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Embryonic frog epidermis: a model for the study of cell-cell interactions in the development of mucociliary disease.

Dubaissi E, Papalopulu N - Dis Model Mech (2010)

Bottom Line: These cells express high levels of ion channels and transporters; therefore, we suggest that they are analogous to ionocytes found in transporting epithelia such as the mammalian kidney.Depletion of ionocytes by foxi1e knockdown has detrimental effects on the development of multiciliated cells, which show fewer and aberrantly beating cilia.These results reveal a newly identified role for ionocytes and suggest that the frog embryonic skin is a model system that is particularly suited to studying the interactions of different cell types in mucociliary, as well as in secretory and transporting, epithelia.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.

ABSTRACT
Specialised epithelia such as mucociliary, secretory and transporting epithelia line all major organs, including the lung, gut and kidney. Malfunction of these epithelia is associated with many human diseases. The frog embryonic epidermis possesses mucus-secreting and multiciliated cells, and has served as an excellent model system for the biogenesis of cilia. However, ionic regulation is important for the function of all specialised epithelia and it is not clear how this is achieved in the embryonic frog epidermis. Here, we show that a third cell type develops alongside ciliated and mucus-secreting cells in the tadpole skin. These cells express high levels of ion channels and transporters; therefore, we suggest that they are analogous to ionocytes found in transporting epithelia such as the mammalian kidney. We show that frog ionocytes express the transcription factor foxi1e, which is required for the development of these cells. Depletion of ionocytes by foxi1e knockdown has detrimental effects on the development of multiciliated cells, which show fewer and aberrantly beating cilia. These results reveal a newly identified role for ionocytes and suggest that the frog embryonic skin is a model system that is particularly suited to studying the interactions of different cell types in mucociliary, as well as in secretory and transporting, epithelia.

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Mosaic analysis confirms ciliary defects. (A) FITC-labelled foxi1e ATG MO was injected at the one-cell stage and fluorescence confirmed at stage 9. Small grafts from morphant embryos were taken from the ventral animal pole (V) at stage 9 and grafted onto the ventral animal pole of wild-type embryos. Embryos developed until stage 28, when the morphant tissue could be distinguished from wild-type tissue in the epidermis by FITC fluorescence. D, dorsal. (B) A transplanted embryo at stage 28 shows tissue injected with MO (green), v1a-expressing cells (red) and ciliated cells (blue). Lower panels show higher-magnification images of the upper panels. Defective ciliated cells (arrowheads) are evident within the transplanted region, but ciliated cells (arrows) at the border of the transplanted tissue and adjacent to ionocytes seem normal. Note that the highlighted ciliated cells (arrows) at the border are green owing to the presence of the MO in these cells and yet the cilia appear normal. The white line in the v1A/AcTub images highlights the border between morphant and wild-type tissue. Scale bars: 50 μm (upper panels); 25 μm (lower panels).
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f8-0040179: Mosaic analysis confirms ciliary defects. (A) FITC-labelled foxi1e ATG MO was injected at the one-cell stage and fluorescence confirmed at stage 9. Small grafts from morphant embryos were taken from the ventral animal pole (V) at stage 9 and grafted onto the ventral animal pole of wild-type embryos. Embryos developed until stage 28, when the morphant tissue could be distinguished from wild-type tissue in the epidermis by FITC fluorescence. D, dorsal. (B) A transplanted embryo at stage 28 shows tissue injected with MO (green), v1a-expressing cells (red) and ciliated cells (blue). Lower panels show higher-magnification images of the upper panels. Defective ciliated cells (arrowheads) are evident within the transplanted region, but ciliated cells (arrows) at the border of the transplanted tissue and adjacent to ionocytes seem normal. Note that the highlighted ciliated cells (arrows) at the border are green owing to the presence of the MO in these cells and yet the cilia appear normal. The white line in the v1A/AcTub images highlights the border between morphant and wild-type tissue. Scale bars: 50 μm (upper panels); 25 μm (lower panels).

Mentions: Our results so far showed that the loss of ionocytes impacts negatively on the maturation and function of the ciliated cells, suggesting that there is a non-cell-autonomous effect from the ionocytes to the neighbouring ciliated cells. To test this idea further, we transplanted foxi1e MO-injected ectoderm (FITC labelled) into a wild-type host, to form a morphant clone of cells for analysis at the tadpole stage (mosaic analysis; Fig. 8A). As expected, the morphant clone showed lack of ionocytes and had abnormal ciliated cells, with fewer cilia. We did not detect abnormal ciliated cells in the wild-type tissue adjacent to the morphant clone, most probably owing to the abundance of wild-type ionocytes. However, normal ciliated cells were found close to the border of the morphant tissue, indicating a rescue of ciliated cells by their wild-type neighbours. Mingling of normal and morphant epidermal cells was observed at the borders of the clone; however, the rescued ciliated cells were clearly labelled with the FITC-tagged MO and were found next to wild-type ionocytes.


