Fig. 3: MGEO models hMGE development and interaction between microglia and hMGE progenitors.

a, Schematic diagram of experimental flow. Transcriptional factors (TFs) include CSF1, IL-34 and TGFβ1. b, MGEOs containing ‘rosette’-like proliferating centres, recapitulating the ventricular zone (VZ)-like and SVZ-like areas of hMGE. c–f, Sequential expression of markers for MGE progenitors and MGE-derived interneurons that mimic the temporal progression of hMGE development in MGEOs including DLX2 and LHX6 (c), GAD67 and NeuN (d), SST (e) and PV (f). g, Clusters of DCX⁺ neuroblasts sprinkled with Ki-67⁺ cells noted in 24-week-old MGEOs, resembling DEN-like structures in hMGE. h,i, IHC images (h) and bar graphs (i) showing iMG survived up to 12 weeks post-iMG transplantation (wpt) in MGEOs. j,k, IHC images (j) and quantification (k) showing the distribution of iMG around rosettes. l, Feature plots of microglial homeostatic markers expressed in FACS-isolated iMG from 6-week-old MGEOs. m, IHC images showing the expression of P2RY12 in iMG. n, Schematic outlining the administration of PBS or DAPT from 10 to 14 dpt before the IHC analysis of iMG distribution. o–q, IHC images of control (o) and DAPT-treated MGEOs (p) and bar graphs (q) showing that DAPT treatment sharply reduced the number of Ki-67⁺ proliferating cells and rosette formation in MGEOs. As proliferation decreased, iMG became more evenly distributed throughout the organoids. The white dashed lines mark the concentric ellipses (zones 1–4) used for binned quantification of iMG density in q. For statistics, n = 8, 8, 8, 7, 8 and 7 (each group in i); n = 6 (k); and n = 8 (q). Unpaired two-tailed t-test (i); one-way repeated measures ANOVA and post hoc Bonferroni’s test (k); two-way repeated measures ANOVA and post hoc Bonferroni’s test (q); data in i,k and q are shown as mean ± s.e.m. Scale bars, 100 μm (b (left),g (left)), 50 μm (b (middle),h,m), 25 μm (c–f (top),g (right)), 10 μm (c–f (bottom)), 20 μm (j). Illustrations in a and n were created using BioRender (https://biorender.com).