We next used confocal imaging to capture the movement of Dlxi1/2b::eGFP-labelled cells in fused hSS-hCS. Interneurons moved in a saltatory pattern followed by extensive pauses (Fig. 2f). This characteristic, cyclical movement involved an extension of the leading process in one direction followed by a transient swelling of the soma and nuclear translocation (nucleokinesis) (Fig. 2g, h). This pattern of migration is similar to that observed in rodents19,20, although the ratio between the length of the leading process and the diameter of the soma in hSS-derived interneurons is almost double the ratio in mouse interneurons (Extended Data Fig. 8). To validate the biological relevance of interneuron migration in hSS-hCS, we performed live imaging of cells labelled with the Dlxi1/2b::eGFP reporter in human forebrain tissue (gestational weeks, GW18 and GW20; Fig. 2i). Dlxi1/2b::eGFP-labeled cells in fetal tissue co-expressed GABA and NKX2–1 (Extended Data Fig. 8a–f) and displayed a similar morphology and pattern of migration (Fig. 2j, k; Extended Data Fig. 8g–l; Supplementary Videos 4 & 5).
