Cdc42 is required for PIP(2)-induced actin polymerization and early development but not for cell viability

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Rho GTPases, including Cdc42, regulate cellular functions via actin reorganization and gene expression.
• Limited evidence exists for upstream regulators of Cdc42 or its role in downstream kinase signaling.
• Cdc42 is essential for yeast viability, but its role in mammalian cell growth and development is unassessed.

Purpose of the Study:

• To investigate the functions of Cdc42 in mammalian cells.
• To assess the necessity of Cdc42 for mammalian cell viability and proliferation.
• To determine the role of Cdc42 in early mammalian development.

Main Methods:

• Gene-targeted mutation to inactivate Cdc42 in mouse embryonic stem (ES) cells and germline.
• Analysis of proliferation and protein kinase phosphorylation in Cdc42-deficient ES cells.
• Assessment of actin cytoskeletal organization and PIP(2)-induced actin polymerization in Cdc42-deficient cells.

Main Results:

• Cdc42-deficient ES cells exhibited normal proliferation and kinase phosphorylation.
• Cdc42 deficiency led to aberrant actin cytoskeletal organization in ES cells.
• Cdc42 deficiency caused very early embryonic lethality in mice.
• Extracts from Cdc42-deficient cells failed to support PIP(2)-induced actin polymerization.

Conclusions:

• Cdc42 is critical for phosphatidylinositol 4,5-bisphosphate (PIP(2))-induced actin assembly.
• Cdc42 is not essential for the viability or proliferation of early mammalian embryonic cells.
• Cdc42 is absolutely required for early mammalian development.