Rac1 mediates PDGFRα regulation of proliferation and migration in MNP cells and MEPMs.

<p>(A) Rac1 G-LISA assay. Rac1 activity is decreased in cKO MNP lysate; recombinant constitutively active (CA) Rac1 is included as a control. (B) Cofilin phosphorylation as seen by immunostaining (red) is attenuated primarily in cKO MNP mesenchymal cells (DAPI blue) (n = 3; asterisk, p<0.05). (C) Western blot analysis shows elevated cofilin phosphorylation in MEPMs following exposure to PDGFAA for 5 and 10 min. N = 3; asterisk, p<0.05. (D) Inhibition of Rac1 activity abrogates PDGFA stimulation of cell proliferation in MEPMs. N = 3; asterisk, p<0.05. (E) Inhibition of Rac1 activity antagonizes the effect of PDGFA on wound healing in MEPMs. N = 9; asterisk, p<0.01. (F–K) Immunostaining of MEPMs at the leading edge of scratch assay. Expression of Vinculin (green), F-actin (red) and nuclei (blue) was examined. G, I and K represent magnification of areas outlined by the dashed lines in F, H and J, respectively. (L) Compared to untreated wild type cells (F, G), inhibition of Rac1 leads to smaller cells, abnormal elongation and disrupted lamellipodia formation (J, K), similar to PDGFRα^fl/fl; Wnt1Cre MEPMs (H, I). N = 50; asterisk, p<0.01.