2018-05-05 19:57:02
The transposons, discovered by the scientist Barbara McClintock, Nobel Prize winner in 1983, are fragments of ADN capable of copying themselves and inserting once copied elsewhere in the genome. Their ability to copy explains why transposons make up a large part of the genomes of many organisms. Our own genome is made up of 44% transposons, but that of maize, with which McClintock made his discovery, is made up of 90%.
Once copied, the transposons are randomly inserted somewhere in the genome. Random insertions cause each cell to end up with a uniquely modified genome, producing a true genetic mosaic in the brain. Depending on where the insertions occur, the functioning of certain genes may be affected.
Researchers at the Salk Institute in La Jolla, California, are exploring whether maternal care might influence the copying and insertion of transposons into individual brain cells. To do this, they carry out experiments with newborn laboratory mice, which they place under the care of foster mothers who are very loving towards the little ones or, on the contrary, rather disdainful towards them.
The results of these studies, published in the journal Science, show that mice that receive little maternal care during the first two weeks of life accumulate transposons of a particular class, called L1, in the brain region called the hippocampus. The hippocampus is very important for the consolidation of memories and spatial memory and is one of the first brain regions affected by Alzheimer’s disease.
The researchers discover that the increased accumulation of transposons in the hippocampus of mice that receive less affection from their mothers also depends on chemical changes in the ADN, similar to those that affect the functioning of genes. Thus, a mechanism of chemical modification explains both the changes in the functioning of genes and the changes in the genome of neurons, generated by transposons, induced by the absence of maternal love.
Referencia: Tracy A. Bedrosian et al. Early life experience drives structural variation of neural genomes in mice. Science 359, 1395–1399 (2018).
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