Ancient Viruses in the Human Genome Linked to Mental Health Conditions
Ancient Viruses in the Human Genome Linked to Mental Health Conditions
People with higher genetic risk for depression, schizophrenia, and bipolar disorder are more likely to have unusual activity levels of "fossil viruses" in their genomes
Ancient viruses that integrated into the human genome millions of years ago may influence the risk of mental health conditions such as depression, schizophrenia, and bipolar disorder. These viruses, remnants of retroviruses known as human endogenous retroviruses (HERVs), can exhibit abnormal activity levels in individuals genetically predisposed to these disorders, according to a recent study.
Unveiling the Role of Fossil Viruses
Retroviruses are a group of viruses that insert their genetic material into the DNA of their host. When these viruses infect germ cells, their genetic sequences can become permanently integrated into the host's genome, passed down through generations as HERVs. Initially considered dormant "fossil viruses," recent studies have suggested that some HERVs remain active, influencing various biological processes, including neurological functions.
Investigating Mental Health Connections
Timothy Powell and colleagues from King’s College London explored1 the potential involvement of HERVs in mental health disorders by analyzing brain tissue from nearly 800 donors. While the study did not document the donors' mental health conditions during their lifetime, it identified altered activity in genes derived from five distinct HERVs associated with genetic variants linked to depression, schizophrenia, and bipolar disorder.
Powell emphasized that the extent of increased risk associated with abnormal HERV activity is likely modest, consistent with the minor impact most genetic variants have on psychiatric conditions. Importantly, the study does not establish causation; rather, it highlights an association that warrants further investigation.
Expert Insights and Cautions
Rachael Tarlinton from the University of Nottingham praised the study's methodology as robust, acknowledging the significance of identifying HERV-related markers for mental health disorders. However, she echoed Powell's caution, emphasizing the need for deeper understanding of how altered HERV activity contributes to these conditions. Tarlinton noted,
"The results are likely real indicators of disease markers, but researchers appropriately emphasize the uncertainty regarding their functional implications."
Implications for Future Research
The study opens new avenues for exploring the complex interplay between genetic predispositions, viral remnants in the genome, and mental health outcomes. Understanding the mechanisms by which HERVs influence neurological functions could pave the way for targeted therapies and interventions.
As research progresses, uncovering the role of ancient viruses in shaping human health not only enriches our understanding of evolutionary biology but also holds promise for addressing the complexities of mental health conditions in diverse populations. The ongoing exploration of HERVs underscores the dynamic relationship between our genetic heritage and the challenges of modern mental health disorders.
Duarte, R.R.R., Pain, O., Bendall, M.L. et al. Integrating human endogenous retroviruses into transcriptome-wide association studies highlights novel risk factors for major psychiatric conditions. Nat Commun 15, 3803 (2024). https://doi.org/10.1038/s41467-024-48153-z