Embryonic frog epidermis: a model for the study of cell-cell interactions in the development of mucociliary disease.

Dubaissi E, Papalopulu N - Dis Model Mech (2010)

Mosaic analysis confirms ciliary defects. (A) FITC-labelled foxi1e ATG MO was injected at the one-cell stage and fluorescence confirmed at stage 9. Small grafts from morphant embryos were taken from the ventral animal pole (V) at stage 9 and grafted onto the ventral animal pole of wild-type embryos. Embryos developed until stage 28, when the morphant tissue could be distinguished from wild-type tissue in the epidermis by FITC fluorescence. D, dorsal. (B) A transplanted embryo at stage 28 shows tissue injected with MO (green), v1a-expressing cells (red) and ciliated cells (blue). Lower panels show higher-magnification images of the upper panels. Defective ciliated cells (arrowheads) are evident within the transplanted region, but ciliated cells (arrows) at the border of the transplanted tissue and adjacent to ionocytes seem normal. Note that the highlighted ciliated cells (arrows) at the border are green owing to the presence of the MO in these cells and yet the cilia appear normal. The white line in the v1A/AcTub images highlights the border between morphant and wild-type tissue. Scale bars: 50 μm (upper panels); 25 μm (lower panels).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3046089&req=5

f8-0040179: Mosaic analysis confirms ciliary defects. (A) FITC-labelled foxi1e ATG MO was injected at the one-cell stage and fluorescence confirmed at stage 9. Small grafts from morphant embryos were taken from the ventral animal pole (V) at stage 9 and grafted onto the ventral animal pole of wild-type embryos. Embryos developed until stage 28, when the morphant tissue could be distinguished from wild-type tissue in the epidermis by FITC fluorescence. D, dorsal. (B) A transplanted embryo at stage 28 shows tissue injected with MO (green), v1a-expressing cells (red) and ciliated cells (blue). Lower panels show higher-magnification images of the upper panels. Defective ciliated cells (arrowheads) are evident within the transplanted region, but ciliated cells (arrows) at the border of the transplanted tissue and adjacent to ionocytes seem normal. Note that the highlighted ciliated cells (arrows) at the border are green owing to the presence of the MO in these cells and yet the cilia appear normal. The white line in the v1A/AcTub images highlights the border between morphant and wild-type tissue. Scale bars: 50 μm (upper panels); 25 μm (lower panels).
Mentions: Our results so far showed that the loss of ionocytes impacts negatively on the maturation and function of the ciliated cells, suggesting that there is a non-cell-autonomous effect from the ionocytes to the neighbouring ciliated cells. To test this idea further, we transplanted foxi1e MO-injected ectoderm (FITC labelled) into a wild-type host, to form a morphant clone of cells for analysis at the tadpole stage (mosaic analysis; Fig. 8A). As expected, the morphant clone showed lack of ionocytes and had abnormal ciliated cells, with fewer cilia. We did not detect abnormal ciliated cells in the wild-type tissue adjacent to the morphant clone, most probably owing to the abundance of wild-type ionocytes. However, normal ciliated cells were found close to the border of the morphant tissue, indicating a rescue of ciliated cells by their wild-type neighbours. Mingling of normal and morphant epidermal cells was observed at the borders of the clone; however, the rescued ciliated cells were clearly labelled with the FITC-tagged MO and were found next to wild-type ionocytes.

Bottom Line: These cells express high levels of ion channels and transporters; therefore, we suggest that they are analogous to ionocytes found in transporting epithelia such as the mammalian kidney.Depletion of ionocytes by foxi1e knockdown has detrimental effects on the development of multiciliated cells, which show fewer and aberrantly beating cilia.These results reveal a newly identified role for ionocytes and suggest that the frog embryonic skin is a model system that is particularly suited to studying the interactions of different cell types in mucociliary, as well as in secretory and transporting, epithelia.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.

ABSTRACT
Specialised epithelia such as mucociliary, secretory and transporting epithelia line all major organs, including the lung, gut and kidney. Malfunction of these epithelia is associated with many human diseases. The frog embryonic epidermis possesses mucus-secreting and multiciliated cells, and has served as an excellent model system for the biogenesis of cilia. However, ionic regulation is important for the function of all specialised epithelia and it is not clear how this is achieved in the embryonic frog epidermis. Here, we show that a third cell type develops alongside ciliated and mucus-secreting cells in the tadpole skin. These cells express high levels of ion channels and transporters; therefore, we suggest that they are analogous to ionocytes found in transporting epithelia such as the mammalian kidney. We show that frog ionocytes express the transcription factor foxi1e, which is required for the development of these cells. Depletion of ionocytes by foxi1e knockdown has detrimental effects on the development of multiciliated cells, which show fewer and aberrantly beating cilia. These results reveal a newly identified role for ionocytes and suggest that the frog embryonic skin is a model system that is particularly suited to studying the interactions of different cell types in mucociliary, as well as in secretory and transporting, epithelia.

Show MeSH