Ablation of coactivator Med1 switches the cell fate of dental epithelia to that generating hair [mixed stage]

Cell fate is defined by specific transcriptional program. Here, we provide evidence that the transcriptional coactivator, Mediator 1 (MED1), is critical in determining the cell fate of ectodermal epithelia. MED1 ablation disrupted enamel formation and generated hair adjacent to the incisors. Deletion of MED1 altered the differentiation of dental epithelia to one expressing epidermal and hair genes similar to the skin. The cellular switch from dental to epidermal/hair lineage was characterized by abnormalities in MED1 deficient dental epithelial stem cells residing in cervical loop. MED1 deficiency caused a failure of dental epithelial stem cells to commit to the dental stratum intermedium regulated by Notch signaling. Instead, MED1 deficient cells retained stem cell potentials expressing Sox2. These cells were eventually adopted an epidermal fate probably through calcium provided through capillary networks, which is originally utilized for enamel formation. Our results demonstrate that MED1 regulates Sox2/Notch1 regulated cell lineage determination in dental epithelia. Our study also shows a potential to regenerate hairs by using genetically engineered dental tissues or cells outside of the skin.

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