Alterations in cellular metabolic pathway and epithelial cell maturation induced by MYO5B defects are partially reversible by LPAR5 activation.

Functional loss of the motor protein, Myosin Vb (MYO5B), induces various defects in intestinal epithelial function and causes a congenital diarrheal disorder, microvillus inclusion disease (MVID). Utilizing the MVID model mice, Vil1-CreERT2;Myo5bflox/flox (MYO5B∆IEC) and Vil1-CreERT2;Myo5bflox/G519R (MYO5B(G519R)), we previously reported that functional MYO5B loss disrupts progenitor cell differentiation and enterocyte maturation that result in villus blunting and deadly malabsorption symptoms. In this study, we determined that both absence and a point mutation of MYO5B impair lipid metabolism and alter mitochondrial structure, which may underlie the progenitor cell malfunction observed in MVID intestine. Along with a decrease in fatty acid oxidation, the lipogenesis pathway was enhanced in the MYO5B∆IEC small intestine. Consistent with these observations in vivo, RNA-sequencing of enteroids generated from the two MVID mouse strains showed similar downregulation of energy metabolic enzymes, including mitochondrial oxidative phosphorylation genes. In our previous studies, lysophosphatidic acid (LPA) signaling ameliorates epithelial cell defects in MYO5B∆IEC tissues and enteroids. The present study demonstrated that the highly soluble LPAR5-preferred agonist, Compound-1, improved sodium transporter localization and absorptive function, and tuft cell differentiation in patient-modeled MVID animals that carry independent mutations in MYO5B. Body weight loss in male MYO5B(G519R) mice was ameliorated by Compound-1. These observations suggest that Compound-1 treatment has a trophic effect on intestine with MYO5B functional loss through epithelial cell-autonomous pathways that can accelerate the differentiation of progenitor cells and the maturation of enterocytes. Targeting LPAR5 may represent an effective therapeutic approach for treatment of MVID symptoms induced by different point mutations in MYO5B.

Rab11FIP1-deficient mice develop spontaneous inflammation and show increased susceptibility to colon damage.

The small GTPase, Rab11a, regulates vesicle trafficking and cell polarity in epithelial cells through interaction with Rab11 family-interacting proteins (Rab11-FIPs). We hypothesized that deficiency of Rab11-FIP1 would affect mucosal integrity in the intestine. Global Rab11FIP1 knockout (KO) mice were generated by deletion of the second exon. Pathology of intestinal tissues was analyzed by immunostaining of colonic sections and RNA-sequencing of isolated colonic epithelial cells. A low concentration of dextran sodium sulfate (DSS, 2%) was added to drinking water for 5 days, and injury score was compared between Rab11FIP1 KO, Rab11FIP2 KO, and heterozygous littermates. Rab11FIP1 KO mice showed normal fertility and body weight gain. More frequent lymphoid patches and infiltration of macrophages and neutrophils were identified in Rab11FIP1 KO mice before the development of rectal prolapse compared with control mice. The population of trefoil factor 3 (TFF3)-positive goblet cells was significantly lower, and the ratio of proliferative to nonproliferative cells was higher in Rab11FIP1 KO colons. Transcription signatures indicated that Rab11FIP1 deletion downregulated genes that mediate stress tolerance response, whereas genes mediating the response to infection were significantly upregulated, consistent with the inflammatory responses in the steady state. Lack of Rab11FIP1 also resulted in abnormal accumulation of subapical vesicles in colonocytes and the internalization of transmembrane mucin, MUC13, with Rab14. After DSS treatment, Rab11FIP1 KO mice showed greater body weight loss and more severe mucosal damage than those in heterozygous littermates. These findings suggest that Rab11FIP1 is important for cytoprotection mechanisms and for the maintenance of colonic mucosal integrity.NEW & NOTEWORTHY Although Rab11FIP1 is important in membrane trafficking in epithelial cells, the gastrointestinal phenotype of Rab11FIP1 knockout (KO) mice had never been reported. This study demonstrated that Rab11FIP1 loss induces mistrafficking of Rab14 and MUC13 and decreases in colonic goblet cells, resulting in impaired mucosal integrity.

Acute tuft cell ablation induces malabsorption and alterations in secretory and immune cell lineages in small intestine.

