CRISPR/Cas9-mediated heterozygous knockout of the autism gene CHD8 and characterization of its transcriptional networks in cerebral organoids derived from iPS cells

Mol Autism. 2017 Mar 20:8:11. doi: 10.1186/s13229-017-0124-1. eCollection 2017.

Abstract

Background: CHD8 (chromodomain helicase DNA-binding protein 8), which codes for a member of the CHD family of ATP-dependent chromatin-remodeling factors, is one of the most commonly mutated genes in autism spectrum disorders (ASD) identified in exome-sequencing studies. Loss of function mutations in the gene have also been found in schizophrenia (SZ) and intellectual disabilities and influence cancer cell proliferation. We previously reported an RNA-seq analysis carried out on neural progenitor cells (NPCs) and monolayer neurons derived from induced pluripotent stem (iPS) cells that were heterozygous for CHD8 knockout (KO) alleles generated using CRISPR-Cas9 gene editing. A significant number of ASD and SZ candidate genes were among those that were differentially expressed in a comparison of heterozygous KO lines (CHD8+/-) vs isogenic controls (CHD8+/-), including the SZ and bipolar disorder (BD) candidate gene TCF4, which was markedly upregulated in CHD8+/- neuronal cells.

Methods: In the current study, RNA-seq was carried out on CHD8+/- and isogenic control (CHD8+/+) cerebral organoids, which are 3-dimensional structures derived from iPS cells that model the developing human telencephalon.

Results: TCF4 expression was, again, significantly upregulated. Pathway analysis carried out on differentially expressed genes (DEGs) revealed an enrichment of genes involved in neurogenesis, neuronal differentiation, forebrain development, Wnt/β-catenin signaling, and axonal guidance, similar to our previous study on NPCs and monolayer neurons. There was also significant overlap in our CHD8+/- DEGs with those found in a transcriptome analysis carried out by another group using cerebral organoids derived from a family with idiopathic ASD. Remarkably, the top DEG in our respective studies was the non-coding RNA DLX6-AS1, which was markedly upregulated in both studies; DLX6-AS1 regulates the expression of members of the DLX (distal-less homeobox) gene family. DLX1 was also upregulated in both studies. DLX genes code for transcription factors that play a key role in GABAergic interneuron differentiation. Significant overlap was also found in a transcriptome study carried out by another group using iPS cell-derived neurons from patients with BD, a condition characterized by dysregulated WNT/β-catenin signaling in a subgroup of affected individuals.

Conclusions: Overall, the findings show that distinct ASD, SZ, and BD candidate genes converge on common molecular targets-an important consideration for developing novel therapeutics in genetically heterogeneous complex traits.

Keywords: Autism; Beta-catenin; Bipolar disorder; Cancer; DLX6-AS1; Distal-less homeobox; Gabaergic; HMGA2; Schizophrenia; TCF4; Wnt; ZNF132.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autism Spectrum Disorder / genetics
  • Bipolar Disorder / genetics
  • CRISPR-Cas Systems
  • Cell Differentiation
  • Cells, Cultured
  • DNA-Binding Proteins / genetics*
  • Gene Expression Profiling / methods*
  • Gene Expression Regulation
  • Gene Knockout Techniques
  • Gene Regulatory Networks*
  • Humans
  • Induced Pluripotent Stem Cells / cytology*
  • Mental Disorders / genetics*
  • Mutation
  • Organoids / cytology*
  • Schizophrenia / genetics
  • Sequence Analysis, RNA / methods*
  • Telencephalon / cytology*
  • Transcription Factors / genetics*

Substances

  • CHD8 protein, human
  • DNA-Binding Proteins
  • Transcription Factors