Biology subjects

Kettenmann, H.

Publications and source records attributed to Kettenmann, H..

4 recordsLinked to original sources

bioRxiv2023

Microglia undergo transcriptional, translational and functional adaptations to dark and light phases in laboratory mice

Microglia cells are increasingly recognized to contribute to brain health and disease. Preclinical studies using laboratory rodents are essential to advance our understanding of the physiological and pathophysiological functions of these cells in the central nervous system. Rodents are nocturnal animals, and they are mostly maintained in a defined light-dark cycle within animal facilities, with many laboratories investigating microglial molecular and functional profiles during the animals light (sleep) phase. However, only a few studies have considered possible differences in microglial functions between the active and sleep phases. Based on initial evidence suggesting that microglial intrinsic clock genes can affect their phenotype, we sought to investigate differences in transcriptional, proteotype and functional profiles of microglia between light (sleep) and dark (active) phases, and how these changes are affected in pathological models. We found marked transcriptional and proteotype differences between microglia harvested during the light or dark phase. Amongst others, these differences related to genes and proteins associated with immune responses, motility, and phagocytosis, which were reflected by functional alterations in microglial synaptic pruning and response to bacterial stimuli. Possibly accounting for such circadian changes, we found RNA and protein regulation in SWI/SNF and NuRD chromatin remodeling complexes between light and dark phases. Importantly, we show that microglial circadian transcriptional changes are impaired in a model of immune-mediated neurodevelopmental disorders. Our findings emphasize the importance of considering circadian factors in studying microglial cells and indicate that implementing a circadian perspective is pivotal for advancing our understanding of their physiological and pathophysiological roles in brain health and disease. This may also open novel avenues towards therapeutic strategies for modulating microglial functions during specific windows of the active or sleep phase.

neuroscience↗

bioRxiv2023

TREM2 promotes glioma progression and angiogenesis mediated by microglia/brain macrophages

TREM2, a myeloid cell-specific signaling molecule, controls essential functions of microglia and impacts on the pathogenesis of Alzheimers disease and other neurodegenerative disorders. TREM2 is also highly expressed in tumor-associated macrophages and plays detrimental roles in an experimental mouse sarcoma model. Here we studied whether TREM2 influences glioma progression. We found a sex- dependent effect of TREM2: the glioma volume is significantly attenuated in TREM2- deficient male but not female mice injected with GL261-EGFP glioma cells. The accumulation of glioma-associated microglia/macrophages (GAMs) and vascularization is reduced in male TREM2-deficient mice. A transcriptomic analysis of glioma tissue revealed that TREM2 deficiency suppresses angiogenic genes and MHC clusters. In an organotypic slice model devoid of functional vascularization, the tumor size was not affected by TREM2-deficiency. In human resection samples from glioblastoma, TREM2 is upregulated in GAMs. Based on the TCGA and CGGA databases, the TREM2 expression levels are negatively correlated with survival. Thus, the TREM2-dependent crosstalk between GAMs and the vasculature formation promotes glioma growth. Graphic abstractTREM2-dependent crosstalk between glioma-associated microglia/macrophages and the vasculature formation promotes glioma growth in male glioma mouse model. Created with BioRender.com O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=137 SRC="FIGDIR/small/540621v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@65bec7org.highwire.dtl.DTLVardef@1d00961org.highwire.dtl.DTLVardef@117ee5eorg.highwire.dtl.DTLVardef@227994_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

In situ Patch-seq analysis of microglia reveals a lack of stress genes as found in FACS-isolated microglia

We applied the patch-seq technique to harvest transcripts from individual microglial cells from cortex, hippocampus and corpus callosum of acute brain slices from adult mice. After recording membrane currents with the patch-clamp technique, the cytoplasm was collected via the pipette and underwent adapted SMART-seq2 preparation with subsequent sequencing. On average, 4138 genes were detected in 113 cells from hippocampus, corpus callosum and cortex, including microglia markers such as Tmem119, P2ry12 and Siglec-H. Comparing our dataset to previously published single cell mRNA sequencing data from FACS-isolated microglia indicated that two clusters of cells were absent in our patch-seq dataset. Pathway analysis of marker genes in FACS-specific clusters revealed association with microglial activation and stress response. This indicates that under normal conditions microglia in situ lack transcripts associated with a stress-response, and that the microglia-isolation procedure by mechanical dissociation and FACS triggers the expression of genes related to activation and stress.

immunology↗

bioRxiv2022

The IgCAM BT-IgSF (IgSF11) is essential for connexin43-mediated astrocyte-astrocyte and ependymal cell-cell coupling

The type I transmembrane protein BT-IgSF is predominantly localized in the brain and testes. It belongs to the CAR subgroup of Ig cell adhesion proteins, which have been hypothesized to regulate connexin expression or localization. Here, we studied the putative link between BT-IgSF and connexins in astrocytes, ependymal cells and neurons of the mouse. Global knockout of BT-IgSF caused an increase in the clustering of connexin43 (Gja1), but not of connexin30 (Gjb6), on astrocytes and ependymal cells. Additionally, knockout animals displayed reduced expression levels of connexin43 protein in the cortex and hippocampus. Importantly, analysis of biocytin spread in hippocampal or cortical slices from mature mice of either sex revealed a decrease in astrocytic cell-cell coupling in the absence of BT-IgSF. Blocking either protein biosynthesis or proteolysis showed that the lysosomal pathway increased connexin43 degradation. Localization of connexin43 in subcellular compartments was not impaired in the mutant. In contrast to connexin43 the localization and expression of connexin36 (Gjd2) on neurons was not affected by the absence of BT-IgSF. Overall, our data indicate that the IgCAM BT-IgSF is essential for correct gap junction-mediated astrocyte-to-astrocyte and ependymal cell-to-ependymal cell communication. Significance StatementAstrocytes regulate a variety of physiological processes in the developing and adult brain that are essential for proper brain function. Astrocytes form extensive networks in the brain and communicate via gap junctions. Disruptions of gap junction coupling are found in several diseases such as neurodegeneration or epilepsy. Here, we demonstrate that the cell adhesion protein BT-IgSF is essential for gap junction mediated coupling between astrocytes in the cortex and hippocampus.

cell biology↗