Branched actin networks in dendritic cell biology

Leithner AF. 2018. Branched actin networks in dendritic cell biology. IST Austria.

OA PhD_thesis_AlexLeithner.pdf 66.05 MB

Thesis | Published | English
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IST Austria Thesis
In the here presented thesis, we explore the role of branched actin networks in cell migration and antigen presentation, the two most relevant processes in dendritic cell biology. Branched actin networks construct lamellipodial protrusions at the leading edge of migrating cells. These are typically seen as adhesive structures, which mediate force transduction to the extracellular matrix that leads to forward locomotion. We ablated Arp2/3 nucleation promoting factor WAVE in DCs and found that the resulting cells lack lamellipodial protrusions. Instead, depending on the maturation state, one or multiple filopodia were formed. By challenging these cells in a variety of migration assays we found that lamellipodial protrusions are dispensable for the locomotion of leukocytes and actually dampen the speed of migration. However, lamellipodia are critically required to negotiate complex environments that DCs experience while they travel to the next draining lymph node. Taken together our results suggest that leukocyte lamellipodia have rather a sensory- than a force transducing function. Furthermore, we show for the first time structure and dynamics of dendritic cell F-actin at the immunological synapse with naïve T cells. Dendritic cell F-actin appears as dynamic foci that are nucleated by the Arp2/3 complex. WAVE ablated dendritic cells show increased membrane tension, leading to an altered ultrastructure of the immunological synapse and severe T cell priming defects. These results point towards a previously unappreciated role of the cellular mechanics of dendritic cells in T cell activation. Additionally, we present a novel cell culture based system for the differentiation of dendritic cells from conditionally immortalized hematopoietic precursors. These precursor cells are genetically tractable via the CRISPR/Cas9 system while they retain their ability to differentiate into highly migratory dendritic cells and other immune cells. This will foster the study of all aspects of dendritic cell biology and beyond.
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First of all I would like to thank Michael Sixt for giving me the opportunity to work in his group and for his support throughout the years. He is a truly inspiring person and the best boss one can imagine. I would also like to thank all current and past members of the Sixt group for their help and the great working atmosphere in the lab. It is a true privilege to work with such a bright, funny and friendly group of people and I’m proud that I could be part of it. Furthermore, I would like to say ‘thank you’ to Daria Siekhaus for all the meetings and discussion we had throughout the years and to Federica Benvenuti for being part of my committee. I am also grateful to Jack Merrin in the nanofabrication facility and all the people working in the bioimaging- , the electron microscopy- and the preclinical facilities.

Cite this

Leithner AF. Branched actin networks in dendritic cell biology. 2018. doi:10.15479/AT:ISTA:th_998
Leithner, A. F. (2018). Branched actin networks in dendritic cell biology. IST Austria.
Leithner, Alexander F. “Branched Actin Networks in Dendritic Cell Biology.” IST Austria, 2018.
A. F. Leithner, “Branched actin networks in dendritic cell biology,” IST Austria, 2018.
Leithner AF. 2018. Branched actin networks in dendritic cell biology. IST Austria.
Leithner, Alexander F. Branched Actin Networks in Dendritic Cell Biology. IST Austria, 2018, doi:10.15479/AT:ISTA:th_998.
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