Endogenous Myc controls mammalian epidermal cell size, hyperproliferation, endoreplication and stem cell...

Area of Science:

• Molecular Biology
• Developmental Biology
• Dermatology

Background:

• The transcription factor Myc (c-Myc) is implicated in cell growth, death, and proliferation, but its precise physiological role, especially in mammals, remains debated.
• While some studies suggest Myc primarily controls cell division and number, others indicate a role in cellular growth and size regulation, independent of cell division.

Purpose of the Study:

• To investigate the physiological function of endogenous Myc in mammalian epidermis.
• To clarify the role of Myc in keratinocyte proliferation, growth, and tissue homeostasis by specifically knocking it out in the epidermis.

Main Methods:

• Generation of Myc epidermal knockout mice.
• Analysis of skin phenotype, keratinocyte proliferation, cell size, endoreplication, and differentiation in knockout mice.
• Assessment of wound healing capabilities in the absence of epidermal Myc.

Main Results:

• Myc epidermal knockout mice were viable but exhibited severe skin defects, including fragility, tearing, and impaired wound healing.
• Steady-state epidermis was thinner, showing a reduced proliferative compartment and premature differentiation.
• Keratinocyte cell size, growth, and endoreplication were significantly reduced, and stem cell amplification was compromised.

Conclusions:

• Endogenous Myc plays a critical role in regulating keratinocyte cell size and growth.
• Myc is essential for maintaining hyperproliferative cycles necessary for epidermal homeostasis and tissue integrity.
• These findings provide direct evidence for Myc's involvement in cellular growth, challenging previous notions focused solely on cell division.