Epithelial cell proliferation in the developing zebrafish intestine is regulated by the Wnt pathway and microbial signaling via Myd88

Abstract

Rates of cell proliferation in the vertebrate intestinal epithelium are modulated by intrinsic signaling pathways and extrinsic cues. Here, we report that epithelial cell proliferation in the developing zebrafish intestine is stimulated both by the presence of the resident microbiota and by activation of Wnt signaling. We find that the response to microbial proliferation-promoting signals requires Myd88 but not TNF receptor, implicating host innate immune pathways but not inflammation in the establishment of homeostasis in the developing intestinal epithelium. We show that loss of axin1, a component of the β-catenin destruction complex, results in greater than WT levels of intestinal epithelial cell proliferation. Compared with conventionally reared axin1 mutants, germ-free axin1 mutants exhibit decreased intestinal epithelial cell proliferation, whereas monoassociation with the resident intestinal bacterium Aeromonas veronii results in elevated epithelial cell proliferation. Disruption of β-catenin signaling by deletion of the β-catenin coactivator tcf4 partially decreases the proliferation-promoting capacity of A. veronii. We show that numbers of intestinal epithelial cells with cytoplasmic β-catenin are reduced in the absence of the microbiota in both WT and axin1 mutants and elevated in animals' monoassociated A. veronii. Collectively, these data demonstrate that resident intestinal bacteria enhance the stability of β-catenin in intestinal epithelial cells and promote cell proliferation in the developing vertebrate intestine.axin1 | β-catenin | germ-free | intestinal epithelial cell | microbiota

Exploring host–microbiota interactions in animal models and humans

“…The gut microbiota stimulates intestinal epithelial cell proliferation (Rawls et al 2004;Bates et al 2006) through MyD88 signaling and not inflammation (Cheesman et al 2011), promotes a shift in epithelial glycan expression (Bates et al 2006), and stimulates the infiltration of gut-associated immune cells (Rawls et al 2004;Bates et al 2007). …”

Regulation of immunity and disease resistance by commensal microbes and chromatin modifications during zebrafish development

“…Thus, they are able to sense the same ligands (15)(16)(17), use similar adaptor molecules for signaling (15), and activate the transcription factor NF-κB (13,15,18). In addition, it has been shown that in zebrafish MyD88 modulates innate immune responses to microbes (19)(20)(21)(22).…”

“…As in other vertebrate models, the main changes involved rapid epidermal degeneration and altered enterocyte morphology and proliferation (36,(38)(39)(40). In addition, a recent study showed that the presence not only of commensals but also of multiple bacterial secretion factors is essential for influencing intestinal epithelial cell proliferation, suggesting that normal gut microbiota exert a direct modulation of the β-cathenin pathway, independent of inflammation (22). In the present study, we used zebrafish larvae as a vertebrate model of innate immunity to test the hypothesis that the contact with commensal microbiota after hatching is an essential external environmental triggering factor to shape the development of immunity and disease resistance.…”

Evidence for a core gut microbiota in the zebrafish

“…We have developed gnotobiotic husbandry methods for the zebrafish, and used them to reveal host responses to the gut microbiota including effects on innate immunity, nutrient metabolism, and intestinal epithelial differentiation and renewal (Rawls et al, 2004(Rawls et al, , 2006Bates et al, 2006Bates et al, , 2007Cheesman and Guillemin, 2007;Cheesman et al, 2011;Kanther and Rawls, 2010). Preliminary insights into the membership of the zebrafish gut microbiota have been provided by sequencing libraries of bacterial 16S rRNA genes amplified from pooled intestinal samples from zebrafish reared in laboratory aquaculture facilities (Rawls et al, 2004(Rawls et al, , 2006Bates et al, 2006;Brugman et al, 2009).…”