Periodic Reporting for period 2 - HEARTLY (Loss of chromosome Y in immune cells: targeting disease mechanisms and tools for clinical applications)
Période du rapport: 2022-12-01 au 2024-05-31
The HEARTLY project focuses on a lasting conundrum in medicine: the fact that men in the entire world live on average 5-6 years shorter lives compared with women. In the project we study the effects from mosaic loss of chromosome Y (mLOY), a male specific somatic mutation that helps explain this bias. Men with mLOY in blood carry a fraction of blood cells without the Y chromosome, due to its loss from hematopoietic progenitor cells during life time. The incidence of mLOY increases with age and is the most common somatic human mutation. The mutation can be detected in at least 5% of peripheral blood cells in about 5%, 20%, 40% and 60% of normally aging men around 50, 60, 70 and 90 years of age. Based on incidence observed in studied cohorts and global demographics data, more than 200 million men might be affected with mLOY in blood. Known risk factors include aging, smoking, genetic predisposition and exposure to various pollutants.
At the onset of the project, it was already established that men with mLOY display an increased risk for all-cause mortality, in part explained by increased risk for several common diseases such as cancer and Alzheimer’s disease. However, it was not known if men with mLOY in blood had an increased risk for the biggest killer of all, i.e. the cardiovascular diseases (CVD). One of the objectives in the HEARTLY project is to investigate risk for CVD in relation to mLOY. During the first period of the project, we have established that men with mLOY in blood indeed have an increased risk for death in CVD overall and interestingly, that mLOY is specifically associated with risk for death in hypertensive heart disease, aortic aneurysm and heart failure. In the continuation of the project we aim to continue our investigations of these and other disease associations using analyses of outcomes in prospective cohorts.
Another objective of the project is to enhance our understanding of causal link(s) between mLOY in blood and disease in other organs. This is a major task and we approach it by several complimentary strategies. A major milestone of the project was the finding that mLOY is causally related with mortality. Furthermore, by studying altered gene expression in LOY-cells, we have discovered that leukocytes without the Y chromosome trigger profibrotic signalling pathways, leading to organ dysfunction and exacerbation of disease. Hence, fibrosis is a major component of many LOY-associated diseases and thus, it is hypothesized that enhanced fibrosis represents a unifying disease mechanism, explaining how mLOY in blood cells is associated with all major causes of death. A next step that is pursued in the project is the identification of specific genetic elements of the Y chromosome that could be responsible for the profound phenotypic effects associated with Y loss. We are using several methods for gene editing and transcriptional silencing in different model systems to achieve this goal.
A long-term goal of our research is an increased survival of men by utilization of mLOY-based clinical applications. Enhanced understanding of detrimental effects from mLOY on human physiology could be a key to improved success rates in various therapies, stratification and discovery of new drug targets. For example, since men with mLOY in blood have on average a higher risk for lethal disease compared with unaffected men, we envision that screening men with mLOY for early symptoms of disease could result in earlier diagnoses and treatment using existing health care options. In the project we are therefore working on developing clinically feasible tools for mLOY detection to improve such translational efforts. Our discovery of profibrotic signalling of LOY-leukocytes represents an important step in this direction, as approved antifibrotic treatments are already used clinically. Overall, the deliverables of the project has the potential to become beneficial for individual patients, health care systems and societies at large.
At the onset of the project, it was already established that men with mLOY display an increased risk for all-cause mortality, in part explained by increased risk for several common diseases such as cancer and Alzheimer’s disease. However, it was not known if men with mLOY in blood had an increased risk for the biggest killer of all, i.e. the cardiovascular diseases (CVD). One of the objectives in the HEARTLY project is to investigate risk for CVD in relation to mLOY. During the first period of the project, we have established that men with mLOY in blood indeed have an increased risk for death in CVD overall and interestingly, that mLOY is specifically associated with risk for death in hypertensive heart disease, aortic aneurysm and heart failure. In the continuation of the project we aim to continue our investigations of these and other disease associations using analyses of outcomes in prospective cohorts.
Another objective of the project is to enhance our understanding of causal link(s) between mLOY in blood and disease in other organs. This is a major task and we approach it by several complimentary strategies. A major milestone of the project was the finding that mLOY is causally related with mortality. Furthermore, by studying altered gene expression in LOY-cells, we have discovered that leukocytes without the Y chromosome trigger profibrotic signalling pathways, leading to organ dysfunction and exacerbation of disease. Hence, fibrosis is a major component of many LOY-associated diseases and thus, it is hypothesized that enhanced fibrosis represents a unifying disease mechanism, explaining how mLOY in blood cells is associated with all major causes of death. A next step that is pursued in the project is the identification of specific genetic elements of the Y chromosome that could be responsible for the profound phenotypic effects associated with Y loss. We are using several methods for gene editing and transcriptional silencing in different model systems to achieve this goal.
