Fig. 2

Heat shifts induce dysmorphology in Sqt-deficient embryos. (A–D) Overnight heat treatment produces severe dysmorphology in MZsqt embryos. Incubation at 34 °C overnight caused relatively mild defects in WT embryos (A, C) but dramatically increased phenotypic expressivity in MZsqt^-/- embryos (B, D). The loss of anterior mesendoderm derivatives and severe cyclopia in the heated MZsqt^cz35/cz35 embryo shown in 2B resembles sqt^-/-;cyc^-/- or sqt^-/-;cyc^+/- compound mutant phenotypes ([Dougan et al., 2003] and [Feldman et al., 1998]). Partial bifurcations of the midline, as shown in Fig. 2D, were often seen in MZsqt^-/- embryos that were heated overnight. (E–F) 1 h heat treatment during the post-MBT blastula stage exclusively induces cyclopia in MZsqt embryos. 1 h heat treatment of WT or MZsqt^-/- embryos (E, F), did not produce any novel abnormalities, but did increase the incidence of cyclopia in MZsqt^-/- embryos.