Telomere-to-telomere genome assembly and a pangenome for the rat.

We report a complete rodent telomere-to-telomere genome assembly from the brown rat, Rattus norvegicus. Annotation was enriched with multi-tissue long-read RNA sequencing and uncovered numerous novel genes. Assembly of both sex chromosomes reveals the absence of gene coding in the presumed pseudo-autosomal regions and the presence of centromeric satellite repeats on distal chromosome Y (chrY). We provide evidence of meiotic conjunction between Xp and Yq. The genome assembly reveals several expanded autosomal regions enriched for testis-expressed genes. Finally, we have generated a pangenome from recent high-quality assemblies of 8 distinct inbred rat strain genomes. This allows the strain-specific distribution of structural variation to be examined. Non-allelic homologous recombination has produced multiple copies of several genes with evidence of transcription from duplicated copies.