Modeling microcephaly with cerebral organoids reveals a WDR62–CEP170–KIF2A pathway promoting cilium disassembly in neural progenitors

Abstract

Primary microcephaly is caused by mutations in genes encoding centrosomal proteins including WDR62 and KIF2A. However, mechanisms underlying human microcephaly remain elusive. By creating mutant mice and human cerebral organoids, here we found that WDR62 deletion resulted in a reduction in the size of mouse brains and organoids due to the disruption of neural progenitor cells (NPCs), including outer radial glia (oRG). WDR62 ablation led to retarded cilium disassembly, long cilium, and delayed cell cycle progression leading to decreased proliferation and premature differentiation of NPCs. Mechanistically, WDR62 interacts with and promotes CEP170’s localization to the basal body of primary cilium, where CEP170 recruits microtubule-depolymerizing factor KIF2A to disassemble cilium. WDR62 depletion reduced KIF2A’s basal body localization, and enhanced KIF2A expression partially rescued deficits in cilium length and NPC proliferation. Thus, modeling microcephaly with cerebral organoids and mice reveals a WDR62-CEP170-KIF2A pathway promoting cilium disassembly, disruption of which contributes to microcephaly.

Cerebral organoid and mouse models reveal a RAB39b–PI3K–mTOR pathway-dependent dysregulation of cortical development leading to macrocephaly/autism phenotypes

“…Dual Smad signaling inhibitors were used in neural induction medium to enhance neuroepithelial expansion (Kadoshima et al 2013). Embryoid bodies (EBs) were added into droplets of Geltrex to enhance complex tissue formation, followed by the growth in a spinning bioreactor to facilitate oxygen exchange and nutrient absorption (Zhang et al 2019). To directly compare RAB39b mutant and isogenic controls in organoid formation, equal numbers (∼9000 starting cells) of dissociated single PSCs were used to generate EBs, which resulted in no differences in morphology or surface areas at culture day 12.…”

“…5A). We quantified the relative thicknesses of SOX2-positive VZ layers according to published methods (Zhang et al 2019). Statistical analysis showed that mutant organoids had a substantial increase of SOX2-positive VZ thickness at weeks 4, 6, and 8 ( Fig.…”

“…Cerebral organoids were generated with published protocols with minor modifications (Lancaster et al 2013;Zhang et al 2019). Two mutant PSC lines were used, including human iPSC line CR0000010 with the 4-bp deletion in exon 1 and human H9 ES cell line with the 5-bp deletion in exon 2.…”

FLS2 is a CDK-like kinase that directly binds IFT70 and is required for proper ciliary disassembly in Chlamydomonas

“…However, deciliation has also been reported as a predominant mode of ciliary disassembly during cell cycle progression in mammalian cells [15]. Defect in ciliary resorption has been shown to inhibit G1-S transition and delays cell cycle progression [16][17][18][19][20], which leads to premature differentiation of neural progenitors [18,20,21]. Several studies also suggest that ciliary disassembly is related to tumorigenesis because primary cilia are disassembled in a variety of cancer types [22].…”

Roles of developmentally regulated KIF2A alternative isoforms in cortical neuron migration and differentiation

“…KIF2A, a MT (microtubule)-depolymerizing kinesin, functions in mitotic spindle assembly 11 and primary cilium disassembly in mitotic cells 12,13 and in axonal pruning in differentiating neurons 14,15 . Recent studies have suggested that KIF2A alternative splicing is regulated by neuron-specific RNA-binding proteins 16 and its isoform abundance dynamically shifts during the neural progenitor-to-neuron transition during development of the cerebral cortex 3 .…”