Hsc70 chaperone activity supports radial neuronal migration and callosal projections in the embryonic neocortex. (A) In utero electroporation of E14.5 mouse embryos with pCIG2 control vector or pCIG2 constructs encoding Hsc70 or Hsc70^D10N. Representative brightfield images of E17.5 coronal brain sections, stained with anti-GFP (green) and the nuclear marker DAPI (blue). Asterisk denotes impaired callosal projections. CP, cortical plate; IZ, intermediate zone; VZ/SVZ, ventricular zone/subventricular zone. Bar, 200 µm. (B) Quantification of the distribution of GFP⁺ neurons in the cortex (pCIG2: 372 neurons from six embryos; Hsc70: 390 neurons from five embryos; Hsc70^D10N: 850 neurons from 11 embryos). Error bars indicate the SEM (*, P < 0.05; ***, P < 0.001; unpaired student’s t test). (C) Morphological comparison of Hsc70^D10N-expressing neurons in the intermediate zone relative to vector control neurons. Bar, 50 µm. (D) High magnification 3D rendering of representative GFP⁺ neurons in the intermediate zone from C revealing impaired neuronal polarization with Hsc70^D10N expression. Left, front view; right: side view. Arrows indicate direction of radial migration. Arrowheads indicate leading processes of migrating GFP⁺ neurons. (E) Quantification of the proportion of GFP⁺ neurons in the intermediate zone with polarized morphology (pCIG2: 288 neurons from seven embryos; Hsc70^D10N: 416 neurons from seven embryos). Error bars indicate the SEM (***, P < 0.001; unpaired student’s t test).