Molecular characterisation of the Dark gene Fbxo34 as a suppressor of mutant Huntingtin toxicity

This project has been funded thanks to the Joint Call Fondazione Cariplo and Fondazione Telethon 2025.

Huntingtons disease (HD) is a genetic disorder caused by a mutation in the HTT gene, leading to the production of a harmful protein, called mutant huntingtin (mHTT) that disrupts brain function and causes the loss of neurons, particularly in a part of the brain called the striatum. While much is known about genes that contribute to HD, many others, particularly those with unclear functions (called Tdark genes), might also play important roles in the disease. Identifying these genes could open up new avenues for understanding and treating HD. To explore this, we created a model of HD using stem cells and performed a comprehensive genetic screen to discover potential genes that could protect against the toxic effects of mHTT. We identified 116 potential protective genes, including 13 Tdark genes. We found that one of these genes, called Fbxo34, is able to reduce mHTT toxicity both in stem cells and in animal models, such as zebrafish and mice. Fbxo34 is part of a protein complex that degrades damaged proteins, like mHTT. In the case of HD, the ability to remove mHTT is impaired. We observed that increasing Fbxo34 levels could reduce mHTT, suggesting that Fbxo34 helps enhance the cell’s ability to clear harmful proteins. We are now studying which parts of the Fbxo34 protein are important for its protective function and whether it directly interacts with mHTT to help remove it. In addition to studying the interaction between Fbxo34 and mHTT, we will use advanced techniques like mass spectrometry to uncover how Fbxo34 affects other proteins, potentially revealing new targets for therapy. We also plan to test this approach in HD mice and human brain organoids to validate the potential of Fbxo34 as a therapeutic target and explore how delivering the Fbxo34 gene could help treat HD.