XB-ART-56520Genes Cells February 1, 2020; 25 (2): 86-99.
Role of TrkA signaling during tadpole tail regeneration and early embryonic development in Xenopus laevis.
Neurotrophic signaling regulates neural cell behaviors in development and physiology, although its role in regeneration has not been fully investigated. Here, we examined the role of neurotrophic signaling in Xenopus laevis tadpole tail regeneration. After the tadpole tails were amputated, the expression of neurotrophin ligand family genes, especially ngf and bdnf, was up-regulated as regeneration proceeded. Moreover, notochordal expression of the NGF receptor gene TrkA, but not that of other neurotrophin receptor genes TrkB and TrkC, became prominent in the regeneration bud, a structure arising from the tail stump after tail amputation. The regenerated tail length was significantly shortened by the pan-Trk inhibitor K252a or the TrkA inhibitor GW-441756, but not by the TrkB inhibitor ANA-12, suggesting that TrkA signaling is involved in elongation of regenerating tails. Furthermore, during Xenopus laevis embryonic development, TrkA expression was detected in the dorsal mesoderm at the gastrula stage and in the notochord at the neurula stage, and its knockdown led to gastrulation defects with subsequent shortening of the body axis length. These results suggest that Xenopus laevis TrkA signaling, which can act in the mesoderm/notochord, plays a key role in body axis elongation during embryogenesis as well as tail elongation during tadpole regeneration.
PubMed ID: 31788928
Article link: Genes Cells
Species referenced: Xenopus
Genes referenced: bdnf btg3 lrr1 ngf ntrk1 ntrk2 ntrk3 sox2
GO keywords: neurotrophin TRKA receptor binding
Article Images: [+] show captions
|Figure 1. Xenopus laevis NGF family genes are up-regulated in the regenerating tails of tadpoles. The expression levels of ngf.L/S (a), bdnf.L/S (b), ntf3. L/S (c) and ntf4. L/S (d) were measured by qRT-PCR. Ten tail tips were collected by cutting at the level of 0.5 mm anterior to the original amputation plane at 0, 1, 3 or 6 days post amputation (dpa). The results of two independent experiments are shown. The expression level of each gene was normalized to that of odc, and the normalized gene expression level at 0 dpa was defined as 1.0 in each experiment.|
|Figure 2. Expression patterns of Xenopus laevis NGF family genes during tadpole tail regeneration. WISH for ngf (a-f), bdnf (g-l), ntf3 (m-r) and ntf4 (s-x) was performed on intact (N=7), 0, 1, 2, 3, or 6 dpa (N=9 for each time-point) tadpoles from two independent experiments. Magnified views of the boxed areas in e, k, q and w are shown in e', k', q', and w', respectively. Arrowheads and arrows indicate the original amputation planes and the regenerating tadpole tips, respectively. The asterisk (m) indicates the staple holding the tadpole during photographing, bf, border between the outer and inner fins; me, mesenchyme. Scale bar, 1mm, except for e', k', q', and w'.|
|Figure 3. Expression patterns of Xenopus laevis Trk family genes during tadpole tail regeneration. WISH for TrkA (a-f), TrkB (g-l) and TrkC (m-r) was performed on intact (N=7), 0, 1, 2, 3, or 6 dpa (N=9 for each time=point) tadpoles from two independent experiments. Magnified views of the boxed areas in e, k, and q are shown in e', k', and q', respectively. Arrowheads and arrows indicate the original amputation planes and the regenerating tail tips, respectively. Broken lines (e', k', and q') indicate the outlines of the regenerating tails. Asterisks (f, k, and r) indicate the staples holding the tadpoles during photographing. nc, notochord; sg, spinal ganglia. Scale bar, 1 mm, except for e', k', and q'.|
|Figure 5. Spatial expression patterns of Xenopus laevis ngf in early development. The expression of ngf at stage 11 (a), 13 (b), 15 (c), 20 (d), 25 (e), 30 (f), 35 (g) and 40 (h) was analyzed via WISH. N=11 in each stage, from two independent experiments. Lateral views with dorsal up (e-h). bf, border between the outer and inner fins; ov, otic vesicle. Scale bar, 1mm.|
|Figure 6. Spatial expression patterns of Xenopus laevis TrkAin early development. The expression of TrkA at stage 11(a), 13 (b), 15 (c), 20 (d), 25 (e), 30 (f), 35 (g), and 40 (h) was analyzed via WISH. N=6 in stage 11, from one experiment; N=11 each in other stages, from two independent experiments. D, dorsal; V, ventral (a-c). Sagittal sections of embryos are shown in right panels with dorsal to the right (a and b). A transverse section of the embryo is shown in the right panel with dorsal up (c). Lateral views with dorsal up (e-h). Magnified views of the boxed areas are shown in right bottom (c) or right (e and f) panels. yp, yolk plug; dm, dorsal mesoderm; vm, ventral mesoderm; nc, notochord; sg, spinal ganglion; tn, trigeminal nerve; vn, vestibulocochlear nerve. Scale bar, 1mm, except for the magnified views in c, e, and f.|