Basal process microtubules grow from CAMSAP-positive foci. (A and B) mEmerald–γ-Tubulin and CAMSAP3-GFP localization in mouse aRG cell apical endfeet and basal process varicosities. N, nucleus. (C and D) GFP-CAMSAP1 and GFP-CAMSAP2 localization in mouse aRG cell basal process varicosities. CAMSAP1 concentrates on the edges of the swellings. (E) Quantification of the percentage of basal process varicosities positive for CAMSAP1, 2, and 3 (n = 88 varicosities from 65 cells, n = 35 varicosities from 20 cells, and n = 120 varicosities from 59 cells, respectively). (F) Live imaging of CAMSAP3-GFP and EB3-mCherry in mouse aRG cell basal process and corresponding kymograph. Blue arrowheads: basally growing microtubules. Yellow arrowhead: apically growing microtubules. (G) Live imaging of GFP-CAMSAP1 and EB3-mCherry in mouse aRG cell basal process and corresponding kymograph. White arrowhead: EB3 comet emanating from CAMSAP1 foci. (H) Quantification of the percentage of EB3 comets emanating from CAMSAP3-positive foci throughout the basal process, in shafts and in varicosities (n = 310 comets from 15 cells). **, P < 0.01; ***, P < 0.001; ****, P < 0.0001 by Mann-Whitney tests. All experiments were performed in at least three independent mice. Error bars indicate SD.