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. 2004 Feb 1;113(3):370–378. doi: 10.1172/JCI19670

Figure 2.

Figure 2

Cytoskeletal stiffness is reduced in lamin A/C–deficient cells. (a) Phalloidin staining for actin stress fibers in WT (Lmna+/+) fibroblasts. Scale bar: 20 μm. (b) Phalloidin staining for actin stress fibers in Lmna–/– cells. Scale bar: 20 μm. (c) Magnetic bead microrheology. Representative examples of magnetic bead displacement in response to applied sinusoidal force (thin black line) for WT (thick black line) and Lmna–/– (thick gray line) fibroblasts. (d) Bead displacement amplitude in response to applied magnetic forces was significantly increased in Lmna–/– fibroblasts, indicating reduced cytoskeletal stiffness in lamin A/C–deficient cells (0.124 ± 0.024 μm vs. 0.226 ± 0.029 μm; P < 0.01, n = 60). (e) Fibroblast with magnetic (diameter 4.5 μm) and polystyrene beads (diameter 2 μm) attached to the cell membrane. Scale bar: 10 μm. (f) Graphic representation of the displacement field after a brief force pulse (2.5 nN for 3 seconds). Bead sizes and positions are drawn to scale, while bead deflections are enlarged by a factor of 10. (g and h) Distance dependence of the angle-corrected radial bead displacement component ur/cosθ as defined in equation 1. The dotted line is an optimal fit to equation 1, yielding estimates for cellular stiffness μ* and dissipation κ for WT (g) and Lmna–/– cells (h), respectively (μ*: 27,537 ± 8,458 pN/μm vs. 2,417 ± 734.7 pN/μm; P < 0.01, n = 128 [WT], 153 [Lmna–/–]; κ: 0.020 ± 0.017 μm–1 vs. 0.201 ± 0.072 μm–1; P < 0.05, n = 128 [WT], 153 [Lmna–/–]). pN, piconewton.