Genomic variation due to ERVs in diverse mouse strains. (A,B) Venn diagrams indicating counts (n) of shared versus distinct ERV elements at individual integration sites (orthologous locations) in previously unsequenced mouse strains. The youngest IAPLTR1 (A) and older IAPEY2 (B) elements were compared at genomic insertion sites in related B6, A/J, and WSB (top) and in divergent B6, CAST, and SPRET (bottom) mouse strains. MOLF integrants are not presented here. Only four of several thousand youngest IAP integrants occur at orthologous loci in the most divergent strains (lower left). (C) Genome-wide distributions of ERV polymorphisms in diverse mouse lineages. Histograms display the numbers of strains containing polymorphic ERVs at orthologous loci within 10-MB genomic bins for (top) IAPLTR1; (middle) IAPLTR2; and (bottom) IAPEY2 elements. (Dark blue) Integrants present in one strain; (light blue) two strains; (purple) three; (light pink) four; (orange) five; (red) all six. (Bottom) Mouse chromosomes 1–19, X, and Y (alternating shading).
