CHD8 is a regulatory gene that binds to the promoters of autism spectrum disorder (ASD) risk genes and remodels chromatin accessibility. It is strongly associated with ASD risk. Protein-disrupting mutations in CHD8 lead to neurological changes that result in ASD and other neurodevelopmental conditions, including seizures in a subset of people.
Rebecca Muhle and colleagues have previously shown that while CHD8 targets ASD risk genes more often than expected by chance, haploinsufficiency of Chd8 in model systems results in subtle, widespread dysregulation of gene expression with preservation of neuroanatomical structure1. Muhle’s lab have also found, in preliminary studies, that Chd8 heterozygous mice exhibit spontaneous seizures.
In the current project, Muhle aims to identify positive and negative modulators of CHD8 expression that can: (i) affect expression of CHD8 and other ASD risk genes during critical developmental windows of ASD risk and (ii) be tested as potential agents to rescue the effects of CHD8 haploinsufficiency in later life.
To address these goals, Muhle and her team propose to identify signaling pathways that regulate ASD risk genes via high-throughput small molecule screening using a CHD8 reporter line in human neural stem cells. Bioactive compounds (or hit compounds) that affect CHD8 expression will be identified using an unbiased, high-throughput cellular assay. They will then generate transcriptomes of cells pre- and post-exposure to hit compounds and use RNA-seq to determine differentially expressed genes and common pathways sensitive to perturbation.
They also plan to characterize cells of the developing cortex from Chd8 heterozygous mice using single cell Assay for Transposase-Accessible Chromatin (scATAC-seq) and chromatin immunoprecipitation (ChIP-seq) to determine changes in chromatin accessibility and the epigenetic landscape as a result of Chd8 loss.
Finally, they plan to examine the molecular and cellular effects of exposing Chd8 heterozygous mice to hit compounds that were identified and validated in the in vitro screening assay. These experiments will help to determine the consequences of negative and positive Chd8 modulation on downstream regulatory networks, as well as testing whether positive Chd8 modulators can decrease seizure incidence in adult mice.
These studies have the potential to provide foundational information for novel paradigms to improve the health of people that carry loss-of-function mutations during brain development.