Fig. 6. Direct Hh signalling is required for acquisition of proper MDT gene expression. Wild-type embryos were injected with a biotin-coupled lineage tracer and grafted into a smu mutant embryo at sphere stage. At 32 hpf, the embryos were fixed and stained for shh/dlx2a or shh/dbx1a by double in situ hybridization, followed by fluorescence detection of the biotin-containing wild-type cells. dlx2a-positive cell clones are detectable anterolateral to the ZLI (A, higher magnification in A'; blue arrows). A section of the same embryo shows co-localization between the red dlx2a with the green biotin (B-B'', blue arrows). dbx1a-positive cell clones are seen posterior to the ZLI (D, higher magnification in D'; yellow arrows). A section of the same embryo shows co-localization between the red dbx1a with the green biotin (E-E'', yellow arrows). (C,F) Summaries of all transplantation experiments showing dlx2a 14 wild-type clones, positive (12 red dots) and negative (2 black dots); and dbx1a 20 wild-type clones, positive (9 red dots) and negative (black dots, 7 anterior and 4 posterior to the ZLI).