Fig. 1.

Plectin-deficient (plectin^−/−) cells are less stiff than wild-type (plectin^+/+) cells. A: phase-contrast images of plectin^+/+ and plectin^−/− cells showing that they are similar in cell spreading after being plated overnight on collagen-I-coated dishes. Scale bars = 40 μm. B: plectin^−/− cells are less stiff than plectin^+/+ cells, but power law slopes are similar in response to varying forcing frequencies. The applied stress was 8.75 Pa. Elastic stiffness data are shown. The weak power law exponent α₁ (equal to 0.18) of plectin^+/+ cells was similar to that of plectin^−/− cells (α₁ = 0.17), although they were statistically different (P < 1 × 10⁻⁵); the strong power law α₂ (equal to 0.78) of plectin^+/+ cells was different from that of plectin^−/− cells (α₂ = 0.82; P < 0.02). n = 415 beads and ∼300 plectin^+/+ cells, and n = 327 beads and ∼250 plectin^−/− cells. When α₁ was compared with α₂ within the same cell type, P < 8.1 × 10⁻⁷ for plectin^+/+ cells and P < 3.1 × 10⁻⁵ for plectin^−/− cells. Values are means ± SE. C: plectin^+/+ cells exhibited higher preexponential factors than plectin^−/− cells. On a log-log scale, the two power law data were fitted with the following equation: G′ = A × (f/f₀)^α, where G′ is the geometeric mean ± geometric SE, f is the loading frequency, and f₀ is the lowest measurable frequency (0.002 Hz). The preexponential factor A (in Pa/nm) can be converted to units of kPa by multiplying by 6.8 (see materials and methods).