Fig. 2

Fig. 2 Rescue of morphological boundary formation by wild-type cells in fused somites/tbx24 mutant hosts. Formation of morphological boundaries in PM of fss/tbx24 host embryos after transplantation of wild-type cells (green), shown in live embryos: dorsal view in panels A–B, anterior up; lateral views in panels C–F, anterior left. (A) Normal segmentation in 6-somite stage wild-type embryo after transplantation of wild-type cells into PM. (B) Morphological boundary formation (arrowheads) in sibling fss/tbx24 host associated with wild-type donor cell clusters. (C) Appearance of somite-like wild-type donor cell clusters at A/P level of somite 6 in paraxial mesoderm of fss/tbx24 host at 12-somite stage, showing strong boundary morphology (arrowheads). Top panel is DIC image, middle panel is fluorescent image of green transplanted wild-type cells and bottom panel is a merge. (D–F) Confocal sections through PM of wild-type (E) and fss/tbx24 (D, D′, F) embryos at 24 hpf. (D, D′) Arrangement of wild-type cells at high-density forming compact cell clusters in fss/tbx24 host embryos. (D) Section through lateral surface of cluster. Arrangement of wild-type cells at low density is indicated with arrows. (D2) More medial section through center of cluster, showing distinctive rostral morphological boundary (arrowheads), and interdigitation of wild-type with fss/tbx24 cells on caudal side of cluster (asterisks). (E) Ends of wild-type muscle fibers at low density align to segmental boundaries in the trunk of wild-type hosts (arrows). (F) Ends of wild-type muscle fibers at low density do not align in the trunk PM of fss/tbx24 host embryos (arrows). cns = central nervous system, pm = paraxial mesoderm, im = intermediate mesoderm, n = notochord.