Fig. 3: ksr3 is expressed dynamically during blastula, gastrula and pluteus stages, first in the skeletogenic mesoderm, then during gastrulation in the endoderm, animal pole-and ciliary band, then in the adult rudiment at pluteus stage and its expression overlaps with domains of ERK activation.

a Time course of ksr3 expression during early development and in the adult rudiment. In situ hybridizations with a ksr3 probe during blastula, gastrula, prism and pluteus stages. ksr3 is first expressed transiently in the PMCs. Note that at 64-cell-stage and very early blastula stages there are 8 micromeres expressing ksr3 while at early blastula and swimming blastula stages there are respectively 16 and 32 PMC precursor cells expressing this gene. During gastrulation, ksr3 is expressed in the invaginating archenteron, in neural cells, most likely serotonergic neurons, of the animal pole. In 3-week old pluteus larvae, ksr3 is expressed in the developing appendages, spines (s) and tube feet (tf) of the adult rudiment. lv lateral view, dv dorsal view, vv vegetal view, ov oral view, sv surface view. Arrows point to the domains of ksr3 expression. b QPCR analysis of ksr3 and pmar1 expression. ksr3 is expressed transiently in the PMC precursors immediately after pmar1. c phospho-ERK immunostaining during gastrulation. The territories in which ksr3 is expressed are largely overlapping with domains of ERK activation. Arrows point to the domains of ERK activation. d ksr1 is expressed at a low level and ubiquitously in different germ layers during development. The number of times the experiments were replicated and the number of embryos analyzed are indicated in See Supplementary Table 1.