bioRxiv Science⌕ Search

Biology subjects

Goldman, S. A.

Publications and source records attributed to Goldman, S. A..

12 recordsLinked to original sources

Critical role of cell competition in gliomagenesis

ABSTRACTMalignant glioma is incurable. Using a mouse genetic mosaic system to generate sporadic Trp53,Nf1-null OPCs, we previously identified oligodendrocyte precursor cell (OPC) as a cell-of-origin of glioma. Here, we report that pre-malignant Trp53,Nf1-null OPCs outcompete wildtype counterparts during their expansion. Blocking competition by mutating/strengthening wildtype OPCs impeded both pre-malignant progression and malignant expansion of glioma. "In-tissue" phosphoproteomic profiling revealed an enrichment of phosphopeptides related to RNA splicing and protein translation at the peak of cell competition, suggesting that competitiveness may stem from unique protein species. Among candidates was mTORC1, whose pharmacological inhibition or genetic disruption resulted in a loss of competitiveness in our mouse model. Finally, analysis of patient biopsies and interrogating the role of individual gliomagenic mutations in OPC competition supported its relevance in human gliomas. Together, these findings identified the driving role of competitive interactions among OPCs in gliomagenesis, and suggest unconventional therapeutic strategies to target this process.

cancer biology↗

Histone hyperacetylation-linked upregulation of KRAB zinc finger proteins impedes glial differentiation in Huntington's disease

Glial differentiation is impaired in Huntington disease (HD), contributing to both the synaptic dysfunction and hypomyelination of HD. Through combined epigenomic and transcriptomic profiling, we found that glial progenitor cells (hGPCs) generated from HD-derived human embryonic stem cells exhibit persistent histone hyperacetylation, enabling the ectopic expression of a broad set of KRAB zinc finger protein (KZFP) transcriptional repressors. Single-cell RNA-Seq analysis of HD hGPCs revealed that their aberrant KZFP expression was attended by the persistent expression of neural progenitor-stage genes relative to wild-type hGPCs. The HD hGPCs over-expressed the MYST family histone acetyltransferase KAT6B, which led to their hyperacetylation at H3K9 and associated DNA demethylation, and displayed abnormally open chromatin, particularly at promoters of chromosome 19 KZFP gene clusters. Among those KZFPs most differentially activated in HD hGPCs was the primate-specific ZNF98, whose overexpression in wild-type hGPCs recapitulated the HD-associated suppression of glial development. These data implicate abnormal histone hyperacetylation in HD glial progenitor cells, and its associated over-expression of recently evolved KZFP transcriptional repressors, as a critical mechanism by which both astrocytic and oligodendrocytic differentiation are impaired in HD.

neuroscience↗

Oligodendroglia as functional effectors of Multiple Sclerosis risk variants

Multiple sclerosis (MS) is a neuroinflammatory disease for which a large number of non-coding single nucleotide polymorphisms (SNPs) have been associated with disease risk/susceptibility. Immune cells have been suggested as the principal functional effector cell types of these common variants. Here, we identify 76 MS-associated SNPs whose loci present accessible chromatin in homeostatic and diseased oligodendroglia (OLG), including both oligodendrocyte precursor cells (OPCs) and mature oligodendrocytes (MOLs). By applying high-throughput functional genomics, we found that a subset of these SNPs led to variant- and cell-specific regulatory effects in human induced pluripotent stem cell-derived oligodendroglia. Phenotypic profiling of these variants indicated that rs483180:PHGDH interfered with human OPC proliferation via long-range chromatin interactions with the S100A6 locus, while variants at rs2248137:CYP24A1 impaired oligodendrocyte differentiation by regulating BCAS1 expression. In addition, variants at rs1415069:DIPK1A enhanced secretion of the cytokine CCL2 by oligodendroglia, suggesting that these variants might be implicated in OLG-driven immune cell recruitment in MS. These findings position oligodendroglia as important drivers of MS pathogenesis through modulation of both their cell-intrinsic oligodendroglial function and intercellular communication by non-coding MS risk variants.

cell biology↗

In vivo selection and glymphatic delivery of AAV5 capsids engineered to target human glial progenitor cells

To establish a means of efficiently transducing human glial progenitor cells (hGPCs) in vivo with therapeutic transgenes, we targeted PDGFRA-driven Cre-recombinase expressing hGPCs in human glial chimeric mice with a library of capsid-modified, recombination-reported adeno-associated viruses (AAVs). PCR screening for gliotropic viral capsid sequences, filtered against visceral organs, identified a set of AAV5-based vectors that preferentially infected human GPCs and/or their derived astrocytes and oligodendrocytes in vivo, with minimal systemic infection. To maximize the intracerebral distribution of these viruses while minimizing their dosing and extracerebral spread, we paired their intracisternal delivery with systemic hypertonicity. This method exploited intracerebral glymphatic flow to bypass the blood-brain barrier, delivering AAV directly into the brain parenchyma. Glymphatic delivery of capsid-modified AAV5s, evolved on human GPCs in vivo, thus enables efficient, brain-wide transgene delivery to human glia and their progenitors in the adult brain, with minimal off-target transduction.

