Human Molecular Genetics Advance Access originally published online on May 10, 2008
Human Molecular Genetics 2008 17(16):2441-2455; doi:10.1093/hmg/ddn144
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Lis1–Nde1-dependent neuronal fate control determines cerebral cortical size and lamination
1 Department of Neurology and Center for Genetic Medicine 2 Department of Pathology, Northwestern University Feinberg School of Medicine, 303 E. Superior Street, Chicago, IL 60611, USA 3 Department of Pediatrics, Institute for Human Genetics, University of California, San Francisco, 513 Parnassus Avenue, HSE901F, San Francisco, CA 94143, USA 4 Division of Genetics, Children's Hospital Boston and Howard Hughes Medical Institute 5 Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
* To whom correspondence should be addressed. Tel: +1 3125031046; Fax: +1 3125035603; Email: yuanyi-feng{at}northwestern.edu
Received April 14, 2008; Revised April 14, 2008; Accepted May 7, 2008
Neurons in the cerebral cortex originate predominantly from asymmetrical divisions of polarized radial glial or neuroepithelial cells. Fate control of neural progenitors through regulating cell division asymmetry determines the final cortical neuronal number and organization. Haploinsufficiency of human LIS1 results in type I lissencephaly (smooth brain) with severely reduced surface area and laminar organization of the cerebral cortex. Here we show that LIS1 and its binding protein Nde1 (mNudE) regulate the fate of radial glial progenitors collaboratively. Mice with an allelic series of Lis1 and Nde1 double mutations displayed a striking dose-dependent size reduction and de-lamination of the cerebral cortex. The neocortex of the Lis1–Nde1 double mutant mice showed over 80% reduction in surface area and inverted neuronal layers. Dramatically increased neuronal differentiation at the onset of corticogenesis in the mutant led to overproduction and abnormal development of earliest-born preplate neurons and Cajal–Retzius cells at the expense of progenitors. While both Lis1 and Nde1 are known to regulate the mitotic spindle orientation, only a moderate alteration in mitotic cleavage orientation was detected in the Lis1–Nde1 double deficient progenitors. Instead, a striking change in the morphology of metaphase progenitors with reduced apical attachment to the ventricular surface and weakened lateral contacts to neighboring cells appear to hinder the accurate control of cell division asymmetry and underlie the dramatically increased neuronal differentiation. Our data suggest that maintaining the shape and cell–cell interactions of radial glial neuroepithelial progenitors by the Lis1–Nde1 complex is essential for their self renewal during the early phase of corticogenesis.