Molecular basis of host-microbiota signaling in the zebrafish gut

描述（由申请人提供）：所有动物都是在一个富含微生物的环境中进化的，其中许多微生物存在于密切的联系中，这些联系塑造了动物宿主的发育和正常生理。我们建立了一个无菌（GF）斑马鱼模型来研究本地微生物群在肠道发育中的作用。我们发现GF斑马鱼消化道表现出多种发育缺陷，包括不能表达成熟的碱性磷酸酶（IAP）活性模式和含有Gala1,3Gal的聚糖。我们已经证明纯化的脂多糖（LPS）足以诱导GF动物的IAP活性。相反，调节半乳糖偶联物需要与本地微生物群的成分定殖。我们进一步表明，这两个独立的途径，使用不同的微生物信号，通过IAP和半乳糖转移酶（步态）基因的转录调控来调节宿主的反应。

DESCRIPTION (provided by applicant): All animals have evolved in an environment rich in microorganisms, many of which exist in intimate associations that shape the animal hosts' development and normal physiology. We have established a germfree (GF) zebrafish model to study the role of the indigenous microbiota in gut development. We find that the GF zebrafish digestive tract exhibits multiple developmental defects, including failure to express mature patterns of alkaline phosphatase (IAP) activity and Gala1,3Gal containing glycans. We have demonstrated that purified lipopolysaccharide (LPS) is sufficient to induce IAP activity in GF animals. In contrast, regulation of the galactoconjugate requires colonization with constituents of the indigenous microbiota. We have further shown that these two independent pathways, using different microbial signals, regulate host responses through the transcriptional regulation of the IAP and galactosyltransferase (GaIT) genes. In this grant we will investigate the molecular basis and functional significance of these two signaling pathways between the host and its microbiota. Our preliminary data demonstrate that IAP activity, which has been shown to dephosphorylated LPS, is required in the intestine to protect against LPS toxicity. We will test the hypothesis that the normal function of this intestinal enzyme is to detoxifies LPS and reduces intestinal inflammation in response to gram-negative commensal and pathogenic bacteria. To investigate the function and microbial regulation of galactoconjugate expression in the zebrafish we have established a zebrafish mono-association model with a genetically tractable bacterium, Aeromonas veronii biovar sobria. We will use bacterial genetic and zebrafish transgenic approaches to identify the microbial signals and the host pathways that regulate GalT transcription. Finally, we will test the hypothesis that intestinal Gala1,3Gal glycan expression promotes the establishment of the appropriate microbiota. The proposed research will teach us about the molecular dialogues in which we engage with our microbiota and will shed light on the ways in which this dialogue is disrupted in diseases such as Gl inflammatory disorders, opportunistic infections, and sepsis.