Xine Volume 5 supplement 1 - September 2005

Dear Colleagues:

Following is a request for letters of support from Prof. Gerhart Ryffel. Prof. Ryffel has developed a set of FLP/Cre recombinase strains of Xenopus laevis that will prove to be very useful for the community. He is now proposing to generate similar lines to facilitate X. tropicalis studies in response to an NIH Program Announcement. As you may know, letters of support are a critical factor in establishing the need and relevance of the project to NIH. If you support the creation of such resorces, please take the time to fax a brief letter of support to Prof. Ryffel.

Establishment of the FLP/Cre recombinase system in Xenopus tropicalis

Program Announcement


Dear colleagues,
You may remember that we applied for a grant to establish the recombinase system in Xenopus tropicalis. Unfortunately, we did not succeed yet, but from the critique obtained and the advice from the program official we strongly believe that a resubmission may be successful. To do that we need some further support from the Xenopus community. Therefore, we would
be very grateful you could send us a letter of support by Fax before September 15. 2005:

Fax No: ++49 201 723 5905
Prof. Gerhart U. Ryffel
Institute for Cell Biology
Universitaetsklinikum Essen
D-45122 Essen, Germany

Please remember that all the transgenic X. tropicalis lines will be freely available to the Xenopus community as already done for the X. laevis strains

(see ).

Thank you very much for any support you may provide.
With best regards

P.S. Below you find a short description of our proposed project:

Establishment of the FLP/Cre recombinase system in Xenopus tropicalis
Principle Investigator: Gerhart U. Ryffel
Co-Investigator: Christoph Waldner
Institut fuer Zellbiologie, Universitaetsklinikum Essen, Germany

We will generate the four following different types of Xenopus tropicalis strains that will be made available to the scientific community.

I: Reporter strains expressing a fluorescent protein that upon Cre or FLP recombinase will express a distinct fluorescent protein or b-galactosidase (lacZ). These strains can be used to label cell lineages in the developing organisms and they are a prerequisite to establish efficiently activator strains expressing Cre or FLP recombinases.

II: Activator strains expressing Cre or FLP recombinases in a conditional manner. The restricted activity will either be achieved by the use of the heat-shock promoter or by fusion of the recombinase with the ligand binding domain of the estrogen receptor. In concert with the reporter strains these activator strains allow a time dependent labeling of cell lineages. They are also essential to get the conditional activation of the regulatory factors of the effector strains.

III: Docking-site strains for site specific integration of transgenes into Xenopus tropicalis. These strains will allow the single-copy integration of any gene-of-interest at a predetermined site of the Xenopus genome using fC31 integrase. This is a novel approach that may be used in other species as well.

IV: Effector strains expressing a fluorescent protein that upon Cre or FLP recombinase will express a regulatory protein. As regulator we will use HNF1b, a transcription factor whose deregulated expression in Xenopus leads to abnormal kidney development.

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