Fig. 2

Motor ganglion lineages and neuron subtype configuration in Ciona. a Dorsal view of a late gastrula-stage Ciona robusta embryo highlighting in false color the bilaterally symmetric right/left pairs of blastomeres in the vegetal neural plate that give rise to the “core” Motor Ganglion and Anterior Caudal Inhibitory Neurons (ACINs) of the nerve cord: A9.30 (red), A9.32 (yellow), and A9.29 (blue). Black dashed line indicated embryo midline. Red dashed outline denotes the right vegetal neural plate annotated in the inset diagram, which indicates the exact cell identities according to the established cell lineage nomenclature [64]. Embryo image adapted from the Four-dimensional Ascidian Body Atlas website (FABA, http://chordate.bpni.bio.keio.ac.jp/faba/1.4/top.html) [65]. b Diagram representing a section of the dorsal hollow neural tube derived from the neural plate after the process of neurulation. Cells of the neural tube are color-coded according to their lineages using the same color scheme as the neural plate diagram in (a). The neural tube is comprised exactly of four single-file rows of cells: 1 dorsal row, 2 lateral rows, and 1 ventral row. Cells of the lateral rows contributing to the bilaterally symmetric motor ganglion are: A11.117-A11.120, derived from A9.30, and A10.64, derived from A9.32. The A9.29 lineage, which gives rise to ACINs and ependymal cells posterior to the MG, is not illustrated in great detail, for the sake of simplicity. At bottom is a diagram of the 5 core MG neuron types. Black lines indicate their descent patterns from those cells at top. ddN = descending decussating neuron, IN1 = interneuron 1, IN2 = interneuron 2, MN1 = motor neuron 1, MN2 = motor neuron 2. Non-neuronal cells are gray. Cells are identical on both left and right sides