Biology subjects

Kohler, J.

Publications and source records attributed to Kohler, J..

7 recordsLinked to original sources

bioRxiv2026

GABAergic inhibition differentially gates recruitment of dentate gyrus interneurons by lateral entorhinal cortex inputs.

By keeping its activity low even when strongly stimulated, the dentate gyrus (DG) serves as the main entry point to the hippocampal circuit and helps separate different patterns of incoming information. However, the mechanisms supporting this low-level activity remain unclear. Here, we used in vitro patch-clamp recordings, two-photon calcium imaging, and optogenetics in hippocampal slices from adult mice to understand how local GABAergic interneurons control lateral entorhinal cortex (LEC) input-mediated drive in the DG. Under control conditions, LEC inputs rarely elicited granule cell (GC) firing because GABAA receptor-mediated inhibition strongly restrained GC excitability. Whole-cell patch clamp recordings of DG interneurons revealed that LEC activation prevalently recruited fast-spiking parvalbumin-expressing and molecular layer interneurons, while most dendrite-targeting interneuron types responded only weakly to LEC input and fired action potentials only after feedback excitation from GCs was enhanced by pharmacological block of GABAA-receptors. Optogenetic inhibition of defined interneuron populations showed that silencing dendrite-targeting interneurons caused a larger increase in GC population spiking than silencing perisomatic-targeting interneurons, suggesting that both molecular layer and feedback-recruited interneurons have a prevalent role in controlling DG recruitment after an increase in LEC drive. In summary, our data indicate that GABAergic inhibition engages distinct DG interneuron types in feedforward and feedback circuits to tightly gate entorhinal inputs. By maintaining sparse GC firing, this dynamic inhibitory gating supports the role of the dentate gyrus in the hippocampal pattern-separation process.

neuroscience↗

bioRxiv2026

mSWI/SNF complex inhibition sensitizes KRAS-mutant lung cancers to targeted therapies via epithelial-mesenchymal subversion

Targeted therapies for KRAS-mutant non-small lung cancer (NSCLC) have shown promising clinical results, however, incomplete tumoral responses and the inevitable emergence of therapeutic resistance remain critical challenges. Here we identify mSWI/SNF chromatin remodeling complexes as critical determinants of (EMT)-mediated KRAS inhibitor inefficacy and resistance in KRAS G12C lung cancers. Treatment with the clinical-grade SMARCA4/2 inhibitor, FHD-286, dampens EMT-mediated acquired resistance in drug-responsive models and similarly resensitizes drug-refractory models by rewiring mSWI/SNF chromatin localization and activities that modulate epithelial transcriptional programs and cell state. Further, synergistic mSWI/SNF and KRAS inhibitor combination treatment sensitizes non-G12C KRAS-mutant NSCLC cells to pan-RAS and G12D-specific inhibitors. Finally, FHD-286 and sotorasib combination treatment results in potent anti-tumor efficacy in both G12Ci-resistant and - sensitive organoid models and in vivo patient-derived xenograft (PDX) systems. These data nominate mSWI/SNF inhibition as a combination strategy to improve KRAS inhibitor efficacy, response duration, and to mitigate emergence of resistance.

cancer biology↗

bioRxiv2026

Siderophore-mediated inhibition of Legionella pneumophila by environmental Pseudomonas isolates

The genus Legionella comprises opportunistic pathogenic bacteria commonly found in natural and engineered water systems, where they interact with environmental microbes and protozoa, primarily in biofilms. Legionella pneumophila is the main causative agent of Legionnaires disease and is transmitted through inhalation of contaminated aerosols. Iron availability is a critical factor for L. pneumophila growth, persistence, and virulence, yet iron is often limited in aquatic environments. To overcome iron scarcity, many bacteria produce siderophores, secondary metabolites that scavenge ferric iron. Because siderophores are chemically diverse and species specific, they play a key role in inter-species competition and can withhold iron from competitors. Here, we investigated the effects of iron depletion and siderophore-mediated competition on L. pneumophila using commercial pyoverdines and extracellular metabolites from environmental Pseudomonas strains. Growth assays showed that L. pneumophila can grow under iron-limited conditions but with lag phases extended by more than 20 hours. Pyoverdines inhibited growth in a concentration-dependent manner, primarily increasing the time to mid-log phase (t_mid). Supernatants and crude pyoverdine extracts from siderophore-producing Pseudomonas strains caused the strongest inhibition, including lag-phase extensions of up to 55 hours or complete growth arrest. These results demonstrate that siderophore-producing bacteria can suppress L. pneumophila by limiting iron availability.

microbiology↗

bioRxiv2025

Plasticity and genetics shape thermal tolerance in non-native populations of the European green crab (Carcinus maenas)

Temperature is a major driver of individual performance in ectotherms, with this impact depending on stressor intensity and duration. Differences in individual response across temperature, time, and populations are shaped by the interplay between evolutionary adaptation and phenotypic plasticity. Some populations are able to thrive in novel and changing environments despite limited genetic diversity, raising the question of how plasticity and adaptation interact after significant genetic diversity loss. The European green crab (Carcinus maenas) is a textbook example of this phenomenon: invasive populations boast a broad thermal tolerance and exceptional thermal flexibility even after repeated genetic bottlenecks. Despite this loss of diversity overall, prior work has found a strong population-level association between variation at a specific extended genomic region (supergene), cold tolerance, and sea surface temperature. We conducted a series of three experiments using righting response to characterize sublethal thermal tolerance and plasticity in introduced green crab populations, then determined if these factors were associated with supergene genotype for individual adult crabs. Crabs showed signs of stress after exposure to a 30{degrees}C heat shock in one experiment. Interestingly, a second experiment exposing C. maenas to repeated 24-hour heat shocks showed that prior heat shock conferred beneficial plasticity during a subsequent event. The third experiment examined cold acclimation over multiple timepoints up to 94 hours. At 5{degrees}C, certain crabs exhibited an acclimatory response where righting slowed dramatically at first, and then gradually sped up after a longer period of cold exposure. Several crabs failed to right at 1.5{degrees}C, which could be indicative of dormancy employed to reduce energy consumption in colder conditions. There were no significant relationships between individual plasticity and supergene genotype in any experiment. Linking population-level genetic associations with individual-level physiology is complex, and reflects the impact of environmental conditions such as temperature throughout life history in shaping adult phenotype. Our results highlight the robust thermal tolerance and plasticity that adult green crabs maintain despite a substantial reduction in genetic diversity, and underscore the importance of probing population-level genotype-phenotype associations at the individual level.

