Any human being has on average 5 million single-nucleotide variants and 13 million nucleotides of insertions, deletions, and other regions present in variable copy numbers compared to the human reference genome. Together these variants must account for all of the genetic contributions to every phenotype of that person, whether it is their height or their familial predisposition to complex diseases. While we can quickly measure the presence of these variants in a genome, we lack the framework to understand which of the variants impact genomic function or how they interact with each other in living, breathing organisms. A core mission of the IGVF Consortium is to identify variants that impact the expression of genes using single-cell techniques and computational modeling. Applying a single-cell genomics approach to selected diverse mouse strains can make a powerful contribution to the mission and to resources of the Consortium. Our Center for Mouse Genomic Variation at Single Cell Resolution will first use 38 mouse Collaborative Cross recombinant inbred lines that possess similar levels of sequence diversity to humans to identify variants that influence gene expression levels and chromatin accessibility at the single-nucleus level in 8 distinct tissues. We will sequence simultaneously a subset of single-nuclei with both short-read sequencing and long-read sequencing to identify variants that impact the expression of different transcript isoforms in different cells across the different mouse strains. We will also measure the relationship of variants in these CC Lines in the response of macrophages in these tissues in response to LPS stimulation. The resulting resource catalogs of cell-type expression QTL, chromatin accessibility QTL, splicing QTL, and response QTL maps will be useful for IGVF modeling groups; for characterizing important variants; and for use by the wider community studying the function of these tissues as well as for designing better pre-clinical models of human diseases.

Our center will study how genetic variants impact function by studying their effects in all cell types of 8 mouse tissues. We will measure the expression of genes as well as the activity of regulatory elements in a large number of individual cells from these tissues to build maps of which variants impact the expression of these genes in different cell types. We will also measure the impact of genetic variation on inflammation. Our results will help interpret the impacts of variants on gene function in humans as well as support the design of better mouse models of human disease.