June 1, 2008;
KazrinA is required for axial elongation and epidermal integrity in Xenopus tropicalis.
is a recently described desmosomal protein that binds the cornified envelope precursor periplakin
. In this study, we have examined kazrin
isoform A expression during the development of Xenopus tropicalis and investigated the consequences of its depletion. Whole mount in situ hybridisation revealed that kazrinA
mRNA is expressed throughout the embryo
at least until tadpole
stages. Xenopus tropicalis embryos that had been injected with antisense morpholino oligonucleotides directed against kazrinA
failed to elongate properly and showed defects in development of the head
, and somites
. We also observed that the epidermis
became disorganised and frequently separated from the underlying mesoderm
, causing the formation of epidermal blisters. Together, our results suggest that loss of kazrinA
causes defects in cell adhesion that affect axial elongation, cell differentiation, and epidermal morphogenesis.
[+] show captions
Figure 1. Expression of Xenopus tropicalis kazrinA analysed by in situ hybridisation at stages (A) 9, (B,C) 11, (D,F,G) 18, and (E) 26. B shows a lateral view and C a lateral view, while F and G show transverse sections. Expression of kazrinA is highest in dorsal and axial tissues, but expression is also detectable in ventral tissues and endoderm; the apparently lower expression in the endoderm is due in part to the high yolk content of these cells. Scale bar = 1 mm.
Figure 2. Over-expression of kazrinA has no detectable effect on the development of Xenopus tropicalis. A: Levels of kazrinA protein are elevated in stage-28 embryos previously injected with 900 pg kazrinA mRNA but not stage-39 embryos. Extracts of single uninjected (U) or injected (I1 and I2) embryos were analysed by Western blotting for expression of kazrinA. Arrow, position of full-length kazrinA. B,C: Immunocytochemical analysis confirms that levels of kazrinA protein are elevated in stage-28 embryos. B is a control embryo and C an embryo injected with 900 pg kazrinA mRNA. D,E: Sections of a control embryo (D) and of an embryo previously injected with 900 pg kazrinA mRNA (E). Both develop normally. F,G: Higher-power views of the embryos in D and E, respectively. Scale bars = 75 mm (B,C), 100 mm (D,E), 50 mm (F,G).
Figure 4. Effects of inhibition of kazrinA on the development of Xenopus tropicalis. Left-hand column shows control embryos and right-hand column shows embryos injected with antisense morpholino oligonucleotide KMO1. Developmental stages are shown in the bottom right-hand corner of each pair of images. A,B: Inhibition of kazrinA expression has no effect on gastrulation movements. C,D: Inhibition of kazrin A inhibits axial elongation of X. tropicalis embryos. E,F: KMO1 disrupts development of the eye and cause ectodermal blisters. G,H: Enlargements of the boxed areas in E and F, respectively. Note the absence of a properly pigmented eye in H and an ectodermal blister (asterisk). I,J: Muscle differentiation, visualised by monoclonal antibody 12/101, is disrupted in embryos injected with KMO1. K,L: Notochord differentiation, visualised by monoclonal antibody MZ15, is disrupted in embryos injected with KMO1. Scale bars = 0.5 mm (A-D), 0.8 mm (E,F), 0.25 mm (G,H), 0.8 mm (I-L).