A G1 Sizer Coordinates Growth and Division in the Mouse Epidermis

Area of Science:

• Cell biology
• Developmental biology
• Mammalian physiology

Background:

• Cell size homeostasis is crucial for organism development and function.
• Cell cycle progression is often coupled to cell growth through mechanisms like "sizers" and "adders."
• Previous studies primarily focused on unicellular organisms or in vitro mammalian cell cultures, leaving in vivo mechanisms unclear.

Purpose of the Study:

• To investigate cell size control mechanisms in mammalian epidermal stem cells in vivo.
• To determine how cell growth and cell-cycle progression are coupled during normal tissue turnover.

Main Methods:

• Analysis of time-lapse images of mouse epidermis over one week.
• Quantification of 3D cell volume growth and cell-cycle progression in single epidermal cells.
• In vivo imaging during normal tissue turnover.

Main Results:

• Epidermal stem cells exhibit a "sizer" mechanism, where cells divide at a similar size regardless of birth size.
• This sizer mechanism operates predominantly during the G1 phase of the cell cycle.
• Findings contrast with the "adder" mechanism commonly observed in in vitro studies.

Conclusions:

• Mammalian epidermal stem cells employ a sizer mechanism for cell size homeostasis in vivo.
• This highlights a discrepancy between in vitro and in vivo cell proliferation studies.
• Further research is needed to elucidate the molecular basis of this in vivo sizer mechanism.