title: Rac1-null mouse embryonic fibroblasts are motile and respond to platelet-derived growth factor.
abstract: Previous studies of Rac1 in fibroblasts have used dominant negative constructs, which may have nonspecific effects. We used a conditional Rac1 allele to critically examine Rac1 function in mouse fibroblasts. Lack of Rac1 had dramatic effects on nonconfluent cells, which were elongated and had extensive blebbing, but no lamellipodia or ruffle formation. However, Rac1-null fibroblasts translocated using pseudopodia-like protrusions without lamellipodia, migrating toward a platelet-derived growth factor (PDGF) gradient as efficiently as their wild-type counterparts. Rac1-null fibroblasts closed wounds in vitro and spread on a fibronectin substrate, although at a slower rate than wild-type cells. However, Rac1-null cells were markedly impaired in proliferation, with a defect in G1 to S transition, although they were capable of surviving in culture for more than 2 wk. These results refine our understanding of the functions of Rac1, indicate that lamellipodia formation is not required for cell motility, and show that PDGF-induced chemotaxis can occur in the absence of both lamellipodia and Rac1.
authors.affiliation: Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. lvidali@gmail.com
authors.forename: Luis
authors.initials: L
authors.lastname: Vidali
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Gregor
authors.initials: G
authors.lastname: Cicchetti
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Ohta
authors.forename: David J
authors.initials: DJ
authors.lastname: Kwiatkowski
mesh_terms: D000199:Actins / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D049109:Cell Proliferation; D002478:Cells, Cultured; D002633:Chemotaxis / Q000235:genetics; D004622:Embryo, Mammalian / Q000166:cytology / Q000187:drug effects; D005347:Fibroblasts / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D022001:Focal Adhesions / Q000235:genetics; D051379:Mice; D008817:Mice, Mutant Strains; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011554:Pseudopodia / Q000235:genetics / Q000502:physiology; D014945:Wound Healing / Q000235:genetics; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000502:physiology*
chemical_list: D000199:Actins; D010982:Platelet-Derived Growth Factor; D020830:rac1 GTP-Binding Protein