Age-dependent and tissue-specific structural changes in the C57BL/6J mouse genome.

We tested the hypothesis that structural changes in the genome parallel age- and organ-specific phenotypes in conjunction with the differential transposition activities of retroelements. The genomes of the liver from C57BL/6J mice were larger than other organs, coinciding with an increase in genomic copies of certain retroelements. In addition, there were differential increments in the genome size of the liver with increasing age, which peaked at 5 weeks. The findings that the genome structure of an individual is variable depending on age and organ type in association with the transposition of retroelements may have broad implications in understanding biologic phenomena.