Fig. 5

tbx2a/b are necessary and sufficient to promote the formation of the DL. (A) Injecting wild-type embryos with either tbx2a or tbx2b cRNA resulted in a significant expansion of the DL as observed by somite counting (smyhc1). (B) In wild-type, 28 ss embryos, the DL (slc12a3) domain and the DE (slc12a1) domain are distinctive. In embryos overexpressing either tbx2a or tbx2b, DE cells and DL cells appear to be co-mingled adjacent to the 13th somite. This observation explains why the DL expands to the 13th somite in tbx2a/b overexpressing embryos but the DE, PST, and PCT domains remain unaltered. DAPI (blue) was used to label nuclei (C) Rescue studies reveal that DL domain changes in tbx2a and tbx2b morphants are specific to loss of tbx2a and tbx2b, rather than toxicity. Wild-type embryos were co-injected with either tbx2a cRNA and tbx2a ATG MO or tbx2b cRNA and tbx2b ATG MO. In addition, fby^c144 mutants were injected with tbx2b cRNA. In all treatments, a wild-type DL was observed some of the time as indicated by somite counting and length measurements. (D) The DL of 5 embryos from each overexpression and rescue treatment was measured in uM. A significant increase in the DL was seen in animals injected with tbx2a cRNA and tbx2b cRNA, but no significant change in DL length was observed in any of the rescue experimental parameters. (*p<0.05, **p<0.001, N.S. = not significant). Abbreviations: cRNA (capped RNA), MO (morpholino), DL (distal late).