Msx2 Prevents Stratified Squamous Epithelium Formation in the Enamel Organ

The study on Msx2 null mice revealed that the Msx2 gene was crucial in preventing the transformation of the outer enamel epithelium (OEE) into a keratinized stratified squamous epithelium during tooth enamel formation. Although early differentiation of ameloblasts and stratum intermedium (SI) cells was normal, later stages showed abnormal OEE proliferation, marked by the expression of stratified squamous epithelium markers and upregulation of hair follicle-specific keratin genes. This led to keratin accumulation, odontogenic cyst formation, and loss of SI cell differentiation ability, disrupting enamel organ organization and preventing normal enamel formation. Instead, ectopic mineralization occurred within the stellate reticulum. The study concluded that Msx2 was essential for repressing OEE transformation and ensuring proper enamel organ development.