Suppression of m6A reader Ythdf2 promotes hematopoietic stem cell expansion

Abstract

Transplantation of hematopoietic stem cells (HSCs) from human umbilical cord blood (hUCB) holds great promise for treating a broad spectrum of hematological disorders including cancer. However, the limited number of HSCs in a single hUCB unit restricts its widespread use. Although extensive efforts have led to multiple methods for ex vivo expansion of human HSCs by targeting single molecules or pathways, it remains unknown whether it is possible to simultaneously manipulate the large number of targets essential for stem cell self-renewal. Recent studies indicate that N-methyladenosine (mA) modulates the expression of a group of mRNAs critical for stem cell-fate determination by influencing their stability. Among several mA readers, YTHDF2 is recognized as promoting targeted mRNA decay. However, the physiological functions of YTHDF2 in adult stem cells are unknown. Here we show that following the conditional knockout (KO) of mouse Ythdf2 the numbers of functional HSC were increased without skewing lineage differentiation or leading to hematopoietic malignancies. Furthermore, knockdown (KD) of human YTHDF2 led to more than a 10-fold increase in the ex vivo expansion of hUCB HSCs, a fivefold increase in colony-forming units (CFUs), and more than an eightfold increase in functional hUCB HSCs in the secondary serial of a limiting dilution transplantation assay. Mapping of mA in RNAs from mouse hematopoietic stem and progenitor cells (HSPCs) as well as from hUCB HSCs revealed its enrichment in mRNAs encoding transcription factors critical for stem cell self-renewal. These mA-marked mRNAs were recognized by Ythdf2 and underwent decay. In Ythdf2 KO HSPCs and YTHDF2 KD hUCB HSCs, these mRNAs were stabilized, facilitating HSC expansion. Knocking down one of YTHDF2's key targets, Tal1 mRNA, partially rescued the phenotype. Our study provides the first demonstration of the function of YTHDF2 in adult stem cell maintenance and identifies its important role in regulating HSC ex vivo expansion by regulating the stability of multiple mRNAs critical for HSC self-renewal, thus identifying potential for future clinical applications.

YTHDF2 promotes mitotic entry and is regulated by cell cycle mediators

“…Recent studies have shown that loss of YTHDF2 results in enhancement of hematopoietic stem cell expansion in both mouse and human [21,22]. In contrast, depletion of YTHDF2 in AML resulted in apoptosis of AML cells [23].…”

“…Likewise, Ythdf2 was confirmed maternally essential for early zygotic development in mice [19], and Ythdf2 depletion also negatively impacts the proliferation and differentiation of neural progenitor cells in mouse [20], suggesting broad impact of Ythdf2 on mRNA degradation in different tissues and cell types in vertebrates. The significant role of YTHDF2 in cell differentiation was further shown with depletion of YTHDF2-blocking differentiation and driving self-renewal of both mouse and human hematopoietic stem cells [21,22]. This protein is also critical to acute myeloid leukemia (AML) [23].…”

Analysis of eEF1Bγ interactome in the nuclear fraction of A549 human lung adenocarcinoma cells

“…It recognized and decayed methylated mRNAs of Cyclin-A2 and kinase CDK2, thereby prolonging cell cycle progression and suppressing adipogenesis [106]. YTHDF2 plays an important role in regulating hematopoietic stem cells ex vivo expansion by regulating the stability of multiple mRNAs critical for HSC self-renewal of these cells [107]. Ythdf2 modulates neural development by promoting m6A-dependent degradation of neural development-related mRNA target [108].…”

N6-methyladenosine mRNA marking promotes selective translation of regulons required for human erythropoiesis

“…In cell-based models, m 6 A has been shown to participate in numerous types of mRNA regulation, including pre-mRNA processing 17,20,21 , mRNA translation efficiency 22 , mRNA stability 16 , and miRNA biogenesis 23 . In the context of hematopoiesis, m 6 A has recently been found to regulate the expansion and self-renewal of hematopoietic stem cells 24,25 , as well as functioning as a negative regulator of myelopoiesis and a potential driver of acute myeloid leukemia (AML) 11,26 .…”