Project description:N6-methyladenosine (m6A) RNA methylation is the most abundant modification on mRNAs and plays important roles in various biological processes. The formation of m6A is catalyzed by a methyltransferase complex including methyltransferase like 3 (METTL3) as a key factor. However, the in vivo functions of METTL3 and m6A modification in mammalian development remain unclear. Here we show that specific inactivation of Mettl3 in mouse nervous system causes severe developmental defects in the brain. Mettl3 conditional knockout mice manifest cerebellar hypoplasia caused by drastically enhanced apoptosis of new born cerebellar granule cells (CGCs) in the external granular layer (EGL). METTL3 depletion induced loss of m6A modification causes extended RNA half-lives and aberrant splicing events, consequently leading to dysregulation of transcriptome-wide gene expression and premature CGC death. Our findings reveal a critical role of METTL3-mediated m6A in regulating the development of mammalian cerebellum.
Project description:XIST is a long non-coding RNA (lncRNA) that mediates transcriptional silencing of X chromosome genes. Here we show that XIST is highly methylated with at least 78 N6-methyladenosine (m6A) residues, a reversible base modification whose function in lncRNAs is unknown. We show that m6A formation in XIST, as well as cellular mRNAs, is mediated by RBM15 and its paralog RBM15B, which bind the m6A-methylation complex and recruit it to specific sites in RNA. This results in methylation of adenosines in adjacent m6A consensus motifs. Furthermore, knockdown of RBM15 and RBM15B, or knockdown of the m6A methyltransferase METTL3 impairs XIST-mediated gene silencing. A systematic comparison of m6A-binding proteins shows that YTHDC1 preferentially recognizes m6A in XIST and is required for XIST function. Additionally, artificial tethering of YTHDC1 to XIST rescues XIST-mediated silencing upon loss of m6A. These data reveal a pathway of m6A formation and recognition required for XIST-mediated transcriptional repression. Three to four biological HEK293T replicates were used to perform iCLIP of endogenous YTH proteins, RBM15, and RBM15B. Crosslinking induced truncations were identified using CIMS-CITS pipeline.
Project description:N6-methyl-adenosine (m6A) is the most abundant modification on messenger RNAs and is linked to human diseases, but its functions in mammalian development are poorly understood. Here we reveal the evolutionary conservation and function of m6A by mapping the m6A methylome in mouse and human embryonic stem cells. Thousands of messenger and long noncoding RNAs show conserved m6A modification, including transcripts encoding core pluripotency transcription factors. m6A is enriched over 3M-bM-^@M-^Y untranslated regions at defined sequence motifs, and marks unstable transcripts, including transcripts turned over upon differentiation. Genetic inactivation or depletion of mouse and human Mettl3, one of the m6A methylases, led to m6A erasure on select target genes, prolonged Nanog expression upon differentiation, and impaired ESCM-bM-^@M-^Ys exit from self-renewal towards differentiation into several lineages in vitro and in vivo. Thus, m6A is a mark of transcriptome flexibility required for stem cells to differentiate to specific lineages. Examing m6A modification differences in two different cell types
Project description:N6-methyladenosine (m6A) methylation of mRNA by the methyltransferase complex (MTC), with core components including METTL3-METTL14 heterodimers and Wilms’ tumor 1-associated protein (WTAP), contributes to breast tumorigenesis, but the mechanism of MTC assembly remains elusive. Here, we identify a novel cleaved form METTL3a (residues 239-580 of METTL3), that is highly expressed in breast cancer. Furthermore, we find that both METTL3a and full-length METTL3 are required for MTC assembly, RNA m6A deposition, as well as cancer cell proliferation. Mechanistically, we find that METTL3a is required for METTL3-METTL3 interaction, which is a prerequisite step for recruitment of WTAP in MTC assembly. Analysis of m6A sequencing data shows that depletion of METTL3a globally disrupts m6A methylation, and METTL3a mediates mTOR activation via m6A-mediated suppression of TMEM127 expression. Consequently, we find that METTL3 cleavage is mediated by proteasome in an mTOR-dependent manner, revealing positive regulatory feedback between METTL3a and mTOR signaling. Our findings reveal METTL3a as an important component for MTC assembly, and suggest the METTL3a-mTOR axis as a potential therapeutic target for breast cancer.
Project description:N6-methyladenosine (m6A) is the most abundant internal modification in the messenger RNA (mRNA) of all higher eukaryotes. This modification has been shown to be reversible in mammals; it is installed by a methyltransferase heterodimer complex of METTL3 and METTL14 bound with WTAP, and reversed by iron(II)- and α-ketoglutarate-dependent demethylases FTO and ALKBH5. This modification exhibits significant functional roles in various biological processes. The m6A modification as a RNA mark is recognized by reader proteins, such as YTH domain family proteins and HNRNPA2B1; m6A can also act as a structure switch to affect RNA-protein interactions for biological regulation. In Arabidopsis thaliana, the methyltransferase subunit MTA (the plant orthologue of human METTL3, encoded by At4g10760) was well characterized and FIP37 (the plant orthologue of human WTAP) was first identified as the interacting partner of MTA. Here we report the discovery and characterization of reversible m6A methylation mediated by AtALKBH10B (encoded by At4g02940) in A. thaliana, and noticeable roles of this RNA demethylase in affecting plant development and floral transition. Our findings reveal potential broad functions of reversible mRNA methylation in plants. m6A peaks were identified from wild type Columbia-0 and atalkbh10b-1 mutant in two biological replicates
Project description:Here we determine the map of RNA methylation (m6A) in mouse embrionic stem cells, and Mettl3 knock out cells Examination of m6A modification sites on the transcriptome of mouse Embryonic stem cells and Embryonic Mettl3 knock out cells, using a m6A specific antibody.
Project description:To investigate the role of METTL3-mediated m6A modification, we performed m6A-sequencing to map the m6A modification in control or METTL3 knockdown BGC823 cells.
Project description:In this study we identify Mettl3, an m6A RNA modification writer, as a critical regulator for terminating naïve pluripotency and a positive maintainer of primed pluripotency in vitro and in vivo. Remarkably, Mettl3 knockout pre-implantation epiblasts and naïve ES cells, entirely lack m6A on coding mRNAs and are viable. Yet, they fail to adequately terminate the naïve pluripotent state, and subsequently undergo aberrant priming and early lineage commitment at the post-implantation stage. A comprehensive functional and genomic analysis involving profiling of m6A, RNA transcription and translation in Mettl3 wild-type and knockout pluripotent and differentiated cells, identified m6A as a critical determinant that destabilizes secondary naïve specific pluripotency genes Esrrb, Klf4 and Nanog, and restrains their transcript stability and translation efficiency. In summary, our findings provide for the first time evidence for a critical role for an mRNA epigenetic modification in early mammalian development in vivo, and identify a mechanism that functionally regulates mouse naïve and primed pluripotency in an opposing manner. Ribosome footprint (Ribo-Seq) was measured from mouse embryonic stem cells and mouse embriod bodies, in WT and Mettl3-KO cell lines.
Project description:To investigate the role of METTL3-mediated m6A modification in liver, we performed m6A-sequencing to map the m6A modification in liver tissues of wild type (WT) and liver-sepcific Mettl3-KO mice.
Project description:To investigate the role of METTL3-mediated m6A modification in macrophage, we performed m6A-sequencing to map the m6A modification in bone-marrow-derived macrophages (BMDMs) in wild type (WT) and Mettl3-/- mice.