Toward a Biology Worthy of Life > Natural Genome Remodeling > Brief excerpt
A project by Stephen L. Talbott

Jumping genes and the brain

It has now been shown that transposons move around in the developing mammalian brain, altering the genome from cell to cell. They provide enough diversity among neurons, according to Gage, so that “you can optimize your response to the variety of environments you might encounter throughout life”. And now it’s being found that transposons also “jump” in other cell types much more readily than was previously thought. This particularly includes various cells of the early embryo, in which case each genetically altered cell propagates its changes into a subset of the mature organism’s tissues, making them genetically distinct from other tissues. “Given how often this may happen in the early embryo, there may be much more genomic variation within individuals than most researchers had assumed,” writes one reporter in Science.

None of this looks particularly haphazard. In embryonic stem cells the regulatory DNA elements known as enhancers of gene expression contain an elevated number of transposons. And germ cells (of which I will have more to say in a moment) are also especially susceptible to these mutable, or mobile, elements. The cell-type-specific and DNA-element-specific nature of transposon activity points to a meaningfully orchestrated process. In general, there is a bias for many transposable elements to insert themselves upstream of transcription start sites, which “prevents damage to functional coding elements and enhances the potential for a constructive regulatory change” (Shapiro 2006).

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