A cluster of cells in the dorsal mesoderm that determines the development of the spinal cord and brain in the early amphibian embryo. Named after German embryologist Hans Spemann (1869–1941), it forms near the lip of the blastopore following gastrulation and releases signal proteins (including follistatin, noggin, and chordin) that diffuse to overlying ectoderm. These signals block the action of two growth factors, bone morphogenetic proteins 1 and 2 (BMP1 and BMP2), and induce cells to differentiate into nervous tissue instead of epidermis, forming the neural plate and subsequently the neural cord. Compare Hensen's node.
Subjects: Biological Sciences — Chemistry.