Biology subjects

Navarron, C. M.

Publications and source records attributed to Navarron, C. M..

5 recordsLinked to original sources

bioRxiv2026

Blade-dependent molecular identity and neurogenic potential in the adult dentate gyrus

The dentate gyrus (DG) is a key hippocampal gateway for cognition and emotion and a major site of adult neurogenesis, yet its organization along the transverse (suprapyramidal- infrapyramidal) axis remains poorly understood. Here, by integrating bulk RNA sequencing of microdissected mouse DG blades with spatial transcriptomics and single-nucleus RNA sequencing, we define the suprapyramidal and infrapyramidal blades (SB and IB) as distinct molecular compartments characterized by anterior-posterior-dependent gene expression programs. Functionally, the SB exhibits enhanced neurogenic activity, particularly in the anterior DG, including increased progenitor proliferation and neuronal differentiation, whereas the IB contains a larger pool of quiescent neural stem cells. Together, these findings reveal molecular and functional specialization along both transverse and longitudinal axes of the DG and provide a framework for interrogating hippocampal subregional organization in health and disease.

neuroscience↗

bioRxiv2023

The hypermorphic PLCγ2 S707Y variant dysregulates microglial cell function: insight into PLCγ2 activation in brain health and disease, and opportunities for therapeutic modulation.

Phospholipase C-gamma 2 (PLC{gamma}2) is highly expressed in hematopoietic and immune cells, where it is a key signalling node enabling diverse cellular functions. Within the periphery, gain-of-function (GOF) PLC{gamma}2 variants, such as the strongly hypermorphic S707Y, cause severe immune dysregulation. The milder hypermorphic mutation PLC{gamma}2 P522R increases longevity and confers protection in central nervous system (CNS) neurodegenerative disorders, implicating PLC{gamma}2 as a novel therapeutic target for treating these CNS indications. Currently, nothing is known about what consequences strong PLC{gamma}2 GOF has on CNS functionality, and more precisely on the specific biological functions of microglia. Using the PLC{gamma}2 S707Y variant as a model of chronic activation we investigated the functional consequences of strong PLC{gamma}2 GOF on human microglia. PLC{gamma}2 S707Y expressing human inducible pluripotent stem cells (hiPSC)-derived microglia exhibited hypermorphic enzymatic activity under both basal and stimulated conditions, compared to PLC{gamma}2 wild type. Despite the increase in PLC{gamma}2 enzymatic activity, the PLC{gamma}2 S707Y hiPSC-derived microglia display diminished functionality for key microglial processes including phagocytosis and cytokine secretion upon inflammatory challenge. RNA sequencing revealed a downregulation of genes related to innate immunity and response, providing molecular support for the phenotype observed. Our data suggests that chronic activation of PLC{gamma}2 elicits a detrimental phenotype that is contributing to unfavourable CNS functions, and informs on the therapeutic window for targeting PLC{gamma}2 in the CNS. Drug candidates targeting PLC{gamma}2 will need to precisely mimic the effects of the PLC{gamma}2 P522R variant on microglial function, but not those of the PLC{gamma}2 S707Y variant. HighlightsO_LIThe impact of strongly hypermorphic variants of PLC{gamma}2 have not been studied in brain and yet PLC{gamma}2 is implicated in modifying risk of CNS disorders including Alzheimers disease C_LIO_LITo address this, we explored the role of the strongly hypermorphic PLC{gamma}2 S707Y variant in hiPSC-derived microglia C_LIO_LIS707Y increases PLC{gamma}2 enzymatic activity and intracellular calcium flux C_LIO_LIPhagocytosis and cytokine production are diminished in PLC{gamma}2 S707Y microglia C_LIO_LIPLC{gamma}2 S707Y downregulates expression of genes related to innate immunity and response C_LIO_LIModulation of PLC{gamma}2 for therapy must recapitulate the positive effects of moderate hypermorphic variants on microglial functions whilst avoiding detrimental effects of strongly hypermorphic variants like PLC{gamma}2 S707Y C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=188 SRC="FIGDIR/small/564579v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@9f0903org.highwire.dtl.DTLVardef@108d26forg.highwire.dtl.DTLVardef@2fb691org.highwire.dtl.DTLVardef@7af80c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

A primary rodent triculture model to investigate the role of glia-neuron crosstalk in regulation of neuronal activity.

