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Ambra1 regulates autophagy and development of the nervous system

Nature volume 447, pages 1121–1125 (2007)Cite this article

Abstract

Autophagy is a self-degradative process involved both in basal turnover of cellular components and in response to nutrient starvation or organelle damage in a wide range of eukaryotes1,2,3. During autophagy, portions of the cytoplasm are sequestered by double-membraned vesicles called autophagosomes, and are degraded after fusion with lysosomes for subsequent recycling4. In vertebrates, this process acts as a pro-survival or pro-death mechanism in different physiological and pathological conditions, such as neurodegeneration and cancer2,5,6,7; however, the roles of autophagy during embryonic development are still largely uncharacterized3. Beclin1 (Becn1; coiled-coil, myosin-like BCL2-interacting protein) is a principal regulator in autophagosome formation, and its deficiency results in early embryonic lethality8,9. Here we show that Ambra1 (activating molecule in Beclin1-regulated autophagy), a large, previously unknown protein bearing a WD40 domain at its amino terminus, regulates autophagy and has a crucial role in embryogenesis. We found that Ambra1 is a positive regulator of the Becn1-dependent programme of autophagy, as revealed by its overexpression and by RNA interference experiments in vitro. Notably, Ambra1 functional deficiency in mouse embryos leads to severe neural tube defects associated with autophagy impairment, accumulation of ubiquitinated proteins, unbalanced cell proliferation and excessive apoptotic cell death. In addition to identifying a new and essential element regulating the autophagy programme, our results provide in vivo evidence supporting the existence of a complex interplay between autophagy, cell growth and cell death required for neural development in mammals.

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Figure 1: Neural tube defects in Ambra1 mutant embryos.
Figure 2: AMBRA1 is a novel BECN1-interacting protein.
Figure 3: AMBRA1 regulates autophagy.
Figure 4: Autophagy is impaired in Ambra1 mutant embryos.

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Acknowledgements

We thank M. Torres and P. Bonaldo for their involvement in the large-scale gene-trap screening. We also thank A. Conrad for the mouse work, S. Hille for DNA sequencing, M. Acuña Villa and M. W. Bennett for editorial and secretarial work, P. Mattioli for help with image processing, and G. Lisi, and G. Bellavia G. Marchetti for research assistance. We are grateful to N. Mizushima for providing us with the GFP–LC3 mice. This work was supported in part by grants from the Telethon Foundation and Compagnia di San Paolo (F.C.), Ricerca Corrente and Ricerca Finalizzata from Ministero della Salute and AIRC (M.P.) and the Max Planck Society (A.S., K.C. and P.G.). We thank the Ministry of University and Research of Italy for financial support.

Author Contributions G.M.F., A.R., S.D.B., C.F. and M.C. performed the protein interaction and autophagy assays. A.S. and K.C. generated the Ambra1 gene-trap line and identified the tagged gene. A.S., L.G., K.C., R.N. and S.D.B. carried out the analysis of the phenotype. R.N. and P.S. performed electron microscopy. A.U. generated the Ambra1gt fusion construct. P.G.’s laboratory devised and performed the large-scale gene-trap screening. F.C., M.P. and G.M.F. wrote the paper. All authors discussed the results and commented on the manuscript.

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Author notes

  1. Gian Maria Fimia, Anastassia Stoykova and Alessandra Romagnoli: These authors contributed equally to this work.

Authors and Affiliations

  1. National Institute for Infectious Diseases IRCCS ‘L. Spallanzani’, 00149 Rome, Italy,

    Gian Maria Fimia, Alessandra Romagnoli, Roberta Nardacci, Marco Corazzari & Mauro Piacentini

  2. Department of Molecular Cell Biology, Max Planck Institute of Biophysical Chemistry, 37077 Göttingen, Germany,

    Anastassia Stoykova, Ahmet Ucar, Peter Gruss & Kamal Chowdhury

  3. Dulbecco Telethon Institute at the Department of Biology,,

    Luigi Giunta, Sabrina Di Bartolomeo, Claudia Fuoco & Francesco Cecconi

  4. Department of Biology, University of Rome ‘Tor Vergata’, 00133 Rome, Italy,

    Mauro Piacentini

  5. Laboratory of Molecular Neuroembryology, IRCCS Fondazione Santa Lucia, 00143 Rome, Italy,

    Luigi Giunta, Sabrina Di Bartolomeo, Claudia Fuoco & Francesco Cecconi

  6. Department of Anatomy and Embryology, University of Göttingen, 37085 Göttingen, Germany,

    Peter Schwartz

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  1. Gian Maria Fimia
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Corresponding authors

Correspondence to Kamal Chowdhury or Francesco Cecconi.

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Competing interests

The sequence for human AMBRA1 cDNA (Supplementary Fig. 1c) has been submitted to GenBank under accession number DQ870924. Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Supplementary information

Supplementary Information 1

This file contains Supplementary Figures S1-S8 with Legends and Supplementary Table 1. (PDF 40771 kb)

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Maria Fimia, G., Stoykova, A., Romagnoli, A. et al. Ambra1 regulates autophagy and development of the nervous system. Nature 447, 1121–1125 (2007). https://doi.org/10.1038/nature05925

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