Biology subjects

Grant, G. A.

Publications and source records attributed to Grant, G. A..

8 recordsLinked to original sources

bioRxiv2026

A genome-wide catalog of sites where peripheral DNA methylation reflects the brain

Epigenetic studies of psychiatric and neurological disorders rely largely on peripheral tissues, yet where peripheral DNA methylation (DNAm) reflects the brain remains unclear. We generated a paired brain and peripheral DNAm dataset from 148 donors in three cohorts and combined it with five published cohorts for consensus brain-peripheral correlations. By cross-validation across cohorts, we defined brain epigenome shared sites (BrESS), more than 100,000 CpGs per tissue at which peripheral DNAm reproducibly predicts brain DNAm. BrESS lay at promoters active in both brain and periphery and in housekeeping genes, and most were not explained by genetic effects. BrESS did not contribute to the heritability of seven disorders, and CpGs from epigenome-wide association studies of these disorders were not enriched at BrESS. Peripheral DNAm reflects the brain mainly in a regulatory compartment shared across tissues, outside which disease signals largely lie, and BrESS separate peripheral signals attributable to the brain from others.

neuroscience↗

bioRxiv2026

Adolescent development accelerates responses to input in human neocortical neurons

Through childhood and adolescence, profound changes to the physiology of individual neurons accompany large-scale network changes in the mammalian neocortex. These physiological changes are well understood in rodent models but far less is known in the human neocortex. Here we combine patch-clamp electrophysiology and single-cell sequencing (Patch-Seq) in neurosurgically-resected pediatric human brain slices and age-matched mouse brain slices to elucidate the unique developmental trajectory of human neurons. We find that human Layer 2/3 pyramidal neurons show distinctive postnatal changes in neuronal physiology that align with the more directed, feedforward network architecture of human neocortex relative to the mouse. Human-specific changes to spike train dynamics include faster spike latencies and selective acceleration of early spiking. By applying linear modeling to our Patch-Seq data, we identify genes that predict physiological variation across single cells. This unbiased approach unexpectedly identifies BK-type calcium-activated potassium channels as key drivers of human postnatal changes in spike train dynamics between childhood and adolescence. We further test this pathway through pharmacology and computational modeling. Together, our results reveal novel mechanisms of postnatal maturation in human neocortical neurons and demonstrate a new application of Patch-Seq to uncover gene-physiology relationships at single-cell resolution.

neuroscience↗

bioRxiv2026

Isolation of postnatal human neural stem cells

While it was once thought that neurogenesis is complete by birth, it is now apparent that the human brain continues to generate new neurons postnatally, at least into childhood. While much attention has been focused on postnatally-born neurons, their presumed progenitor - the postnatal neural stem cell (NSC) - remains poorly characterized. Using index sorting, we identify and prospectively isolate two subsets of NSCs from the postnatal human brain, and describe their differentiation dynamics using clonal barcoding and in vivo xenotransplantation. We demonstrate an A2B5+EGFR+ population biased towards interneuron and oligodendrocyte fates (NINO), and an A2B5-EGFRhi population biased towards an astrocyte fate (NAC). Profiling of human brains across lifespan shows that the frequency of NSCs declined exponentially across the first two decades of life, but stabilized thereafter, still present in the brains of donors as old as 90 years. Our study provides a framework for the functional study of postnatal human NSCs and their potential roles in development, aging, and disease.

neuroscience↗

bioRxiv2025

Antigen-specific CD8 T cells are generated and reactivated in the bone marrow following viral brain infections and impact the bone marrow niche