neuroscience↗

Charting the transition from in vitro gliogenesis to the in vivo maturation of transplanted human glial progenitor cells

Neither rodent models nor in vitro studies of human cells adequately describe the molecular ontogeny of human glial progenitor cells (hGPCs). Here, we used scRNA-seq together with scATAC-Seq and CUT&TAG assessment of chromatin availability to track the in vitro genesis and in vivo differentiation of hGPCs from pluripotent stem cells (PSCs). In vitro, the hGPC pool comprised 4 transcriptionally-distinct subpopulations, each associated with a distinct pattern of chromatin accessibility and histone modification of stage-dependent genes. After the neonatal transplant of these cells into myelin-deficient shiverer mice, they differentiated further as astrocytes and oligodendrocytes. A combination of gene co-expression, motif enrichment, cell-trajectory, and cell-cell interaction analyses revealed that the host environment potentiated the context-dependent differentiation of the hGPCs, via their activation of distinct gene regulatory networks. Together, these data chart the process by which human PSC-derived GPCs are generated in vitro and diversify in vivo to mature as astrocytes and oligodendrocytes.

neuroscience↗

Glymphatic clearance is enhanced during sleep

We here revisited the concept that glymphatic clearance is enhanced by sleep and anesthesia. Utilizing dynamic magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and fluorescent fiber photometry, we report brain glymphatic clearance is enhanced by both sleep and anesthesia, and sharply suppressed by wakefulness. Another key finding was that less tracer enters the brains of awake animals and that brain clearance across different brain states can only be compared after adjusting for the injected tracer dose.

neuroscience↗

Co-Transplantation-Based Human-Mouse Chimeric Brain Models to Study Human Glial-Glial and Glial-Neuronal Interactions

Human-mouse chimeric brain models, generated by transplanting human induced pluripotent stem cell (hiPSC)-derived neural cells, are valuable for studying the development and function of human neural cells in vivo. Understanding glial-glial and glial-neuronal interactions is essential for unraveling the complexities of brain function and developing treatments for neurological disorders. To explore these interactions between human neural cells in vivo, we co-engrafted hiPSC-derived neural progenitor cells together with primitive macrophage progenitors into the neonatal mouse brain. This approach creates human-mouse chimeric brains containing human microglia, macroglia (astroglia and oligodendroglia), and neurons. Using super-resolution imaging and 3D reconstruction techniques, we examine the dynamics between human neurons and glia, and observe human microglia pruning synapses of human neurons, and often engulfing neurons themselves. Single-cell RNA sequencing analysis of the chimeric brain uncovers a close recapitulation of the human glial progenitor cell population, along with a dynamic stage in astroglial development that mirrors the processes found in the human brain. Furthermore, cell-cell communication analysis highlights significant neuronal-glial and macroglial-microglial interactions, especially the interaction between adhesion molecules neurexins and neuroligins between neurons and astroglia, emphasizing their key role in synaptogenesis. We also observed interactions between microglia and astroglia mediated by SPP1, crucial for promoting microglia growth and astrogliosis, and the PTN-MK pathways, instrumental in homeostatic maintenance and development in macroglial progenitors. This innovative co-transplantation model opens up new avenues for exploring the complex pathophysiological mechanisms underlying human neurological diseases. It holds particular promise for studying disorders where glial-neuronal interactions and non-cell-autonomous effects play crucial roles.

neuroscience↗

Single-nuclei histone modification profiling of the adult human central nervous system unveils epigenetic memory of developmental programs

The adult human central nervous system (CNS) is remarkably complex, with neural cells displaying extensive transcriptional heterogeneity. However, how different layers of epigenetic regulation underpin this heterogeneity is poorly understood. Here, we profile the adult human CNS from distinct regions, for chromatin accessibility at the single-nuclei level. In addition, we simultaneously co-profiled the histone modifications H3K27me3 and H3K27ac at the single nuclei-level, providing their first map in all major human CNS cell types. We unveil primed chromatin signatures at HOX loci in spinal cord-derived human oligodendroglia (OLG) but not microglia. These signatures were reminiscent of developmental OLG but were decoupled from robust gene expression. Moreover, using high-resolution Micro-C, we show that induced pluripotent stem cell (iPS) derived human OLGs exhibit a HOX chromatin architecture compatible with the primed chromatin in adult OLGs, and bears a strong resemblance not only to OLG developmental architecture, but also high-grade pontine gliomas. Thus, adult OLG retain epigenetic memory from developmental states, which might enable them to promptly transcribe Hox genes, in contexts of regeneration, but also make them susceptible to gliomagenesis.

