Hox Genes Determine the Position of the Early Tbx5-Positive Forelimb Field
(A and B) Stage 15 embryos electroporated at stage 4 with GFP (A; n = 4 embryos) or Hoxb4 dn-GFP (B; n = 9 embryos). Note that intense signal in the anterior somite and neural tube in (B) is non-specific auto-fluorescence. (A’ and B’) Tbx5 expression in corresponding embryos is shown. Note the decrease in Tbx5 expression on the electroporated side of Hoxb4 dn-GFP electroporated embryo (B’; red brackets; n = 7/9 embryos).
(C–F) Embryos electroporated with GFP alone (C; n = 20 embryos) or in combination with Hoxb4 (D; n = 16 embryos), Hoxb4+Hoxc9 dn (E; n = 19 embryos), or Hoxc9 dn (F; n = 15 embryos) in the interlimb domain at stage 14 and re-incubated for 24 hr. Note that variation in the position of the electroporated domain is due to technical variation. (C’–F’) Tbx5 expression in corresponding embryos is shown. Ectopic Tbx5 expression in the interlimb region is denoted by red arrowheads compared to normal endogenous expression denoted by green arrowheads (E’; n = 9/19 embryos).
Scale bars are 100 μm. See also Figure S3.