Biology subjects

Szigeti-Buck, K.

Publications and source records attributed to Szigeti-Buck, K..

4 recordsLinked to original sources

bioRxiv2021

LINE-1 activation in the cerebellum drives ataxia

Previous studies have revealed that dysregulation of long interspersed nuclear element 1 (LINE-1), a dominant class of transposable elements in the human genome, correlates with neurodegeneration1-3. Yet whether LINE-1 dysregulation is causal to disease pathogenesis has not been proven directly. Here, we demonstrate that expression of evolutionarily younger LINE-1 families is elevated in the cerebella of ataxia telangiectasia (AT) patients, which was correlated with extensive downregulation of epigenetic silencers. To examine whether LINE-1 activation causes neurologic disease, we established an approach to directly target and activate the promoter of a young family of LINE-1 in mice. LINE-1 activation in the cerebellum was sufficient to lead to robust progressive ataxia. Purkinje cells in the diseased mice exhibited marked electrophysiological dysfunctions and degeneration with a significant accumulation of cytoplasmic ribonucleoprotein LINE-1Orf1p aggregates, endoplasmic reticulum (ER) stress, and DNA damage. Treatment with lamivudine, a nucleoside reverse transcriptase inhibitor, blunted the disease progression by reducing DNA damage, attenuating gliosis and interferon gene signature, and recovering the loss of key functional molecules for calcium homeostasis in Purkinje cells. This study provides direct evidence that young LINE-1 activation drives ataxia phenotype, and points to its pleiotropic effects leading to DNA damage, inflammation, and dysfunction and degeneration of neurons.

neuroscience↗

bioRxiv2020

Neuroinvasive potential of SARS-CoV-2 revealed in a human brain organoid model

Although COVID-19 is considered to be primarily a respiratory disease, SARS-CoV-2 affects multiple organ systems including the central nervous system (CNS). Yet, there is no consensus whether the virus can infect the brain, or what the consequences of CNS infection are. Here, we used three independent approaches to probe the capacity of SARS-CoV-2 to infect the brain. First, using human brain organoids, we observed clear evidence of infection with accompanying metabolic changes in the infected and neighboring neurons. However, no evidence for the type I interferon responses was detected. We demonstrate that neuronal infection can be prevented either by blocking ACE2 with antibodies or by administering cerebrospinal fluid from a COVID-19 patient. Second, using mice overexpressing human ACE2, we demonstrate in vivo that SARS-CoV-2 neuroinvasion, but not respiratory infection, is associated with mortality. Finally, in brain autopsy from patients who died of COVID-19, we detect SARS-CoV-2 in the cortical neurons, and note pathologic features associated with infection with minimal immune cell infiltrates. These results provide evidence for the neuroinvasive capacity of SARS-CoV2, and an unexpected consequence of direct infection of neurons by SARS-CoV-2.

microbiology↗

bioRxiv2020

Single-cell longitudinal analysis of SARS-CoV-2 infection in human bronchial epithelial cells

SARS-CoV-2, the causative agent of COVID-19, has tragically burdened individuals and institutions around the world. There are currently no approved drugs or vaccines for the treatment or prevention of COVID-19. Enhanced understanding of SARS-CoV-2 infection and pathogenesis is critical for the development of therapeutics. To reveal insight into viral replication, cell tropism, and host-viral interactions of SARS-CoV-2 we performed single-cell RNA sequencing of experimentally infected human bronchial epithelial cells (HBECs) in air-liquid interface cultures over a time-course. This revealed novel polyadenylated viral transcripts and highlighted ciliated cells as a major target of infection, which we confirmed by electron microscopy. Over the course of infection, cell tropism of SARS-CoV-2 expands to other epithelial cell types including basal and club cells. Infection induces cell-intrinsic expression of type I and type III IFNs and IL6 but not IL1. This results in expression of interferon-stimulated genes in both infected and bystander cells. We observe similar gene expression changes from a COVID-19 patient ex vivo. In addition, we developed a new computational method termed CONditional DENSity Embedding (CONDENSE) to characterize and compare temporal gene dynamics in response to infection, which revealed genes relating to endothelin, angiogenesis, interferon, and inflammation-causing signaling pathways. In this study, we conducted an in-depth analysis of SARS-CoV-2 infection in HBECs and a COVID-19 patient and revealed genes, cell types, and cell state changes associated with infection.

microbiology↗

bioRxiv2019

Prokaryotic SPHINX sequences are conserved in mammalian brain and participate in neurodegeneration

A new class of circular mammalian \"SPHINX\" DNAs, represented by the 1.8 and 2.4kb elements, were discovered in highly infectious cytoplasmic particles isolated from Creutzfeldt-Jakob Disease (CJD) and scrapie samples. These DNAs contained replication initiation sequences (REPs) with [~]70% homology to Acinetobacter phage REP segments. Antibodies against REP peptides from the 1.8kb DNA highlighted a 41kDa protein (spx) on Western blots, and in-situ studies revealed its tissue and cell-type specific expression, e.g., in pancreatic islet cells, keratinocytes and kidney tubules but not pancreatic exocrine cells, alveoli, and striated muscle. An intense spx signal in oocytes implicated maternal inheritance of the SPHINX 1.8 genome, a feature known only for bacterially derived mitochondrial DNA in mammals. To determine if spx concentrated at specific neurons and synapses, and also maintained a conserved pattern of architectural organization in mammals, we evaluated mouse, rat, hamster, Guinea Pig and human brains. Most outstanding was the cross-species concentration of spx in huge excitatory synapses of mossy fibers and small internal granule neuron synapses, the only excitatory neuron within the cerebellum. This synaptic localization was also demonstrable at the ultrastructural level. Vacuolar loss of these synaptic complexes, thinning of the internal granule cell layer, and pathological fibrillar spx accumulations within Purkinje neurons were obvious in CJD Guinea pig brains. In rats, these fibrillar changes marked hippocampal Pyramidal neurons and preceded prion protein misfolding. Spx may define different causes or processes of neurodegeneration. The evolutionary origin, persistence and modulation of SPHINX 1.8 opens an unexpected chapter in mammalian symbiosis.

evolutionary biology↗