The brain tissue of brain cells is apparently less homogeneous than previously suspected: The nerve cells in the brain of an individual differ significantly in the so-called repetitive DNA sequences, researchers have found around Nicole Coufal from the Salk Institute in La Jolla. These sequences are understood to mean certain sections of the genome that repeat themselves several times and that scientists have hitherto attributed no great importance to the human organism. The large differences observed in these sequences now shed new light on the evolution of the human brain and the emergence of individuality. The genome of each cell usually remains constant after its early development. The exception is specialized cells of the immune system. Their task is the detection of antigens and the formation of compatible antibodies. They are therefore dependent on being variable in order to increase the range of possible antibodies. All other cells change their genome until shortly after their formation, but then no longer. So there are small differences between body cells of the same person, but on the whole they are identical.

The international team around Coufal has now also found an unexpectedly large genetic diversity in brain cells. The cells studied were unmistakably from the same individual, but differed in the repetitive DNA segments both among themselves and from heart and liver cells. The role of these sections is still unclear. Researchers believe it is important in lower organisms such as yeasts or plants, but rather insignificant for humans, although about 50 percent of human DNA consists of repetitive elements. The repetitive sequences were therefore considered as remnants of evolution similar to the cecum.

The results shed new light on the role of repetitive sequences, which are apparently more important than previously thought. In addition, the results can provide new insights into brain development and the development of neuronal diseases and aging processes. They can also provide explanations as to how the individuality of people arises. Among other things, this originates in the brain, but so far neither neurobiologists nor geneticists can say anything more precise.

Nicole Coufal (Salk Institute in California) et al .: Nature, doi: 10.1038 / nature08248. ddp / wde - Martina Bisculm ad


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