Biology subjects

Dietrich, L.

Publications and source records attributed to Dietrich, L..

6 recordsLinked to original sources

bioRxiv2026

Nuclear receptor LRH-1 regulates early T cell development in mice

T cell development in the thymus requires tightly coordinated transcriptional programs that regulate lineage commitment, proliferation and differentiation. While key transcription factors controlling these processes have been extensively characterized, the contribution of the low expressed nuclear receptor Liver Receptor Homolog 1 (LRH-1, Nr5a2) in T cell development remains unexplored. Here, we investigated the role of LRH-1 in thymocyte maturation using an inducible ex vivo deletion system and in vivo Lck-Cre- and CD4-Cre-mediated LRH-1 knockout mouse models. We demonstrate that inducible LRH-1 deletion impairs early thymocyte development, identifying LRH-1 as a critical regulator of the double negative (DN)2/DN3 to DN4 transition. Early Lck-Cre-mediated deletion of LRH-1, but not CD4-Cre-mediated deletion at the double positive stage, resulted in markedly reduced thymic size and cellularity, indicating a stage-specific requirement for LRH-1 during thymopoiesis. Lck-Cre-mediated LRH-1 deletion led to a decreased frequency of mature CD4 T cells in peripheral lymphoid organs, while the remaining mature T cells were predominantly Cre reporter-negative and therefore escaped LRH-1 deletion. CD4 T cells that escaped Cre-mediated LRH-1 deletion exhibited impaired T cell activation marker expression and cytokine secretion. In vivo, these defects resulted in attenuated T cell effector function and compromised regulatory T cell-mediated protection in a T cell transfer model of colitis, indicating impaired effector and regulatory T cell function under (patho)physiological conditions. Collectively, our findings identify LRH-1 as a critical, previously unrecognized regulator of early thymocyte development, and establish its essential role in shaping functional peripheral CD4 T cell-mediated immune responses.

immunology↗

bioRxiv2025

Correlative MS Imaging for cellular identification and analysis of in situ cryo-ET

In situ cryo-electron tomography (cryo-ET) offers direct access to protein structures in their native state and environment. A central challenge for this technique is the identification and classification of imaged cells, as sample heterogeneity with respect to cell type and functional state can significantly impact the data. Currently, cells can be classified using subtomogram averaging or fluorescent labeling, which require sufficiently distinguishable macromolecules, genetic modifications, or the availability of suitable labels. In MALDI-MS Imaging (MSI) individual cells can be identified and classified reliably, making use of the distributions of phospholipid species, metabolites and small proteins with characteristic profiles for specific cell types. Here we present an integrated pipeline combining MSI and in situ cryo-ET for single-cell identification and classification. Our approach enables MSI data acquisition directly from EM grids and can be used on any eukaryotic single-cell cryo-ET sample without prior modification in less than 36 h. We apply this workflow to describe cell-to-cell heterogeneity in cultured HeLa cells, to distinguish between distantly related HeLa and Polytomella cells, and between primary cultured rat neurons and glial cells. Finally we present a data integration workflow combining cryo-ET, light microscopy and MSI aligned in the same coordinate system to facilitate efficient data visualization and interpretation. We anticipate that this approach will change the way that structural biologists can approach cellular heterogeneity in cryo-ET, as cells can be identified and classified reliably post acquisition.

biophysics↗

bioRxiv2025

Sequestration of the phagocyte metabolite itaconate by P. aeruginosa RpoN promotes successful pulmonary infection

AbstractThe phagocyte immunometabolite itaconate, normally toxic to bacteria, functions as a signal to stimulate the adaptation of the pulmonary pathogen Pseudomonas aeruginosa to the lung. Itaconate is actively transported into P. aeruginosa where it induces {sigma}54 rpoN expression and co-valently binds cysteine residues on RpoN. RpoN not only functions as a sink to limit itaconate toxicity but S- itaconated RpoN promotes increased utilization of the Entner Doudoroff pathway, optimizing bacterial metabolism in the setting of inflammation. S-itaconation of RpoN directs a global metabolic response that fuels pulmonary infection.

microbiology↗

bioRxiv2024

In situ structure and rotary states of mitochondrial ATP synthase in whole cells

Cells depend on a continuous supply of ATP, the universal energy currency. In mitochondria, ATP is produced by a series of redox reactions, whereby an electrochemical gradient is established across the inner mitochondrial membrane. The ATP synthase harnesses the energy of the gradient to generate ATP from ADP and inorganic phosphate. We determined the structure of ATP synthase within mitochondria of the unicellular alga Polytomella by electron cryo-tomography. Sub-tomogram averaging revealed six rotary positions of the central stalk, subclassified into 21 substates of the F1 head. The Polytomella ATP synthase forms helical arrays with multiple adjacent rows defining the cristae ridges. The structure of ATP synthase under native operating conditions in the presence of a membrane potential represents a pivotal step toward the analysis of membrane protein complexes in situ.

molecular biology↗

bioRxiv2024

A constricted mitochondrial morphology optimizes respiration.

Mitochondria assemble in a dynamic tubular network with a morphology governed by mitochondrial fusion and fission, which regulate all mitochondrial functions including oxidative phosphorylation 1-4. Yet, the link between mitochondrial morphology and respiration remains unclear 5-9. Here, we discover a previously unknown mitochondrial morphology dedicated to respiratory growth of Saccharomyces cerevisiae, which we refer to as "Ringo". The Ringo morphology is characterized by stable constrictions of mitochondrial tubules. Ringo constrictions are mediated by the yeast dynamin Dnm1 and, unlike mitochondrial fission 10-12, occur in the absence of contacts with the endoplasmic reticulum. Our data show that the Ringo morphology regulates mitochondrial DNA homeostasis during respiration to ensure stoichiometric assembly of OXPHOS complexes, demonstrating that the shape of mitochondria actively contributes to optimal respiration. One-Sentence Summary: We report a new mitochondrial morphology that actively contributes to optimal respiration in yeast.

cell biology↗

bioRxiv2020

Subnanometer-resolution structure determination in situ by a hybrid subtomogram averaging - single particle cryoEM - workflow

Cryo electron tomography (cryo-ET) combined with subtomogram averaging (StA) enables structural determination of macromolecules in their native context. A few structures were reported by StA at resolution higher than 4.5 [A], however all of these are from viral structural proteins or vesicle coats. Reaching high resolution for a broader range of samples is uncommon due to beam-induced sample drift, poor signal-to-noise ratio (SNR) of images, challenges in CTF correction, limited number of particles. Here we propose a strategy to address these issues, which consists of a tomographic data collection scheme and a processing workflow. Tilt series are collected with higher electron dose at zero-degree tilt in order to increase SNR. Next, after performing StA conventionally, we extract 2D projections of the particles of interest from the higher SNR images and use the single particle analysis tools to refine the particle alignment and generate a reconstruction. We benchmarked our proposed hybrid StA (hStA) workflow and improved the resolution for tobacco mosaic virus from 7.2 to 5.2 [A] and the resolution for the ion channel RyR1 in crowded native membranes from 12.9 to 9.1 [A]. We demonstrate that hStA can improve the resolution obtained by conventional StA and promises to be a useful tool for StA projects aiming at subnanometer resolution or higher.

biochemistry↗