m ⁶ A mRNA methylation decorates genes involved in fibrinogen synthesis to regulate liver regeneration in mice

The role of <i>N</i>⁶-methyladenosine (m⁶A) RNA methylation in liver regeneration is unclear. This study aimed to determine the role of m⁶A methylation in liver regeneration after a 70% hepatectomy (HEPA) using liver-specific methyltransferase-like 14 (Mettl14) knockout (KO) male mice. Analysis was conducted on postoperative <i>days 1</i>, <i>3</i>, or <i>7</i> (HEPA1, 3, or 7) in control (Flox) mice. In Flox mice, cyclin D1 protein expression was highest on postoperative <i>day 3</i> (HEPA3) consistent with a dynamic increase in hepatocyte replication. The abundance of Mettl14 protein presented a similar pattern on HEPA3. Then, we performed hepatectomy in Mettl14 KOs (M14KO) and Flox controls and observed significantly higher postsurgical mortality in mutants. In Flox mice, cyclin D1 protein levels and Ki-67 were markedly increased on HEPA3 compared to sham operation, while being downregulated in M14KO. Characterizing the m⁶A epitranscriptomic changes in Flox mice after hepatectomy and contrasting them to hepatectomy in M14KO in HEPA3 revealed enrichment for gene ontology terms associated with endoplasmic reticulum, inflammation, and apoptosis. Differentially methylated genes in M14KO compared to Flox on HEPA3 were also enriched for peroxisome proliferator-activated receptor (PPAR) and AMPK signaling. Finally, we identified hypomethylated transcripts involved in fibrinogen synthesis, such as Fga, Fgb, and Fgg, by comparing differentially m⁶A-decorated genes in M14KO vs. Flox on HEPA3. Knockdown of fibrinogen leads to suppression of proliferation via activation of p21 protein in AML12 cells. Together, these data point to m⁶A RNA methylation being significant in decorating genes involved in fibrinogen synthesis in liver regeneration.<b>NEW & NOTEWORTHY</b> This study uncovers a previously unrecognized mechanism for regulation of the fibrinogen pathway in <i>N</i>⁶-methyladenosine (m⁶A) RNA methylation-mediated liver regeneration.