Genetic mutants indicate that <i>her7</i> and <i>her1</i> have distinct functions.

<p>(A) Wildtype (wt, left) and <i>her1</i> mutant (right) embryos at 34 hours post fertilization (hpf) stained for <i>cb1045</i> expression to visualize segmentation. Anterior segmentation defects in <i>her1</i> mutant embryos were of variable severity, and a representative embryo is shown. See <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001364#pbio.1001364.s004" target="_blank">Figure S4D</a> for a quantitative analysis of segmentation defects in <i>her1</i> mutants. (B–D) wt (upper row) and <i>her1</i> mutant (lower row) embryos at the 10-somite stage in situ stained for <i>her7</i> (B), <i>dlc</i> (C), or <i>her1</i> (D) mRNA expression. <i>her1</i> and <i>dlc</i> expression patterns (C and D) were visualized using tyramide chemistry and displayed in FIRE lookup table to distinguish onset of expression waves (high intensity punctate signal in insets) from later phases of the oscillation cycle (punctae with lower intensity or diffuse signal). (E) wt (left) and <i>her7</i> mutant (right) embryos at 34 hpf stained for <i>cb1045</i> expression to visualize segmentation. Red arrowhead points to anterior-most segmentation defects in <i>her7</i> mutants. (F–H) wt (upper row) and <i>her7</i> mutant (lower row) embryos at the 10-somite stage in situ stained for <i>her7</i> (F), <i>dlc</i> (G), or <i>her1</i> (H) mRNA expression. (A) and (E–H) are whole mount preparations, and (B–D) are flat mount preparations. (B–D) and (F–H) Two representative examples per condition are shown to illustrate oscillatory expression, except for <i>her7</i> mutants (F–H). Scale bar: 300 µm for (A and E), and 100 µm for all other panels.