Lecture: Humans are 8% Virus - Ancient Viral DNA and Its Role in Human Disease and Development

Introduction

• Ancient viral DNA sequences, remnants of past pandemics, are part of the human genome.
• Recent research shows these viral sequences are still active in healthy individuals.
• Human Endogenous Retroviruses (HERVs) make up about 8% of the human genome.

Human Endogenous Retroviruses (HERVs)

• What are HERVs?
  • Left by ancient retroviral infections in primate ancestors.
  • Similar to modern HIV, they insert their genetic material into host genomes.
  • Some infected germ cells, passing DNA to future generations.
• Distribution and Influence
  • Fixed in human, chimpanzee, gorilla, and other primate genomes.
  • Active in diseased tissues and during embryonic development.

Recent Findings on HERV Activity

• Research focused on a group called HML-2, active less than 5 million years ago.
• Study Findings
  • Analysis of 14,000 tissue samples revealed 37 active HML-2 proviruses.
  • All samples showed activity of one or more proviruses, with potential protein production.
• Implications
  • Presence of HERV genes in healthy tissues complicates disease association.
  • Challenges the use of HERVs as drug targets and cancer biomarkers.

Role in Human Health and Disease

• Potential Health Implications
  • Related viruses cause breast cancer and AIDS-like disease in animals.
  • Associations with diseases such as ALS, multiple sclerosis, and schizophrenia.
• Protective and Beneficial Roles
  • Syncytin, derived from HERVs, is crucial for placenta formation in mammals.
  • Other HERVs may provide protection against related ancient viruses.

Ongoing Questions and Research

• HERVs’ full role and benefits are still unclear.
• Key Areas of Investigation
  • Mechanisms driving HERV activity in the human body.
  • Whether these genes are translated into proteins and their functions.
• Understanding HERVs may reveal insights into human evolution and disease resistance.

Conclusion

• The study of HERVs offers a glimpse into how ancient viral DNA continues to interact with the human genome.
• Further research is needed to comprehend their potential benefits and implications for human health.