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Mutations in Traf3ip1 reveal defects in ciliogenesis, embryonic development, and altered cell size regulation.

ABSTRACT: Tumor necrosis factor alpha receptor 3 interacting protein 1 (Traf3ip1), also known as MIPT3, was initially characterized through its interactions with tubulin, actin, TNFR-associated factor-3 (Traf3), IL-13R1, and DISC1. It functions as an inhibitor of IL-13-mediated phosphorylation of Stat6 and in sequestration of Traf3 and DISC1 to the cytoskeleton. Studies of the Traf3ip1 homologs in C. elegans (DYF-11), Zebrafish (elipsa), and Chlamydomonas (IFT54) revealed that the protein localizes to the cilium and is required for ciliogenesis. Similar localization data has now been reported for mammalian Traf3ip1. This raises the possibility that Traf3ip1 has an evolutionarily conserved role in mammalian ciliogenesis in addition to its previously indicated functions. To evaluate this possibility, a Traf3ip1 mutant mouse line was generated. Traf3ip1 mutant cells are unable to form cilia. Homozygous Traf3ip1 mutant mice are not viable and have both neural developmental defects and polydactyly, phenotypes typical of mouse mutants with ciliary assembly defects. Furthermore, in Traf3ip1 mutants the hedgehog pathway is disrupted, as evidenced by abnormal dorsal-ventral neural tube patterning and diminished expression of a hedgehog reporter. Analysis of the canonical Wnt pathway indicates that it was largely unaffected; however, specific domains in the pharyngeal arches have elevated levels of reporter activity. Interestingly, Traf3ip1 mutant embryos and cells failed to show alterations in IL-13 signaling, one of the pathways associated with its initial discovery. Novel phenotypes observed in Traf3ip1 mutant cells include elevated cytosolic levels of acetylated microtubules and a marked increase in cell size in culture. The enlarged Traf3ip1 mutant cell size was associated with elevated basal mTor pathway activity. Taken together, these data demonstrate that Traf3ip1 function is highly conserved in ciliogenesis and is important for proper regulation of a number of essential developmental and cellular pathways. The Traf3ip1 mutant mouse and cell lines will provide valuable resources to assess cilia function in mammalian development and also serve as a tool to explore the potential connections between cilia and cytoskeletal dynamics, mTor regulation, and cell volume control.

SUBMITTER: Berbari NF

PROVIDER: S-EPMC4059607 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Mutations in Traf3ip1 reveal defects in ciliogenesis, embryonic development, and altered cell size regulation.

Berbari Nicolas F NF Kin Nicholas W NW Sharma Neeraj N Michaud Edward J EJ Kesterson Robert A RA Yoder Bradley K BK

Developmental biology 20110916 1

Tumor necrosis factor alpha receptor 3 interacting protein 1 (Traf3ip1), also known as MIPT3, was initially characterized through its interactions with tubulin, actin, TNFR-associated factor-3 (Traf3), IL-13R1, and DISC1. It functions as an inhibitor of IL-13-mediated phosphorylation of Stat6 and in sequestration of Traf3 and DISC1 to the cytoskeleton. Studies of the Traf3ip1 homologs in C. elegans (DYF-11), Zebrafish (elipsa), and Chlamydomonas (IFT54) revealed that the protein localizes to the ...[more]

PMID: 21945076

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Project description:Homozygous nonsense mutations in CEP55 are associated with several congenital malformations that lead to perinatal lethality suggesting that it plays a critical role in regulation of embryonic development. CEP55 has previously been studied as a crucial regulator of cytokinesis, predominantly in transformed cells, and its dysregulation is linked to carcinogenesis. However, its molecular functions during embryonic development in mammals require further investigation. We have generated a Cep55 knockout (Cep55-/-) mouse model which demonstrated preweaning lethality associated with a wide range of neural defects. Focusing our analysis on the neocortex, we show that Cep55-/- embryos exhibited depleted neural stem/progenitor cells in the ventricular zone as a result of significantly increased cellular apoptosis. Mechanistically, we demonstrated that Cep55-loss downregulates the pGsk3β/β-Catenin/Myc axis in an Akt-dependent manner. The elevated apoptosis of neural stem/progenitors was recapitulated using Cep55-deficient human cerebral organoids and we could rescue the phenotype by inhibiting active Gsk3β. Additionally, we show that Cep55-loss leads to a significant reduction of ciliated cells, highlighting a novel role in regulating ciliogenesis. Collectively, our findings demonstrate a critical role of Cep55 during brain development and provide mechanistic insights that may have important implications for genetic syndromes associated with Cep55-loss. Author summary Despite extensive investigation on the roles of CEP55 in tumorigenesis, its physiological role during development has remained largely uncharacterized. Recently, homozygous CEP55 mutations have been linked to two lethal fetal syndromes, MKS-like Syndrome and MARCH, demonstrating the importance of CEP55 in embryogenesis and neural development. These syndromes exhibit multiple severe clinical manifestations that lead to perinatal lethality. However, the exact molecular mechanism underlying complex Cep55-deficient developmental phenotypes remain elusive. To address this question, we have generated a Cep55-/- (KO) mouse model and to bridge the gap between the mouse model and human disease, we have used brain organoids generated from pluripotent stem cells as a promising approach to investigate the mechanism of Cep55-associated neurodevelopment phenotype. Our detailed mechanistic studies suggest that Cep55 regulates neural development through the Akt-downstream effector, Gsk3β, and its mediators β-Catenin and Myc, which are known regulators of neural proliferation and differentiation. Additionally, we discovered a critical role for Cep55 in regulating cilia formation. Together, these results illustrate an important role of Cep55 in regulating neurogenesis and ciliogenesis via regulation of the Akt pathway.

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Mutations in Traf3ip1 reveal defects in ciliogenesis, embryonic development, and altered cell size regulation.

Publications

Mutations in Traf3ip1 reveal defects in ciliogenesis, embryonic development, and altered cell size regulation.

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