Bone marrow is the primary immune organ responsible for stem cell maintenance and hematopoiesis. However, the contribution of the bone marrow niche for the generation of adaptive immune responses is less well-understood. We therefore assessed the capacity of virus antigen-specific CD8 T cells to be generated and expanded in bone marrow following acute neurotropic virus infection. Intracranial infection with the neurotropic Theilers Murine Encephalomyelitis Virus (TMEV) results in an acute infection in the C57BL/6 mouse which is cleared within 4 weeks post infection due to the generation of an antigen-specific CD8 T cell response against the immunodominant epitope VP2121-130. We determined that 1-10% of CD8 T cells present in the femoral, and sternal bone marrow were virus antigen-specific 5-7 days after intracranial TMEV infection. We determined that antigen-specific CD8 T cells were generated in the bone marrow with similar kinetics to that of conventional responses in the secondary lymphoid organs. Importantly, continuous treatment with FTY720, which sequesters T cells outside of the blood, did not eliminate antigen-specific CD8 T cells in the bone marrow compartment indicating generation within the bone marrow niche. Similarly, injection of Poly I:C admixed with fluorescently labeled ovalbumin into the brain generated a similar antigen-specific CD8 T cell response in the bone marrow indicating these responses occur following various brain insults. This model also identified the likely antigen presenting cell (APC) responsible for scavenging antigens from the brain and trafficking into the bone marrow as a migratory myeloid-derived APC. Moreover, following clearance of TMEV infection, CD8 T cells in the bone marrow established durable memory. Antigen-specific memory CD8 T cells in the bone marrow reactivated and expanded upon cognate antigen reencounter. Antigen-specific reactivation of memory CD8 T cells within the bone marrow caused a concurrent increase in Lineage-, Sca-1+, c-Kit+ (LSK) and CD11b+ MHCII+ myeloid cells. This increase in the LSKs and myeloid cells in the bone marrow niche was abrogated with CD8 T cell depletion. We conclude that brain viral infections induce in situ effector and memory T cell responses within the bone marrow compartment. Memory recall CD8 T cell responses induce niche dysregulation by expanding LSK cells and lead to an influx of MHCII+ myeloid cells. Our data pave the way for crucial studies of bone marrow resident antigen-specific CD8 T cells in health and diseases.

immunology↗

bioRxiv2025

mTORC1 activation drives astrocyte reactivity in cortical tubers and brain organoid models of TSC

Tuberous Sclerosis Complex (TSC) is a genetic neurodevelopmental disorder associated with early onset epilepsy, intellectual disability and neuropsychiatric disorders. A hallmark of the disorder is cortical tubers, which are focal malformations of brain development containing dysplastic cells with hyperactive mTORC1 signaling. One barrier to developing therapeutic approaches and understanding the origins of tuber cells is the lack of a model system that recapitulates this pathology. To address this, we established a genetically mosaic cortical organoid system that models a somatic "second-hit" mutation, which is thought to drive the formation of tubers in TSC. With this model, we find that loss of TSC2 cell-autonomously promotes the differentiation of astrocytes, which exhibit features of a disease-associated reactive state. TSC2-/- astrocytes have pronounced changes in morphology and upregulation of proteins that are risk factors for neurodegenerative diseases, such as clusterin and APOE. Using multiplexed immunofluorescence in primary tubers from TSC patients, we show that tuber cells with hyperactive mTORC1 activity also express reactive astrocyte proteins, and we identify a unique population of cells with expression profiles that match those observed in organoids. Together, this work reveals that reactive astrogliosis is a primary feature of TSC that arises early in cortical development. Dysfunctional glia are therefore poised to be drivers of pathophysiology, nominating a potential therapeutic target for treating TSC and related mTORopathies.

neuroscience↗

bioRxiv2023

Clinically relevant concurrent BRAF and MEK inhibition alters differentiation states and sensitizes BRAF V600E-mutated high-grade gliomas to immune checkpoint blockade

Resistance to BRAF plus MEK inhibition (BRAFi+MEKi) in BRAFV600E-mutant gliomas drives rebound, progression, and high mortality, yet it remains poorly understood. This study addresses the urgent need to develop treatments for BRAFi+MEKi-resistant glioma in novel mouse models and patient-derived materials. BRAFi+MEKi reveals glioma plasticity by heightening cell state transitions along glial differentiation trajectories, giving rise to astrocyte- and immunomodulatory oligodendrocyte (OL)-like states. PD-L1 upregulation in OL-like cells links cell state transitions to tumor evasion, possibly orchestrated by Galectin-3. BRAFi+MEKi induces interferon response signatures, tumor infiltration, and suppression of T cells. Combining BRAFi+MEKi with immune checkpoint inhibition enhances survival in a T cell-dependent manner, reinvigorates T cells, and outperforms individual or sequential therapies in mice. Elevated PD-L1 expression in BRAF-mutant versus BRAF-wildtype glioblastoma supports the rationale for PD-1 inhibition in patients. These findings underscore the potential of targeting glioma plasticity and highlight combination strategies to overcome therapy resistance in BRAFV600E-mutant HGG. In briefXing et al. show that combined BRAF and MEK inhibitor (BRAFi+MEKi) treatment induces cell state transitions in BRAFV600E-mutant high-grade glioma cells linked with programmed death-ligand (PD-L1) upregulation and T cell suppression, potentially orchestrated through the secretion of galectin-3. These tumor-intrinsic adaptations may be overcome by concurrent immune checkpoint inhibition (ICI), as demonstrated in murine studies, offering novel therapeutic opportunities. HighlightsO_LIBRAFV600E-mutant HGG exhibits cell plasticity induced by BRAFi+MEKi, which links cell state transitions towards glial differentiation with immune evasion C_LIO_LIBRAFi+MEKi enhances anti-tumor immunity and simultaneously suppresses T cells via PD-L1 upregulation C_LIO_LIBRAF-mutant glioblastoma has elevated PD-L1 expression compared to BRAF-wildtype counterparts, providing a criterion for PD-1 inhibition therapy C_LIO_LIConcurrent BRAFi+MEKi and immune checkpoint inhibition enhance T cell-mediated anti-tumor activity and boost survival more effectively than sequential treatment in mice, guiding clinical translation C_LI

