Xenopus laevis as a model organism

We are employing Xenopus as a model system because it is well suited for the study of early development. Due to pigment differences in the 4 to 8 cleavage cell embryos (see middle panel), it is possible to target microinjections into prospective tissue regions. The right panel shows embryos that have been injected with GFP-RNA in one of 4 cells. At neurula stage the fluorescent signal can be seen to be localized strictly to one half of the embryo.

Renal development

Our main focus is on renal development in X. laevis. We are investigating proteins involved in early renal development and cystic kidney disease. Xenopus embryos can be easily manipulated and have a functional early kidney (pronephros) after 2 days of development. Therefore they serve as an excellent model organism to study genes and proteins involved in tubular patterning and differentiation.

The images show one embryo that was injected on the left side with a oligonucleotide that interferes with renal development. The uninjected right side of the same embryos serves as an internal control. After staining with a tubule specific antibody, the pronephric system becomes visible.

When a flourescent dye is injected into the coelomal cavity of the tadpole, the pronephric tubules can be functionally analyzed. (see left image) We are not only able to visualize the gross morphology, but also the rate of flow inside the tubules of a living embryo. Urinary outflow of dye indicates that the embryo at this stage is already excreting a considerable amount of fluid. We are investigating how genes involved in cystic kidney disease help shape the pronephros and the functional implications of a loss of function.


Cilia and Cysts

The multiple studies in recent days linking ciliary function and cystic kidney disease have let us to a new area of focus. X. laevis tadpoles have cilia on their epidermis that are very accessible for visualization. The image shows two epidermal cells, that have been stained against tubulin and scanned by confocal microscopy. These ciliated cells are highly polarized and thus serve as an excellent model to study the effect of "cystproteins" on polarity in ciliated cells. We are closely collaborating with the "Live Imaging Centre" to obtain high resolution confocal images

Universität Freiburg Universitätsklinikum Freiburg DFG