Neuroinflammation and hyperexcitability have been implicated in the pathogenesis of neurodegenerative disease, and new models are required to investigate the cellular crosstalk involved in these processes. We developed an approach to generate a quantitative and reproducible triculture system that is suitable for pharmacological studies. While primary rodent cells were previously grown in a coculture medium formulated to support only neurons and astrocytes, we now optimised a protocol to generate tricultures containing neurons, astrocytes and microglia by culturing in a medium designed to support all three cell types and adding exogenous microglia to cocultures. Immunocytochemistry was used to confirm the intended cell types were present. The percentage of ramified microglia in the tricultures decreases as the number of microglia present increases. Multi-electrode array (MEA) recordings indicate that microglia in the triculture model suppress neuronal activity in a dose-dependent manner. Neurons in both cocultures and tricultures were responsive to the potassium channel blocker 4-aminopyridine (4-AP) suggesting that neurons remained viable and functional in the triculture model. Furthermore, suppressed neuronal activity in tricultures correlated with decreased densities of dendritic spines and of the postsynaptic protein Homer1 along dendrites, indicative of a direct or indirect effect of microglia on synapse function. We thus present a functional triculture model, which, due to its more complete cellular composition, is a more relevant model than standard cocultures. The model can be used to probe glia-neuron interactions and subsequently aid the development of assays for drug discovery, using neuronal excitability as a functional endpoint.

neuroscience↗

bioRxiv2021

Sublayer- and cell-type-specific neurodegenerative transcriptional trajectories in hippocampal sclerosis

Hippocampal sclerosis, the major neuropathological hallmark of temporal lobe epilepsy, is characterized by different patterns of neuronal loss. The mechanisms of cell-type specific vulnerability, their progression and histopathological classification remain controversial. Here using single-cell electrophysiology in vivo and immediate early gene expression, we reveal that superficial CA1 pyramidal neurons are overactive in epileptic rats and mice in vivo. Bulk tissue and single-nucleus expression profiling disclosed sublayer-specific transcriptomic signatures and robust microglial pro-inflammatory responses. Transcripts regulating neuronal processes such as voltage-channels, synaptic signalling and cell adhesion molecules were deregulated by epilepsy differently across sublayers, while neurodegenerative signatures primarily involved superficial cells. Pseudotime analysis of gene expression in single-nuclei and in situ validation revealed separated trajectories from health to epilepsy across cell types, and identified a subset of superficial cells undergoing a later stage in neurodegeneration. Our findings indicate sublayer- and cell type-specific changes associated with selective CA1 neuronal damage contributing to progression of hippocampal sclerosis.

neuroscience↗

bioRxiv2019

Neuronal identity is maintained in the adult brain through KAT3-dependent enhancer acetylation

Very little is known about the mechanisms responsible for maintaining cell identity in mature tissues. The paralogous type 3 lysine acetyltransferases (KAT3) CBP and p300 are both essential during development, but their specific functions in nondividing differentiated cells remains unclear. Here, we show that when both proteins are simultaneously knocked-out in excitatory neurons of the adult brain, the mice express a rapidly progressing neurological phenotype associated with reduced dendritic complexity and electrical activity, the transcriptional shutdown of neuronal genes, and a dramatic loss of H3K27 acetylation and pro-neural transcription factor binding at neuronal enhancers. The neurons lacking both KAT3 rapidly acquire a molecularly undefined fate with no sign of dedifferentiation, transdifferentiation or death. Restoring CBP expression or lysine acetylation reestablished neuronal-specific transcription. Our experiments demonstrate that KAT3 proteins act as fate-keepers in excitatory neurons and other cell types by jointly safeguarding chromatin acetylation levels at cell type-specific enhancers throughout life.

cell biology↗