Biology subjects

Wallace, O.

Publications and source records attributed to Wallace, O..

9 recordsLinked to original sources

bioRxiv2026

Appearance of Amyloid-β Early in Life Initiates Neuronal Hyper-excitability, Mitochondrial Decay, and Loss of Dendritic Complexity in the Hippocampal CA1 Region of 5xFAD Mice

Alzheimers disease (AD) is characterized by progressive cognitive decline and stereotyped neuropathology, yet the earliest cellular events that precede overt plaque burden and measurable behavioral impairment remain incompletely defined. Here, we tested the hypothesis that synaptic hyperexcitability and subcellular metabolic dysfunction emerge early in the 5xFAD mouse model and contribute to region-specific neuronal vulnerability before substantial amyloid plaque deposition. Using the 5xFAD heterozygous mouse, we first established the onset of transgene expression and the timing of plaque accumulation. Robust transgene expression was detected by postnatal day 15 and significant plaque accumulation by 4 months of age. Ex vivo electrophysiology revealed an early hyperexcitable phenotype at 1 month of age, including both increased AMPA receptor-mediated transmission and N-methyl-D-aspartate receptor signaling associated with the GluN2B subunit. Given the tight coupling between glutamatergic hyperactivity, calcium dysregulation, and mitochondrial health, we assessed mitochondrial structure and function at this pre-plaque stage. Mitochondrial abnormalities consistent with impaired bioenergetic homeostasis were evident. Morphological analyses further demonstrated that these early changes were associated with altered dendritic architecture in the CA1 and dentate gyrus regions, revealing hippocampal subregional susceptibility. Finally, spatial transcriptomics supported this anatomical selectivity by identifying regionally enriched molecular signatures consistent with differential vulnerability. The CA1 region exhibited more reductions in mitochondria-related transcripts than CA3 or dentate gyrus and these reductions were specifically associated with CA1 pyramidal cell neurons. Together, these findings define a pre-plaque window in 5xFAD mice marked by GluN2B-linked glutamatergic hyperexcitability, early mitochondrial disruption, and selective dendritic and transcriptional vulnerability across hippocampal subregions. This integrated timeline suggests that synaptic and metabolic dysfunctions arise before substantial plaque deposition and may represent tractable early targets for intervention aimed at delaying or preventing downstream neurodegeneration in AD.

neuroscience↗

bioRxiv2024

Mining the CRBN Target Space Redefines Rules for Molecular Glue-induced Neosubstrate Recognition

The CRL4CRBN ubiquitin ligase is leveraged by molecular glue degraders, small molecules that reprogram ligase specificity to induce degradation of clinically relevant neosubstrate proteins. Known CRBN neosubstrates share a generalizable {beta}-hairpin G-loop recognition motif, yet systematic exploration of the CRBN target landscape is still pending. Through computational mining of the human proteome using structure-based approaches, we predict over 1,400 CRBN-compatible {beta}-hairpin G-loop proteins across diverse target classes, identify novel mechanisms of neosubstrate recognition through structurally differentiated helical motifs and molecular surface mimicry, and validate 22 representative neosubstrates with clinical implications. This work broadens the CRBN target space, redefines rules for neosubstrate recognition and establishes a platform for the elimination of challenging drug targets by repurposing CRL4CRBN through next-generation molecular glue degraders.

biochemistry↗

bioRxiv2022

Immunogenic fusion proteins induce neutralizing SARS-CoV-2 antibodies in the serum and milk of sheep

Antigen-specific polyclonal immunoglobulins derived from the serum, colostrum, or milk of immunized ruminant animals have potential as scalable therapeutics for the control of viral diseases such as COVID-19. Enhancing the efficacy of vaccine antigens to induce robust and specific antibody responses remains central to developing highly effective formulations. The direct fusion of immunoglobulin (IgG) Fc domains or other immune-stimulating proteins to antigens has shown promise in several mammalian species but has not yet been tested and optimized in commercially-relevant ruminant species. Here we show that the immunization of sheep with fusions of the receptor binding domain (RBD) of SARS-CoV-2 to ovine IgG2a Fc domains promotes significantly higher levels of antigen-specific antibodies compared to native RBD or full-length spike antigens. This antibody population was shown to contain elevated levels of neutralizing antibodies that suppress binding between the RBD and soluble hACE2 receptors in vitro. The parallel evaluation of a second immune-stimulating fusion candidate, Granulocyte-macrophage colony-stimulating factor (GM-CSF), induced high neutralizing responses in select animals but narrowly missed achieving significance at the group level. Furthermore, we demonstrate that the antibodies induced by these fusion antigens are transferred from maternal serum into colostrum/milk. These antibodies also demonstrate cross-neutralizing activity against diverse SARS-CoV-2 variants including delta and omicron. Our findings highlight a new pathway for recombinant antigen design in ruminant animals with applications in immune milk production and animal health.

