Mammalian genes can combine to make previously unknown mRNAs and proteins

Mammalian genes can combine to make previously unknown mRNAs and proteins Researchers at Harvard Medical School have uncovered a novel mechanism by which mammalian genes can merge to form chimeric mRNAs, leading to the production of previously unknown, functional proteins. Published in Nature, the study reveals that these chimeric transcripts arise through the fusion of genetic material from different genes, sometimes located on separate chromosomes, and result in hybrid proteins with potential biological significance. This discovery challenges long-held assumptions about gene expression and opens new avenues for understanding cellular function and disease mechanisms. The breakthrough stems from the application of advanced RNA sequencing technologies, specifically direct RNA sequencing, which allows for the detection of rare and complex RNA structures. Traditional methods often failed to identify chimeric mRNAs due to their low abundance and structural complexity. Using this technique, the team compiled a catalog of over 30,000 chimeric mRNAs observed in mammalian cells, describing them as a “dark genome” library, genetic sequences previously undetectable or unexplored. These findings suggest that the human genome may encode significantly more proteins than previously estimated, expanding the known proteome. Among the identified chimeric mRNAs, the researchers focused on a specific example involving the genes encoding GSDMD and TMEM106A. GSDMD is known for triggering pyroptosis, a type of programmed cell death associated with inflammation. When combined with TMEM106A, the resulting chimeric mRNA produced a hybrid protein that exhibited distinct biochemical properties compared to either parent protein. This suggests that such chimeric proteins might play specialized roles in immune responses and other physiological processes. The study also revealed that healthy chromosomes can physically interact within mouse cells during immune responses, bringing distant genes into close proximity. This spatial rearrangement facilitates the transcription of chimeric mRNAs, highlighting a dynamic interplay between genomic structure and gene regulation. The ability of chromosomal loops to generate new transcripts underscores the adaptability of the genome and its capacity to respond to environmental cues. The implications of this discovery extend beyond basic science. Chimeric proteins could represent untapped resources for therapeutic innovation, offering potential targets for drug development. However, the researchers caution that not all chimeric mRNAs necessarily lead to functional proteins or contribute meaningfully to cellular activity. Further investigation is required to determine the prevalence and relevance of these phenomena across different tissues and conditions. The work was led by Ruaidhrí Jackson, an assistant professor of immunology at Harvard Medical School’s Blavatnik Institute, alongside co-first authors Harry Kane and Olivia Venezia. Their findings challenge existing paradigms in molecular biology and emphasize the need for updated methodologies to fully explore the complexities of gene expression. As the field continues to evolve, this research sets the stage for deeper exploration into the hidden layers of the genome and their impact on health and disease.