XB-IMG-48692
Xenbase Image ID: 48692
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Fig. 6. XHoxa2 induction after NC migration results in homeosis of mandibular arch skeletal elements. (A) Luciferase activity from COS cell extracts transiently transfected with the pAdML ARE reporter, β-gal, and Pbx1 together with either Xenopus (XHoxa2), mouse (mHoxa2), zebrafish (zHoxa2) or DEX inducible (XHoxa2:GR) cDNA constructs. Bars represent the mean luciferase activity.e.m. of six independent experiments after normalising to β-gal activity. (B) Distribution of normal (N), segmentation (S) and homeotic (H) phenotypes in XHoxa2:GR-injected tadpoles after DEX treatment at stages (st) 15, 20, 26, 28 and 30. In C, embryos have been co-injected with GFP and selected at stage 49 for high levels of GFP expression in the branchial region. Note the significant enrichment of homeotic phenotypes in stage 26 and 28, but not stage 30, in DEX-treated GFP-selected embryos, when compared with (B). (D) Dorsal view of a whole-mount Alcian Blue-stained skeleton of a stage 49 injected tadpole, DEX-treated at stage 28, showing the loss (vertical arrow) of the muscular process (MP) of the palatoquadrate (Q) on the injected side (right); the broken red line marks the palatoquadrate edge. (E) Skeletal flat-mount of a stage 49 tadpole, treated with DEX at stage 28, showing a mirror-image homeotic transformation of the palatoquadrate and the proximal portion of the Meckel
(M) cartilage into ceratohyal (C2) on the injected side. The red and black broken lines indicate the distal part of the Meckel and the axis of symmetry, respectively. (F,G) Lateral views of the uninjected (F) and injected (G) sides of a stage 37 embryo, treated with DEX at stage 28 and hybridised with Xbap. In F, expression is in the precursors of palatoquadrate and proximal part of the Meckel cartilage (arrow, Q+M). In G, a selective loss of Xbap expression (arrow) at the level of these precursors is observed. (H,I) Lateral views of uninjected (H) and injected (I) sides of a stage 37 embryo, treated with DEX at stage 28, and hybridised with Xgsc. Fusion of 1st and 2nd arch expression domains is indicated in I and J (arrows). (J) Ventral view of the embryo in H,I after dissection of the cement gland. Spatial reorganisation of Xgsc transcripts is evident in 1st arch (PA1, arrowhead). C, ceratoyal; E, eye; Et, ethmoid; I, infrarostral; PA2, 2nd pharyngeal arch. Image published in: Pasqualetti M et al. (2000) Copyright © 2000. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License.
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