A team of researchers from Harvard Medical School has uncovered evidence that challenges a long-held belief in genetics. Traditionally, it was thought that each gene corresponds to a single protein, but the study, published in September 2026 in the journal Nature, suggests this model may be incomplete. The researchers found that instructions from two distinct genes—sometimes located on different chromosomes—can fuse to create chimeric messenger RNAs. These RNA molecules then produce hybrid proteins that were previously unknown. The study was led by researcher Peter Jackson. Using a technique called direct RNA sequencing, the team identified more than 30,000 chimeric messenger RNAs in mammalian cells. This method is more sensitive than traditional techniques for detecting these unusual RNA junctions. The number is significant when compared to the 20,000 genes cataloged in the human genome, suggesting that there may be more chimeric combinations than there are genes themselves. The process by which these genetic fusions occur is linked to the physical structure of chromosomes, particularly during the immune response. In mouse cells, healthy chromosomes can fold over each other, bringing genes that are normally far apart into closer proximity. This allows the transcription machinery to create a chimeric RNA that combines parts of the sequences from each gene, resulting in a hybrid protein. Importantly, this process does not involve genetic mutations or breaks in DNA. This phenomenon is distinct from classical genetic errors, such as chromosomal translocations often seen in cancers. Instead, it occurs at the RNA level on otherwise normal chromosomes. This suggests the body may produce these chimeric molecules naturally, without any underlying genetic defects. To confirm the biological relevance of one such hybrid protein, the team studied a combination involving genes for GSDMD and TMEM106A, both of which are involved in immune responses. The resulting hybrid protein was found to actively regulate immune responses, proving that these chimeric molecules are not just laboratory artifacts. The study indicates that the body’s catalog of messenger RNAs is more extensive than previously believed. Jackson noted that the scientific community once thought the list of messenger RNAs in the human body was complete, but now realizes it was only the beginning. This discovery suggests that large sections of the proteome— the complete set of proteins produced by the body—remain to be explored, even in healthy individuals. While the researchers are excited by their findings, they remain cautious about immediate medical applications. They are still investigating the molecular signals that drive the formation of these chimeric RNAs, including why the gene segments always connect at specific points and what triggers the interaction between specific genes. The full mechanism behind these processes is still largely unknown. The researchers aim to explore the potential medical applications of these chimeric molecules, particularly those that might be involved in currently incurable diseases. Jackson’s lab is currently studying several chimeric RNAs in the context of cancer, inflammatory diseases, and neurodegenerative conditions. However, the path from identifying a promising molecule in the lab to developing a viable treatment for humans is often long, often spanning years or even decades.