Fig. 6. Somite transplants restore the normal PMN subtype pattern in ntl;spt mutants. (A) Schematic of blastula stage transplants. (B-D,F) Islet antibody + islet2 in situ hybridization + anti-fluorescein antibody staining at 18-22 hpf. Islet antibody staining is nuclear and brown; islet2 staining is blue and cytoplasmic; red staining is fluorescent and shows wild-type donor cells that contain fluorescein dextran. Brown-only cells (^*) express only islet1 and hence are MiPs; blue + brown cells express islet2 and possibly also islet1, and are therefore CaPs or hybrid PMNs. (B) ntl;spt MO-injected host embryo with its spinal cord completely filled with wild-type donor cells but devoid of wild-type somite cells. No MiPs (brown-only cells) are present in this embryo, so the PMNs probably still all have a hybrid identity. (C) Bright-field microscopy and (D) fluorescence microscopy of the same cross-section of another ntl;spt MO-injected host embryo with its spinal cord completely filled with wild-type donor cells but devoid of wild-type somite cells. Two triple-labeled PMNs are indicated with arrowheads. (E) Schematic of whole somite transplants. (F) ntl;spt MO-injected host embryo with transplanted wild-type somites. Several MiPs (brown-only cells; ^*) are present adjacent to the wild-type somites (red). These MiPs are separated by blue + brown cells that are probably CaPs. Insert shows a different ntl;spt host embryo with transplanted wild-type somites; in this case, the somite boundaries are clearly visible (broken lines). As in wild-type embryos, MiPs were adjacent to these somite boundaries. Scale bar: 50 µm.