Fig. 1: Microglia are in proximity to MGE progenitors in the developing human brain.

a–d, IHC images (a–c) and bar graphs (d) showing microglia in the developing hMGE at GW15 (a,d), GW23 (b,d) and GW40 (c,d). Microglia were highly concentrated in the iSVZ and oDENs of oSVZ at GW22–25. e,f, IHC images showing the spatial relationship between Ki-67⁺ proliferating progenitors and microglia in the GW23 hMGE sections; f provides a magnified view of the region indicated in e. g, Three-dimensional reconstruction revealing the close proximity between microglia and Ki-67⁺ proliferating progenitors in the oSVZ of GW23 hMGE. Arrowheads point to the Ki-67⁺ clusters near the microglia in oSVZ. h,i, Bar graphs showing the density (h) and percentage (i) of Ki-67⁺ progenitors in GW22–25 hMGE. j, Percentage of Ki-67⁺ and Ki-67⁻ cells as their distance to microglia increased in the oSVZ of hMGE. k, Cell composition analysis of Ki-67⁺ progenitors showing Ki-67⁺ cells in proximity to microglia comprising SOX2⁺DCX⁻ radial glia and SOX2⁺DCX⁺ neuroblasts. l, IHC images and 3D reconstruction indicating that microglia closely contacted NESTIN⁺ projections in GW23 hMGE. For statistics, n (biological repeats) = 3, 5 and 6 (d); n = 4 (h,i); n = 4 (j,k). One-way analysis of variance (ANOVA) and post hoc Bonferroni’s test for d,h and i; two-way repeated measures ANOVA for j and k showed significant interaction effects (P = 0.006 (j) and P < 0.0001 (k)). Data in d and h–k are shown as mean ± s.e.m. Scale bars, 200 μm (a–c (left)), 100 μm (a–c (middle)), 10 μm (a–c (right),l (right)), 50 μm (e), 20 μm (f,g,l (left)).