Four populations are labelled in rhombic lip electroporations. A. Schematic diagram of electroporation and flat-mount preparation where rhombic lip of cerebellum (cb) in red and hindbrain (hb) in black borders the fourth ventricle (IV) roof plate (yellow). B. Four populations of neurons (①②③④) are labelled at st.31/E7 following green fluorescent protein (GFP) electroporation at st.22/E4. Site of electroporation is indicated by arrows. Rhombic lip (rl) of cb shown by red dashed line. C. Positions of each population are summarised in schematic diagram of the intact midbrain/hindbrain region. D. In a subset of experiments, GFP was detected in additional axon tracts (arrowheads). E. Electroporation of Atoh1-cre + stop-GFP into cerebellar rhombic lip confirms that infrequently labelled, additional axons in D are not rhombic lip derived. Dashed line highlights the rhombic lip with red region indicating cerebellar rhombic lip. Arrows (B-E) show site of electroporation. r, rhombomere; a, anterior; p, posterior; d, dorsal; v, ventral. In this and subsequent figures, AP axis runs left to right. Scale Bars: 200 μm in B, D and E.