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Lack of de novo phosphatidylinositol synthesis leads to endoplasmic reticulum stress and hepatic steatosis in cdipt-deficient zebrafish.

ABSTRACT: Hepatic steatosis is the initial stage of nonalcoholic fatty liver disease (NAFLD) and may predispose to more severe hepatic disease, including hepatocellular carcinoma. Endoplasmic reticulum (ER) stress has been recently implicated as a novel mechanism that may lead to NAFLD, although the genetic factors invoking ER stress are largely unknown. During a screen for liver defects from a zebrafish insertional mutant library, we isolated the mutant cdipthi559Tg/+ (hi559). CDIPT is known to play an indispensable role in phosphatidylinositol (PtdIns) synthesis. Here we show that cdipt is expressed in the developing liver, and its disruption in hi559 mutants abrogates de novo PtdIns synthesis, resulting in hepatomegaly at 5 days postfertilization. The hi559 hepatocytes display features of NAFLD, including macrovesicular steatosis, ballooning, and necroapoptosis. Gene set enrichment of microarray profiling revealed significant enrichment of endoplasmic reticulum stress response (ERSR) genes in hi559 mutants. ER stress markers, including atf6, hspa5, calr, and xbp1, are selectively up-regulated in the mutant liver. The hi559 expression profile showed significant overlap with that of mammalian hepatic ER stress and NAFLD. Ultrastructurally, the hi559 hepatocytes display marked disruption of ER architecture with hallmarks of chronic unresolved ER stress. Induction of ER stress by tunicamycin in wild-type larvae results in a fatty liver similar to hi559, suggesting that ER stress could be a fundamental mechanism contributing to hepatic steatosis.cdipt-deficient zebrafish exhibit hepatic ER stress and NAFLD pathologies, implicating a novel link between PtdIns, ER stress, and steatosis. The tractability of hi559 mutant provides a valuable tool to dissect ERSR components, their contribution to molecular pathogenesis, and evaluation of novel therapeutics of NAFLD.

SUBMITTER: Thakur PC

PROVIDER: S-EPMC3140628 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature

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Lack of de novo phosphatidylinositol synthesis leads to endoplasmic reticulum stress and hepatic steatosis in cdipt-deficient zebrafish.

Thakur Prakash C PC Stuckenholz Carsten C Rivera Marcus R MR Davison Jon M JM Yao Jeffrey K JK Amsterdam Adam A Sadler Kirsten C KC Bahary Nathan N

Hepatology (Baltimore, Md.) 20110502 2

<h4>Unlabelled</h4>Hepatic steatosis is the initial stage of nonalcoholic fatty liver disease (NAFLD) and may predispose to more severe hepatic disease, including hepatocellular carcinoma. Endoplasmic reticulum (ER) stress has been recently implicated as a novel mechanism that may lead to NAFLD, although the genetic factors invoking ER stress are largely unknown. During a screen for liver defects from a zebrafish insertional mutant library, we isolated the mutant cdipthi559Tg/+ (hi559). CDIPT is ...[more]

PMID: 21488074

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Project description:Dysregulated phosphatidylinositol (PI) signaling has been implicated in human gastrointestinal (GI) malignancies and inflammatory states, underlining the need to study pathophysiological roles of PI in an in vivo genetic model. Here, we study the significance of PI in GI pathophysiology using the zebrafish mutant cdipt(hi559), which lacks PI synthesis, and unravel a crucial role of PI in intestinal mucosal integrity and inflammation. The cdipt(hi559) mutants exhibit abnormal villous architecture and disorganized proliferation of intestinal epithelial cells (IECs), with pathologies reminiscent of inflammatory bowel disease (IBD), including apoptosis of goblet cells, abnormal mucosecretion, bacterial overgrowth and leukocyte infiltration. The mutant IECs exhibit vacuolation, microvillus atrophy and impaired proliferation. The cdipt(hi559) gene expression profile shows enrichment of acute phase response signaling, and the endoplasmic reticulum (ER) stress factors hspa5 and xbp1 are robustly activated in the mutant GI tissue. Temporal electron micrographic analyses reveal that PI-deficient IECs undergo sequential ER-Golgi disruption, mitochondrial depletion, macroautophagy and cell death, consistent with chronic ER-stress-mediated cytopathology. Furthermore, pharmacological induction of ER stress by inhibiting protein glycosylation or PI synthase inhibition in leukocyte-specific reporter lines replicates the cdipt(hi559) inflammatory phenotype, suggesting a fundamental role of PI metabolism and ER stress in mucosal inflammation. Antibiotics and anti-inflammatory drugs resolved the inflammation, but not the autophagic necroapoptosis of IECs, suggesting that bacterial overgrowth can exacerbate ER stress pathology, whereas persistent ER stress is sufficient to trigger inflammation. Interestingly, the intestinal phenotype was partially alleviated by chemical chaperones, suggesting their therapeutic potential. Using zebrafish genetic and pharmacological models, this study demonstrates a newly identified link between intracellular PI signaling and ER-stress-mediated mucosal inflammation. The zebrafish cdipt mutants provide a powerful tool for dissecting the fundamental mechanisms of ER-stress-mediated human GI diseases and a platform to develop molecularly targeted therapies.

Dataset Information

Lack of de novo phosphatidylinositol synthesis leads to endoplasmic reticulum stress and hepatic steatosis in cdipt-deficient zebrafish.

Publications

Lack of de novo phosphatidylinositol synthesis leads to endoplasmic reticulum stress and hepatic steatosis in cdipt-deficient zebrafish.

Similar Datasets

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