Remnants of ancient viral DNA are still active in the genomes of animals today. In this study, researchers suggest they have characterized 2 retrovirus-derived genes, which fight infections in the brains of eutherians (mammals who give birth birth to live young). Dr. Kaneko-Ishino, a geneticist at Tokai University in Japan, and their colleagues discovered 2 RTL (retrotransposon Gag-like) genes RTL5 and RTL6. Genetic engineers attached fluorescent proteins to the end of the RTL proteins in mice and found RTL5 and RTL6 were localized in immune cells in the brain called microglia. The signal was weak, so Dr. Kaneko-Ishino decided to enhance the signal by injecting fluorescently labeled toxins (LPS and nonmethylated DNA and double-strand RNA) directly into the mice's brains. The researchers conclude that after LPS injections a sharp increase in the amount of RTL6 proteins in the brain at injection site was present. Moreover, LPS existed longer in the brains of RTL6 knockout mice than their normal counterparts. Furthermore, RTL5 knockout mice were slower at clearing double-strand RNA. Thus, Dr.Kaneko-Ishino hypothesized the 2 RTL proteins could clear out pathogenic substances during infection. However, RTL6 and RTL5 gene expression levels did not increase even in the presence of toxins and that they "...seem to be expressed all the time" (Kaneko-Ishino)
In my opinion, the study was interesting, however I think more could have been done. For example, the study could have included observation whether the gens are only expressed in microglia only or in immune cells too. I find it fascinating Dr. Kinoko-Ischino's work took over three decades. I wonder if it would take the same time if they were to begin their research today?
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