Biology subjects

Welby, E.

Publications and source records attributed to Welby, E..

6 recordsLinked to original sources

bioRxiv2026

Astrocyte targeted SMN1 gene therapy and forskolin application improves astrocyte filopodia actin defects and motor neuron synaptic dysfunction in human SMA disease pathology

BackgroundPeri-synaptic astrocyte processes (PAPs) play a fundamental role in synapse formation and function. Central afferent synapse loss and astrocyte dysfunction greatly impede sensory-motor circuitry in spinal muscular atrophy (SMA) disease progression, however mechanisms underpinning tripartite synapse dysfunction remains to be fully elucidated. The aims of this study were to further define PAP and motor neuron synaptic defects in human SMA disease pathology and implement a therapeutic intervention strategy to improve motor neuron function. MethodsWe derived astrocyte monocultures and motor neuron astrocyte co-cultures from healthy and SMA patient induced pluripotent stem cell (iPSC) lines to assess intrinsic astrocyte filopodia defects and phenotypes occurring at the synapse-PAP interface, respectively, using cell surface capture mass spectrometry proteomics, confocal and super resolution microscopy, synaptogliosome isolation, and electrophysiology. ResultsSMA astrocytes demonstrated intrinsic filopodia actin defects featuring low abundance of actin-associated cell surface N-glycoproteins, and decreased filopodia density and CDC42-GTP levels after actin remodeling stimulation. This phenotype is likely driven by the significant reduction of CD44 and phosphorylated ezrin, radixin and moesin ERM proteins (pERM) within SMA astrocyte filopodia. The dual combination of SMN1 gene therapy and forskolin treatment, an adenylyl cyclase activator leading to increased cyclic adenosine monophosphate (cAMP) levels and actin signaling pathway stimulation, led to extensive branching and increased filopodia density of SMA astrocytes during actin remodeling. SMA patient-derived motor neuron and astrocyte co-cultures, particularly samples derived from male patient iPSC lines, demonstrated a significant decrease in synapse number, actin-associated pre-synaptic neurotransmitter release protein, synapsin I (SYN1), and PAP-associated expression of pERM and glutamate transporter, EAAT1. Our astrocyte-targeted SMN1 augmentation and forskolin treatment paradigm restored SYN1 protein levels within the SMA synaptogliosome, resulting in significant increases in motor neuron synapse formation and function, but did not fully restore PAP-associated proteins levels at the synapse. ConclusionsSMA astrocytes demonstrate intrinsic actin-associated defects within filopodia, which correlates with decreased pERM levels at tripartite motor neuron synapses. We also define a SMN- and cAMP-targeted treatment paradigm that significantly increases pre-synaptic neurotransmitter release protein levels to improved SMA motor neuron synapse formation and function. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/714618v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1257ab8org.highwire.dtl.DTLVardef@19c0010org.highwire.dtl.DTLVardef@c84552org.highwire.dtl.DTLVardef@3f1e62_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Diminished motor neuron activity driven by abnormal astrocytic GLAST glutamate transporter activity in spinal muscular atrophy is not fully restored after lentiviral SMN delivery

Spinal muscular atrophy (SMA) is a pediatric neuromuscular disease characterized by the loss of the lower spinal motor neurons due to survival motor neuron (SMN) deficiency. Motor neuron dysfunction at the glutamatergic afferent synapse is observed during early stages of SMA disease progression, which could be targeted therapeutically prior to cell death. However, the motor neuron cell autonomous and non-cell autonomous disease mechanisms driving this phenotype remain unclear. Our study reveals a non-cell autonomous SMN-associated disease mechanism affecting glutamate transporter (GLAST) activity in astrocytes that contributes to human motor neuron dysfunction in SMA. Transcriptomic analysis of SMA patient human induced pluripotent stem cell (iPSC)-derived astrocytes identified a significant downregulation of genes associated with astrocytic regulation of the synapse, including glutamate neurotransmission. This finding was substantiated by our microelectrode array analysis of motor neuron activity, which was severely diminished specifically in the presence of patient-derived astrocytes. Co-culturing patient-derived motor neurons with healthy-derived astrocytes showed comparable firing rates and bursting activity to healthy-derived motor neurons, suggesting diminished neural activity is an astrocyte-mediated phenotype in this system. Towards defining astrocyte-intrinsic defects that could induce motor neuron dysfunction, we identified abnormally low levels of excitatory amino acid transporter (EAAT1/GLAST) in patient-derived astrocytes, which when selectively inhibited in healthy co-cultures could phenocopy the diminished neural activity previously observed in patient-derived co-cultures. Caveolin-1, an SMN-interacting lipid raft protein associated with glutamate transporter regulation, showed increased protein levels and accumulation in patient astrocytes. Both GLAST and caveolin-1 phenotypes could be partially rescued via lentiviral-mediated SMN re-expression in patient astrocytes. Together, our work defines a novel SMN-associated disease mechanism involving abnormal glutamate transporter activity and regulation in astrocytes that can directly diminish motor neuron function in SMA.

neuroscience↗

bioRxiv2021

Viral mediated knockdown of GATA6 in SMA iPSC-derived astrocytes prevents motor neuron loss and microglial activation

