Biology subjects

Boesen, T.

Publications and source records attributed to Boesen, T..

21 records · Page 2Linked to original sources

bioRxiv2019

Connectivity characterization of the mouse basolateral amygdalar complex

The basolateral amygdalar complex (BLA) is implicated in behavioral processing ranging from fear acquisition to addiction. Newer methods like optogenetics have enabled the association of circuit-specific functionality to uniquely connected BLA cell types. Thus, a systematic and detailed connectivity profile of BLA projection neurons to inform granular, cell type-specific interrogations is warranted. In this work, we applied computational analysis techniques to the results of our circuit-tracing experiments to create a foundational, comprehensive, multiscale connectivity atlas of the mouse BLA. The analyses identified three domains within the classically defined anterior BLA (BLAa) that house target-specific projection neurons with distinguishable cell body and dendritic morphologies. Further, we identify brain-wide targets of projection neurons located in the three BLAa domains as well as in the posterior BLA (BLAp), ventral BLA (BLAv), lateral (LA), and posterior basomedial (BMAp) nuclei. Projection neurons that provide input to each nucleus are also identifed. Functional characterization of some projection-defined BLA neurons were demonstrated via optogenetic and recording experiments. Hypotheses relating function to connection-defined BLA cell types are proposed.

neuroscience↗

bioRxiv2019

Structure and autoregulation of a P4-ATPase lipid flippase

P4-ATPases are lipid flippases that drive active transport of phospholipids from the exoplasmic or lumenal to the cytosolic leaflets of eukaryotic membranes to maintain their asymmetric lipid composition. The molecular architecture of P4-ATPases and how they work in lipid recognition and transport has remained elusive. Using cryo-electron microscopy we have determined the structures of a P4-ATPase, specifically of the Saccharomyces cerevisiae Drs2p-Cdc50p, which is a phosphatidylserine and phosphatidylethanolamine specific lipid flippase. Drs2p-Cdc50p is autoinhibited by the Drs2p C-terminal tail and activated by phosphatidylinositol-4 phosphate (PI4P). We present three structures representing an autoinhibited, an intermediate, and a fully activated state. The analysis highlights specific features of P4-ATPases and reveals sites of auto-inhibition and PI4P-dependent activation. We observe the opening of a putative flippase pathway engaging conserved residues Ile508 of transmembrane segment 4 and Lys1018 and polar residues of transmembrane segment 5 in the centre of the lipid bilayer.

molecular biology↗

bioRxiv2018

Namdinator - Automatic Molecular Dynamics flexible fitting of structural models into cryo-EM and crystallography experimental maps

Model building into experimental maps is a key element of structural biology, but can be both time consuming and error-prone. Here we present Namdinator, an easy-to-use tool that enables the user to run a Molecular Dynamics Flexible Fitting (MDFF) simulation in an automated manner through a pipeline system. Namdinator will modify an atomic model to fit within cryo-EM or crystallography density maps, and can be used advantageously for both the initial fitting of models, and for a geometrical optimization step to correct outliers, clashes and other model problems. We have benchmarked Namdinator against 39 deposited models and maps from cryo-EM and observe model improvements in 34 of these cases (87%). Clashes between atoms were reduced, and model-to-map fit and overall model geometry were improved, in several cases substantially. We show that Namdinator is able to model large scale conformational changes compared to the starting model. Namdinator is a fast and easy way to create suitable initial models for both cryo-EM and crystallography. It can fix model errors in the final steps of model building, and is usable for structural model builders at all skill levels. Namdinator is available as a web service (https://namdinator.au.dk), or can be run locally as a command-line tool.\n\nSynopsisA pipeline tool called Namdinator is presented that enables the user to run a Molecular Dynamics Flexible Fitting (MDFF) simulation in a fully automated manner, both online and locally. This provides a fast and easy way to create suitable initial models for both cryo-EM and crystallography and help fix errors in the final steps of model building.

biophysics↗