The Essential Role of Centrosomal NDE1 in Human Cerebral Cortex Neurogenesis

Abstract

We investigated three families whose offspring had extreme microcephaly at birth and profound mental retardation. Brain scans and postmortem data showed that affected individuals had brains less than 10% of expected size (≤10 standard deviation) and that in addition to a massive reduction in neuron production they displayed partially deficient cortical lamination (microlissencephaly). Other body systems were apparently unaffected and overall growth was normal. We found two distinct homozygous mutations of NDE1, c.83+1G>T (p.Ala29GlnfsX114) in a Turkish family and c.684_685del (p.Pro229TrpfsX85) in two families of Pakistani origin. Using patient cells, we found that c.83+1G>T led to the use of a novel splice site and to a frameshift after NDE1 exon 2. Transfection of tagged NDE1 constructs showed that the c.684_685del mutation resulted in a NDE1 that was unable to localize to the centrosome. By staining a patient-derived cell line that carried the c.83+1G>T mutation, we found that this endogeneously expressed mutated protein equally failed to localize to the centrosome. By examining human and mouse embryonic brains, we determined that NDE1 is highly expressed in neuroepithelial cells of the developing cerebral cortex, particularly at the centrosome. We show that NDE1 accumulates on the mitotic spindle of apical neural precursors in early neurogenesis. Thus, NDE1 deficiency causes both a severe failure of neurogenesis and a deficiency in cortical lamination. Our data further highlight the importance of the centrosome in multiple aspects of neurodevelopment.

Recessive loss of function of the neuronal ubiquitin hydrolase UCHL1 leads to early-onset progressive neurodegeneration

“…These regions, which together comprised 27.16 MB, presumably contained the disease-causing mutation (Table S3). We next performed whole-exome sequencing of the index case using Nimblegen solid-phase array capture and the Illumina Genome Analyzer IIx instrument and focused on variants located within these shared regions (2)(3)(4)11). A single lane of sequencing on Illumina's Genome Analyzer IIX with single-read chemistry and a read length of 74 bases yielded ∼38 million reads.…”

“…Whole-genome genotyping of the samples was performed on the Illumina Platform with Illumina Human 610K Quad Beadchips using the manufacturer's protocol (Illumina) and as previously described (2,3,11).…”

Cilia and cell cycle re-entry

“…28 The effect of Nde1 on ciliary length was also shown in zebrafish embryos, where embryos depleted of Nde1 showed increased ciliary length and a reduction in the number of proliferating cells of the Kupffer's vesicle, an organ analogous to the embryonic node that determines left-right patterning in zebrafish. 28 Interestingly, naturally occurring mutations in NDE1 have been recently described in patients with severe forms of microcephaly, 29,30 a defect seen also in mice lacking Nde1. 31 Microcephaly is a pathologic condition characterized by the severe thinning of the superficial cortical The mechanism(s) by which entry into G 1 /G 0 triggers the differentiation of the centrosome to a basal body, perhaps the earliest stage(s) of ciliogenesis, was extensively discussed in a recent review in reference 7.…”

Interkinetic Nuclear Movement in the Ventricular Zone of the Cortex

“…Microdeletions encompassing the human NDE1 gene have been to be one of the risk factors for microcephaly, mental retardation, and epilepsy (Hannes et al 2009). Furthermore, mutations in NDE1 result in extreme microcephaly and grossly simplified cortical gyral structure, a condition referred to as microlissencephaly (Alkuraya et al 2011;Bakircioglu et al 2011). Mutated NDE1 proteins were found to be unstable, incapable of binding cytoplasmic dynein, and did not localize properly to the centrosome.…”

“…In humans, mutations in NDE1 result in severe microcephaly (Alkuraya et al 2011;Bakircioglu et al 2011). Double knockout of Nde1 and Lis1 resulted in a marked reduction in brain size (80% decrease).…”