A faulty protein called the Androgen Receptor is hijacking the genetic instructions in muscle cells, causing them to waste away in men with spinal and bulbar muscular atrophy (SBMA), and researchers now plan to watch this process unfold in real time using a microscope that tracks single molecules. This matters because SBMA is a progressive, untreatable neuromuscular disease that leaves adult men severely disabled. The fundamental gap is that no one understands exactly how the mutated receptor corrupts the cell’s gene-reading machinery to trigger muscle loss. Without that knowledge, drug development has stalled. If the team succeeds, they will have proof-of-principle evidence that restoring the receptor’s normal transcriptional activity can reverse muscle atrophy. They plan to test this using a “muscle-on-a-chip” — a 3D bundle of human muscle cells that mimics real tissue architecture — and then validate the findings in a mouse model. The work is primarily fundamental science, probing the core mechanisms of gene regulation in health and disease. But a deeper understanding of how transcription factors control muscle maintenance could eventually open treatment avenues not just for SBMA, but for the many other conditions — from cancer cachexia to age-related sarcopenia — where skeletal muscle is lost.
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Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease affecting adult males worldwide, resulting in progressive and yet untreatable motor dysfunction and severe disability. Previous studies from my group and others have shown that skeletal muscle is primarily affected in this disease and therapies exclusively directed at restoring the muscle atrophy are sufficient to rescue the disease phenotype in animal models. SBMA is caused by mutations in the Androgen Receptor (AR), a protein that is critical in maintaining skeletal muscle young and strong and whose functions is to bind DNA and turn specific genes on or off. Proteins like AR are called 'Transcription Factors'. How this transcription factor exerts such effects and why muscles become weak and atrophic in SBMA are key unanswered and interconnected questions: such lack of understanding of these mechanisms of control of muscle function in health and disease is precisely the reason why no treatments are yet available for SBMA patients and, as a matter of fact, for most diseases characterised by skeletal muscle loss. During the course of this Fellowship, my plan is to understand how the SBMA mutation hijacks AR ability to instruct the cell (i.e. coordinate transcription), leading to muscle atrophy and weakness. To achieve this goal, we will use relevant disease models, such as skeletal muscle cells and muscle biopsies derived from patients, which is key to generate meaningful data, and employ state-of-the-art molecular biology tools which allow the investigation of these very specific functions. In particular, we have recently set up in the lab a powerful and innovative microscopy technique, called single-molecule tracking, which enables the study of transcription factor dynamics in living cells and at high resolution, giving important information regarding the diffusion and binding behaviour of these proteins in their own environment. What's most exciting about this research is its potential for therapeutic impact. Using genetic approaches to either enhance or suppress AR ability to regulate transcription, we aim to test whether restoration of mutant AR transcriptional activity is sufficient to treat SBMA. To perform these experiments, we have devised a platform to grow muscle in a 3D bundle (muscle-on-a-chip), which recapitulates the architectural and structural complexities of muscle, effectively representing a replica of skeletal muscle outside of the body. Lastly, key findings will be functionally validated in vivo in a SBMA mouse model. Through application of these innovative and fully integrated cell and molecular biology techniques in humans and model systems, these studies will provide a substantial advancement in the understanding of the mechanisms of disease and provide proof-of-principle evidence of targeting transcriptional activity as a treatment strategy for SBMA and other diseases characterized by skeletal muscle loss.
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