Chromosome repositioning is inhibited by short interference RNA (siRNA) that suppresses nuclear myosin1β. Chromosome positioning was determined with 2D-FISH (fluorescence in situ hybridization) and erosion analysis, and the normalized position data plotted as histograms in control cells, in cells transfected with the negative control, and in cells transfected with the MYO1C siRNA construct. In control human dermal fibroblasts (HDFs) and in HDFs transfected with negative control, siRNA chromosome 10 is repositioned from an intermediate nuclear location (a and g, respectively) to the nuclear periphery (d, j) after 15 minutes of incubation in low serum. Chromosome 18 territories, conversely, are repositioned from the nuclear periphery (b, h) to the nuclear interior (e, k) after 15 minutes of incubation in low serum in control HDFs and in HDFs transfected with negative control siRNA. In HDFs transfected with the MYO1C siRNA construct, chromosomes 10 (m, p) and 18 (n, q) do not show repositioning after 15 minutes of incubation in low serum. Chromosome X remains at the nuclear periphery at all times (c, f, i, l, o, r). Unpaired, unequal variances two-tailed Students t tests were performed to assess statistical differences. The solid squares indicate a significant difference (P < 0.05) from cells not incubated in, and the solid circles indicate a significant difference (P < 0.05) from control HDFs.