Molecular Interaction Involving L1 RNA Could Cause Progeria Syndromes

Researchers in Saudi Arabia have found a new target for treating progeroid disorders like Werner Syndrome and Hutchinson Gilford Progeria Syndrome. Such diseases cause patients to develop symptoms and pathologies normally associated with aging, like osteoporosis and cataracts.

While such aging is characterized by the progressive loss of nuclear architecture and an underlying tissue-specific genetic program, the causes are still unknown. In a new study—published recently in Science Translational Medicine—a team from King Abdullah University of Science & Technology (KAUST) have identified a promising new target for treating these syndromes by preventing the loss of nuclear architecture.

“Based on theoretical considerations, we postulated that a molecular interaction between L1 RNA and a specific enzyme controlling heterochromatin stability could be the cause of premature aging in progeria syndromes,” says KAUST research scientist Francesco Della Valle.

L1 RNA, or long interspersed nuclear element-1 RNA, is a family of repeat sequences encompassing about 17–20% of the mammalian genome whose functions are largely unknown. These sequences are kept inactive by the tightly packed DNA architecture called heterochromatin. There is evidence that heterochromatin loss during normal aging is associated with their activation.

Sequencing analyses, conducted by teams from KAUST and the United States, demonstrated increased expression of L1 RNA in cells taken from patients with progeroid syndromes. Further tests showed that this increased L1 RNA expression was responsible for deactivating an enzyme, called SUV39H1, which led to the heterochromatin loss and changes in gene expression that cause cell aging.

The researchers were able to block L1 RNA expression and reverse the aging process in cells taken from patients with progeroid syndromes and in mice that are genetically modified to simulate premature aging. They did this using short synthetic nucleotide chains called antisense oligonucleotides (ASO) that specifically target and lead to the degradation of L1 RNA. Their L1 ASO was modified to improve its ability to enter and stay stable within cells. Blocking L1 RNA in the cells restored heterochromatin and counteracted aging-related genes. The L1 ASOs also prolonged the life span of the progeria-like mice.

“Among other observations, our work establishes an important rule,” says bioscientist Valerio Orlando. “Contrary to what was previously thought, aberrant expression of L1 RNA is not a consequence of the initiation of aging but a cause of it, at least in progeria. And now, for the first time, we report a specific, rather than global, target that acts as an essential factor in aging.”

Further research will need to determine whether other mechanisms, acting in parallel with SUV39H1 inhibition, might compromise heterochromatin stability in progeria syndromes.

“Given the similarities between Progeroid syndromes and chronological aging-associated diseases, targeting LINE-1 RNA may be an effective way to treat progeroid syndromes, as well as other age-related diseases characterized by LINE-1 aberrant expression, such as neurodegenerative, metabolic and cardiovascular disorders, and cancer,” says Orlando. “This study opens the way to new strategies that we think might help extend human life expectancy.”