Physical properties of the nucleus studied by micropipette aspiration.

Understanding the physical properties of the cell nucleus is critical for developing a deeper understanding of nuclear structure and organization as well as how mechanical forces induce changes in gene expression. We use micropipette aspiration to induce large, local deformations in the nucleus, and microscopy to image nuclear shape as well as the response of fluorescently labeled components in the inner nucleus (chromatin and nucleoli) and the nuclear envelope (lamins and membranes). By monitoring the response of nuclear structures to these deformations, we gain insights into the material properties of the nucleus. Here we describe the experimental protocols for micropipette aspiration of nuclei in living cells as well as isolated nuclei. In addition to confocal imaging, deformed nuclei can be imaged by brightfield or epifluorescence microscopy.