Cerebral organoids containing an AUTS2 missense variant model microcephaly

Abstract

Variants in the AUTS2 gene are associated with a broad spectrum of neurological conditions characterized by intellectual disability, microcephaly, and congenital brain malformations. Here, we use a human cerebral organoid (CO) model to investigate the pathophysiology of a heterozygous de novo missense AUTS2 variant identified in a patient with multiple neurological impairments including primary microcephaly and profound intellectual disability. Proband COs exhibit reduced growth, deficits in neural progenitor cell (NPC) proliferation and disrupted NPC polarity within ventricular zone-like regions compared to control COs. We used CRISPR-Cas9-mediated gene editing to correct this variant and demonstrate rescue of impaired organoid growth and NPC proliferative deficits. Single-cell RNA sequencing revealed a marked reduction of G1/S transition gene expression and alterations in WNT-β-Catenin signaling within proband NPCs, uncovering a novel role for AUTS2 in NPCs during human cortical development. Collectively, these results underscore the value of COs to investigate molecular mechanisms underlying AUTS2 syndrome.

AUTS2, a causative gene for microcephaly, regulates division of intermediate progenitor cells and production of upper-layer neurons

“…A previous study demonstrated that a patient with the AUTS2 T534P missense mutation displayed reduced cortical area and ventriculomegaly on MRI and that a human cerebral organoid study indicated that the AUTS2 T534P missense mutation impairs organoid growth 8 . In its mutant organoids, the division of neural progenitor cells, presumably apical RGCs, is reduced compared to controls during the early neurogenic phase 8 . These suggest that cerebral organoids with AUTS2 missense mutation can reproduce the microcephaly of the AUTS2 syndrome and that AUTS2 may have some roles in neurogenesis.…”

“…In addition, several common pathological features have been reported frequently in the AUTS2 syndrome, particularly that 65% of the patients present with microcephaly 4,6,7 . Recently, magnetic resonance imaging (MRI) analysis has reported cortical volume loss, cerebellar hypoplasia, and corpus callosum (CC) hypoplasia in patients with AUTS2 syndrome 8,9 . Auts2 -deficient mice show behavioral abnormalities that mimic some of the human symptoms, such as impaired memory and learning and social behavior 10–13 .…”

Modeling congenital brain malformations with brain organoids: a narrative review

“…Brain organoids have helped reveal the mechanisms of microcephaly and illuminated the surprising roles of centrosomes and primary cilia in regulating neurogenesis. Brain organoids derived from microcephaly patients with mutations in centrosome-associated genes such as CDK5RAP2 showed premature neuronal differentiation and a smaller size ( 13 , 22 , 24 , 26 ). Gabriel et al ( 19 ) developed iPS-derived organoids which harbored a splice-site mutation in CPAP and observed longer cilia, retarded cilium disassembly, and delayed cell cycle re-entry leading to premature differentiation of NPCs.…”

Keeping the balance: Trade-offs between human brain evolution, autism, and schizophrenia

“…Auts2 -deficient mice feature hyperactivation of excitatory synapses and display behavioral and cognitive changes which partially mirror symptoms observed in human autistic patients ( Hori et al, 2015 ), providing a strong link between AUTS2 and ASD. Transcriptomic data from acutely isolated human tissue showed strong expression of AUTS2 in neurons as well as in astrocytes ( Zhang et al, 2016 ; Karlsson et al, 2021 ), in human cerebral organoids, AUTS2 is expressed in excitatory neurons, radial glia and intermediate progenitors ( Fair et al, 2022 ). Heterozygous de novo missense mutation in AUTS2 detected in ASD patients alters the cell cycle dynamics of neural progenitors, which could hint at the mechanism by which this gene may contribute to the regulation of brain size ( Fair et al, 2022 ).…”

“…Transcriptomic data from acutely isolated human tissue showed strong expression of AUTS2 in neurons as well as in astrocytes ( Zhang et al, 2016 ; Karlsson et al, 2021 ), in human cerebral organoids, AUTS2 is expressed in excitatory neurons, radial glia and intermediate progenitors ( Fair et al, 2022 ). Heterozygous de novo missense mutation in AUTS2 detected in ASD patients alters the cell cycle dynamics of neural progenitors, which could hint at the mechanism by which this gene may contribute to the regulation of brain size ( Fair et al, 2022 ). In humans, there are two major protein isoforms of AUTS2 ( Biel et al, 2022 ).…”