Biology subjects

Scherer, N. M.

Publications and source records attributed to Scherer, N. M..

3 recordsLinked to original sources

bioRxiv2025

Human TDP-43 overexpression in zebrafish motor neurons triggers MND-like phenotypes through gain-of-function mechanism

Dysregulation of the TAR DNA-binding protein 43 (TDP-43), including intraneuronal cytoplasmic mislocalisation and aggregation is a feature of multiple neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), frontotemporal lobar dementia (FTLD), limbic-predominant age-related TDP-43 encephalopathy (LATE) and alzheimers disease (AD). Unravelling the causes and functional consequences of TDP-43 dysregulation is paramount to understanding disease mechanisms as well as identifying effective therapeutic targets. Here we present a comprehensive in vivo characterisation of three stable transgenic zebrafish models that express human TDP-43 variants in motor neurons. We demonstrate that overexpression of predominantly nuclear wildtype TDP-43, cytoplasm-targeted TDP-43, and an ALS-linked variant (G294V) each induce toxic gain-of-function effects, leading to impaired motor function, motor neuron loss, and muscle atrophy. Importantly, these models reveal distinct phenotypes, with the ALS-linked mutant exhibiting axonal transport deficits and neuromuscular junction disruption, while cytoplasmic mislocalised TDP-43 heightened susceptibility to oxidative stress. Two FDA-approved drugs used to treat ALS, edaravone and riluzole, were examined in these models and revealed that edaravone, but not riluzole, was effective in rescuing motor deficits associated with cytoplasmic TDP-43 expression and, to a lesser extent, mutant TDP-43G294V. Collectively, these findings reveal distinct pathological consequences of TDP-43 dysregulation, providing neuron-centric mechanistic insights, and establish the humanised TDP-43 zebrafish as an efficient system for preclinical therapeutic testing. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=147 SRC="FIGDIR/small/663393v1_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@18c4a50org.highwire.dtl.DTLVardef@162df7forg.highwire.dtl.DTLVardef@3f2848org.highwire.dtl.DTLVardef@6d9439_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

The post-translational modification SUMO affects TDP-43 phase separation, compartmentalization, and aggregation in a zebrafish model

TDP-43 is a nuclear RNA-binding protein that can undergo liquid-liquid phase separation (LLPS) and forms pathological insoluble aggregates in frontotemporal dementia and amyotrophic lateral sclerosis (ALS). Perturbations of TDP-43 function are linked to mislocalization and neurodegeneration. By studying TDP-43 in vivo, we confirmed for the first time that TDP-43 undergoes LLPS and forms biomolecular condensates in spinal motor neurons (MNs). Importantly, we discovered that interfering with the K136 SUMOylation site of TDP-43 altered its phase separation behavior, reducing cytoplasmic mislocalization and aggregation. Introduction of the ALS-linked mutation G294V did not alter these LLPS characteristics, indicating that posttranslational modifications such as lysine-specific alterations can modulate TDP-43 pathogenesis through regulating phase separation. Altogether, our in vivo characterization of TDP-43 confirms the formation of dynamic nuclear TDP-43 condensates in zebrafish spinal neurons and establishes a critical platform to validate the molecular grammar of phase separation that underpins TDP-43 aggregation in ALS and other proteinopathies.

molecular biology↗

bioRxiv2020

In Vivo Validation of Bimolecular Fluorescence Complementation (BiFC) to Investigate Aggregate Formation in Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a form of motor neuron disease (MND) that is characterized by the progressive loss of motor neurons within the spinal cord, brainstem and motor cortex. Although ALS clinically manifests as a heterogeneous disease, with varying disease onset and survival, a unifying feature is the presence of ubiquitinated cytoplasmic protein inclusion aggregates containing TDP-43. However, the precise mechanisms linking protein inclusions and aggregation to neuronal loss are currently poorly understood. Bimolecular Fluorescence Complementation (BiFC) takes advantage the association of fluorophore fragments (non-fluorescent on their own) that are attached to an aggregation prone protein of interest. Interaction of the proteins of interest allows for the fluorescent reporter protein to fold into its native state and emit a fluorescent signal. Here, we combined the power of BiFC with the advantages of the zebrafish system to validate, optimize and visualize of the formation of ALS-linked aggregates in real time in a vertebrate model. We further provide in vivo validation of the selectivity of this technique and demonstrate reduced spontaneous self-assembly of the non-fluorescent fragments in vivo by introducing a fluorophore mutation. Additionally, we report preliminary findings on the dynamic aggregation of the ALS-linked hallmark proteins Fus and TDP-43 in their corresponding nuclear and cytoplasmic compartments using BiFC. Overall, our data demonstrates the suitability of this BiFC approach to study and characterize ALS-linked aggregate formation in vivo. Importantly, the same principle can be applied in the context of other neurodegenerative diseases and has therefore critical implications to advance our understanding of pathologies that underlie aberrant protein aggregation.

neuroscience↗