Fig. 3.

Fate of dorsal and ventral cells marked at the four-cell embryos: dorsal cells give rise to the midline even in half embryos. (A) Diagram of lineage tracing in whole embryos. A mixture of GFP mRNAs was microinjected into the two ventral blastomeres while RFP mRNAs were injected into dorsal ones, embryos cultured until tailbud, and sectioned with a Vibratome. (B–F) Sections showing that the entire epidermis (except for a few cells in the dorsal midline) and most of the lateral somite was derived from the ventral side (in green), while midline trunk organs, such as the CNS, notochord, dorsal endoderm, and medial somite were derived from the dorsal side (in red) (n = 28). (G) Experimental diagram of lineage tracing in half embryos bisected at midblastula. (H–L) Section of a right-side half embryo showing that tissues in the dorsal midline derived from the dorsal side, while the epidermis and lateral somite were still of ventral origin (n = 20). The 5× objective lens of LSM880 Zeiss confocal microscope was used for images. En, endoderm; epi, epidermis; L, left; L-So, lateral somite; m-So, medial somite; No, notochord; R, right.