bioengineering↗

bioRxiv2021

Fragile X syndrome patient-derived neurons developing in the mouse brain show FMR1 -dependent phenotypes

Abnormal neuronal development in Fragile X syndrome (FXS) is poorly understood. Data on FXS patients remain scarce and FXS animal models have failed to yield successful therapies. In vitro models do not fully recapitulate the morphology and function of human neurons. Here, we co-injected neural precursor cells (NPCs) from FXS patient-derived and corrected isogenic control induced pluripotent stem cells into the brain of neonatal immune-deprived mice. The transplanted cells populated the brain and a proportion differentiated into neurons and glial cells. Single-cell RNA sequencing of transplanted cells revealed upregulated excitatory synaptic transmission and neuronal differentiation pathways in FXS neurons. Immunofluorescence analyses showed accelerated maturation of FXS neurons after an initial delay. Additionally, increased percentages of Arc- and Egr1-positive FXS neurons and wider dendritic protrusions of mature FXS striatal medium spiny neurons pointed to an increase in synaptic activity and synaptic strength as compared to control. This transplantation approach provides new insights into the alterations of neuronal development in FXS by facilitating physiological development of cells in a 3D context, and could be used to test new therapeutic compounds correcting neuronal development defects in FXS.

neuroscience↗

bioRxiv2021

Spatially coordinated heterochromatinization of distal short tandem repeats in fragile X syndrome

Short tandem repeat (STR) instability is causally linked to pathologic transcriptional silencing in a subset of repeat expansion disorders. In fragile X syndrome (FXS), instability of a single CGG STR tract is thought to repress FMR1 via local DNA methylation. Here, we report the acquisition of more than ten Megabase-sized H3K9me3 domains in FXS, including a 5-8 Megabase block around FMR1. Distal H3K9me3 domains encompass synaptic genes with STR instability, and spatially co-localize in trans concurrently with FMR1 CGG expansion and the dissolution of TADs. CRISPR engineering of mutation-length FMR1 CGG to normal-length preserves heterochromatin, whereas cut-out to pre-mutation-length attenuates a subset of H3K9me3 domains. Overexpression of a pre-mutation-length CGG de-represses both FMR1 and distal heterochromatinized genes, indicating that long-range H3K9me3-mediated silencing is exquisitely sensitive to STR length. Together, our data uncover a genome-wide surveillance mechanism by which STR tracts spatially communicate over vast distances to heterochromatinize the pathologically unstable genome in FXS. One-Sentence SummaryHeterochromatinization of distal synaptic genes with repeat instability in fragile X is reversible by overexpression of a pre-mutation length CGG tract.

genomics↗

bioRxiv2019

P38α Regulates Expression of DUX4 in Facioscapulohumeral Muscular Dystrophy

FSHD is caused by the loss of repression at the D4Z4 locus leading to DUX4 expression in skeletal muscle, activation of its early embryonic transcriptional program and muscle fiber death. While progress toward understanding the signals driving DUX4 expression has been made, the factors and pathways involved in the transcriptional activation of this gene remain largely unknown. Here, we describe the identification and characterization of p38 as a novel regulator of DUX4 expression in FSHD myotubes. By using multiple highly characterized, potent and specific inhibitors of p38/{beta}, we show a robust reduction of DUX4 expression, activity and cell death across FSHD1 and FSHD2 patient-derived lines. RNA-seq profiling reveals that a small number of genes are differentially expressed upon p38/{beta} inhibition, the vast majority of which are DUX4 target genes. Our results reveal a novel and apparently critical role for p38 in the aberrant activation of DUX4 in FSHD and support the potential of p38/{beta} inhibitors as effective therapeutics to treat FSHD at its root cause. VISUAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=160 SRC="FIGDIR/small/700195v2_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@d2d55corg.highwire.dtl.DTLVardef@1b5c8fcorg.highwire.dtl.DTLVardef@19e4667org.highwire.dtl.DTLVardef@202b96_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2019

Small molecule inhibitors of G9a reactivate the maternal PWS genes in Prader-Willi-Syndrome patient derived neural stem cells and differentiated neurons

