohydrases that can affect the digestibility of different carbohydrates, including prebiotics. Conclusion: There is a necessity to standardize and enhance the small intestine simulators to study the in vitro digestibility of carbohydrates.

PACSIN2-dependent apical endocytosis regulates the morphology of epithelial microvilli

ABSTRACTApical microvilli are critical for the homeostasis of transporting epithelia, yet mechanisms that control the assembly and morphology of these protrusions remain poorly understood. Previous studies in intestinal epithelial cell lines suggested a role for F-BAR domain protein PACSIN2 in normal microvillar assembly. Here we report the phenotype of PACSIN2 KO mice and provide evidence that through its role in promoting apical endocytosis, this molecule functions in controlling microvillar morphology. PACSIN2 KO enterocytes exhibit reduced numbers of microvilli and defects in microvillar ultrastructure, with membranes lifting away from rootlets of core bundles. Dynamin2, a PACSIN2 binding partner, and other endocytic factors were also lost from their normal localization near microvillar rootlets. To determine if loss of endocytic machinery could explain defects in microvillar morphology, we examined the impact of PACSIN2 KD and endocytosis inhibition on live intestinal epithelial cells. These assays revealed that when endocytic vesicle scission fails, tubules are pulled into the cytoplasm and this, in turn, leads to a membrane lifting phenomenon reminiscent of that observed in PACSIN2 KO brush borders. These findings lead to a new model where inward forces generated by endocytic machinery on the plasma membrane control the membrane wrapping of cell surface protrusions.Highlight for TOCApical microvilli increase the functional surface area of transporting epithelia. Here we report that the F-BAR domain-containing protein PACSIN2, through its ability to promote apical endocytosis, plays a critical role in controlling the morphology of intestinal brush border microvilli.