Biology subjects

Cremer, H.

Publications and source records attributed to Cremer, H..

9 recordsLinked to original sources

bioRxiv2025

Integrated 3D Light-Sheet and 2D Multiplex Imaging for Deep Histological Profiling of a Somatic Mouse Glioblastoma Model

Glioblastoma is a devastating brain cancer. Despite intense research, patient survival has not significantly increased over the past decades and efficient treatment is currently not available. Therefore, the fundamental understanding of the disease, based on the development of relevant animal models, combined with the development of efficient tools for their deep analysis, represents a priority. Neural Stem cells in the subventricular zone of the forebrain have been identified as cells of origin for glioblastoma, leading to the development of new somatic lineage models based on in vivo brain electroporation. While such models have been characterized in depths by sequencing approaches, systematic histological analyses are currently scarce. Here we present the multimodal histological characterization of a transgenesis independent somatic glioblastoma model in mice. Using 3D light sheet imaging we demonstrate that the model is highly reproducible, allowing quantitative evaluation of tumor growth over large cohorts. Using multiplex imaging by MICS technology we systematically characterize the cellular landscape and molecular composition of the induced tumors, as well as their micro- and macro-environments, and provide a resource of mouse compatible antibodies for cancer research. Finally, we use the model to show that tissue clearing and 3D light sheet microscopy of whole brains can be combined with subsequent multiplex imaging, allowing deep spatial characterization of the tumor proteome in pre-identified brain regions.

cancer biology↗

bioRxiv2025

In Vivo AGO-APP For Cell-Type- and Compartment-Specific miRNA Profiling in the Mouse Brain

AGO-APP through the expression of the T6B peptide permits the isolation of Ago-bound miRNAs. Here we present the generation and characterization of two transgenic mouse lines allowing to perform AGO-APP in vivo. First, we generated mice for CRE-dependent expression of T6B in the cytoplasm. Using this line we performed Ago-APP in olfactory bulb (OB) inhibitory interneurons and cerebral cortex excitatory neurons. Bioinformatic analysis validated the high reproducibility of the approach. It also demonstrated that, despite global miRNome conservation between the two cell types, a set of miRNAs including the miR-200 family and the miR-183/96/182 cluster, is massively enriched in OB interneurons which is consistent with previous observations. In the second mouse line T6B is fused to the postsynaptic protein PSD95. Isolation of T6B-PSD95 fractions from OB and cortical neurons identified specific sets of post-synapse enriched miRNAs. Gene ontology analyses confirmed that these miRNAs preferentially target mRNAs related to synaptic functions. MotivationCollectively, miRNAs are required for all biological processes in eukaryotes. However, due to a lack of appropriate methodological tools, the actual mode of action of individual miRNAs in a given cell is currently poorly understood. In this article, we describe a novel approach to study the specific expression of miRNAs in vivo, at the level of cell type and in a specific cell compartment.

neuroscience↗

bioRxiv2023

Gliogenesis from the subventricular zone modulates the extracellular matrix at the glial scar after brain ischemia

Activation of the subventricular zone (SVZ) following cerebral ischemia is one of the brains early responses to counteract neuron loss and minimize tissue damage. Impaired brain regions communicate with the SVZ through various chemotactic signals that promote cell migration and differentiation, primarily involving neural stem cells (NSC), neuroblasts, or glioblasts. However, the activation of gliogenesis and the role of newly formed astrocytes in the post-ischemic scenario remain subjects of debate. We have previously demonstrated that adenosine release after brain ischemia prompts the SVZ to generate new astrocytes. Here, we used transient brain ischemia in mice to identify the cellular origin of these astrocytes within the SVZ neurogenic niche and to investigate their role in the pathological process. By combining immunofluorescence, BrdU-tracing, and genetic cell labeling, we tracked the migration of newborn astrocytes, positive for the proteoglycan marker Thbs4, from the dorsal and medial SVZ to the perilesional barrier surrounding the ischemic core, known as the "glial scar". We found that these Thbs4-positive astrocytes modulate the dense extracellular matrix at the lesion border by both synthesizing and degrading hyaluronan. We also show that while the accumulation of hyaluronan at the lesion site is sufficient to recruit newborn astrocytes, its degradation at the SVZ correlates with gliogenesis. These findings suggest that newborn astrocytes could be a promising pharmacological target for modulating the glial scar after brain ischemia and facilitate tissue regeneration.

neuroscience↗

bioRxiv2023

Dynamic intraglomerular neuronal ensembles represent odor identity and concentration

The olfactory system has been extensively studied from an anatomical and functional point of view, yet how and where certain basic odor characteristics such as identity and concentration are represented in the brain remains poorly understood. The glomerular layer of the olfactory bulb is the first brain region that integrates olfactory signals and enables a topographic representation of odor identity. We investigated this odor encoding at the intraglomerular network level using genetic labeling, in vivo imaging, and computational methods. Our analyses demonstrated that glomerular glutamatergic neurons encode both odor identity and concentration. Furthermore, in vivo structural and functional imaging of sister neurons revealed the emergence of intraglomerular neuronal ensembles governed by odor identity and concentration. These findings revealed a novel network mechanism that enables the simultaneous coding of odor identity and concentration within glomerular modules, suggesting a potential mechanism for odor decorrelation and a new model for odor information processing in the olfactory bulb. One-sentence summaryUnraveling the scent puzzle: Discovery of intraglomerular neuronal ensembles sheds light on odor representation in the brain.

neuroscience↗

bioRxiv2023

In vivo AGO-APP identifies a module of microRNAs cooperatively controlling exit from neural stem cell state

