Figure 7

Time-restricted inhibition of Nodal signaling reveals that LR asymmetry is specified at neurula stages. (A) Inhibition of Nodal signaling by SB505124 results in three larval (L2) phenotypes, designated as ‘wild-type’, ‘mild’, and ‘strong’, and defined by differential expression of Lhx3 as a marker of the preoral pit and Krox as a marker of the dorsal part of the club-shaped gland. The mild phenotype involves a loss of the ventral portion of the pharynx (small arrowheads) and reduced Lhx3 expression, indicative of a reduced preoral pit (arrowhead). The strong phenotype involves a loss of the ventral portion of the pharynx (small arrowheads), complete loss of the preoral pit, and an ectopic club-shaped gland on the left side (arrow). (B) Long-term treatments were performed to demonstrate that Nodal inhibition during the neurula stages results in altered phenotypes. (C) Short-term treatments were performed to demonstrate that Nodal inhibition results in altered phenotypes, especially when administered at the N0 to N2 stages. All images are from B. lanceolatum.