Biology subjects

Goncalves, J. T.

Publications and source records attributed to Goncalves, J. T..

6 recordsLinked to original sources

bioRxiv2025

Controlled Delivery of a Neurotrophic Factor in the Adult Mouse Brain Using Engineered Microglia

Microglia, the resident immune cells of the central nervous system, have been proposed as vehicles for delivering therapeutic biologics. These cells can be genetically engineered in vitro and transplanted into host animals following ablation of endogenous microglia, enabling repopulation of the brain parenchyma. However, current replacement strategies often rely on radiation or transgenic models, limiting their clinical relevance. CSF1R inhibitors offer a more translational approach to microglia ablation, though surviving host cells can compete with transplanted microglia during repopulation. In this study, we successfully ablated endogenous microglia using a CSF1R inhibitor in adult mice and developed a method to transplant engineered microglia expressing Brain-Derived Neurotrophic Factor (BDNF) in a doxycycline-inducible manner. To enhance engraftment, transplanted cells also expressed a constitutively active CSF1R mutant (caCSF1R). BDNF-expressing transplanted microglia spread through large areas of host mice brains, displayed similar morphology and transcriptional profile to repopulating host microglia, and responded to pro-inflammatory stimuli. Treatment with doxycycline resulted in increased BDNF expression and TrkB phosphorylation in the host brain. Expression of caCSF1R provided transplanted cells with a competitive advantage over endogenous repopulating cells, resulting in the accelerated spread of the transplants. Our results demonstrate the functional integration and therapeutic potential of microglia as vehicles for delivering neurotrophic factors to the brain in a controllable manner. Furthermore, we show that caCSF1R expression is able to enhance the spread of transplanted microglia. SIGNIFICANCEThis study demonstrates the potential of engineered microglia to deliver the protein Brain-Derived Neurotrophic Factor to the brain parenchyma, under the control of orally-administered doxycycline. The technique can be generalized to a wide array of proteins, offering a novel paradigm for neurological therapy.

neuroscience↗

bioRxiv2023

Delayed formation of neural representations of space in aged mice

Aging is associated with cognitive deficits, with spatial memory being very susceptible to decline. The hippocampal dentate gyrus (DG) is important for processing spatial information in the brain and is particularly vulnerable to aging, yet its sparse activity has led to difficulties in assessing changes in this area. Using in vivo two-photon calcium imaging, we compared DG neuronal activity and representations of space in young and aged mice walking on an unfamiliar treadmill. We found that calcium activity was significantly higher and less tuned to location in aged mice, resulting in decreased spatial information encoded in the DG. However, with repeated exposure to the same treadmill, both spatial tuning and information levels in aged mice became similar to young mice, while activity remained elevated. Our results show that spatial representations of novel environments are impaired in the aged hippocampus and gradually improve with increased familiarity. Moreover, while the aged DG is hyperexcitable, this does not disrupt neural representations of familiar environments.

neuroscience↗

bioRxiv2022

Adult neurogenesis improves spatial information encoding in the mouse hippocampus

Adult neurogenesis is a unique form of neuronal plasticity in which newly generated neurons are integrated into the adult dentate gyrus in a process that is modulated by environmental stimuli. Adult-born neurons can contribute to spatial memory but it is unknown whether they alter neural representations of space in the hippocampus. Using in vivo two-photon calcium imaging, we found that mice that were previously housed in an enriched environment, which triggers an increase in neurogenesis, had increased spatial information encoding in the hippocampal dentate gyrus during novel context exposure. Ablating adult neurogenesis by prior focal irradiation of the hippocampus blocked the effect of enrichment and lowered spatial information content, as did the chemogenetic silencing of adult-born neurons. Both ablating neurogenesis and silencing adult-born neurons decreased the calcium activity rates of dentate gyrus neurons, resulting in a decreased amplitude of place-specific responses. These findings are in contrast to previous studies that suggested a predominantly inhibitory action for adult-born neurons. We propose that adult neurogenesis improves neural representations of space by increasing the gain of dentate gyrus neurons and thereby improving their ability to tune to spatial features. This mechanism may mediate the beneficial effects of environmental enrichment on spatial learning and memory.

neuroscience↗

bioRxiv2021

Silencing of hippocampal synaptic transmission impairs spatial reward search on a head-fixed tactile treadmill task

Head-fixed linear treadmill tasks have been used to study hippocampal physiology in mice. Although some hippocampal neurons establish place fields along linear treadmills, it is not clear if the hippocampus is required for spatial memory on this task. Using a Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) approach, we found that silencing hippocampal output on rewarded treadmill tasks impaired search for rewards signaled by spatial cues but did not impair search for rewards signaled by local cues, recapitulating findings from other behavior tasks. These findings serve to contextualize data on hippocampal physiology from mice performing this task.

neuroscience↗

bioRxiv2020

AAV Ablates Neurogenesis in the Adult Murine Hippocampus

Recombinant adeno-associated virus (rAAV) has been widely used as a viral vector across mammalian biology and has been shown to be safe and effective in human gene therapy. We demonstrate that neural progenitor cells (NPCs) and immature dentate granule cells (DGCs) within the adult murine hippocampus are particularly sensitive to rAAV-induced cell death. Cell loss is dose dependent and nearly complete at experimentally relevant viral titers. rAAV-induced cell death is rapid and persistent, with loss of BrdU-labeled cells within 18 hours post-injection and no evidence of recovery of adult neurogenesis at 3 months post-injection. The remaining mature DGCs appear hyperactive 4 weeks post-injection based on immediate early gene expression, consistent with previous studies investigating the effects of attenuating adult neurogenesis. In vitro application of AAV or electroporation of AAV2 inverted terminal repeats (ITRs) is sufficient to induce cell death. Efficient transduction of the dentate gyrus (DG)--without ablating adult neurogenesis--can be achieved by injection of rAAV2-retro serotyped virus into CA3. rAAV2-retro results in efficient retrograde labeling of mature DGCs and permits in vivo 2-photon calcium imaging of dentate activity while leaving adult neurogenesis intact. These findings expand on recent reports implicating rAAV-linked toxicity in stem cells and other cell types and suggest that future work using rAAV as an experimental tool in the DG and as a gene therapy for diseases of the central nervous system (CNS) should be carefully evaluated.

neuroscience↗

bioRxiv2016

Multidimensional imbalances in cortical circuit activity in Fragile-X Syndrome mice

A leading theory for multiple brain disorders, such as schizophrenia and autism, is that they arise from developmental imbalances in excitatory and inhibitory (E/I) brain circuitry. However, it is unclear whether this simple 1-dimensional model is sufficiently rich to capture the set of key alterations of neural circuit processing in brain disorders. Here we used a combination of computational modeling and large-scale analysis of in vivo 2-photon Ca2+ imaging data from somatosensory cortex of wild-type and Fmr1 knock-out (KO) mice, a model of Fragile X syndrome, to test the E/I imbalance model. Our main findings were: 1) the E/I imbalance model was not rich enough to capture the alterations in neural activity statistics in Fmr1 KO mice; 2) in a computational model we found greatly varying magnitudes and directions of effects of synaptic and cellular properties on network activity; 3) evidence for opposite changes in circuit properties of Fmr1 KO mice at different stages of development; 4) a reduction in the entropy of circuit activity in young Fmr1 KO mice compared to wild-type, but an opposite increase in adult Fmr1 KO mice. These findings suggest qualitatively new strategies for developing treatments for Fragile-X Syndrome and related disorders.

neuroscience↗