neuroscience↗

Liver-secreted fluorescent blood plasma markers enable chronic imaging of microcirculation

Studying blood microcirculation is vital for gaining insights into vascular diseases. Acute administration of fluorescent tracers is currently used for deep tissue blood flow imaging. This is invasive, and the plasma fluorescence decreases within an hour of administration. We report a novel approach for the longitudinal study of vasculature. Using a single systemic administration of viral vectors, we express fluorescent secretory albumin-fusion proteins in the liver to label the blood in mice. All segments of the vasculature in brain and peripheral tissue are observable by two-photon microscopy within two weeks of vector administration. This approach allows for observation of circulation without the need for repeated administration for several months. We demonstrate the chronic assessment of vascular functions at micro-and mesoscopic scales. This genetic plasma labeling approach represents a versatile and cost-effective method for the chronic investigation of vasculature functions across the body in health and disease.

physiology↗

Pathway-based approach reveals differential sensitivity of glioblastoma to E2F1 inhibition

Targeting glioblastoma (GBM) based on molecular subtyping have not yet translated into successful therapies. Here, we used gene set enrichment analysis (GSEA) to conduct an unsupervised clustering analysis to condense the gene expression data from bulk patient samples and patient-derived gliomasphere lines into new gene lists. We then identified key molecular pathways differentially regulated between tumors. These gene lists associated not only with cell cycle and stemness signatures, but also with cell-type specific markers and different cellular states of GBM. We identified the transcription factor E2F1 as a key regulator of tumor cell proliferation and self-renewal in only the subset of proliferating gliomasphere cultures predicted to be E2F1-activated and validated its functional significance in tumor formation capacity. E2F1 inhibition also sensitized E2F1-activated gliomasphere cultures to radiation treatment. Our findings indicate that a pathway-based approach can be leveraged to deconstruct inter-tumoral heterogeneity and uncover key therapeutic vulnerabilities for targeting GBM.

cancer biology↗

Conservation and divergence of vulnerability and responses to stressors between human and mouse astrocytes

Human-mouse differences are a major barrier in translational research. Astrocytes play important roles in neurological disorders such as stroke, injury, and neurodegeneration. However, the similarities and differences between human and mouse astrocytes are largely unknown. Combining analyses of acutely purified astrocytes, experiments using serum-free cultures of primary astrocytes, and xenografted chimeric mice, we found extensive conservation in astrocytic gene expression between human and mouse. However, genes involved in defense response and metabolism showed species differences. Human astrocytes exhibited greater susceptibility to oxidative stress than mouse astrocytes, due to differences in mitochondria physiology and detoxification pathways. Mouse astrocytes, but not human astrocytes, activate a molecular program for neural repair under hypoxia. Human astrocytes, but not mouse astrocytes, activate the antigen presentation pathway under inflammatory conditions. These species-dependent properties of astrocytes may contribute to differences between mouse models and human neurological and psychiatric disorders.

neuroscience↗

Human glial progenitor cells effectively remyelinate the demyelinated adult brain

Human glial progenitor cells (hGPCs) can completely myelinate the brains of congenitally hypomyelinated shiverer mice, rescuing the phenotype and extending or normalizing the lifespan of these mice. We asked if implanted hGPCs might be similarly able to broadly disperse and remyelinate the diffusely and/or multicentrically-demyelinated adult CNS. In particular, we asked if fetal hGPCs could effectively remyelinate both congenitally hypomyelinated adult axons, and axons acutely demyelinated in adulthood, using adult shiverer mice and cuprizone-demyelinated mice, respectively. We found that hGPCs broadly infiltrate the adult CNS after callosal injection, and robustly myelinate congenitally-unmyelinated axons in adult shiverer. Moreover, implanted hGPCs similarly remyelinated denuded axons after cuprizone demyelination, whether they were delivered prior to or after initial cuprizone demyelination. Extraction and FACS of hGPCs from cuprizone-demyelinated brains in which they had been resident, followed by RNA-seq of the isolated human hGPCs, revealed their activation of transcriptional programs indicating their initiation of oligodendrocyte differentiation and myelination. These data indicate the ability of transplanted hGPCs to disperse throughout the adult CNS, to myelinate dysmyelinated regions encountered during their parenchymal colonization, and to also be recruited as myelinating oligodendrocytes at later points in life, upon demyelination-associated demand.

neuroscience↗