METTL3 facilitates hepatic fibrosis progression via m6A-YTHDF2 dependent silencing of GPR161

Hepatic fibrosis (HF) is a very common condition seen in millions of patients with various liver diseases. N6-methyladenosine (m6A) plays critical roles in various biological and pathological processes. However, the role of m6A and its main methyltransferase METTL3 in HF remains obscure. Here, we reported that METTL3 expression was elevated in HSCs from CCl4 induced fibrotic liver. METTL3 knockdown in HSCs mediated by recombinant adeno-associated-virus serotype 9 packed short hairpin RNA against METTL3 alleviated liver injury and fibrosis compared to empty carrier group. Mechanistically, the decreased liver fibrosis in CCl4-treated HSC-specific METTL3 knockdown mice was due to the increased GPR161 that is a suppressor of Hedgehog pathway, a well-known pathway to activate in liver injury and regeneration. As expect, GPR161 transferred into HSCs alleviated liver fibrosis and HSC activation. Forced GPR161 expression inhibited Gli3 activated form nuclear accumulation and subsequently suppressed fibrosis-associate gene expression. Conclusion, HSC-specific deletion of METTL3 inhibits liver fibrosis via elevated GPR161 expression, which subsequently suppressed Hedgehog pathway activation and fibrosis-associated genes expression, providing novel therapeutic targets for HF therapy. Synopsis O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/472749v1_ufig1.gif" ALT="Figure 1"> View larger version (78K): org.highwire.dtl.DTLVardef@1245f3aorg.highwire.dtl.DTLVardef@e7effdorg.highwire.dtl.DTLVardef@13ce319org.highwire.dtl.DTLVardef@61be8b_HPS_FORMAT_FIGEXP M_FIG C_FIG The role of RNA m6A methyltransferase METTL3 in the progression of hepatic fibrosis is unclear. Here, we reveal that suppresses m6A modification by depletion of METTL3 in Hepatic Stellate Cells (HSCs), stabilizes the GPR161 transcripts, that involved in suppressing Hedgehog signaling pathway, through YTHDF2, thereby alleviating the fibrosis feature of CCl4-induced liver injury. O_LIDisruption of m6A methyltransferases METTL3 in HSCs alleviates liver fibrosis feature. C_LIO_LIMETTL3 depletion in liver HSCs suppresses its activation by suppressing Hedgehog signaling pathway through stabilizing GPR161 transcripts in an m6A-YTHDF2 dependent manner. C_LIO_LIGPR161 activates PKA that mediates phosphorylation and degradation of full-length Gli3 (Gli3-FL) protein, then the short Gli3 (Gli3-R) translocated into the nucleus and suppresses the fibrosis associated gene transcription. C_LIO_LIThe elevated METTL3 expression is attribute to its promoter H3K27ac modification. C_LI