A long-term goal of our research is an increased survival of men by utilization of mLOY-based clinical applications. Enhanced understanding of detrimental effects from mLOY on human physiology could be a key to improved success rates in various therapies, stratification and discovery of new drug targets. For example, since men with mLOY in blood have on average a higher risk for lethal disease compared with unaffected men, we envision that screening men with mLOY for early symptoms of disease could result in earlier diagnoses and treatment using existing health care options. In the project we are therefore working on developing clinically feasible tools for mLOY detection to improve such translational efforts. Our discovery of profibrotic signalling of LOY-leukocytes represents an important step in this direction, as approved antifibrotic treatments are already used clinically. Overall, the deliverables of the project has the potential to become beneficial for individual patients, health care systems and societies at large.
A major unsolved question before the HEARTLY project was how the LOY-mutation is blood cells can cause disease in other organs. A main objective of the project was therefore to understand the functional consequences of mLOY, i.e. if Y loss of circulating immune cells cause disease directly. As planned we have been studying transcriptomic alterations in immune cells with LOY and discovered profibrotic signaling of LOY-leukocytes. A major delivery from project so far is our results showing that mLOY cause disease directly by triggering such fibrotic processes in other organs. This discovery was published in Science and help explain how mLOY in blood increase risk for death. We also have ongoing work to decipher the molecular mechanisms behind dysregulation of autosomal genes in LOY-cells. We are using complimentary methods for gene editing and transcriptional silencing in different model systems, such as CRISPR-Cas9 and siRNA. These projects are ongoing and our preliminary data suggest that a specific gene(s) on chromosome Y could be responsible for much of the observed effects. However, our results from these analyses are preliminary and needs to be validated by independent experiments before publication. Furthermore, the first paper from the planned work to study the relationship between mLOY and other CHIP-mutations have been published. The results show a frequent co-occurrence of these two types of mutations and future investigations will continue for the duration of the project.
Another major task in the HEARTLY project is further epidemiological investigations of occurrence of somatic mutations in blood cells and risk for disease in other organs. During the first part of the project, we have discovered and published milestone results showing that men with mLOY in blood have an increased risk for CVD, the major cause of human death. In addition, our so far unpublished results in the project show increased risk for other common diseases in men with mLOY. Furthermore, one of the aims in the project is to elucidate if mLOY in specific types of immune cells is associated with increased risk for different types of CVD and other diseases. In the project, we have already showed that mLOY in monocytes is a major risk factor for CVD, and this result will be further explored in upcoming studies within the project. These upcoming studies will also include investigations of associations between other somatic mutations and risk for diseases, as planned.
We also aim to develop clinically feasible tools to improve the clinical utility of our research and benefit future translational efforts. In brief, we are generating a model system for Y loss in cell lines of hematopoietic origin using CRISPR-Cas9 elimination of Y, and will use this resource to validate a set of candidate cell surface proteins as markers for Y loss in single cells. This work is progressing within the planned timeframe and will continue during the continuation of the project.
Another major task in the HEARTLY project is further epidemiological investigations of occurrence of somatic mutations in blood cells and risk for disease in other organs. During the first part of the project, we have discovered and published milestone results showing that men with mLOY in blood have an increased risk for CVD, the major cause of human death. In addition, our so far unpublished results in the project show increased risk for other common diseases in men with mLOY. Furthermore, one of the aims in the project is to elucidate if mLOY in specific types of immune cells is associated with increased risk for different types of CVD and other diseases. In the project, we have already showed that mLOY in monocytes is a major risk factor for CVD, and this result will be further explored in upcoming studies within the project. These upcoming studies will also include investigations of associations between other somatic mutations and risk for diseases, as planned.
We also aim to develop clinically feasible tools to improve the clinical utility of our research and benefit future translational efforts. In brief, we are generating a model system for Y loss in cell lines of hematopoietic origin using CRISPR-Cas9 elimination of Y, and will use this resource to validate a set of candidate cell surface proteins as markers for Y loss in single cells. This work is progressing within the planned timeframe and will continue during the continuation of the project.
The major breakthrough in the HEARTLY project so far is the identification of a disease mechanism that help explain why men with mLOY in blood are at increased risk for diseases manifesting in other organs. Hence, we have discovered that enhanced organ fibrosis is an effect from Y loss in circulating leukocytes. This mechanism has do far been demonstrated for cardiac fibrosis and heart failure, however, the universality of this mechanism needs to be validated. Before the end of the project, I hope to show that LOY-driven fibrosis is a universal disease mechanism that help explain the high mortality of men with mLOY. Furthermore, I expect to have found what gene(s) on the Y that are involved in this process and how this information can be used clinically to alleviate fibrotic conditions.