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. 2012 Jul 1;367-540(1-7):55–65. doi: 10.1016/j.ydbio.2012.04.025

Fig. 2.

Fig. 2

The Otx2/Gbx2 boundary separates otic and trigeminal precursors. (A) Diagram showing HH 7 stage chick embryo: the distance from the center of Hensen's node to the anterior tip of prechordal plate (hn-pc) and from the midline to the edge of the neural plate (ml-np) were set to 100%, respectively. The position of DiI label was measured and expressed as percentage of each distance. (A′). The position of the Gbx2/Otx2 boundary was measured using the same landmarks. In total 9 embryos were measured with the boundary on average at 35±7%; most anterior position measured: 42%, most posterior position: 24.5%. (B) Diagram combining labels from this study and published fate maps (Streit, 2002; Xu et al., 2008); gray: labels contributing to the trigeminal placode; blue: labels contributing to the otic placode. Circles: labels from published fate maps; squares: labels with dual fate from the current study; stars: labels from the current study. 35% indicates the average position of the Otx2/Gbx2 boundary (dotted line)±standard deviation (small arrow); note: mixed trigeminal and otic fates mostly locate near this boundary. (C) HH7 embryo with DiI labeled cells posterior to the average position of the Otx2/Gbx2 boundary (white line). (D) and (E) At HH12 their descendants contribute to the otic placode as shown in whole mount (D) and in transverse sections (E) and (F). HH7 embryo with DiI label anterior to the average position of the Otx2/Gbx2 boundary (black line). (G) and (H) At HH11 their descendants overlap with Pax3 protein (green) in the trigeminal placode. In total, 21 labels were placed into the Otx2+ and 12 into the Gbx2+ domain. (I) Diagram showing the experimental design: blastomeres were injected at the 64-cell stage in Xenopus and their position scored at stage 14. Arrows show the orientation of all embryos. (J)–(L) Neighboring blastomeres were injected with nGFP and nRFP and grown until stage 14. Descendants from injected cells are intermingled as indicated by red and green outlines in L (100%, n=10). (M)–(O) When injected with nGFP/Otx2 and nRFP/Gbx2 descendants from adjacent blastomeres do not mix (boundary in 79% of embryos, n=14). Red and green outlines in O show the distribution of cells.