Figure 5

sin3a mRNA expression pattern in chick embryos. Chick embryos staged HH9- and HH14 were processed for in situ hybridization using a probe for chick sin3a. Transverse sections at the indicated AP levels on stage HH9- embryo are shown. In all embryos, sin3a is expressed in the neural plate (np) and along the entire neural tube AP axis (nt), is absent from the PSM (section 5, psm; brackets in whole embryos) and is upregulated in the rostral part of the PSM, the region that will give rise to the prospective somites (whole embryos and section 4, ps) and in already formed somites (whole embryos and section 3, s).