During the project period, we and others have published new disease associations showing clear links between mosaic Y loss in blood and increased risk for morbidity and mortality in affected men. Notably, we published a new association with LOY and risk for Alzheimer’s disease and several papers established increased risk for different types of cancer, diabetes, age-related macular degeneration, to mention few. Importantly, our results first published in 2014 (showing an increased risk for death overall) has been reproduced and validated.
An important task in the DIALOY project was to take these epidemiological results further, and study if men diagnosed with different types of disease were affected with LOY in different types of leukocytes, i.e. circulating immune cells in blood. This would indicate a direct effect from LOY on different types of disease. To this end, we collected and analyzed LOY in six major types of leukocytes in men diagnosed with prostate cancer and Alzheimer's disease and controls. Remarkably, our results (accepted for publication 2021) show that men with Alzheimer’s disease were primarily affect with LOY in NK-cells while men with prostate cancer displayed an increased level of LOY in T-cells and granulocytes. In another published paper in the project, we showed that the frequency of leukocytes with LOY typically increase in frequency over time within the blood of serially studied men. These results show similarities between LOY and the process of clonal hematopoiesis; a result that will be further studied in future projects.
Another goal of the DIALOY project was to investigate functional consequences of LOY in immune cells of blood. To this end, we have been studying changes in gene expression as a consequence of LOY, both in different cell types sorted from blood by FACS and RNAseq, as well as by single-cell transcriptomic analyses using the 10X Chromium system. Results from this project shows that leukocytes without the Y chromosome display a disturbed expression of about 500 autosomal genes important for various biological functions, including genes important for immune checkpoint regulation and other normal immune functions such as immune surveillance. These results (accepted for publication 2021) suggest that LOY might have negative effects on vital immune system functions, connected with accelerated pathological processes in the entire body and increased risk for mortal disease. Hence, our results reinforce the hypothesis that LOY could play a direct physiological role in the etiology of all disease with strong immune component. In addition, we describe in a paper published in Nature 2019 that LOY shares a genetic predisposition with cancer susceptibility, diabetes as well as reproductive ageing in women. The shared risk variants for LOY and disease highlight genes involved in cell cycle regulation, DNA damage response, genomic imbalance and apoptosis. These results help explain why some men are affected by LOY while others are not, results that are complementary to our previous finding showing that age and smoking are important risk factors. Thus, the overlap in genetic predisposition for LOY and disease suggest that LOY could be a barometer of genomic instability and disease risk in other organs and it is likely that such predisposition acts in parallel with a direct physiological effect from LOY in leukocytes.
We also investigated and developed new and improved methodology for LOY-detection with increased sensitivity and specificity to promote the clinical utility of LOY testing. First, we assisted in the development of a custom SNP-array for best practice LOY-analyses, a product that is now on the market and used by us and other research groups. Furthermore, we developed a sensitive ddPCR protocol that can be used in research for robust and quick LOY-assessment and validation. We have also worked on developing a novel method for LOY detection using cell surface markers. This would enable rapid and sensitive LOY analysis with improved clinical utility. Preliminary results from a successful pilot project is currently prepared for publication.
