In this study researchers identified natural differences in the quality and abundance of maternal care provided by mice based upon measures of time they spent grooming and nursing their pups. They identified groups of animals that provided either high or low maternal care. They then examined brains of their pups for differences in markers of genomic change.
Many of the differences in the genomes of nerve cells are due to the presence of mobile genetic elements called retrotransposons. These are stretches of DNA that can be copied and, as the name suggests transposed or incorporated into other areas of the genome. This study measured the accumulation of these mobile genetic elements in the brain as a consequence of maternal care. Mobile genetic elements accumulated in specific regions of the brains of mouse pups if the pups had poor maternal care. If a pup was born to a mother animal that provided low maternal care, but raised by a mother animal that provided high maternal care that accumulation of mobile genetic elements was eliminated. This supported the idea that the accumulation of genetic elements was due to the care provided by the mothers rather than some inherited difference. Most of the excess was found in the hippocampus, a region of the brain involved in memory, but not in other regions of the brain, nor in a completely different organ like the heart, suggesting a very specific impact on brain mosaicism.