cancer biology↗

bioRxiv2021

Human Astrocytes Exhibit Tumor Microenvironment-, Age-, and Sex-Related Transcriptomic Signatures

Astrocytes are dynamic cells with important roles in brain function and neurological disease. There are notable species differences between human astrocytes and commonly used animal models. However, changes of the molecular attributes of human astrocytes across disease states, sex, and age are largely unknown, which is a barrier in understanding human astrocyte biology and its potential involvement in neurological diseases. To better understand the properties of human astrocytes, we acutely purified astrocytes from the cerebral cortices of over 40 humans across various ages, sexes, and disease states. We performed RNA sequencing to generate transcriptomic profiles of these astrocytes and identified genes associated with these biological variables. Here, we identified a robust transcriptomic signature of human astrocytes in the tumor-surrounding microenvironment, including upregulation of proliferation processes, along with downregulation of genes involved in ionic homeostasis and synaptic function, suggesting involvement of peri-tumor astrocytes in tumor-associated neural circuit dysfunction. In aging, we also found downregulation of synaptic regulators and upregulation of markers of astrocyte reactivity, while in maturation we identified changes in ionic transport with implications for calcium signaling. In addition, we identified some of the first transcriptomic evidence of sexual dimorphism in human cortical astrocytes, which has implications for observed sex differences across many neurological disorders. Overall, genes involved in synaptic function exhibited dynamic changes in multiple conditions. This data provides powerful new insights into human astrocyte biology in several biologically relevant states, that will aid in generating novel testable hypotheses about homeostatic and reactive astrocytes in humans. Significance StatementAstrocytes are an abundant class of cells playing integral roles in the central nervous system. Astrocyte dysfunction is implicated in a variety of human neurological diseases. Yet our knowledge of astrocytes is largely based on mouse studies. Direct knowledge of human astrocyte biology remains limited. Here, we present transcriptomic profiles of human cortical astrocytes, and we identified molecular differences associated with age, sex, and disease state. We found changes suggesting involvement of peritumor astrocytes in tumor-associated neural circuit dysfunction, aging-associated decline in astrocyte-synapse interactions, ionic transport changes with brain maturation, and some of the first evidence of sexual dimorphism in human astrocytes. These data provide necessary insight into human astrocyte biology that will improve our understanding of human disease.

neuroscience↗

bioRxiv2017

Wide-field dynamic monitoring of immune cell trafficking in murine models of glioblastoma

Leukocyte populations, especially tumor-associated macrophages (TAMs), are capable of mediating both anti- and pro-tumor processes and play significant roles in the tumor microenvironment. Moreover, TAMs have been shown to exert substantial influence on the efficacy of various cancer immunotherapy treatment strategies. Laboratory investigation into the behavior of TAMs has been limited by a lack of methods capable of resolving the in vivo distribution and dynamics of this cell population across wide fields of view. Recent studies have employed magnetic resonance imaging and intravital microscopy in conjunction with nanoparticle labeling methods to detect TAMs and observe their responses to therapeutic agents. Here we describe a novel method to enable high-resolution, wide-field, longitudinal imaging of leukocytes based on contrast-enhanced Speckle-Modulating Optical Coherence Tomography (SM-OCT), which substantially reduces imaging noise. We were able to specifically label TAMs and activated microglia in vivo with large gold nanorod contrast agents (LGNRs) in an orthotopic murine glioblastoma model. After labeling, we demonstrated near real-time tracking of leukocyte migration and distribution within the tumors. The intrinsic resolution, imaging depth, and sensitivity of this method may facilitate detailed studies of the fundamental behaviors of TAMs in vivo, including their intratumoral distribution heterogeneity and the roles they play in modulating cancer proliferation. In future studies, the method described herein may also provide the necessary means to characterize TAM responses to immunotherapeutic regimens in a range of solid tumors.

bioengineering↗