eIF4F complex dynamics are important for the activation of the integrated stress response

Laboratory investigation of METTL7A driving MSC osteogenic differentiation through YAP1 translation enhancement via eIF4F recruitment

AIM

Effective control of mesenchymal stem cell (MSC) differentiation towards osteogenic lineages is fundamental for bone regeneration. This study elucidates the regulatory role of methyltransferase like 7A (METTL7A) in the osteogenic differentiation of MSCs.

METHODOLOGY

Alkaline phosphatase staining, Alizarin Red S staining, western blotting, and in vivo studies were conducted to determine the effects of METTL7A depletion or overexpression on the osteogenic differentiation of various types of MSCs. Then the downstream signalling pathways regulated by METTL7A in MSCs were further investigated.

RESULTS

Our findings indicate that METTL7A expression significantly increases during the osteogenic differentiation of MSCs. Furthermore, depletion of METTL7A hindered, whereas its overexpression enhanced, the osteogenic differentiation of MSCs. Mechanistically, METTL7A influences MSC osteogenic differentiation by activating the YAP1-TEAD1 signalling pathway. It enhances YAP1 expression not only by stabilising YAP1 mRNA but also, crucially, by recruiting the eIF4F complex, thereby boosting the translation efficiency of YAP1 mRNA. Additionally, the YAP1/TEAD1 complex transcriptionally regulates METTL7A expression, creating a positive feedback loop that amplifies osteogenic differentiation.

CONCLUSIONS

Overall, our study uncovers a previously unknown molecular mechanism of MSC osteogenic differentiation and suggests that activating METTL7A could offer new avenues for enhancing bone regeneration.

eIF4E integrates into stress response

In this issue, Diamond et al.1 and Kim et al.2 report that depletion of eIF4E leads to translational upregulation of GCN4, a key player in the integrated stress response, in an eIF2α phosphorylation-independent manner, suggesting a new mode of translational adaptation.