Geometry of the nuclear envelope determines its flexural stiffness

Area of Science:

• Cell Biology
• Biophysics
• Computational Biology

Background:

• During closed mitosis in fission yeast, microtubules deform the nuclear envelope, leading to nuclear division.
• The nuclear envelope's resistance to bending (flexural stiffness) is crucial for microtubule-driven shape changes.
• Previous computational models relied on simplified scaling arguments for flexural stiffness, potentially overlooking the envelope's complex structure.

Purpose of the Study:

• To computationally analyze the bending mechanics of the nuclear envelope under force, considering its geometry.
• To determine the effective bending modulus of the nuclear envelope and compare it to its components.
• To investigate the influence of nuclear envelope geometry on its mechanical properties.

Main Methods:

• Computational modeling of nuclear envelope mechanics.
• Analysis of nuclear envelope bending under applied force.
• Inclusion of envelope geometry in mechanical models.

Main Results:

• The effective bending modulus of the nuclear envelope is significantly larger (order of magnitude) than a single membrane and approximately five times greater than the nuclear lamina.
• The separation between the two nuclear membranes (45 nm) contributes to a larger bending modulus by supporting greater bending moments.
• The effective bending modulus is highly sensitive to nuclear envelope geometry, varying significantly (twofold to an order of magnitude) compared to a single membrane.

Conclusions:

• The nuclear envelope possesses a substantially larger effective bending modulus than previously estimated, influenced by its bilayer structure and geometry.
• Spatial variations in nuclear envelope geometry and mechanical environment may lead to heterogeneous flexural stiffness within a single nucleus.
• These findings suggest the nuclear envelope can withstand significant mechanical stresses in yeast and potentially in cells of higher organisms.