Spinal muscular atrophy (SMA), a pediatric genetic disorder, is characterized by the profound loss of spinal cord motor neurons and subsequent muscle atrophy and death. Although the mechanisms underlying motor neuron loss are not entirely clear, data from our work and others support the idea that glial cells contribute to disease pathology. GATA6, a transcription factor that we have previously shown to be upregulated in SMA astrocytes, is negatively regulated by SMN and can increase the expression of inflammatory regulator NF{kappa}B. In this study, we identified upregulated GATA6 as a contributor to increased activation, pro-inflammatory ligand production, and neurotoxicity in spinal-cord patterned astrocytes differentiated from SMA patient induced pluripotent stem cells. Reducing GATA6 expression in SMA astrocytes via lentiviral infection ameliorated these effects to healthy control levels. Additionally, we found that SMA astrocytes contribute to SMA microglial phagocytosis, which was again decreased by lentiviral-mediated knockdown of GATA6. Together these data identify a role of GATA6 in SMA astrocyte pathology and further highlight glia as important targets of therapeutic intervention in SMA.

neuroscience↗

bioRxiv2021

Assessment of CSF biomarkers and microRNA-mediated disease mechanisms in SMA

ObjectiveCerebral spinal fluid (CSF) is a promising biospecimen for the detection of central nervous system (CNS) biomarkers to monitor therapeutic efficacy at the cellular level in neurological diseases. Spinal muscular atrophy (SMA) patients receiving intrathecal antisense oligonucleotide (nusinersen) therapy tend to show improved motor function, but the treatment effect on cellular function remains unknown. The objective of this study was to assess the potential of extracellular RNAs and microRNAs in SMA patient CSF as indicators of neuron and glial health following nusinersen treatment. MethodsCSF samples from SMA Type 1-3 patients were screened using quantitative RT-PCR to assess expression of extracellular RNAs associated with inflammation and cellular stress, and microRNAs previously implicated in SMA pathogenesis. We also used mRNA sequencing and multi-electrode array approaches to assess the transcriptional and functional effects of astrocyte-associated miR-146a on healthy and SMA induced pluripotent stem cell (iPSC)-derived motor neurons. ResultsExtracellular RNA analysis is suggestive of ongoing cellular stress, even in nusinersen treated samples. microRNAs previously associated with SMA pathology tended to show improvement in expression levels in nusinersen treated samples, with the exception of the astrocyte-secreted miR-146a. miR-146a treated iPSC-derived motor neurons showed a downregulation of extracellular matrix genes found in the synaptic perineuronal net and decreased spontaneous activity. InterpretationExtracellular RNAs and microRNAs can be detected in SMA patient CSF samples, potentially serving as useful biomarkers to monitor cellular health during nusinersen treatment. Astrocyte health and response to nusinersen are important aspects to address in SMA pathogenesis and treatment strategies.

neuroscience↗

bioRxiv2019

Transcriptome-based molecular staging of human stem cell-derived retinal organoids uncovers accelerated photoreceptor differentiation by 9-cis retinal

Retinal organoids generated from human pluripotent stem cells exhibit considerable variability in temporal dynamics of differentiation. To assess the maturity of neural retina in vitro, we performed transcriptome analyses of developing organoids from human embryonic and induced pluripotent stem cell lines. We show that the developmental variability in organoids was reflected in gene expression profiles and could be evaluated by molecular staging with the human fetal and adult retinal transcriptome data. We also demonstrated that addition of 9-cis retinal, instead of widely-used all-trans retinoic acid, accelerated rod photoreceptor differentiation in organoid cultures, with higher rhodopsin expression and more mature mitochondrial morphology evident by day 120. Our studies thus provide an objective transcriptome-based modality for determining the differentiation state of retinal organoids, which should facilitate disease modeling and evaluation of therapies in vitro.\n\nSummary StatementThree-dimensional organoids derived from human pluripotent stem cells have been extensively applied for investigating organogenesis, modeling diseases and development of therapies. However, substantial variations within organoids pose challenges for comparison among different cultures and studies. We generated transcriptomes of multiple distinct retinal organoids and compared these to human fetal and adult retina gene profiles for molecular staging of differentiation state of the cultures. Our analysis revealed the advantage of using 9-cis retinal, instead of the widely-used all-trans retinoic acid, in facilitating rod photoreceptor differentiation. Thus, a transcriptome-based comparison can provide an objective method to uncover the maturity of organoid cultures across different lines and in various study platforms.

developmental biology↗

bioRxiv2018

Generation of human neural retina transcriptome atlas by single cell RNA sequencing

The retina is a highly specialized neural tissue that senses light and initiates image processing. Although the functional organisation of specific cells within the retina has been well-studied, the molecular profile of many cell types remains unclear in humans. To comprehensively profile cell types in the human retina, we performed single cell RNA-sequencing on 20,009 cells obtained post-mortem from three donors and compiled a reference transcriptome atlas. Using unsupervised clustering analysis, we identified 18 transcriptionally distinct clusters representing all known retinal cells: rod photoreceptors, cone photoreceptors, Muller glia cells, bipolar cells, amacrine cells, retinal ganglion cells, horizontal cells, retinal astrocytes and microglia. Notably, our data captured molecular profiles for healthy and early degenerating rod photoreceptors, and revealed a novel role of MALAT1 in putative rod degeneration. We also demonstrated the use of this retina transcriptome atlas to benchmark pluripotent stem cell-derived cone photoreceptors and an adult Muller glia cell line. This work provides an important reference with unprecedented insights into the transcriptional landscape of human retinal cells, which is fundamental to our understanding of retinal biology and disease.

systems biology↗