A mitochondrial surveillance mechanism activated by SRSF2 mutations in hematologic malignancies
Xiaolei Liu, … , Omar Abdel-Wahab, Peter S. Klein
Xiaolei Liu, … , Omar Abdel-Wahab, Peter S. Klein
Published May 7, 2024
Citation Information: J Clin Invest. 2024;134(12):e175619. https://doi.org/10.1172/JCI175619.
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Research Article Hematology Oncology

A mitochondrial surveillance mechanism activated by SRSF2 mutations in hematologic malignancies

Abstract

Splicing factor mutations are common in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but how they alter cellular functions is unclear. We show that the pathogenic SRSF2P95H/+ mutation disrupts the splicing of mitochondrial mRNAs, impairs mitochondrial complex I function, and robustly increases mitophagy. We also identified a mitochondrial surveillance mechanism by which mitochondrial dysfunction modifies splicing of the mitophagy activator PINK1 to remove a poison intron, increasing the stability and abundance of PINK1 mRNA and protein. SRSF2P95H-induced mitochondrial dysfunction increased PINK1 expression through this mechanism, which is essential for survival of SRSF2P95H/+ cells. Inhibition of splicing with a glycogen synthase kinase 3 inhibitor promoted retention of the poison intron, impairing mitophagy and activating apoptosis in SRSF2P95H/+ cells. These data reveal a homeostatic mechanism for sensing mitochondrial stress through PINK1 splicing and identify increased mitophagy as a disease marker and a therapeutic vulnerability in SRSF2P95H mutant MDS and AML.

Authors

Xiaolei Liu, Sudhish A. Devadiga, Robert F. Stanley, Ryan M. Morrow, Kevin A. Janssen, Mathieu Quesnel-Vallières, Oz Pomp, Adam A. Moverley, Chenchen Li, Nicolas Skuli, Martin Carroll, Jian Huang, Douglas C. Wallace, Kristen W. Lynch, Omar Abdel-Wahab, Peter S. Klein

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Figure 3

GSK-3i is associated with global alterations in gene expression and splicing in human leukemic cells.

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GSK-3i is associated with global alterations in gene expression and spli...
(A) Schematic of deep RNA-Seq in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells treated with DMSO or 3 μM CHIR for 24 hours. (B) Bar graphs show numbers of differential splicing events (FDR < 0.05, dPSI > 10%) in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells treated with CHIR versus DMSO controls. A3SS, alternative 3′ splice site; A5SS, alternative 5′ splice site; MXE, mutually exclusive exon; RI, retained intron; SE, skipped exon. (C) Venn diagram showing the number of overlapping alternatively spliced genes between CHIR and DMSO in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells. (D) Heatmap of PSI values for overlapping alternatively spliced genes comparing CHIR and DMSO in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells. (E) Scatterplots of cassette exon inclusion in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells treated with 3 μM CHIR relative to DMSO-treated controls. Numbers in brown (left) and purple (right) indicate number of cassette exons whose inclusion is repressed or promoted, respectively, in CHIR- relative to DMSO-treated cells. P values were determined by 1-way ANOVA with Šidák’s multiple-comparison test. (F) Bar graphs show numbers of alternative 3′ splice site events upon CHIR treatment compared with DMSO in WT, SRSF2P95H/+, and SF3B1K700E/+ K562 cells. Purple and orange indicate intron-proximal 3′ splice sites whose usage is repressed or enhanced, respectively, in CHIR-treated relative to DMSO-treated cells. (G) Left: Sashimi plots of DEPDC1 in WT and SRSF2P95H/+ cells treated with DMSO or CHIR. Right: Bar plots show quantification of percentage of exon inclusion based on rMATS analysis (top) and on isoform-specific qPCR validation (bottom). Percentage of exon inclusion was quantified by RT-qPCR analysis of mRNA levels containing the cassette exons normalized to total mRNA levels. Data are presented as the mean ± SD. P values were determined by 2-way ANOVA with Šidák’s multiple-comparison test.