Figure 2.

Nuclear movement during neuronal migration. (A) Nuclear translocation during neuronal migration in a wild-type neuron. Neuronal progression is achieved by the succession of three steps. (1) After extension of the leading process, the centrosome positioned in front of the nucleus is pulled in the direction of the leading edge. (2) The nucleus moves toward the centrosome by contraction of the microtubules. (3) The trailing process retracts, and as a result the whole neuron is moved forward. This sequence is repeated many times during cortical migration. Box: Model for a LINC complex spanning the neuron nuclear envelope, based on the similarities between phenotypes in Lmnb2, Syne-1/2 and Sun1/2 mutant mice. A complex involving lamin B2, SUN1/2 and Syne1/2 proteins might provide anchoring of the nucleus to the network of microtubules. Syne1/2 interaction with the microtubules is mediated by binding to motors that move along the microtubules.³⁸ (B) A possible mechanism for defective neuronal migration in the setting of lamin B2 deficiency. Lamin B2 deficiency might impair the mechanical properties of nuclei in neurons, and an increase in nuclear deformability could prevent nuclear translocation and adversely affect neuronal migration. NE, nuclear envelope.