Mkl1-dependent gene activation is sufficient to induce actin cap assembly

Area of Science:

• Cell Biology
• Biophysics
• Molecular and Structural Biology

Background:

• Actin-dependent forces regulate nuclear position and shape.
• Mechanisms of nuclear shape determination by actin filaments are less understood.
• LINC complexes and RhoA signaling are implicated in nuclear positioning and gene activation.

Purpose of the Study:

• To investigate how actin filaments determine nuclear shape.
• To elucidate the role of LINC complexes in mediating the connection between actin cytoskeleton and nuclear morphology.
• To explore the involvement of Sun2 and RhoA in regulating nuclear shape.

Main Methods:

• Immunofluorescence microscopy to visualize LINC complexes and stress fibers.
• Biochemical assays to study RhoA activation.
• Genetic manipulation to assess the function of LINC complexes and Sun2.

Main Results:

• A subset of stress fibers associates with the apical nuclear envelope via LINC complexes containing Sun2.
• LINC complexes facilitate stress fiber assembly through RhoA activation and Mkl1-dependent gene activation.
• Apical stress fibers are shown to couple cell and nuclear morphology.

Conclusions:

• LINC complexes, particularly Sun2-containing ones, are crucial for connecting the actin cytoskeleton to the nuclear envelope.
• Regulation of RhoA signaling by LINC complexes contributes to the determination of nuclear shape.
• This study provides insights into the mechanical control of nuclear morphology by the actin cytoskeleton.