Zebrafish knockout models of the amyotrophic lateral sclerosis associated genes TDP-43 and hnRnpA1 both result in striking vascular phenotypes Lara Jansen1, Bettina Schmid1, 2 1German Center for Neurodegenerative Diseases (DZNE) e. V Munich, Germany; 2Munich Cluster for Systems Neurology (SyNergy)
Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease for which currently no effective therapies are available, mainly due to the limited understanding of the disease-causing molecular mechanisms. Increasing evidence points to a central role of RNA-binding proteins (RBP) since the pathological hallmark of 97% of ALS cases is the aggregation of the heterogeneous ribonucleoprotein (hnRNP) TDP-43. Additionally, a striking number of genetic mutations associated with familial ALS are found in RBPs, which impact RNA processes, such as gene transcription and RNA translation, suggesting impaired RNA metabolism as a common disease causing mechanism. Recently another member of the hnRNP family, hnRNPA1, was linked to familial ALS. This protein has numerous functions in RNA processing, but its role in the central nervous system is poorly understood. The aim of this study is to identify the in vivo function of hnRnpA1 in a zebrafish knockout (KO) model. We further ask whether loss of its function is necessary and sufficient to elicit ALS related pathology. Double mutants of both hnRnpA1 orthologues in zebrafish are lethal at a late embryonic stage and show strikingly similar phenotypes as our previously generated TDP-43 KO fish, such as weak or absent blood flow. However, a closer look at the vascular system of the hnRnpA1 KO revealed complete lack of intersomitic vessel formation whereby the TDP-43 KO fish show endothelial hypersprouting. Future experiments aim to better describe the angiogenic defects and to identify misregulated pathways eliciting this vascular phenotype. Additionally, ALS related phenotypes will be analyzed such as muscle integrity and motor neuron outgrowth. Lastly, in an unbiased approach to determine affected molecular pathways, RNA sequencing and proteomic analysis will be performed on the mutant embryos and identified hits will be compared to our TDP-43 KO data. Shared hits will be analyzed in sporadic and familial ALS patients and validated for disease relevance. These studies will elicit potential converging pathways in TDP-43 and hnRnpA1 mutants with potential disease relevance thereby possibly identifying new molecular targets for therapy.
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