STXBP1 and epilepsy: On the other hand, effects of expression of epilepsy-causative mutants (mMunc18–1-C180Y, −R406H, −M443R or -G544 V) could not be determined since these mutants were presumed to be degradated in cortical neurons as in the case of Neuro2A, PC12 and COS cells (Fig. 3d) [12, 18], suggestive of pathophysiological significance of MUNC18–1 haploinsufficiency for the abnormal cortical neuron migration.