Biology subjects

Pena-Ortiz, M. A.

Publications and source records attributed to Pena-Ortiz, M. A..

3 recordsLinked to original sources

bioRxiv2025

Astrocytic Chromatin Remodeler ATRX Gates Hippocampal Memory Consolidation through Metabolic and Synaptic Regulation

Astrocytes are increasingly recognized as active regulators of synaptic transmission and memory, yet the epigenetic mechanisms underlying their contribution to cognitive processes remain poorly defined. Here, we investigated the role of the chromatin remodeler ATRX in astrocytes by generating mice with inducible, astrocyte-specific Atrx deletion (aiKO) using tamoxifen administration at postnatal days 10-12, resulting in ATRX loss in approximately half of hippocampal and cortical astrocytes. Transcriptomic profiling of hippocampal tissue at one and three months revealed a progressive increase in differentially expressed genes, with early enrichment for cytoskeletal and immune pathways and later dysregulation of energy metabolism, ion transport, and synaptic gene sets. Electrophysiological recordings from CA1 pyramidal neurons in aiKO slices demonstrated increased neuronal excitability, reduced membrane capacitance, and decreased frequency of spontaneous excitatory postsynaptic currents, indicating non-cell-autonomous neuronal dysfunction. Morphological analysis identified a transient reduction in dendritic branching at one month and a selective loss of thin dendritic spines by three months, without changes in total dendrite length or overall spine density. Behaviorally, aiKO mice displayed normal locomotion, anxiety, and short-term memory, but exhibited deficits in 24-hour novel object recognition and long-term spatial memory in the Morris water maze. These findings demonstrate that ATRX-mediated chromatin remodeling in astrocytes is essential for maintaining hippocampal transcriptional homeostasis, neuronal function, and long-term memory. Our results highlight a critical role for astrocytic epigenetic regulation in cognitive processes and suggest that astrocyte dysfunction may contribute to the pathogenesis of ATR-X syndrome and related intellectual disability disorders, underscoring the importance of targeting multiple cell types for therapeutic intervention. HighlightsO_LIAstrocytic ATRX loss causes non-cell-autonomous neuronal hyperexcitability C_LIO_LIInducing ATRX deficiency in astrocytes causes selective long-term memory deficits C_LIO_LIDynamic transcriptomic changes reveal metabolic and synaptic pathway dysregulation C_LI

neuroscience↗

bioRxiv2022

Systemic and intrinsic functions of ATRX in glial cell fate and CNS myelination

Neurodevelopmental disorders are often characterized by abnormal production of myelin, an extension of the oligodendrocyte plasma membrane wrapped around axons to facilitate nerve conduction. However, the molecular mechanisms that control myelination during brain development are incompletely resolved. Here, we provide evidence that loss of ATRX, encoded by the gene mutated in the ATR-X intellectual disability syndrome, leads to myelin deficits in the mouse CNS. While postnatal systemic thyroxine administration can improve myelination, the rescue is incomplete, pointing to additional roles of ATRX in this process. We show that targeted inactivation of ATRX in postnatal oligodendrocyte progenitor cells (OPCs), but not in neurons, also leads to myelination deficits, demonstrating cell-intrinsic effects of ATRX deficiency. A subset of ATRX-null OPCs express lower levels of oligodendrocyte specification and differentiation markers, including the basic helix-loop-helix Olig2 transcription factor. Mechanistically, we provide evidence that ATRX occupies genomic sites in OPCs marked by H3K27Ac, CHD7 and CHD8 and demonstrate that reduced Olig2 expression is associated with decreased H3K27Ac. Finally, our data suggest that ATRX-null OPCs acquire a more plastic state and can exhibit astrocyte-like features in vitro and in vivo, supporting a model in which ATRX regulates the onset of myelination by promoting OPC identity and suppressing astrogliogenesis. These previously unrecognized functions of ATRX might explain white matter pathogenesis in ATR-X syndrome patients.

neuroscience↗

bioRxiv2021

Selective isolation of mouse glial nuclei optimized for reliable downstream omics analyses

BackgroundIsolation of cell types of interest from the brain for molecular applications presents several challenges, including cellular damage during tissue dissociation or enrichment procedures, and low cell number in the tissue in some cases. Techniques have been developed to enrich distinct cell populations using immunopanning or fluorescence activated cell/nuclei sorting. However, these techniques often involve fixation, immunolabeling and DNA staining steps, which could potentially influence downstream omics applications. New MethodTaking advantage of readily available genetically modified mice with fluorescent-tagged nuclei, we describe a technique for the purification of cell-type specific brain nuclei, optimized to decrease sample preparation time and to limit potential artefacts for downstream omics applications. We demonstrate the applicability of this approach for the purification of glial cell nuclei and show that the resulting cell-type specific nuclei obtained can be used effectively for omics applications, including ATAC-seq and RNA-seq. ResultsWe demonstrate excellent enrichment of fluorescently-tagged glial nuclei, yielding high quality RNA and chromatin. We identify several critical steps during nuclei isolation that help limit nuclei rupture and clumping, including quick homogenization, dilution before filtration and loosening of the pellet before resuspension, thus improving yield. Sorting of fluorescent nuclei can be achieved without fixation, antibody labelling, or DAPI staining, reducing potential artifactual results in RNA-seq and ATAC-seq analyses. We show that reproducible glial cell type-specific profiles can be obtained in transcriptomic and chromatin accessibility assays using this rapid protocol. Comparison with existing methodsOur method allows for rapid enrichment of glial nuclei populations from the mouse brain with minimal processing steps, while still providing high quality RNA and chromatin required for reliable omics analyses. ConclusionsWe provide a reproducible method to obtain nucleic material from glial cells in the mouse brain with a quick and limited sample preparation. Highlights- Fast and easy isolation and sorting of glial nuclei from the mouse brain - Reproducible and versatile processing of enriched nuclei for omics applications

molecular biology↗