A-D, Dorsal view of myoD expression in 24hpf embryos. A-C, WT, chd, and spt embryos form organized somites even if it is only in the tail (spt). chd;spt mutants do not form organized somites. (60/65 have no organized somites. The remaining 5 only had 2-3 somites form.) (D). E-H, dorsal view of ntn1b expressing muscle cells and tbx6 expressing MPCs in 11hpf embryos. E-G, WT, chd, and spt embryos have MPCs in tailbud as well as differentiated muscle cells outside the tailbud. chd;spt embryos have an accumulation of MPCs in the tailbud and no differentiated muscle cells. I-L, lateral view of papc expression in 24hpf embryos. WT and mutant embryos have MPCs in the tailbud with spt and chd;spt embryos having a large accumulation of progenitor cells.