Characterization of Neuronal Development in Autism Using iPSCs Reveals Disease-Specific Changes in Axon Formation and Expression of Synaptic Function Genes

Background:   Autism spectrum disorders (ASD) comprise a genetically and phenotypically heterogeneous group of complex neurodevelopmental conditions. Although tremendous progress had been made in identifying ASD risk loci, the impact that these genetic variants have on ASD pathophysiology remains largely unknown. This is largely a result of the lack of genetically-relevant human disease models. The advent of human induced pluripotent stem cell (iPSC) technology and advances in neural differentiation methodologies, have made it possible to study the cellular and molecular mechanisms that underlie ASD. It is now possible to functionally analyze specific populations of developing neurons derived from ASD-affected individuals. These stem cell-based differentiation approaches mimic in vivo neurogenesis and, as such, provide valuable information about activity-dependent maturation of synapses during neural network formation.

Objectives:   The objective of the current study is to functionally characterized ASD-specific phenotypes in iPSC-derived neuronal cultures.

Methods:   We have generated a collection of iPSC lines from peripheral blood mononuclear cells attained from clinically and genetically well-characterized patients affected with idiopathic ASD. These iPSC lines have been differentiated into forebrain neurons by mimicking the steps in neurodevelopment from stem cells through to embryoid bodies, neural progenitor cells, immature neurons, and onto differentiated neuronal cultures. Given the developmental nature of ASD, we focused on analyzing ASD-associated cellular phenotypes by employing microscopy based analysis of neurite outgrowth coupled to transcriptome analysis.

Results:  Comparative analysis of ASD-specific and control iPSC-derived forebrain neurons has revealed disease-specific alterations in neurite outgrowth. In addition, high content transcriptome analyses has revealed abnormalities in the expression of key genes involved in neuronal development and axonal growth, including pathways associated with the extracellular matrix and the development of supporting cells such as oligodendrocytes.

Conclusions: ASD-specific iPSC-derived neurons have altered phenotypes compared to those from control individuals. Consistent with its developmental nature, these alterations are observable even at early time points during neural development.