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Figure 6.
Thapsigargin treatment inhibits convergent extension but does not affect mesodermal cell fate. (a) Control embryos at stage 12 have almost finished blastopore closure (dorsal view is shown; anterior at top). Xnot staining reveals long, narrow notochords. (b) Embryos treated with thapsigargin fail to close their blastopores by stage 12. Xnot staining indicates that notochords have failed to converge and extend. In a few cases (far right embryo), some convergent extension occurs and the anterior notochord elongates, though the posterior notochord remains broad. (c) Control embryos stained for Xnot. (d) Embryos treated with BHQ fail to close their blastopores, and notochords do not converge and extend, though Xnot is expressed strongly. (e) Control embryos hybridized to MyoD; somites are elongated along each side of the notochord. (f) Thapsigargin treated embryos express MyoD at normal levels, though somites fail to converge and elongate; MyoD expression domains remain short and broad. (g) Quantitation of convergent extension by measurement of the length-to-width ratio (mean ± standard error) of Xnot expression domains in control and thapsigargin-treated embryos. The total area of the Xnot expression domains differed by less than 3% between control and experimental embryos (h) Length-to-width ratios of Xnot expression domains in control and BHQ-treated embryos. Slight differences in stages account for differences in control LWRs in THAP and BHQ experiments (see [a] and [c]) |