Background & Aims: Intestinal tuft cells have recently been the interest of studies in several human gastrointestinal diseases. However, the impact of tuft cell deletion on intestinal physiological functions are not fully understood. This study investigated the effects of acute tuft cell loss on nutrient absorption and cell lineage differentiation. Methods: Tuft cell deletion was induced in DCLK1-IRES-GFP-CreERT2/+;Rosa-DTA (DCLK1-DTA) mice by a single tamoxifen injection concomitant with littermate controls. Intestinal tissues were analyzed two-, four-, or seven-days post tamoxifen injection. Results: DCLK1-DTA mice showed significantly shortened small intestinal length and body weight loss on day 4. Impaired activities of Na + -dependent glucose transporter 1 (SGLT1) and cystic fibrosis transmembrane regulator (CFTR) were observed in Ussing chamber experiments. Tissue immunostaining revealed a transient deletion of intestinal and biliary tuft cells, which was maximal on day 4 and recovered by day 7. On day 4 post tamoxifen, cholecystokinin (CCK)+ enteroendocrine cell numbers were increased particularly in the ileum. Correlated with the tuft cell reduction, the frequency of mislocalized Paneth cells, which were co-labeled by Paneth and goblet cell markers, was increased in the villus regions. In the lamina propria, fewer mast cells and leukocytes were found in the day 4 DCLK1-DTA mice than in controls. Conclusion: Ablation of intestinal tuft cells may induce nutrient malabsorption through alterations in epithelial cell proliferation and differentiation along with changes in mucosal defense response. These observations elucidate a new role for tuft cells in regulating intestinal absorption and mucosal regeneration.

Altered cellular metabolic pathway and epithelial cell maturation induced by MYO5B defects are partially reversible by LPAR5 activation.

Functional loss of the motor protein, Myosin Vb (MYO5B), induces various defects in intestinal epithelial function and causes a congenital diarrheal disorder, microvillus inclusion disease (MVID). Utilizing the MVID model mice, Vil1-Cre ERT2 ;Myo5b flox/flox (MYO5BΔIEC) and Vil1-Cre ERT2 ;Myo5b flox/G519R (MYO5B(G519R)), we previously reported that functional MYO5B loss disrupts progenitor cell differentiation and enterocyte maturation that result in villus blunting and deadly malabsorption symptoms. In this study, we determined that both absence and a point mutation of MYO5B impair lipid metabolism and alter mitochondrial structure, which may underlie the progenitor cell malfunction observed in MVID intestine. Along with a decrease in fatty acid oxidation, the lipogenesis pathway was enhanced in the MYO5BΔIEC small intestine. Consistent with these observations in vivo , RNA-sequencing of enteroids generated from two MVID mouse strains showed similar downregulation of energy metabolic enzymes, including mitochondrial oxidative phosphorylation genes. In our previous studies, lysophosphatidic acid (LPA) signaling ameliorates epithelial cell defects in MYO5BΔIEC tissues and enteroids. The present study demonstrates that the highly soluble LPAR5-preferred agonist, Compound-1, improved sodium transporter localization and absorptive function, and tuft cell differentiation in patient-modeled MVID animals that carry independent mutations in MYO5B. Body weight loss in male MYO5B(G519R) mice was ameliorated by Compound-1. These observations suggest that Compound-1 treatment has a trophic effect on intestine with MYO5B functional loss through epithelial cell-autonomous pathways that may improve the differentiation of progenitor cells and the maturation of enterocytes. Targeting LPAR5 may represent an effective therapeutic approach for treatment of MVID symptoms induced by different point mutations in MYO5B. NEW & NOTEWOTHY: This study demonstrates the importance of MYO5B for cellular lipid metabolism and mitochondria in intestinal epithelial cells, a previously unexplored function of MYO5B. Alterations in cellular metabolism may underlie the progenitor cell malfunction observed in microvillus inclusion disease (MVID). To examine the therapeutic potential of progenitor-targeted treatments, the effects of LPAR5-preferred agonist, Compound-1, was investigated utilizing several MVID model mice and enteroids. Our observations suggests that Compound-1 may provide a therapeutic approach for treating MVID.