Biology subjects

Levitt, J.

Publications and source records attributed to Levitt, J..

3 recordsLinked to original sources

bioRxiv2023

Cardiomyocyte mechanical memory is regulated through the talin interactome and DLC1 dependent regulation of RhoA

Mechanical properties are cues for many biological processes in health or disease. Likewise, in the heart it is becoming clearer that mechanical signals are critically involved in the disease progression. Cardiomyocytes sense the mechanical properties of their environment at costameres through integrins and associated proteins, including the mechanosensitive protein talin as an integral component. Our previous work indicated different modes of talin tension, depending on the extracellular matrix stiffness. Here, we wanted to study how this leads to downstream mechanotransduction changes, further influencing the cardiomyocyte phenotype. Combining immunoprecipitations and Fluorescence Recovery after Photobleaching (FRAP) experiments, we identify that the talin interacting proteins DLC1, RIAM and paxillin each preferentially bind to talin at specific extracellular matrix stiffness and this interaction is preserved even in absence of tension. This demonstrates a mechanical memory, which we confirm further in vivo in mouse hearts. The mechanical memory is regulated through adhesion related kinase pathways. Optogenetic experiments using the LOVTRAP systems confirm direct competition between the individual proteins, which again is altered through phosphorylation. DLC1 regulates RhoA activity in a stiffness dependent way and both loss and overexpression of DLC1 results in myofibrillar disarray. Together the study demonstrates a mechanism of imprinting mechanical information into the talin-interactome to finetune RhoA activity, with impacts on cardiac health and disease.

cell biology↗

bioRxiv2022

EEG-LLAMAS: an open source, low latency, EEG-fMRI neurofeedback platform

Simultaneous EEG-fMRI is a powerful multimodal technique for imaging the brain, but its use in neurofeedback experiments has been limited by EEG noise caused by the MRI environment. Neurofeedback studies typically require analysis of EEG in real time, but EEG acquired inside the scanner is heavily contaminated with ballistocardiogram (BCG) artifact, a high-amplitude artifact locked to the cardiac cycle. Although techniques for removing BCG artifacts do exist, they are either not suited to real-time, low-latency applications, such as neurofeedback, or have limited efficacy. We propose and validate a new open-source BCG removal software called EEG-LLAMAS (Low Latency Artifact Mitigation Acquisition Software), which adapts and advances existing artifact removal techniques for low-latency experiments. We first used simulations to validate LLAMAS in data with known ground truth. We found that LLAMAS performed better than the best publicly-available real-time BCG removal technique, optimal basis sets (OBS), in terms of its ability to recover EEG waveforms, power spectra, and slow wave phase. To determine whether LLAMAS would be effective in practice, we then used it to conduct real-time EEG-fMRI recordings in healthy adults, using a steady state visual evoked potential (SSVEP) task. We found that LLAMAS was able to recover the SSVEP in real time, and recovered the power spectra collected outside the scanner better than OBS. We also measured the latency of LLAMAS during live recordings, and found that it introduced a lag of less than 50ms on average. The low latency of LLAMAS, coupled with its improved artifact reduction, can thus be effectively used for EEG-fMRI neurofeedback. This platform enables closed-loop experiments which previously would have been prohibitively difficult, such as those that target short-duration EEG events, and is shared openly with the neuroscience community.

neuroscience↗

bioRxiv2020

Nance-Horan Syndrome-like 1 protein negatively regulates Scar/WAVE-Arp2/3 activity and inhibits lamellipodia stability and cell migration.

Cell migration is important for development and its aberrant regulation contributes to many diseases. The Scar/WAVE complex is essential for Arp2/3 mediated lamellipodia formation during mesenchymal cell migration and several coinciding signals activate it. However, so far, no direct negative regulators are known. We have identified Nance-Horan Syndrome-like 1 protein (NHSL1) as a novel, direct binding partner of the Scar/WAVE complex, which co-localise at protruding lamellipodia. This interaction is mediated by the Abi SH3 domain and two binding sites in NHSL1. Furthermore, active Rac binds to NHSL1 at two regions that mediate leading edge targeting of NHSL1. Surprisingly, NHSL1 inhibits cell migration through its interaction with the Scar/WAVE complex. Mechanistically, NHSL1 may reduce cell migration efficiency by impeding Arp2/3 activity, as measured in cells using a novel Arp2/3 FRET-FLIM biosensor, resulting in reduced F-actin density of lamellipodia, and consequently impairing the stability of lamellipodia protrusions.

cell biology↗