Human gene duplications in neurodevelopment and disease

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PROJECT SUMMARY/ABSTRACT Despite significant efforts to identify genes important in human neurodevelopment and disease, a large proportion of genes and variants remain undiscovered. Duplicated parts of the genome are largely understudied due to historical errors in the reference and bioinformatic pipelines that filter reads mapping to multiple locations in the genome. With the recent publication of a complete telomere-to-telomere human genome, genes and variants can be more effectively assayed across complex loci, but modified computational approaches are necessary. The proposed study will leverage diverse expertise in functional genomics and human genetics to test the hypothesis that a subset of human duplicated genes both contribute to neurological features and cause disorders exclusive to modern-day humans. Duplicated genes have previously been shown to play a role in early brain development and are enriched at genomic hotspots where recurrent copy-number variants are associated with neurodevelopmental disorders. Starting with a comprehensive list of thousands of human duplicated genes, functions of a subset of genes expressed during human corticogenesis will be tested using CRISPR knockout of orthologs and expression of human paralogs in zebrafish to determine their effects on general morphology, synaptic function, and brain development. The ability to test tens to hundreds of genes in parallel and conservation of basic developmental processes—such as neural proliferation, axonal guidance, and synaptogenesis—make zebrafish an ideal model to test these genes. Second, a genetic screen will be performed in human population cohorts to identify conserved duplicated genes. Since standard methods filter variants across many complex genomic loci, an improved bioinformatics approach leveraging short-read data will be devised and optimized using available sequencing benchmarks. Further, conserved genes will be screened for de novo and rare variants in autistic individuals using published datasets. Leveraging this multifaceted approach will enable systematic assessment of duplicated genes and their putative roles in human neurological traits and disorders. The zebrafish toolkit will be generally applicable to assaying functions of additional (non-duplicated) genes important in brain development, while the improved bioinformatics approach will enable additional screens of duplicated genes in other disease cohorts. This project will not only provide important insights into what it means to be human, but also it has the capability to discover missing genetic risk and elucidate the etiology of complex genetic neural traits and disorders.