Unraveling the interplay between the transcriptional co-regulator Cited2 and maternal folic acid in the regulation of neocortical development - PROJECT SUMMARY / ABSTRACT Disruptions in neuronal development and connectivity within the neocortex, the area of the brain responsible for high cognitive function, are found in many neurodevelopmental disorders (NDDs), including autism spectrum disorders, intellectual disability, and schizophrenia. What causes this atypical development is still poorly understood, but likely includes a combination of genetic, epigenetic, and environmental factors, including maternal nutrition. We thus propose to study how genetic, epigenetic, and maternal nutrition factors intersect to regulate two major developmental convergence points for NDDs: the proliferation and differentiation of neuronal progenitors, and the establishment of appropriate local and long-distance neuronal connections. To investigate these mechanisms, we will employ Cited2 forebrain-specific conditional knockout (cKO) mice, which our previous work demonstrated have disruptions in these conversion points of neocortical development, and display behavioral abnormalities associated with human NDDs. CITED2 is a transcriptional co-regulator that recruits the histone acetyltransferase complex CBP/p300, thus Cited2 loss-of-function (LOF) leads to disruptions in the epigenome and alterations in the transcriptome. Importantly, maternal folic acid supplementation rescues neural tube closure defects in Cited2-null embryos; whether it also modifies neocortical phenotypes is unknown although maternal folic acid supplementation in humans is associated with reduced risk of NDDs. We hypothesize that maternal folic acid supplementation will rescue the atypical neocortical development and behavior in Cited2 cKO mice. We propose to test this hypothesis by examining regulation of progenitor proliferation and differentiation, precise axonal connectivity, and behavior in Cited2 cKO and wildtype littermates, with sufficient vs. supplemented maternal folic acid diets (Aim 1). Folic acid is a methyl donor and alters DNA methylation, an important epigenetic modification associated with gene silencing. Thus, to determine whether the alteration of neocortical development with folic acid occurs due to modification of gene regulatory networks disrupted with Cited2 LOF directly, or whether compensatory pathways are modified, we propose to employ antibody-based fluorescence activated cell sorting to purify Cited2 cKO and wildtype neocortical intermediate progenitor cells (IPCs) at E15.5, with both sufficient and supplemented maternal FA, and perform RNA-seq and Methyl-seq (Aim 2). Together, these approaches have the potential to identify entirely novel genes and pathways underpinning gene x environment interactions controlling neocortical development, and to open new avenues for investigation.
