PMC

The Δ Leading process length of both the control and the L1-KD neurons decreased by almost the same degree. In contrast, the Δ Curvature index of the L1-KD neurons increased, while the control neurons did not show much change.

The migration velocity of L1-KD neurons decreased in the IZ, which resulted in delayed radial migration. The L1-KD neurons showed longer and undulated leading processes in the upper cortical plate and the retraction of leading processes, along with somal translocation, were disrupted during the terminal translocation of the soma in the PCZ.

(A) Illustration of the strategy of in utero electroporation and slice culture. (B) Average velocity of migrating neurons in the IZ from Div1 to Div2 or Div2 to Div3. Data were presented as Mean ± SEM, *** P<0.005, unpaired Student's t-test compared with the control (ctrl).

(A) The leading process of a control neuron was nearly straight as it extended to the MZ. (B,C) Some L1-KD neurons had undulating processes and others could not reach the MZ, along with aberrant morphology of the leading process. The dotted line indicates the top of the cerebral cortex. The arrow indicates an edge of the leading process, and the arrowhead indicates a soma of a neuron.

(A) This scatter plot shows the relationship between the distance of the somal translocation and the Δ Leading process length. The black filled circles (•) indicate control neurons. The gray filled diamonds (♦) indicate L1-KD neurons. (B) The Δ Leading process length and the distance of the somal translocation in the L1-KD was lower than that of the control neurons. Data were presented as Mean ± SEM, *p<0.05, unpaired Student's t-test.

(A) The open circles (○) indicate control neurons at 0 h. The black filled circles (•) indicate control neurons at 1 h. The black open triangles (▵) indicate L1-KD neurons at 0 h. The gray filled triangles (▴) indicate L1-KD neurons at 1 h. (B) The curvature index of the leading processes of the L1-KD neurons was larger than that of the control neurons. Data were presented as Mean ± SEM, *P<0.05, unpaired Student's t-test.

(A) The leading process of a control neuron in the upper CP that was near the pia was shortened in a smooth fashion as the soma migrated towards the pia. (B) On the other hand, the leading process of a L1-KD neuron did not properly retract and was transiently undulated. Displayed on the top of the frame, the time 0 h was considered the time that the tip of the leading process first reached the pia. The arrowhead indicates the soma of a neuron, and the arrow indicates the abnormally undulating part of the leading process.