FIGURE 5. MACF1 deletion disrupts callosal axon growth and innervation.

(A) A schematic illustration of callosal axons that traverse the cortical midline and arrive at the contralateral cortex during the first postnatal week. Red rectangles indicate the different regions shown in panel B to E. (B) Control (MACF1^loxP/+) or MACF1^loxP/loxP; embryos were electroporated in utero with Dcx-cre-iGFP at E14.5 to target cortical pyramidal neurons. The electroporated mice were then sacrificed at P14 and GFP-positive pyramidal neurons in the lateral cerebral cortex (region 1) were visualized (upper panes). Lower panels showed low magnification images of in utero electroporated brain samples. (C–E) Neuron-specific deletion of MACF1 leads to abnormal callosal axon growth in the developing cerebral cortex. GFP-positive callosal axons project toward the lower layers of the cerebral cortex (C, region 2), traverse in the cortical midline (D, region 3), arrive the contralateral cortex (E, region 4). (F) The numbers of callosal axons in each region shown in (B–E) were assessed. n = 21 sections from 5 mice for each condition. Statistical significance was determined by two-tailed Student's t-test. ***p < 0.001. (G) Representative traces of axon branches in region 4. (H) The numbers of axonal branches shown in (G) were quantified. n = 128 axons for control and 46 axons using 5 mice for each condition. Statistical significance was determined by two-tailed Student's t-test. ***p < 0.001.