Drp1 controls cortical astrocyte organization during postnatal development. (A) Representative images of V1 mouse cortices with astrocytes expressing mCherry-CAAX–tagged shRNA (magenta) against Drp1 (shDrp1) or scrambled control (shControl) and their EGFP mitochondria (green) at P7, P14, and P21. Scale bar, 200 µm. (B) Quantification of astrocyte individual or cluster area per field of view at P7, P14, and P21. N = 3–4 male and female mice/condition (big circles), three cortical sections/mouse (small gray dots). Data points are mean ± SEM. Nested t test. (C) Representative images of shControl (top) and shDrp1 (bottom) P21 astrocytes expressing mCherry-CAAX shRNAs (magenta) and stained with Sox9 (green). Yellow arrows note Sox9+ astrocytic nuclei within mCherry+ astrocytes. Scale bar, 40 µm. (D and E) Quantification of the number of Sox9+ astrocyte nuclei and (E) nearest neighbor distance between astrocytes per astrocyte cluster in P21 shControl and shDrp1 astrocytes. N = 4–5 male and female mice/condition (large circles), n = 2–6 cells or clusters/condition, 20 cells or clusters total/condition (small gray dots). Data are mean ± SEM. Nested t test. (F) Representative images of V1 astrocytes expressing mCherry-CAAX (magenta) and shControl (top row) or shDrp1 (bottom two rows, shDrp1 clusters or single astrocytes) stained with Cx43 (cyan) at P21. Scale bars, 20 µm. (G) Quantification of Cx43 expression within mCherry-CAAX astrocytes. N = 6 male and female animals/condition (large circles), n = 1–8 cells or clusters/animal, 10–25 cells total/condition (small gray dots). Data are mean ± SEM. Nested one-way ANOVA.