title: Inhibition of Rho family GTPases by Rho GDP dissociation inhibitor disrupts cardiac morphogenesis and inhibits cardiomyocyte proliferation.
abstract: Studies of Rho GTPases in Drosophila and Xenopus suggest that Rho family proteins may play an important role in embryogenesis. A reverse genetic approach was employed to explore the role of Rho GTPases in murine cardiac development. Cardiac-specific inhibition of Rho family protein activities was achieved by expressing Rho GDIalpha, a specific GDP dissociation inhibitor for Rho family proteins, using the alpha-myosin heavy chain promoter, active at embryonic day (E)8.0 during morphogenesis of the linear heart tube. RhoA, Rac1 and Cdc42 activities were significantly inhibited, as shown by decreased membrane translocation of these proteins in the transgenic hearts. Transgenic F1 mice for each of two independent lines expressing the highest levels of the transgene, died around E10.5. Homozygotes of the middle copy-number lines, in which Rho GDIalpha expression was increased four-fold over normal levels, were also embryonic lethal. Cardiac morphogenesis in these embryos was disrupted, with incomplete looping, lack of chamber demarcation, hypocellularity and lack of trabeculation. Cell proliferation was inhibited in the transgenic hearts, as shown by immunostaining with anti-phosphohistone H3, a marker of mitosis. In addition, ventricular hypoplasia was associated with up-regulation of p21, an inhibitor of cyclin-dependent kinases, and with down-regulation of cyclin A, while cell survival was not affected. These results reveal new biological functions for Rho family proteins as essential determinants of cell proliferation signals at looping and chamber maturation stages in mammalian cardiac development.
authors.affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Wei
authors.forename: Kyoko
authors.initials: K
authors.lastname: Imanaka-Yoshida
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Song
authors.initials: S
authors.lastname: Zhan
authors.forename: Michael D
authors.initials: MD
authors.lastname: Schneider
authors.forename: Francesco J
authors.initials: FJ
authors.lastname: DeMayo
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002417:Cattle; D002455:Cell Division / Q000235:genetics; D005313:Fetal Death / Q000235:genetics; D005318:Fetal Heart / Q000166:cytology / Q000196:embryology* / Q000201:enzymology*; D015870:Gene Expression; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics / Q000378:metabolism*; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors*; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: C569639:Arhgdia protein, mouse; D020730:Guanine Nucleotide Dissociation Inhibitors; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020741:rho GTP-Binding Proteins