physiology↗

bioRxiv2021

Drug-driven reclassification of multiple tumour subtypes reveals intrinsic molecular concordance of therapy across histologically disparate cancers

Cancers that are histologically defined as the same type of cancer often need a distinct therapy based on underlying heterogeneity; likewise, histologically disparate cancers can require similar treatment approaches due to intrinsic similarities. A comprehensive analysis integrated with drug response data and genomic alterations, particularly to reveal therapeutic concordance mechanisms across histologically disparate tumour subtypes, has not yet been fully exploited. In this study, we used pharmacogenomic profiling data provided from the Cancer Genome Project (CGP) in a systematic in silico investigation of the pharmacological subtypes of cancers and the intrinsic concordance of molecular mechanisms leading to similar therapeutic responses across histologically disparate tumour subtypes. We further developed a novel approach to redefine cell-to-cell similarity and drug-to-drug similarity from the therapeutic concordance, providing a new point of view to study cancer heterogeneity. Our study identified that histologically different tumours, such as malignant melanoma and colorectal adenocarcinoma, could belong to the same pharmacological subtype regarding drug sensitivity to MEK inhibitors, which was determined by their genomic alterations, high occurrence of BRAF or KRAS mutations. Therapeutic concordance for chemotherapy drugs was identified across histologically disparate hematological tumors mainly due to the extraordinary activation of the cell cycle in blood cancers. A subcluster of SCLC had a more similar profile with hematological tumors, and was associated with the malignant phenotype, with a higher level of MYC expression. We developed a website to store and visualize the pharmacological subtypes of drugs, as well as their connected genomic and expression alterations.

bioinformatics↗

bioRxiv2019

Identifying hetero-protein complexes in the nuclear envelope

The nucleus is delineated by the nuclear envelope (NE), which is a double membrane barrier composed of the inner and outer nuclear membranes as well as a ~40 nm wide lumen. In addition to its barrier function, the NE acts as a critical signaling node for a variety of cellular processes which are mediated by protein complexes within this subcellular compartment. While fluorescence fluctuation spectroscopy (FFS) is a powerful tool for characterizing protein complexes in living cells, it was recently demonstrated that conventional FFS methods are not suitable for applications in the NE because of the presence of slow nuclear membrane undulations. We previously addressed this challenge by developing time-shifted mean-segmented Q (tsMSQ) analysis and applied it to successfully characterize protein homo-oligomerization in the NE. However, many NE complexes, such as the linker of the nucleoskeleton and cytoskeleton (LINC) complex, are formed by heterotypic interactions, which single-color tsMSQ is unable to characterize. Here, we describe the development of dual-color (DC) tsMSQ to analyze NE hetero-protein complexes built from proteins that carry two spectrally distinct fluorescent labels. Experiments performed on model systems demonstrate that DC tsMSQ properly identifies hetero-protein complexes and their stoichiometry in the NE by accounting for spectral crosstalk and local volume fluctuations. Finally, we applied DC tsMSQ to study the assembly of the LINC complex, a hetero-protein complex composed of Klarsicht/ANC-1/SYNE homology (KASH) and Sad1/UNC-84 (SUN) proteins, in the NE of living cells. Using DC tsMSQ, we demonstrate the ability of the SUN protein SUN2 and the KASH protein nesprin-2 to form a hetero-complex in vivo. Our results are consistent with previously published in vitro studies and demonstrate the utility of the DC tsMSQ technique for characterizing NE hetero-protein complexes.\n\nStatement of SignificanceProtein complexes found within the nuclear envelope (NE) play a vital role in regulating cellular functions ranging from gene expression to cellular movement. However, the assembly state of these complexes within their native environment remains poorly understood, which is compounded by a general lack of fluorescence techniques suitable for quantifying the oligomeric state of NE protein complexes. This study aims at addressing this issue by introducing dual-color time-shifted mean-segmented Q analysis as a fluorescence fluctuation method specifically designed to identify the average oligomeric state of hetero-protein complexes within the NE of living cells.

biophysics↗

bioRxiv2018

Bright split red fluorescent proteins with enhanced complementation efficiency for the tagging of endogenous proteins and visualization of synapses

Self-associating split fluorescent proteins (FPs) have been widely used for labeling proteins, scaffolding protein assembly and detecting cell-cell contacts. Newly developed self-associating split FPs, however, have suffered from suboptimal fluorescence signal. Here, by investigating the complementation process, we have demonstrated two approaches to improve split FPs: assistance through SpyTag/SpyCatcher interaction and directed evolution. The latter has yielded two split sfCherry3 variants with substantially enhanced overall brightness, facilitating the tagging of endogenous proteins by gene editing. Based on sfCherry3, we have further developed a new red-colored trans-synaptic marker called Neuroligin-1 sfCherry3 Linker Across Synaptic Partners (NLG-1 CLASP) for multiplexed visualization of neuronal synapses in living animals, demonstrating its broad applications.

cell biology↗