Gut disturbances are unusually common in individuals with autism spectrum disorder (ASD), but the basis of these gut irregularities is not yet known. As ASD causes alterations to sociobehavioral functions, much effort has been placed on understanding changes in the central nervous system (CNS) while intrinsic differences in cells in the gut of people with ASD remain unexplored.
The enteric nervous system (ENS), colloquially known as the “second brain,” contains unique neuronal and glial cell types that collectively control gastrointestinal function. In some gastrointestinal conditions, abnormal enteric glia can impair gut function. While the ENS originates from the neural crest and develops separately from the CNS, enteric glia express numerous ASD risk genes that have previously been thought to be CNS specific, including but not limited to ANK2, CHD8, KANK1, PLXNB1, SCN2A and UPF3B.
To model human intestines, Paul Tesar and his colleagues at Case Western Reserve University School of Medicine plan to generate three-dimensional intestinal and colonic organoids innervated with the ENS. The organoids will be derived from induced pluripotent stem cells (iPSCs) from individuals with idiopathic ASD, from individuals with genetically-defined ASD (with an initial focus on ASD risk genes known to be expressed in the ENS) and from neurotypical individuals. This system provides the opportunity to investigate how cells in the intestine, independent from any CNS input, contribute to gastrointestinal disturbances in ASD.
Tesar and his team plan to combine sequencing technologies with imaging (including single nuclei RNAsequencing and 3D optical clearing) to identify cellular and molecular changes in ASD organoids compared to neurotypical organoids. The result will be molecular blueprints that reveal the putative functions and intercellular wiring of cell types in the ASD intestine.
These molecular maps can be further teased apart to identify cellular and molecular drivers underpinning pervasive gut disturbances in ASD. Findings from this study are expected to shed light on the intrinsic role of the ENS in ASD-related gut disturbances, providing the foundation for longer-term, follow-up studies to then pinpoint the functional consequences of changes in enteric glia in the intestine of individuals with ASD.