The complete diploid reference genome of RPE-1 identifies human phased epigenetic landscapes

Abstract

SUMMARYComparative analysis of recent human genome assemblies highlights profound sequence divergence that peaks within polymorphic loci such as centromeres. This raises the question about the adequacy of relying on human reference genomes to accurately analyze sequencing data derived from experimental cell lines. Here, we generated the complete diploid genome assembly for the human retinal epithelial cells (RPE-1), a widely used non-cancer laboratory cell line with a stable karyotype, to use as matched reference for multi-omics sequencing data analysis. Our RPE1v1.0 assembly presents completely phased haplotypes and chromosome-level scaffolds that span centromeres with ultra-high base accuracy (>QV60). We mapped the haplotype-specific genomic variation specific to this cell line including t(Xq;10q), a stable 73.18 Mb duplication of chromosome 10 translocated onto the microdeleted chromosome X telomere t(Xq;10q). Polymorphisms between haplotypes of the same genome reveals genetic and epigenetic variation for all chromosomes, especially at centromeres. The RPE-1 assembly as matched reference genome improves mapping quality of multi-omics reads originating from RPE-1 cells with drastic reduction in alignments mismatches compared to using the most complete human reference to date (CHM13). Leveraging the accuracy achieved using a matched reference, we were able to identify the kinetochore sites at base pair resolution and show unprecedented variation between haplotypes. This work showcases the use of matched reference genomes for multi-omics analyses and serves as the foundation for a call to comprehensively assemble experimentally relevant cell lines for widespread application.HighlightsWe generated the complete phased genome assembly of one of the most widely used non-cancer cell lines (RPE-1) with a stable diploid karyotypeWe used this genome as a matched reference to analyze sequencing data from RPE-1Mapping to the RPE1v1.0 genome improves alignment quality, faithful assignment of reads to each haplotype, and epigenome peak calling accuracy uncovering inter-haplotype variationUse of the matched reference genome enables epigenetic precision in identifying for the first time the kinetochore site at base pair resolution for each haplotypeThe RPE-1 genome represents a new telomere-to-telomere (T2T) human diploid reference for the scientific community that will advance genetic and epigenetic research across fields using this cell line