Nested concentric expression domains pattern the axial ectoderm of sea star, P. miniata , blastulae. Embryos are oriented with the animal pole up. (A-G) Whole mount in situ hybridization (WMISH). (A) zic, (B) foxq2, (C) rx, and (D) nk2.1 expression is restricted to the animal-most ectoderm. Transcripts of (E) six3 and (F) klf13 are detected in the ectoderm and in the vegetal plate endomesoderm. Arrows in (E) and (F) point to a clearing above the vegetal pole where no or few transcripts are detected. (G) nk1 transcripts are localized to a ring above the vegetal pole. (H) The boundary between the vegetal-most ectoderm (nk1, red) and the endoderm (gatae, green) as visualized by fluorescence in situ hybridization (FISH). Colocalization is in yellow. (I and J) WMISH. Transcripts of (I) foxj1 and (J) pea3 are detected throughout the entire ectoderm. pea3 is weakly detected in the vegetal plate endomesoderm. Arrows in Figure 1J point to the limits of foxj1 expression. (K) Schematic shows the patterns described above as five nested domains of expression along the AV axis. For simplicity, nk2.1 is grouped here with the concentric domains of foxq2 and rx expression. Gene names are listed next to their cognate expression domains. Vertical bars approximate the expression boundaries of associated genes. The color gradient spans the animal (orange) to vegetal (yellow) limits of the ectoderm.