A study reveals that transposable elements, once thought to be parasitic, are crucial for early human development. Researchers from Sinai Health have shown that these genomic segments, known as “selfish DNA,” particularly LINE-1, actively contribute to the proper formation of human embryos. Historically regarded as harmful, these elements account for around 20% of the human genome, despite our functional genes making up less than 2%. Transposons and Early Embryo Development Transposons, which have the ability to move around within the genome, were initially likened to viruses because of their capacity to replicate and disrupt normal genes. Dr Juan Zhang, a senior co-author and postdoctoral fellow, observed that LINE-1 RNA is particularly active in the early stages of embryo development, contrary to the longstanding belief that these elements primarily cause diseases like cancer or haemophilia. Crucial Insights From Blocking LINE-1 Dr Zhang’s team found that when LINE-1 activity was blocked in human embryonic stem cells, the cells reverted to a stage known as the 8-cell stage. Cells can still develop into both embryonic and placental cells …