Xenbase Image ID: 49549

Figure 6. Chordin Is Required for Spemann Organizer Activity (A) Experimental design of the isotopic and isochronic transplantation experiment. Embryos were injected twice into dorsal blastomeres with BDA (biotin dextran amine lineage tracer) alone or with Chd-MO(1 2). Dorsal lip explants were isolated from these donor embryos and transplanted at gastrula into unlabeled host embryos. After the embryos were sectioned in paraffin wax, BDA was detected with streptavidin conjugated alkaline phosphatase and BM purple. (B) Transplantation of an organizer injected with lineage tracer alone allowed normal development in most cases, but some embryos developed shortened axes (12%, n 33). Histological sections showed that BDA staining was detected in the notochord (no) and floor plate (fp) throughout the embryo and in anterior dorsal endoderm (de). Seven embryos were serially sectioned, stained with Streptavidin-AP, and developed with BMP purple. (C) Embryos that received Chd-MO(1 2)-injected organizer transplants developed with shortened body axes (100%, n 15) and small eyes (47%, n 15) or no eyes (20%, n 15). Lineage label was detected in the notochord, anterior dorsal endoderm, and medial somite (so). Surprisingly, transplanted cells stained the epidermis of the host embryo (epi) in the posterior and were excluded from neural tissue. Six embryos were serially sectioned. (D) Dorsal lip explants transplanted into the ventral side of a host embryo recapitulate the classical Spemann-Mangold experiment. (E) The transplantation of a wild-type organizer induced the formation of secondary axes (100%, n 17), of which most (82%) were complete axes containing heads and eyes. In the 11 embryos serially sectioned, BDA could be detected in the notochord, floor plate, and dorsal endoderm of the secondary axes. (F) Transplantation of a Chd-MO(1 2)-injected organizer blocked the axis-inducing activity of the explant. A few embryos formed protrusions (31%, n 16), the strongest of which is shown here. In the seven embryos serially sectioned, BDA staining was detected in the ventral mesoderm (vm), ventral endoderm (ve), and epidermis (epi). Note that Chd-MO(1 2)-injected grafts did not induce the CNS, somites, or notochord. Image published in: Oelgeschläger M et al. (2003) Copyright © 2003. Image reproduced with permission of the Publisher, Elsevier B. V. Larger Image Printer Friendly View

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