Biology subjects

Biever, A.

Publications and source records attributed to Biever, A..

4 recordsLinked to original sources

bioRxiv2024

Therapeutically targeting the classical complement pathway with antisense oligonucleotides in Alzheimer's disease

The complement classical pathway (CP) is a key mediator of synapse loss and neurodegeneration in mouse models of Alzheimers (AD) and other neurodegenerative diseases. We analyzed human brain proteomics and found consistent elevations of all CP proteins, but not other complement pathways, in AD patient brains. We performed human genetics analysis that identified a rare variant in the C1S gene within the Finnish population that is associated with AD and we found that a common AD-associated C1S variant correlates with increased C1S protein levels. A targeted assay detected elevated C1S activation in AD patient CSF. Given this specific implication of the CP in AD, we next evaluated the therapeutic approach of targeting the CP in the brain using antisense oligonucleotides (ASOs). To identify promising CP targets for knockdown using ASOs we first tested for rescue of synapse loss in an AD mouse model using heterozygous and homozygous complement knockout mice and examined the relative brain expression levels of different CP genes. Based on these experiments we prioritized C1r, C1s and C4 as promising targets for therapeutic knockdown using ASOs. We then screened for ASOs for each target, evaluating in vitro and in vivo knockdown and toxicity, and identified optimal ASOs targeting C1r, C1s and C4. Experiments with AD model mice demonstrated significant rescue of synapse loss following treatment with C1r, C1s or C4 ASOs. Overall, our findings provide proof of concept for using nucleic acid-based medicine to target the CP in AD and demonstrate the translational potential of this approach.

neuroscience↗

bioRxiv2024

TDP43 proteinopathy exhibits disease, tissue, and context-specific cryptic splicing signatures

Mislocalization of the nuclear TAR DNA-binding protein 43 (TDP43) is a hallmark of ALS and FTD which leads to de-repression and inclusion of cryptic exons (CEs), promising biomarkers of TDP43 pathology in a spectrum of neurodegenerative diseases. However, most CEs to date have been identified from in vitro models or a single cortical FTD dataset, and little is known about cryptic splicing in the spinal cord, or within different neuronal subtypes. We meta-analyzed published bulk RNAseq datasets representing 1,778 RNAseq profiles of ALS and FTD post-mortem tissue, and in vitro models with experimentally depleted TDP43. We identified 142 cryptic splices, including 68 novel events. We found divergent cryptic splicing primarily between the spinal cord and cortex, validated in an independent ALS cohort by qPCR and supported by in situ hybridization (ISH). We also identified a set of cryptic splices observed in tissue but not in vitro, and, being present in either SOD1-ALS or MAPT-FTD subjects, likely TDP43 independent. Finally, leveraging multiple public single-nucleus RNAseq datasets of ALS and FTD motor and frontal cortex, we confirmed the elevation of cortical-enriched splices in disease and localized them to layer-specific neuronal populations. We provide a web interface to browse the meta-analysis results at https://go.roche.com/CrypticSplicingLandscape. This catalog of cryptic splices will inform efforts to develop biomarkers for tissue-specific and cell type-specific TDP43 pathology.

neuroscience↗

bioRxiv2020

The mRNA translation landscape in the synaptic neuropil.

To form and modify synaptic connections and store information, neurons continuously remodel their proteomes. The impressive length of dendrites and axons imposes unique logistical challenges to maintain synaptic proteins at locations remote from the transcription source (the nucleus). The discovery of thousands of mRNAs near synapses suggested that neurons overcome distance and gain autonomy by producing proteins locally1. It is not known, however if, how and when localized mRNAs are translated into protein. To investigate the translational landscape in neuronal subregions, we performed simultaneous RNA-seq and Ribo-seq from microdissected rodent brain slices to identify and quantify the transcriptome and translatome in cell bodies as well as dendrites and axons (neuropil). More than 4800 transcripts were translated in synaptic regions. Thousands of transcripts were differentially translated between somatic and synaptic regions, with scaffold and signaling molecules mostly arising from local sources. Furthermore, specific mRNA features were identified that regulate the efficiency of mRNA translation. The findings overturn the view that local translation is a minor source of synaptic protein2 and indicate that on-site translational control is an important mechanism to control synaptic strength.

neuroscience↗

bioRxiv2019

Monosomes actively translate synaptic mRNAs in neuronal processes

In order to deal with their huge volume and complex morphology, neurons localize mRNAs and ribosomes near synapses to produce proteins locally. A relative paucity of polyribosomes (considered the active sites of translation) detected in electron micrographs of neuronal processes (axons and dendrites), however, has suggested a rather limited capacity for local protein synthesis. Polysome profiling together with ribosome footprinting of microdissected synaptic regions revealed that a surprisingly high number of dendritic and/or axonal transcripts were predominantly associated with monosomes (single ribosomes). Contrary to prevailing views, the neuronal monosomes were in the process of active protein synthesis (e.g. they exhibited elongation). Most mRNAs showed a similar translational status in both compartments, but some transcripts exhibited differential ribosome occupancy in the somata and neuropil. Strikingly, monosome-preferred transcripts often encoded high-abundance synaptic proteins. This work suggests a significant contribution of monosome translation to the maintenance of the local neuronal proteome. This mode of translation can presumably solve some of restricted space issues (given the large size of polysomes) and also increase the diversity of proteins made from a limited number of ribosomes available in dendrites and axons.

neuroscience↗