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The human genome is “littered” with remnants of ancient retrovirus infections that invaded the germline of our primate ancestors. Only one of these may still be proliferating in modern humans named HERV-K HML-2 (HK2), and not all humans have the same HK2 viruses in their genomes. One specific uncommon HK2, which lies close to a gene involved in dopaminergic activity in the brain (RASGRF2), is more frequently found in drug addicts and thus is significantly associated with addiction.
The Oxford University and University of Athens research teams have shown that HK2 can manipulate nearby genes in research published in Proceedings of the National Academy of Sciences (PNAS). Their study provides strong evidence that uncommon HK2 integrations can be responsible for the unappreciated pathogenic burden of addictive behaviours.