Fig. 3

tor mutant embryos exhibit distinct disruptions in the expression of Notch pathway genes and subtle disruptions in somite polarity. (A–D and I–N) Dynamically expressed Notch pathway genes, deltaC (dlC), deltaD (dlD), and her7, are misexpressed in tor mutant embryos in a manner similar to her1, with normal stripes and ectopic expression between stripes, although the timing of disruption is delayed relative to her1. Arrows in Panels B and J indicate ectopic expression in tor mutant PSM. (E–H) An intronic probe for deltaC was used to detect nascent and/or unprocessed transcript. At 12 and 18 somite stages, the pattern of deltaC transcription in tor mutant embryos appears normal (compare to exonic probe hybridization in Panels A–D). (O–T) Markers of somite polarity exhibit subtle disruptions in tor mutant embryos. In mutant embryos, papc expression is normal within the PSM, but expression is detected longer after somites form; after 3 h of coloration detection, we see 3 to 4 stripes of papc expression in wild type embryos (O) and 4 to 6 stripes in tor mutant embryos (P). The polarized expression of mespa in the presumptive anterior compartments is apparent in wild type and tor mutant embryos (Q, R); however, low levels of transcript are also detected in the posterior compartment of presumptive somites in mutant embryos (arrows in R). The posterior polarity of myoD is maintained in tor mutant embryos, although myoD stripes are not as distinct as in wild type, and some transcript is detected in the anterior compartment (S,T). myoD expression in slow muscle precursors (arrowheads in S and T) is normal in tor mutant embryos. Panels are dorsal views, anterior top. Genotype, stage, and probe are indicated on each panel.