Researchers report that ancient viruses may be to thank for myelin -- and, by extension, our large, complex brains. The team found that a retrovirus-derived genetic element or 'retrotransposon' is essential for myelin production in mammals, amphibians, and fish. The gene sequence, which they dubbed 'RetroMyelin,' is likely a result of ancient viral infection, and comparisons of RetroMyelin in mammals, amphibians, and fish suggest that retroviral infection and genome-invasion events occurred separately in each of these groups.
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