Fig. 4. Somites in her1+7 MO-injected embryos are enlarged in the AP dimension. All panels are confocal micrographs with black and white inversed, side views of ß-catenin staining in 17- to 18-somite embryos. A'-F', are the same confocal micrographs as A-F, without any pseudocoloring. (A,B) Wild-type embryo. (A) Anterior somites are chevron-shaped and posterior somites are more block shaped. Red-brown and blue colors denote alternating somites. The anteriormost somite shown in (A) is somite 11, panels C and E are at approximately the same AP position. (B) A higher magnification view of A showing the epithelial, cuboidal border cells (yellow and pink) that flank the intersomitic boundary. (C-F) her1+7 MO-injected embryos. Somites in these embryos are larger in the AP dimension. It is important to note that the stronger somite boundaries that are denoted by pseudocoloring are defined as such by their 3-dimensional structure: these boundaries occupy at least 90% of the dorsal-ventral dimension and 30% of the mediolateral dimension (as determined by viewing all of the focal planes, not just the one shown). (D,F) Some weak attempts at boundary formation in between stronger boundaries (arrowheads) are seen in these confocal sections. The weak boundaries do not meet our stronger boundary criteria.