%0 Generic
%A Köster, Isabelle
%D 2010
%F heidok:11247
%K GTPase aktivierende Proteine , RhoGAP , Git , Gewebstrennungsverhalten , Konvergente ExtensionGTPase activating proteins , tissue separation , convergent extension , paraxial protocadherin
%R 10.11588/heidok.00011247
%T Transcriptional regulation of tissue separation during gastrulation of Xenopus laevis
%U https://archiv.ub.uni-heidelberg.de/volltextserver/11247/
%X During Xenopus gastrulation, the involuting mesoderm gets into contact with the inner layer of the blastocoel roof. However, the two tissues do not fuse but remain separated from each other by Brachet’s cleft. Key molecules for tissue separation are Paraxial Protocadherin (PAPC) and the Xenopus Frizzled 7-receptor (xFz7), which contribute to non-canonical Wnt-signalling and activate Rho, JNK and PKC. To determine whether PAPC and xFz7 also play a role in regulating the transcription of target genes to elicit tissue separation, microarray analysis was performed on the Agilent Xenopus oligo microarray system. I compared the transcriptomes of wildtype animal caps to animal caps in which tissue separation behaviour was induced by the overexpression of PAPC and xFz7. In animal cap tissue ectopically expressing PAPC and xFz7, I identified 56 upregulated and 58 downregulated genes. The array results were confirmed for a subset of these genes by qRT-PCR and “whole mount” in situ-hybridisations.  Among the group of downregulated genes, I identified xGit2 and xRhoGAP 11A, two GTPase-activating proteins (GAP) for small GTPases. Both proteins are not described in Xenopus yet and were named after their human homologues Git2 and RhoGAP 11A. xGit2 and xRhoGAP 11A are expressed in the dorsal ectoderm, and their transcription is downregulated in the involuting dorsal mesoderm by PAPC and xFz7. Overexpression of xGit2 and xRhoGAP 11A inhibits RhoA activity and impairs convergent extension movements as well as tissue separation behaviour. Therefore I propose that Rho activity in the involuting mesoderm is enhanced through inhibition of xGit2 and xRhoGAP 11A transcription by PAPC and xFz7. xRhoGAP 11A and xGit2 are restricted to the dorsal ectoderm by PAPC and xFz7, while Rho signalling is inhibited.