Pathogenic mechanisms underlying adverse neurodevelopmental outcome in congenital heart disease

Gabriel, G. C.; Yagi, H.; Tan, T.; Bais, A. S.; Glennon, B.; Stapleton, M. C.; Huang, L.; Reynolds, W. T.; Shaffer, M. G.; Xu, X.; Ganapathiraju, M.; Simon, D.; Panigrahy, A.; Wu, Y. L.; Lo, C. W.

Background: Hypoplastic left heart syndrome (HLHS), a severe congenital heart disease, is associated with poor neurodevelopmental outcomes, microcephaly, reduced cortical brain volume, brain dysmaturation, and neurobehavioral disorders such as autism. The involvement of patient intrinsic factors was indicated, but the mechanism is largely unknown. Methods: Ohia mice with HLHS causing mutations in chromatin modifier Sin3A-associated protein 130 (Sap130) and cell adhesion protein ProtocadherinA9 (Pcdha9) were investigated for brain abnormalities by histology, immunomicroscopy, and molecular profiling by RNAseq, Sap130 ChIPseq, and genome-wide methylome analysis. Additionally, adult viable Pcdha9m/m and Emx1-cre:Sap130f/- mice with forebrain deletion of Sap130 were examined by brain MRI and behavioral assessments. Results: Ohia mice have brain abnormalities comprising forebrain hypoplasia and microcephaly in conjunction with a cortical neurogenesis defect. This is associated with loss of intermediate progenitors due to mitotic arrest and apoptosis from multipolar spindle formation, a mechanism also observed in primary microcephaly. Brain RNAseq showed perturbation of REST transcriptional regulation of neurogenesis, disruption of CREB signaling regulating synaptic plasticity and memory, and defects in neurovascular coupling indicating perturbation of brain-sparing cerebral autoregulation. Disease pathways recovered included autism, intellectual disability, and other neurobehavioral/neurological deficits. These same pathways were observed upon intersection of genes that are differentially expressed with those that are differentially methylated and also are ChIPseq targets of Sap130, suggesting the transcriptional changes are epigenetically regulated. Adult viable mice harboring either the Pcdha9 mutation or forebrain-specific Sap130 deletion showed similar learning/memory deficits and autism-like behavior, suggesting they act on convergent pathways. Conclusions: Our observations indicate the intrinsic factors contributing to the adverse neurodevelopmental outcome associated with HLHS involve spindle defects causing impaired corticoneurogenesis, and brain and behavioral deficits associated with perturbed epigenetic regulation of neurodevelopmental pathways.