Biology subjects

Marichal, N.

Publications and source records attributed to Marichal, N..

5 recordsLinked to original sources

bioRxiv2026

Functional recruitment of astrocyte-derived neurons into the mouse visual cortex

Inducing neurogenesis from glia could permit circuit remodeling and neuron replacement in the brain. Indirect evidence suggests that glia-to-neuron reprogramming is feasible, but the dynamics of conversion have not been directly observed, and it remains unclear whether glia-derived cortical neurons can functionally integrate into brain circuits. Here, we use two-photon imaging to visualize the reprogramming of astroglia into induced neurons in the mouse cortex in vivo. We track the emergence of spontaneous neuron-like calcium transients in astrocyte-derived induced neurons, demonstrating their functional activity in vivo. Importantly, these induced neurons exhibit orientation tuned, visually evoked calcium responses, demonstrating their functional integration into cortical circuitry - a prerequisite for their utility in circuit repair. Thus, astrocytes can be recruited to generate functional neurons in the postnatal cortex, enabling circuit remodeling in perinatal injury or neurodevelopmental disorders without relying on external cellular sources.

neuroscience↗

bioRxiv2026

Dlx2 reprograms the transcriptome and laminar position of glia-derivedAscl1-induced interneurons

Direct lineage reprogramming of glial cells into neurons offers a promising strategy to repair diseased brain circuits, but engineering defined neuronal subtypes remains challenging. We found that a phospho-site-deficient Ascl1 variant, Ascl1SA6, but not wildtype Ascl1, induces hallmarks of parvalbumin fast-spiking interneurons, raising the question of how closely these induced neurons resemble canonical cortical interneurons and what transcriptional events underlie this process. Single-cell transcriptomic analysis revealed that Ascl1SA6-induced neurons only partially recapitulated canonical interneuron programs and failed to induce the transcription factor Dlx2 and its downstream targets. Co-expression of Dlx2 with Ascl1SA6 restored a more canonical interneuron-like transcriptome, including genes involved in migration, and resulted in neurons occupying laminar positions more typical of endogenous interneurons. These findings provide molecular insights into how Ascl1 posttranslational modifications regulate its transcriptional activity and demonstrate a strategy to engineer induced cortical interneurons that more closely resemble their native counterparts, offering a framework for layer-specific restoration of inhibitory circuits in neurological diseases.

neuroscience↗

bioRxiv2025

Brain injury reactivates a developmental program driving genesis and integration of transient LGE-class interneurons

Brain lesions can unlock a latent neurogenic potential in parenchymal astrocytes. However, the identity of their neuronal progeny has remained unclear. Here, we show that neurons generated by striatal astrocytes following excitotoxic lesions are transient, yet they reach advanced stages of morphological and functional maturation and integrate into cortico-striatal-thalamic circuits. Single-cell RNA-seq mapping onto an embryonic reference revealed that these cells are not related to adult striatal neuron types but instead belong to the LGE-MEIS2/PAX6 interneuron class. Notch abrogation, which mimics neurogenic activation, drives both cortical and striatal astrocytes toward this same interneuron class, revealing a shared intrinsic commitment. In primates, LGE-MEIS2/PAX6 cells transiently populate the embryonic striatum and cortex, and through spatial transcriptomics, we reveal that in mice these cells are also present and widely distributed throughout the telencephalon during embryonic and postnatal development. Thus, unlike other vertebrates in which adult telencephalic astroglia preserve the potential to generate constitutive region-specific neurons, the homologous cells in mammals converge on the generation of a specific transient neuron class, possibly representing a reservoir for circuit plasticity in adult life.

neuroscience↗

bioRxiv2023

Reprogramming early cortical astroglia into neurons with hallmarks of fast-spiking parvalbumin-positive interneurons by phospho-site deficient Ascl1

Cellular reprogramming of mammalian glia to an induced neuronal fate holds potential for restoring diseased brain circuits. While the proneural factor Ascl1 is widely used for neuronal reprogramming, in the early postnatal mouse cortex Ascl1 fails to induce glia-to-neuron conversion, instead promoting proliferation of oligodendrocyte progenitor cells (OPC). Since Ascl1 activity is post-translationally regulated, here we investigated the consequences of mutating six serine phospho-acceptor sites to alanine (Ascl1SA6) on lineage reprogramming in vivo. Ascl1SA6 exhibited increased neurogenic activity in glia of the early postnatal mouse cortex, an effect enhanced by co-expression of Bcl2. Genetic fate-mapping revealed that most induced neurons originated from astrocytes while only a few derived from OPCs. Intriguingly, many Ascl1SA6/Bcl2-induced neurons expressed parvalbumin and were capable of high-frequency action potential firing. Our study demonstrates authentic conversion of astroglia into neurons featuring subclass hallmarks of cortical interneurons, advancing our scope of engineering neuronal fates in the brain.

neuroscience↗

bioRxiv2022

Low-efficiency conversion of proliferative glia into induced neurons by Ascl1 in the postnatal mouse cerebral cortex in vivo

The proneural transcription factor Achaete-scute complex-like 1 (Ascl1) is a major regulator of neural progenitor fate, implicated both in neurogenesis and oligodendrogliogenesis. Ascl1 has been widely used to reprogram non-neuronal cells into induced neurons. In vitro, Ascl1 induces efficient reprogramming of proliferative astroglia from the early postnatal cerebral cortex into interneuron-like cells. Here, we examined whether Ascl1 can similarly induce neuronal reprogramming of glia undergoing proliferation in the postnatal mouse cerebral cortex in vivo. Toward this, we targeted cortical glia at the peak of proliferative expansion (i.e., postnatal day 5) by injecting a retrovirus encoding for Ascl1 into the mouse cerebral cortex. In sharp contrast to the very efficient reprogramming in vitro, Ascl1-transduced glial cells were converted into doublecortin-immunoreactive neurons only with low efficiency in vivo. Interfering with the phosphorylation of Ascl1 by mutation of six conserved proline-directed serine/threonine phosphorylation sites (Ascl1SA6) has been previously shown to increase its neurogenic activity in the early embryonic cerebral cortex. We therefore tested whether transduction of proliferative glia with a retrovirus encoding Ascl1SA6 improved their conversion into neurons. While in vitro glia-to-neuron conversion was markedly enhanced, in vivo reprogramming efficiency remained low. However, both wild-type and mutant Ascl1 reduced the relative number of cells expressing the astrocytic marker glial fibrillary acidic protein (GFAP) and increased the relative number of cells expressing the oligodendroglial marker Sox10 in vivo. Together, our results indicate that the enhanced neurogenic response of proliferative postnatal glia to Ascl1SA6 versus Ascl1 observed in vitro is not recapitulated in vivo.

neuroscience↗