LIS1: Activity Assays

Lissencephaly (LIS), literally meaning smooth brain, has multiple causes. Agyria, i.e., brain without convolutions or gyri, was considered a rare malformation until recent progress in neuroradiology. With this technical advantage, a number of lissencephaly syndromes have been distinguished. Classic lissencephaly (type I) is a brain malformation caused by abnormal neuronal migration at 9 to 13 weeks' gestation, resulting in a spectrum of agyria, mixed agyria / pachygyria, and pachygyria. It is characterized by an abnormally thick and poorly organized cortex with 4 primitive layers, diffuse neuronal heterotopia, enlarged and dysmorphic ventricles, and often hypoplasia of the corpus callosum. Lissencephaly is found in association with facial abnormalities in Miller-Dieker syndrome and without other major anomalies in X-linked lissencephaly and isolated lissencephaly sequence (ILS). Subcortical band heterotopia (SBH) are bilateral and symmetric ribbons of gray matter found in the central white matter between the cortex and the ventricular surface and comprise the less severe end of the lissencephaly spectrum of malformations.