Figure 2. Asymmetric Gene Expression Is Randomized in Xenopus by Inhibition of 5-HT Signaling through R3 or R4
Embryos were exposed to blockers of R3 or R4 during early stages and processed for in situ hybridization with the laterality markers XNR-1
and Xlefty. Embryos exposed to vehicle only (controls) exhibited the normal left-sided pattern of XNR-1 (A) expression. In contrast, embryos
in which the activity of MAO, R3, or R4 was inhibited exhibited bilateral (C), right-sided (D), or absent (E) expression of XNR-1 in addition to
the left-sided expression (B). This effect was statistically significant (see numerical data and analysis in Table S9). Red arrows indicate regions
of expression; white arrows indicate lack of expression.