👤 Heinrich Leonhardt

Thoracic aortic aneurysms frequently go undetected until serious complications like acute dissections or ruptures arise. Therefore, this study aims to identify potential blood circulating biomarkers enabling an easy and early diagnosis of thoracic aortic disease. Potential biomarker candidates were identified through two different techniques, untargeted and targeted proteomic as well as extracellular vesicle (EV) analyses. The biomarker levels were compared between two patient groups with thoracic aortic aneurysms and two control groups without thoracic aortic disease. In total, 80 patients (TAA group (n = 40) vs. control group (n = 40)) were matched for untargeted and targeted proteome analysis, and 85 for EV analysis (TAA group (n = 42) vs. control group (n = 43)), based on the availability of blood samples and excised aortic tissue. Levels of biomarker candidates were correlated with aortic diameter, patient age, and histological alterations in aortic tissue using linear and logistic regression models. The untargeted proteomic and EV analysis identified 1,037 and 1,077 proteins, respectively, of which 11 and 28 proteins showed significant differences in concentration between the study groups. Of these, 9 proteins correlated with the aortic diameter: ACTN1 (Regression coefficient B = 1.633, p < 0.001), CRP (B = 0.001, p = 0.004), TGM3 (B=-0.293, p = 0.010), KRT84 (B=-0.477, p = 0.010), IGHG3 (-0.267, p = 0.018), DPYSL2 (B = 0.644, p = 0.020), TSPAN8 (B-0.838, p = 0.042), IGKV3D-11 (B=-0.242, p = 0.046), and VDAC1 (B=-0.491, p = 0.047). Moreover, IGKV3D-11 (B=-3.257, p = 0.029), IGHG3 (B=-0.003, p = 0.034), and APOC3 (B=-2.104, p = 0.037) showed significant correlations with the grade of aortic medial layer degeneration. None of the proteins correlated with patient age. The study identified 9 biomarker candidates correlating with the aortic diameter. To enable the clinical use for diagnosis and prognostic assessment, these biomarkers need to be validated in larger external cohorts. Show less

Heterochromatin binding protein HP1β plays an important role in chromatin organization and cell differentiation, however the underlying mechanisms remain unclear. Here, we generated HP1β-/- embryonic stem cells and observed reduced heterochromatin clustering and impaired differentiation. We found that during stem cell differentiation, HP1β is phosphorylated at serine 89 by CK2, which creates a binding site for the pluripotency regulator KAP1. This phosphorylation dependent sequestration of KAP1 in heterochromatin compartments causes a downregulation of pluripotency factors and triggers pluripotency exit. Accordingly, HP1β-/- and phospho-mutant cells exhibited impaired differentiation, while ubiquitination-deficient KAP1-/- cells had the opposite phenotype with enhanced differentiation. These results suggest that KAP1 regulates pluripotency via its ubiquitination activity. We propose that the formation of subnuclear membraneless heterochromatin compartments may serve as a dynamic reservoir to trap or release cellular factors. The sequestration of essential regulators defines a novel and active role of heterochromatin in gene regulation and represents a dynamic mode of remote control to regulate cellular processes like cell fate decisions. Show less