Keratin 15 Regulates Cell Proliferation in Outer Enamel Epithelium

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Tooth development involves complex coordination of various dental epithelial cell types.
• The specific function of the outer enamel epithelium (OEE) during this process has remained largely unclear.
• Understanding OEE's role is crucial for insights into tooth morphogenesis.

Purpose of the Study:

• To elucidate the gene expression profile and functional role of the outer enamel epithelium (OEE) in mouse tooth development.
• To identify specific marker genes for OEE and investigate their regulatory functions.
• To explore the molecular mechanisms underlying OEE differentiation and proliferation.

Main Methods:

• Single-cell RNA-sequence (scRNA-seq) analysis of mouse tooth germ at different developmental stages (P7 incisors, E14 P1 molars).
• Identification of specific marker genes, such as keratin 15 (Krt15), for OEE.
• Ex vivo organ culture of tooth germ with Krt15 knockdown to assess functional impacts.
• In vitro studies using the CLDE dental epithelial cell line to investigate Krt15's molecular mechanisms.

Main Results:

• Keratin 15 (Krt15) was identified as a specific marker for OEE, with Krt15-negative inner enamel epithelial (IEE) cells giving rise to Krt15-positive OEE cells.
• Krt15 knockdown in tooth germ explants led to ectopic Ki67 expression in OEE and abnormal dental epithelial structures.
• Krt15-depleted CLDE cells exhibited altered morphology, dysregulated cytokeratin expression, increased proliferation (Mki67 upregulation), and activation of the p38 MAPK pathway.

Conclusions:

• Krt15 plays a critical role in regulating OEE development and function during tooth morphogenesis.
• Krt15 acts as a suppressor of dental epithelial cell proliferation by inhibiting the p38 MAPK pathway.
• These findings enhance the understanding of OEE's contribution to tooth development and the underlying molecular mechanisms.