Abstract/SummaryPatients with Prader-Willi-Syndrome (PWS) display intellectual impairment, hyperphagia, and various behavioral problems during childhood that converge on a neurologic deficit. The majority of PWS patients have genetic deletions of the paternal 15q11-q13 chromosomal region, with their maternal PWS locus intact but epigenetically silenced by hypermethylation and repressive histone modulation of the PWS imprinting center (PWS-IC). Inhibition of the euchromatin histone methyltransferase G9a by small molecules has been recently reported to reactivate PWS genes in patient fibroblasts and a mouse model. However, it is unknown if inhibition of G9a could have similar effect in human PWS neural cells, the cell types that have direct pathophysiological relevance to PWS. Here, we use neural progenitor cells (NPCs) and cortical excitatory neurons derived from a patient iPSC to model PWS, and quantitatively profile the expression of PWS genes using a NanoString panel. We demonstrated that the methylation of the PWS-IC is stable during neuronal lineage conversion, and that the maternal PWS genes remain silenced in PWS NPCs and neurons. Multiple small molecule inhibitors of G9a activate maternal PWS genes in a dose dependent manner in both NPCs and neurons. In addition, G9a inhibitors induce GNRH1 and HTR2C, two neuronal specific genes that contribute to PWS pathology in neurons. Interestingly, distinct from 5-Azacytidine, G9a inhibition does not induce methylation changes of the maternal PWS-IC, indicating that disruption of the histone repressive complex alone is sufficient to drive an open chromatin state at the PWS-IC that leads to partial reactivation of PWS genes. HighlightsO_LIModeling PWS disease in a dish using patient derived NPCs and neurons C_LIO_LIG9a inhibition activates maternal PWS genes in patient-derived neural cells C_LIO_LIG9a inhibition activates maternal SNORD116 and other PWS genes in patient-derived neurons C_LIO_LIInhibition of G9a induces PWS downstream genes GNRH1 and HTR2C in PWS neurons C_LI

cell biology↗

bioRxiv2019

Partial FMRP expression is sufficient to normalize neuronal hyperactivity in Fragile X neurons

Fragile X Syndrome (FXS) is the most common genetic form of intellectual disability caused by a CGG repeat expansion in the 5-UTR of the Fragile X mental retardation gene FMR1, triggering epigenetic silencing and the subsequent absence of the protein, FMRP. Reactivation of FMR1 represents an attractive therapeutic strategy targeting the genetic root cause of FXS. However, largely missing in the FXS field is an understanding of how much FMR1 reactivation is required to rescue FMRP-dependent mutant phenotypes. Here, we utilize FXS patient derived excitatory neurons to model FXS in vitro and confirm that the absence of FMRP leads to neuronal hyperactivity. We further determined the levels of FMRP and the percentage of FMRP positive cells necessary to correct this phenotype utilizing a mixed and mosaic neuronal culture system and a combination of CRISPR, antisense and expression technologies to titrate FMRP in FXS and WT neurons. Our data demonstrate that restoration of greater than 5% of overall FMRP expression levels or greater than 20% FMRP expressing neurons in a mosaic pattern is sufficient to normalize a FMRP-dependent, hyperactive phenotype in FXS iPSC-derived neurons.\n\nHighlightsO_LICRISPR gene editing to generate FMRP KO and CGG-deleted isogenic iPSCs\nC_LIO_LIMEA as an approach to identify FMR1 dependent phenotype in NGN2 neurons derived from FXS and FMRP KO iPSCs\nC_LIO_LICell mixing paradigm as mosaicism in a dish to rescue phenotype\nC_LIO_LIMinimal level of FMRP determined by FMR1 mRNA and targeted demethylation of CGG repeats to correct the hyperactive phenotype in FXS neurons\nC_LIO_LIASO titration-validated partial expression of FMRP is sufficient to normalize increased neuronal activity\nC_LI

neuroscience↗

bioRxiv2018

Recombinant expression of Proteorhodopsin and biofilm regulators in Escherichia coli for nanoparticle binding and removal in a wastewater treatment model

The small size of nanoparticles is both an advantage and a problem. Their high surface-area-to-volume ratio enables novel medical, industrial, and commercial applications. However, their small size also allows them to evade conventional filtration during water treatment, posing health risks to humans, plants, and aquatic life. This project aims to remove nanoparticles during wastewater treatment using genetically modified Escherichia coli in two ways: 1) binding citrate-capped nanoparticles with the membrane protein Proteorhodopsin, and 2) trapping nanoparticles using Escherichia coli biofilm produced by overexpressing two regulators: OmpR234 and CsgD. We demonstrate experimentally that Escherichia coli expressing Proteorhodopsin binds to 60 nm citrate-capped silver nanoparticles. We also successfully upregulate biofilm production and show that Escherichia coli biofilms are able to trap 30 nm gold particles. Finally, both Proteorhodopsin and biofilm approaches are able to bind and remove nanoparticles in simulated wastewater treatment tanks. We envision integrating our trapping system in both rural and urban wastewater treatment plants to efficiently capture all nanoparticles before treated water is released into the environment.\n\nFinancial DisclosureThis work was funded by the Taipei American School. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.\n\nCompeting InterestsThe authors have declared that no competing interests exist.\n\nEthics StatementN/A\n\nData AvailabilityYes - all data are fully available without restriction. Sequences for the plasmids used in this study are available through the Registry of Standard Biological Parts. Links to raw data are included in Supplementary Information.

synthetic biology↗