The human genome comprises 23 pairs of chromosomes, which are essentially the blueprint of what makes humans unique. A surprising discovery from genetic research reveals that about 8% of our DNA consists of remnants from ancient viruses, which embedded themselves into our genetic ancestry through the course of evolution. This interesting finding uncovers a more complex relationship between our DNA and the world of viruses than previously understood.
Within our genetic material lie segments known as transposable elements (TEs), which are often referred to as “jumping genes.” These TEs can replicate and integrate themselves throughout the genome. Initially regarded as “junk” DNA lacking any significant function, recent studies have shifted this perception, positing that these ancient viral remnants may indeed play crucial roles, particularly during the early stages of human development. An international team of researchers has undertaken the task of sequencing TEs, unveiling patterns that suggest they may be pivotal in modulating gene regulation – a process essential for turning genes on and off.
The findings of this research were published on July 18 in the journal *Science Advances*. Dr. Fumitaka Inoue, an associate professor at Kyoto University specializing in functional genomics, emphasized that while the human genome was sequenced many years ago, the functions of numerous segments remain unclear. He noted that transposable elements are thought to hold significant importance in the evolution of our genome, and their relevance is likely to become clearer with ongoing research.
Understanding the activation of gene expression by TEs yields many potential benefits for science. Dr. Xun Chen, a computational biologist and lead researcher from the Shanghai Institute of Immunity and Infection within the Chinese Academy of Sciences, asserted that studying TEs could elucidate their roles in human evolution, establish connections between these sequences and various human diseases, and potentially guide targeted gene therapies. Furthermore, researchers hope to uncover how endogenous retroviruses (ERVs) contribute to what makes humans distinct.
Historically, when our primate ancestors encountered viral infections, segments of the viruses integrated into the host’s chromosomes. As a result, these ancient viral components became substantial parts of our genome. Dr. Lin He, a molecular biologist from the University of California, Berkeley, affirmed that ancient viruses are adept at infiltrating ancestral genomes and evolving into significant genomic constituents. The human genome is armed with multiple mechanisms to control these remnants, mitigating any potential negative impacts associated with their presence.
While generally inactive and not perceived as threats, recent studies have indicated that certain transposable elements may significantly influence human diseases. For instance, a study published in July 2024 explored the possibility of silencing specific TEs to enhance the efficacy of cancer treatments. Dr. He explained that over evolutionary time, some viruses have become reduced in function or expression, while others have been “domesticated” to serve beneficial roles within the human genome.
Nonetheless, the repetitive nature of TEs poses challenges in terms of study due to difficulties in organization and documentation. While researchers categorize TE sequences into families and subfamilies according to their functionality and similarities, many remain inadequately classified, potentially impacting evolutionary and functional analyses.
The presented study focused specifically on a subset of TE sequences known as MER11, found in primate genomes. By employing a new classification system and investigating DNA’s influence on gene activity, researchers successfully identified four previously unrecognized subfamilies. Among these, the MER11_G4 sequence was indicated to enhance gene expression in human stem cells and early-stage neural cells – suggesting significant roles in early human development and adaptability to developmental signals or environmental stimuli.
Tracing the evolutionary changes of these sequences indicated that viral TEs impacted not only human evolution but also that of other animals, such as chimpanzees and macaques. Gaining insights into the evolution of our genome can provide foundational understandings regarding what distinguishes humans, ultimately equipping researchers with tools to navigate human biology, genetic diseases, and evolution.
Although further research is necessary to clarify the precise roles and implications of TEs in the evolutionary process, the study presents new insights into the impact of these sequences. Dr. Steve Hoffmann, a computational biologist at the Leibniz Institute on Aging in Germany, remarked on how TEs, once deemed insignificant, could offer vital understanding regarding genome evolution.
By delving into the historical progression of genomes, researchers can identify stable sequences, those that have been lost, and those that emerged recently. Understanding these dynamics is crucial for clarifying why certain diseases afflict humans while sparing other animals. Ultimately, increasing comprehension of genome regulation could yield novel therapeutic avenues and strategies for medical interventions.
As highlighted by Taylor Nicioli, a freelance journalist based in New York, the intricate links between ancient viruses and human genetic makeup extend far beyond simple remnants, suggesting a rich tapestry of evolutionary history that shapes modern human biology, offering potential breakthroughs in medical science.
