Cells respond to mechanical cues from their environment in part through changes in gene expression. But how is an external force transmitted to the genome? One possibility is that the stiffness of the nuclear envelope, which is physically connected to the chromatin through a network of lamin filaments, is involved in force transmission. By osmotically swelling Xenopus oocytes, Dennis Discher and colleagueshave devised an experimental system in which the mechanical properties of the intact nuclear envelope (membranes, pore complexes and the underlying lamin network) can be studied without interference from chromatin or nucleoplasm (see p. 4779). Their studies reveal that although the oocyte nuclear envelope is elastic - it can be expanded to twice its original area - it cannot be compressed below its normal size. The authors propose that the nuclear lamina in oocytes (and probably somatic cells) forms a network of interconnected rigid rods that acts as a molecular shock absorber. This model helps to explain the changes in nuclear mechanical properties seen in laminopathies.
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