SRA

Somatic SF3b1 mutations occur in many cancers, and the highly conserved H662 residue is one of the most frequently mutated sites. To address their mechanism on splicing alteration and effects on development, we constructed mutant strains at the corresponding residue H698 in Drosophila using CRISPR-Cas9 system. Two mutations, H698D and H698R, were selected due to their presence in patients and the significantly opposite charges. Both the sf3b1-H698D and –H698R mutant flies exhibit developmental defects including less egg-laying, decreased hatching rates, delayed morphogenesis and shorter lifespan. Interestingly, the H698D mutant has decreased resistance to fungi infection, while the H698R mutant has impaired climbing ability. Further RNA-seq data finds altered expression of immunity response genes and changed alternative splicing of muscle and neural-related genes in the two mutants respectively. Lariat sequencing reveal that the sf3b1-H662 mutations cause aberrant selection of multiple intronic branch sites and the H698R mutant prefers to use upstream branch sites in the alternative splicing changed events. This study provides in vivo evidence from Drosophila to elucidate how the highly conserved SF3b1 cancer mutations alter splicing and their consequences in the development and immune systems. Overall design: Transcriptional profiles of the 5d adults WT, SF3b1-H698D and -H698R mutant strains