# MFAP5 Activates ITGA5 to Drive Tooth Germ Mineralization Through the MAPK/ERK Pathway: Insights from Single-Cell Transcriptomics

## TL;DR

This study identifies MFAP5 as a key protein that helps teeth develop properly by activating a specific signaling pathway.

## Contribution

The discovery of MFAP5 as a novel regulator of tooth mineralization through the ITGA5-MAPK/ERK pathway is new to the field.

## Key findings

- MFAP5 is essential for mesenchymal differentiation and matrix mineralization in tooth development.
- MFAP5 activates ITGA5 to promote odontoblast differentiation and dentin formation via the MAPK/ERK pathway.
- Single-cell RNA sequencing revealed cell-state-specific signaling during tooth germ mineralization.

## Abstract

Tooth germ development is a precisely orchestrated process dependent on integrated cellular interactions and molecular signals, yet its regulatory mechanisms remain incompletely defined. Here, we constructed a high-resolution cellular atlas of miniature pig tooth germs using 10× single-cell RNA sequencing to investigate the molecular mechanisms underlying tooth mineralization. By leveraging cellular heterogeneity and dynamic gene expression trajectories in epithelial and mesenchymal populations, we identified microfibril-associated protein 5 (MFAP5) as a previously unrecognized regulator of the odontogenic program. Functional assays demonstrate that MFAP5, an extracellular matrix component, is indispensable for mesenchymal differentiation and matrix mineralization in vitro. Mechanistically, MFAP5 engages Integrin alpha-5 (ITGA5) to activate Extracellular Signal-Regulated Kinase/Mitogen-Activated Protein Kinase (ERK/MAPK) signaling in odontoblast-lineage cells, thereby promoting odontoblast differentiation and dentin deposition. Collectively, our single-cell–resolved analyses uncovered a MFAP5–ITGA5–ERK/MAPK signaling axis that operates in a cell-state–specific manner during tooth germ mineralization, providing new mechanistic insights into odontogenic differentiation and a potential molecular basis for dental tissue regeneration strategies.