Novel insights into autophagosome biogenesis revealed by cryo-electron tomography

Autophagosome biogenesis, from the appearance of the phagophore to elongation and closure into an autophagosome, is one of the long-lasting open questions in the autophagy field. Recent studies utilising cryo-electron tomography and detailed analysis of the image data have revealed new information on the membrane dynamics of these events, including the shape and dimensions of omegasomes, phagophores and autophagosomes, and their relationships with the organelles around them. One of the important predictions from the new results is that 60-80% of the autophagosome membrane area is delivered by direct lipid transfer or lipid synthesis. Cryo-electron tomography can be expected to provide new directions for autophagy research in the near future. Recent studies utilising cryo-electron tomography and detailed analysis of the image data have revealed novel information on the membrane dynamics of autophagosome biogenesis, including the shape and dimensions of omegasomes, phagophores and autophagosomes, and their relationships with the organelles around them. This review summarises the findings of three recent papers revealing new exciting information on phagophore biogenesis.image