Fig. 1. Gpc4 expression during early development of Xenopus embryos. Arrowheads (B-F) point to the dorsal blastopore lip. (A) Blastula (stage 7) showing localization of Gpc4 transcripts in the animal hemisphere. AP, animal pole; VP, vegetal pole. (B) Expression of Gpc4 at the onset of gastrulation (stage 10). (C) Dorso-vegetal view of an early gastrula stage embryo (stage 10.5). The broken line indicates the plane of the hemi-sections shown in panels D-F and I. (D-F) Hemi-sections of embryos cut along the dorsoventral axis (stage 10.5). (D) Gpc4 transcripts in prechordal endomesoderm and chordamesoderm (asterisk) and in the neuroectodermal cell layer (arrow). (E) Distribution of Noggin transcripts in the prechordal endomesoderm and chordamesoderm (asterisk). (F) Sox2 in the neuroectodermal cell layer (arrow). (G) Frontal view of an early neural plate embryo (stage 14). Note Gpc4 transcripts in the anterior neural plate (black arrow) and presumptive spinal cord (white arrow). (H) Frontal view of a stage 14 embryo showing Bf1 expression in the anterior forebrain. (I) Expression of Gpc4 in a hemi-sectioned embryo (stage 14). Anterior is to the left. The white arrowhead points to decreasing expression in the prechordal plate. (J) Frontal view of a mid-neurula (stage 17). Asterisks point to Gpc4 transcripts in the presumptive dorsal forebrain. (K) Emx2 expression in the presumptive dorsal forebrain (stage 17; asterisks). (L) Expression of Gpc4 following closure of the anterior neural tube (stage 20). Arrow points to transcripts in the forebrain.