Human iPSC-Derived Cerebral Organoids Model Cellular Features of Lissencephaly and Reveal Prolonged Mitosis of Outer Radial Glia

Abstract

SUMMARY Classical lissencephaly is a genetic neurological disorder associated with mental retardation and intractable epilepsy, and Miller Dieker Syndrome (MDS) is the most severe form of the disease. In this study, to investigate effects of MDS on human progenitor subtypes that control neuronal output and influence brain topology, we analyzed cerebral organoids derived from control and MDS induced pluripotent stem cells (iPSCs) using timelapse imaging, immunostaining, and single cell RNA sequencing. We saw a cell migration defect that was rescued when we corrected the MDS causative chromosomal deletion, and severe apoptosis of the founder neuroepithelial stem cells accompanied by increased horizontal cell divisions. We also identified a mitotic defect in outer radial glia, a progenitor subtype that is largely absent from lissencephalic rodents but critical for human neocortical expansion. Our study therefore deepens understanding of MDS cellular pathogenesis and highlights the broad utility of cerebral organoids for modeling human neurodevelopmental disorders.

Genetics and mechanisms leading to human cortical malformations

“…One possible explanation for this observation could be the low proportion of bRGCs in lissencephalic animal models such as mice and rats [11,298,[313][314][315]. Particularly, there is a known debate on the use of lissencephalic species in the study of abnormalities of gyration presented in humans.…”

“…A more frequent incidence of horizontal vs vertical cleavage planes and a significantly reduced average cleavage angle was observed in the MDS neuroepithelium (implying inappropriate progenitor divisions), as well as defective radial migration of cortical neurons was observed in 5 week organoids compared to control. Defective neuronal migration was rescued with a ring chromosome containing a compensatory copy of the chromosome 17 [298]. It was also shown that MDS bRG cells remained in mitosis for prolonged periods prior to cytokinesis and thus, authors suggest the possible involvement of bRG cell dysfunction in the pathogenesis of human LIS [298].…”

“…Mutant brain organoids showed fewer Tuj1+ neurons, and these neurons failed to migrate compared to controls [278]. Another interesting study involved the generation of patient-derived iPSCs to study the molecular bases of MDS, as previously mentioned, a severe LIS MCD characterized by nearly absent cortical folding often associated with reduced brain size, craniofacial dysmorphisms, ID and intractable epilepsy (see section 2.2.1) [298]. In this work cerebral organoids derived from control and MDS-iPSCs showed apoptosis of NECs leading to a reduced size, consistent with the clinical manifestation of the patients' microcephaly.…”

“…Defective neuronal migration was rescued with a ring chromosome containing a compensatory copy of the chromosome 17 [298]. It was also shown that MDS bRG cells remained in mitosis for prolonged periods prior to cytokinesis and thus, authors suggest the possible involvement of bRG cell dysfunction in the pathogenesis of human LIS [298]. A second study has also used patient-specific forebrain-type organoids to study MDS pathology [299].…”

Translational potential of human brain organoids

“…Their results identified several cellular features of this classical form of lissencephaly, including aberrant cell cycle of outer radial glia and non–cell‐autonomous alteration of WNT signaling 42, 43…”