Figure 1

Inhibitory interactions between progenitor cells bias the distribution of NSC activation events

(A–A’’') Confocal dorsal views of a whole-mount adult telencephalon showing the germinal layer of the pallium in a 3mpf Tg(gfap:GFP) fish immunostained for GFP (green, NSCs), PCNA (magenta, proliferating cells), and Gfap (Zrf1 antibody, cyan). Anterior left, pallial subdivisions (Dl: lateral, Dm: medial, Da: anterior) indicated by dotted lines.

(A and A’) Dorsal (apical) view and high magnification of the NSC layer, showing merged and single channels (color-coded). Arrowheads: purple to aNSCs, orange to aNPs. aNSCs are GFP⁺,Gfap⁺, aNPs are negative for both markers.

(A’’ and A’’’) Examples of aNSCs with a process (red arrows) visible using the GFP or the Zrf1 markers, respectively (left and right panels: different backgrounds to ease observation).

(B–B’’) Similar sample stained for GFP (green, NSCs) and PCNA (magenta, proliferating cells).

(B and B’) Merged and single-channel views (color-coded).

(B’’) Close-up in Dm showing progenitor cell states (merged image, individual channels and segmentation): quiescent NSCs (qNSCs; GFP⁺ only; green), activated NSCs (aNSCs; GFP⁺,PCNA⁺; magenta), and proliferating neural progenitors (aNPs; PCNA⁺ only; orange) (see also Figures S1A–A”).

(A, B, and B') Stitches of 4 tiles with 10% overlap.

(C) Main pallial NSC lineage (arrows: lineage transitions).

(D) Proportions of qNSCs, aNSCs, and aNPs relative to each other in Dm (see also Figures S1B–B’’’).

(E) Besag’s L function assessing spatial correlations for the same fish between aNSCs (left) and between aNSCs and aNPs (right) (aNSCs include pre-division aNSCs—singlets—and immediately post-division NSCs—doublets, scheme on left). L_(obs)(r) (red line): experimental value, L_{(H0, mean)}(r) (black dotted line): mean under the random labeling null hypothesis (the state of any cell is independent of other cells and of its position), r: mean cell diameter in this brain (r = 0: cell of reference, r = 1: immediate neighbor), gray regions: 95% confidence envelopes. High magnification shows significant dispersion (see also Figures S2A–S2E).

(F) Range and strength of this interaction determined with functions g (left) and M (right). Green bar: 95^th centile of the distance to the furthest direct neighbor of aNPs.

Scale: (A), (B), and (B’) 100 μm; (A’) 10 μm; (A’’), (A’’’) 7 μm; (B’’) 30 μm.