Splicing factor 3b subunit 1(SF3B1) is a key component of the spliceosome, a large protein complex essential for regulating gene expression. Genomic mutations in this protein have been linked to various cancers and neurodegenerative diseases. Using a zebrafish sf3b1 loss-of-function model, previous studies have demonstrated that homozygous mutants exhibit severe DNA damage and apoptosis, especially in neural tissue. DNA damage can trigger several signaling pathways via the activation of distinct kinases, such as Ataxia Telangiectasia Mutated (ATM) in response to double strand breaks, and ATM and RAD3-related (ATR) in response to single strand breaks or replication stress. The specific signaling pathway that triggers cell death in sf3b1 mutants remains unknown. Levels of phosphorylated Checkpoint Kinase 2 (Chk2), a direct substrate of the activated ATM kinase, are elevated in sf3b1 mutants compared to their wild type siblings, suggesting that the ATM pathway is active. To determine if ATM signaling mediates the apoptotic phenotype in sf3b1 mutants, we treated whole embryos at 6 hours post fertilization (hpf) with an ATM kinase inhibitor, KU60019, then assessed levels of apoptosis by immunostaining for the pro-apoptotic marker, active-Caspase 3 in 24 hpf embryos. Zebrafish sf3b1 mutants treated with the ATM kinase inhibitor displayed less apoptosis than vehicle control treated mutants. This result indicates ATM acts as a key mediator of apoptosis in sf3b1 mutants. Our results suggest that ATM inhibition could be a novel therapeutic for degenerative diseases with SF3B1 mutations.

ATM signaling pathway mediates apoptosis in SF3B1 mutant zebrafish

2019 Spring National Meeting

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