# METTL1-mediated m7G modification regulates osteogenic differentiation of human periodontal ligament stem cells

## TL;DR

This study shows that METTL1 helps human periodontal ligament stem cells become bone cells by stabilizing key genes through a specific RNA modification called m7G.

## Contribution

The study reveals a novel role of METTL1-mediated m7G modification in regulating osteogenic differentiation of PDLSCs.

## Key findings

- METTL1 expression increases during osteogenic differentiation of PDLSCs.
- METTL1 stabilizes RUNX2 mRNA via m7G modification, promoting bone cell formation.
- Reducing METTL1 impairs osteogenesis, which can be partially reversed by RUNX2 overexpression.

## Abstract

•METTL1 expression increases in PDLSCs during osteogenic differentiation.•METTL1 mediates RUNX2 mRNA stability in PDLSCs through m7G modification.•High METTL1 boosts PDLSC osteogenesis through m7G-dependent RUNX2 activation.

METTL1 expression increases in PDLSCs during osteogenic differentiation.

METTL1 mediates RUNX2 mRNA stability in PDLSCs through m7G modification.

High METTL1 boosts PDLSC osteogenesis through m7G-dependent RUNX2 activation.

Human Periodontal Ligament Stem Cells (PDLSCs) represent a subset of mesenchymal stem cells originating from the periodontal ligament, a connective tissue responsible for anchoring teeth to alveolar bone. This study explored the functional role of Methyltransferase-Like-1 (METTL1)-mediated N7-methylguanosine (m7G) modification in regulating the osteogenic differentiation capacity of PDLSCs.

PDLSCs were isolated from periodontal ligament tissues. Osteogenic differentiation was assessed through Alkaline Phosphatase (ALP) activity assays and Alizarin Red S (ARS) staining. Expression levels of Runt-related Transcription Factor-2 (RUNX2), Osteocalcin (OCN), and Osteopontin (OPN) were quantified using Real-Time quantitative Polymerase Chain Reaction (RT-qPCR). Western blot analysis was employed to detect protein expression of METTL1, NOP2/Sun RNA Methyltransferase-2 (NSUN2), and WD Repeat Domain-4 (WDR4). Total m7G content in PDLSCs was measured via m7G dot blot assays. The interaction between METTL1 and RUNX2 was validated using luciferase reporter assays.

The present findings demonstrated that METTL1 exhibited elevated expression levels in PDLSCs, with further upregulation during osteogenic induction. METTL1 knockdown significantly impaired osteogenic differentiation, characterized by decreased ALP activity, reduced ARS staining intensity, and downregulated osteogenic marker gene expression. Mechanistically, the authors identified that METTL1 enhanced m7G modification of key osteogenic genes, including RUNX2, OCN, and OPN, thereby improving their mRNA stability and translational efficiency. Notably, forced overexpression of RUNX2 partially reversed the osteogenic differentiation defects induced by METTL1 suppression.

METTL1 promotes osteogenic differentiation in PDLSCs through m7G modification-mediated stabilization of RUNX2 expression. This discovery unveils a novel epigenetic regulatory mechanism involving m7G modification in periodontal tissue regeneration, offering potential therapeutic targets for bone defect repair applications.