MicroRNAs (miRNAs) are essential regulators of all developmental processes. Their function is particularly important during neurogenesis, when the production of large numbers of neurons from a limited number of neural stem cells depends on the precise control of determination, proliferation and differentiation. However, miRNA regulation of target mRNAs is highly promiscuous, one miRNA can target many mRNAs and vice versa, raising the question of how specificity is achieved to elicit a precise regulatory response. Here we introduce AGO-APP, a novel approach to purify Argonaute-bound miRNAs directly from cells and tissues in vivo, to isolate actively inhibiting miRNAs from different neural cell populations in the larval Drosophila central nervous system. We identify a defined group of miRNAs that redundantly target all iconic genes known to control the transition from neuroblasts to neurons. In vivo functional studies demonstrate that knockdown of individual miRNAs does not induce detectable cellular phenotypes. However, simultaneous knockdown of multiple miRNAs leads to precocious stem cell differentiation, demonstrating functional interdependence. Thus, miRNAs cooperate within a regulatory module to specify the targeted gene network.

developmental biology↗

bioRxiv2022

Sensory deprivation triggers phenotypic adjustment of dopaminergic interneurons in the mouse olfactory bulb

Olfactory sensory activity is a main factor factor controlling intergration and survival of neurons in the olfactory bulb. However, its impact on specific neuronal subtypes is unclear. Using reversible unilateral naris closure in concert with longitudinal in vivo imaging we show here that newborn GABAergic interneurons undergo significant cell death under sensory deprivation. In contrast, dopaminergic OB neurons survive under deprivation, but react with a reversible downregulation of tyrosine hydroxylase expression. long abstractNeurogenesis persists in the mammalian subventricular zone after birth, producing various populations of olfactory bulb (OB) interneurons. These include GABAergic and mixed dopaminergic/GABAergic double neurotransmitter neurons for the glomerular layer. While olfactory sensory activity is one of the main factors controlling newborn neuron integration, its effect on specific neuronal subtypes is far less clear. Here we use a reversible unilateral deprivation paradigm in combination with longitudinal in vivo imaging to characterize the behavior of newborn glomerular neurons. We find that a substantial fraction of purely GABAergic neurons die after four weeks of sensory deprivation. Tyrosine Hydroxylase (TH) positive dopaminergic/ GABAergic neurons show no signifficant cell death under deprivation, but react with an important decrease in TH expression levels. Importantly, this effect reverses after naris reopening, pointing to a specific adaptation of this neuron population to the level of sensory activity. We conclude that sensory deprivation induces adjustments in the excitation/inhibition balance of the OB implicating cell death and adaptation of neurotransmitter use in specific neuron types.

neuroscience↗

bioRxiv2020

Regulatory interactions between Vax1, Pax6, and miR-7 regionalize the lateral Ventricular-Subventricular Zone during post-natal Olfactory Bulb neurogenesis in mice

Several subtypes of interneurons destined for the olfactory bulb are continuously generated after birth by neural stem cells located in the ventricular-subventricular zones of the lateral ventricles. Future neuronal identity depends on the positioning of pre-determined neural stem cells along the ventricle walls, which, in turn, depends on delimited expression domains of transcription factors and their cross regulatory interactions. However, mechanisms underlying positional identity of neural stem cells are still poorly understood. Here we show that the transcription factor Vax1 controls the production of two specific neuronal sub-types. First, it is directly necessary to generate Calbindin expressing interneurons from ventro-lateral progenitors. Second, it represses the generation of dopaminergic neurons by dorso-lateral progenitors through inhibiting Pax6 expression in the dorso-lateral wall. We provide evidence that this repression occurs via activation of microRNA miR-7, targeting Pax6 mRNA.

neuroscience↗

bioRxiv2018

Morphofunctional deficits in the cerebral cortex of NeuroD2 mutant mice are associated with autism/schizophrenia-like behaviors

We identified seven families associating NEUROD2 pathogenic mutations with ASD and intellectual disability. To get insight into the pathophysiological mechanisms, we analyzed cortical development in Neurod2 KO mice. Cortical projection neurons (CPNs) over-migrated during embryogenesis, inducing abnormal thickness and laminar positioning of cortical layers. At juvenile ages, dendritic spine turnover and intrinsic excitability were increased in L5 CPNs. Differentially expressed genes in Neurod2 KO mice were enriched for voltage-gated ion channels, and the human orthologs of these genes were strongly associated with ASD. Furthermore, adult Neurod2 KO mice exhibited core ASD-like behavioral abnormalities. Finally, by generating Neurod2 conditional mutant mice we demonstrate that forebrain excitatory neuron-specific Neurod2 deletion recapitulates cellular and behavioral ASD phenotypes found in full KO mice. Our findings demonstrate crucial roles for Neurod2 in cortical development and function, whose alterations likely account for ASD and related symptoms in the newly defined NEUROD2 mutation syndrome.

neuroscience↗

bioRxiv2018

Neuronal integration in the adult olfactory bulb is a non-selective addition process

Adult neurogenesis is considered a competition in which neurons scramble during a critical period for integration and survival. Moreover, newborn neurons are thought to replace preexisting ones that die. Despite a wealth of evidence supporting this model, systematic in vivo observations of the process are still scarce. We used 2-photon imaging to study neuronal integration and survival directly in the olfactory bulb (OB) of living mice. Long-term tracking of over 1400 neurons demonstrated that cell-loss in the OB is virtually absent. Neuronal death resembling a critical period was induced by standard doses of BrdU or EdU, but disappeared when low doses of EdU were used, demonstrating toxicity. Finally, we demonstrate that the OB grows throughout life. This shows that neuronal selection during OB-neurogenesis does not occur during integration and argues against the existence of a critical period. Moreover, the OB is not a \"turnover\" system but shows lifelong neuronal addition.

neuroscience↗