Canonical notch signaling functions as a commitment switch in the epidermal lineage

Area of Science:

• Cell Biology
• Developmental Biology
• Dermatology

Background:

• Mammalian epidermis forms a protective skin barrier through progenitor cell differentiation.
• Epidermal differentiation involves progenitor cells moving upward and undergoing distinct developmental stages.
• The molecular mechanisms initiating epidermal cell commitment to terminal differentiation are not fully understood.

Purpose of the Study:

• To investigate the role of Notch signaling in the early commitment of epidermal progenitor cells.
• To elucidate the function of the Notch intracellular domain (NICD) and RBP-J in epidermal differentiation.
• To determine how Notch signaling regulates the transition from basal to suprabasal epidermal fates.

Main Methods:

• Utilized loss-of-function studies using RBP-J conditional null epidermis.
• Employed gain-of-function studies with transgenic elevation of Notch1 signaling in epidermis.
• Analyzed gene expression patterns and cell fate markers in manipulated epidermal models.

Main Results:

• Active NICD and RBP-J are crucial at the basal/suprabasal layer junction for epidermal differentiation.
• Loss of RBP-J abrogates spinous layer formation, while Notch1 activation expands these layers.
• RBP-J mediates both the induction of spinous genes and repression of basal genes.

Conclusions:

• RBP-J and Notch signaling play an essential, early role in committing epidermal cells to terminal differentiation.
• Spinous gene induction is Hes1-dependent, a target of NICD/RBP-J.
• Basal gene repression by NICD/RBP-J occurs independently of Hes1, highlighting distinct regulatory pathways.