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Sea Urchin Maternal Gene Breaks Radial Symmetry

A new study by Haillot et al. reveals that Panda—a member of the TGF-β family of signaling molecule—is encoded by maternal mRNA and helps to break radial symmetry and orient the dorsal-ventral axis of the developing sea urchin embryo. The image shows 48-hour-old embryos rendered deficient for panda but then rescued by local injection of panda mRNA at the 2-cell stage. An antisense morpholino oligonucleotide targeting panda was first injected into the egg (red color), and then panda mRNA was injected into one blastomere at the 2-cell stage. Local expression of Panda (green color) rescues dorsal-ventral polarity and imposes a dorsal identity on the cells.

Image Credit: Emmanuel Haillot