Abstract
Lifelong hematopoiesis relies on the homeostasis of hematopoietic stem cells(HSCs), but the underlying mechanisms remain incompletely understood. Here, we identified a critical role for DHX16, a member of DEAH-box RNA helicase, in the maintenance of HSCs. After inducing deletion of Dhx16 gene in mice, the knockout animals developed pancytopenia within 5-7 days and died within two weeks. Flow cytometric analyses demonstrated that Dhx16-deficient mice had significantly reduced hematopoietic stem and progenitor cells, altered cell cycle dynamics with decreased G0 phase and increased G2/M phase, and increased apoptosis of HSCs. Competitive BM transplantation assays convinced the impaired self-renewal ability of Dhx16 knockout mice. To identify Dhx16-dependent genes and molecular pathways involved in the regulation of HSC function, we performed the RNA-Seq and long-read Iso-Seq analysis to compare the transcriptome between the Dhx16-deficient HSCs and Dhx16 fl/fl HSCs. RNA-Seq results showed that signaling pathways in Dhx16-deficient hematopoietic stem cells, including ribosome and spliceosome assembly, G2/M checkpoint, and p53 pathway were significantly affected. While long-read Iso-Seq revealed 210 genes with splicing alterations. Through further study, we confirmed that Dhx16-deficiency led to the retention of intron 4 in Emg1, a gene essential for ribosome biogenesis, resulting in a premature termination and nonsense-mediated mRNA decay. Therewith, decreased Emg1 expression in HSCs impaired ribosome biogenesis, activated the p53 pathway, and resulted in the rapid exhaustion of HSCs. In conclusion, these findings reveal a critical role for DHX16 in HSC survival and function and uncover an unsuspected link between RNA helicases, alternative splicing, ribosome biogenesis, and HSC homeostasis.
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