Dissecting Cell Type Specific Functions of CHD7 in Development of the Neocortex

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PROJECT SUMMARY/ABSTRACT The aim of this proposal is to determine how heterozygous mutation of the chromatin remodeler CHD7 (Chromodomain Helicase DNA-binding protein 7) disrupts development of the neocortex, leading to the neurodevelopmental anomalies associated with CHARGE syndrome. CHARGE syndrome is characterized by substantial behavioral and cognitive problems, including executive dysfunction and Autism Spectrum Disorder (ASD). The proposed research team recently identified abnormalities in the neocortex of Chd7 heterozygous mice, implicating CHD7 in key, temporally distinct developmental processes. Preliminary data suggest that anterior-posterior (A-P) patterning of the neocortex is disrupted in these mice and that CHD7 directly regulates the expression of a master regulator of A-P patterning, Nr2f1 (COUP-TF1). These mice also exhibit cortical hypoplasia, implicating Chd7 in cortical growth. Furthermore, excitatory and inhibitory synapses onto deep layer principal neurons of the prefrontal cortex (PFC) are affected by Chd7 haploinsufficiency. Both executive dysfunction and ASD have been linked to PFC dysfunction. Thus, these findings provide the long-sought opportunity to identify the mechanisms whereby CHD7 haploinsufficiency disrupts neocortical development. Chd7 function is context-dependent; hence, a significant focus will be to define sex-, region- and cell-type-specific functions and mechanisms. This project's specific aims are to 1) test the hypothesis that Chd7 haploinsufficiency disrupts A-P patterning of the neocortex, 2) define the molecular and cellular functions of Chd7 in neural stem/progenitor cells of the neocortex and subpallium and 3) test the hypothesis that Chd7 has cell-type-specific functions in the development of synapses in the PFC. The team will use standard and innovative methods to visualize and quantify the expression patterns and levels of markers of A-P patterning, and quantify region-, cell- and sex-specific abnormalities in excitatory and inhibitory neurogenesis. Bulk and single cell next generation sequencing approaches will be used to identify transcriptional and chromatin changes in different regions and cell types of the Chd7-deficient developing neocortex in both sexes. The multi-institute team brings together expertise in neurodevelopmental functions of CHD proteins (Basson), translational and modeling studies of CHARGE syndrome (Martin), genomics of cortical development (Kwan), and synapse physiology (Andreae). Together, this work will provide a comprehensive understanding of the impacts of CHD7 haploinsufficiency on multiple processes in development of the neocortex and identify cell-type-specific functions for CHD7 in neural progenitor differentiation and PFC circuit assembly. Successful completion of this work will generate the knowledge and tools necessary to identify the neurodevelopmental mechanisms and circuits that underlie specific behavioral and cognitive phenotypes associated with CHARGE syndrome and other related disorders.