Molekulare Analysen zur Selbst-/Nichtselbsterkennung bei Urochordaten

Kürn, Ulrich

Almost nothing is known about the molecular mechanisms, underlying allorecognition in invertebrates. In this work two different approaches were used to get insights into how the urochordate Ciona intestinalis distinguishes self from non-self. In the first approach a yeast two-hybrid system was used to search for the ligand of the previously identified Nk-cell receptor ciCD94-1. This is of a particular interest, because the conventional ligands of CD94 in jawed vertebrates are MHC-class I proteins (HLA-E), which have not been identified outside the jawed vertebrates so far. Therefore, the goal of this approach was the identification of a presumably novel ligand for the conserved CD94-like receptor in Ciona. Within the five identified possible candidate ligands, according to the results of the controls and its protein structure, one protein seems to be a good potential interaction partner of ciCD94-1. Nevertheless the interaction shown in the yeast two-hybrid system has to be proven by an independent method. In the second approach a new unbiased screening method based on suppression subtractive hybridization was established to identify variable, proteins which are present in ovaries of Ciona intestinalis and which may be responsible for self-incompatibility reactions. Several groups of variable molecules were identified. Two of them were selected for further detailed analysis. One group of proteins shows homology to the self sterility receptor HrVC70 from Halocynthia roretzi and the other one shows structural similarity to complement receptors of vertebrates. All candidates proved to be more variable than the control genes, therefore they belong to a class of variable genes in Ciona intestinalis. The genes, showing homology to HrVC70, were shown to be expressed in oocytes. The other gene (vCRL1) with structural similarities to complement receptors showed an exceptional high inter- and intraindividual variability. Due to the fact, that vCRL1 is expressed in follicle cells, vCRL1 seems to be a good candidate gene for a self sterility receptor in Ciona intestinalis. Therefore, complement-like proteins may play a role in self/non-self recognition in urochordates



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Kürn, Ulrich: Molekulare Analysen zur Selbst-/Nichtselbsterkennung bei Urochordaten. 2006.


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