Biology subjects

Wijegunawardana, D.

Publications and source records attributed to Wijegunawardana, D..

3 recordsLinked to original sources

bioRxiv2023

Aberrant splicing exonizes C9ORF72 repeat expansion in ALS/FTD

A nucleotide repeat expansion (NRE) in the first annotated intron of the C9ORF72 gene is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). While C9 NRE-containing RNAs can be translated into several toxic dipeptide repeat proteins, how an intronic NRE can assess the translation machinery in the cytoplasm remains unclear. By capturing and sequencing NRE-containing RNAs from patient-derived cells, we found that C9 NRE was exonized by the usage of downstream 5' splice sites and exported from the nucleus in a variety of spliced mRNA isoforms. C9ORF72 aberrant splicing was substantially elevated in both C9 NRE+ motor neurons and human brain tissues. Furthermore, NREs above the pathological threshold were sufficient to activate cryptic splice sites in reporter mRNAs. In summary, our results revealed a crucial and potentially widespread role of repeat-induced aberrant splicing in the biogenesis, localization, and translation of NRE-containing RNAs.

neuroscience↗

bioRxiv2023

Nanoscale imaging of pT217-tau in aged rhesus macaque entorhinal and dorsolateral prefrontal cortex: Evidence of interneuronal trafficking and early-stage neurodegeneration

Structured Abstract INTRODUCTIONpT217-tau is a novel fluid-based biomarker that predicts onset of Alzheimers disease (AD) symptoms, but little is known about how pT217-tau arises in brain, as soluble pT217-tau is dephosphorylated postmortem in humans. METHODSWe utilized multi-label immunofluorescence and immunoelectron-microscopy to examine the subcellular localization of early-stage pT217-tau in entorhinal and prefrontal cortices of aged macaques with naturally-occurring tau pathology and assayed pT217-tau levels in plasma. RESULTSpT217-tau was aggregated on microtubules within dendrites exhibiting early signs of degeneration, including autophagic vacuoles. It was also seen trafficking between excitatory neurons within synapses on spines, where it was exposed to the extracellular space, and thus accessible to CSF/blood. Plasma pT217-tau levels increased across the age-span and thus can serve as a biomarker in macaques. DISCUSSIONThese data help to explain why pT217-tau predicts degeneration in AD and how it gains access to CSF and plasma to serve as a fluid biomarker.

neuroscience↗

bioRxiv2023

Ataxin-2 polyglutamine expansions aberrantly sequester TDP-43, drive ribonucleoprotein condensate transport dysfunction and suppress local translation

Altered RNA metabolism is a common pathogenic mechanism linked to familial and sporadic Amyotrophic lateral sclerosis (ALS). ALS is characterized by mislocalization and aggregation of TDP-43, an RNA-binding protein (RBP) with multiple roles in post-transcriptional RNA processing. Recent studies have identified genetic interactions between TDP-43 and Ataxin-2, a polyglutamine (polyQ) RBP in which intermediate length polyQ expansions confer increased ALS risk. Here, we used live-cell confocal imaging, photobleaching and translation reporter assays to study the localization, transport dynamics and mRNA regulatory functions of TDP-43/Ataxin-2 in rodent primary cortical neurons. We show that Ataxin-2 polyQ expansions aberrantly sequester TDP-43 within ribonucleoprotein (RNP) condensates, and disrupt both its motility along the axon and liquid-like properties. Our data suggest that Ataxin-2 governs motility and translation of neuronal RNP condensates and that Ataxin-2 polyQ expansions fundamentally perturb spatial localization of mRNA and suppress local translation. Overall, these results indicate Ataxin-2 polyQ expansions have detrimental effects on stability, localization, and translation of transcripts critical for axonal and cytoskeletal integrity, particularly important for motor neurons.

cell biology↗