Identification and characterization of novel peroxisomal disorders

Peroxisomes are vital organelles found in virtually every human cell. Defects in peroxisomes may lead to peroxisomal disorders, for example the autosomal recessive Zellweger Spectrum Disorders (ZSDs) which are caused by mutations in different PEX genes. Although many peroxisomal disorders have already been characterized, there is still a number of patients suffering from to date unidentified peroxisomal defects. In this thesis, we studied such cases to identify the cause of disease, and thus to improve the laboratory diagnosis of future patients. Understanding the underlying disease mechanisms also provides valuable insights into the functioning of peroxisomes and the phenotypical consequences of their defects, which can eventually help to identify potential treatment options. We discovered (1) one entirely novel peroxisomal disease, caused by the loss of the peroxisomal protein ACBD5, (2) one novel genetic disease mechanism causing ZSDs, i.e. the promotion of a mutant PEX6 allele by allelic expression imbalance; a mechanism potentially also involved in other recessive diseases, (3) the to date mildest form of ZSDs (by identifying the genetic cause of Heimler syndrome as PEX1 or PEX6 defects). (4) that autophagy inhibition is not an option for curative treatment of peroxisomal diseases. Finally, this thesis highlights the importance of functional assays to prove the disease-causing character of genetic variants, and to confirm in multiple approaches the effect of potential treatment options

Clinical utility of magnetic resonance imaging in first-episode psychosis

Background There is no consensus as to whether magnetic resonance imaging (MRI) should be used as part of the initial clinical evaluation of patients with first-episode psychosis (FEP). Aims (a) To assess the logistical feasibility of routine MRI; (b) to define the clinical significance of radiological abnormalities in patients with FEP. Method Radiological reports from MRI scans of two FEP samples were reviewed; one comprised 108 patients and 98 healthy controls recruited to a research study and the other comprised 241 patients scanned at initial clinical presentation plus 66 healthy controls. Results In the great majority of patients, MRI was logistically feasible. Radiological abnormalities were reported in 6% of the research sample and in 15% of the clinical sample (odds ratio (OR) = 3.1, 95% CI 1.26–7.57, χ2(1) = 6.63, P = 0.01). None of the findings necessitated a change in clinical management. Conclusions Rates of neuroradiological abnormalities in FEP are likely to be underestimated in research samples that often exclude patients with organic abnormalities. However, the majority of findings do not require intervention

Single-Cell RNA Sequencing Maps Endothelial Metabolic Plasticity in Pathological Angiogenesis

Endothelial cell (EC) metabolism is an emerging target for anti-angiogenic therapy in tumor angiogenesis and choroidal neovascularization (CNV), but little is known about individual EC metabolic transcriptomes. By single-cell RNA sequencing 28,337 murine choroidal ECs (CECs) and sprouting CNV-ECs, we constructed a taxonomy to characterize their heterogeneity. Comparison with murine lung tumor ECs (TECs) revealed congruent marker gene expression by distinct EC phenotypes across tissues and diseases, suggesting similar angiogenic mechanisms. Trajectory inference predicted that differentiation of venous to angiogenic ECs was accompanied by metabolic transcriptome plasticity. ECs displayed metabolic transcriptome heterogeneity during cell- cycle progression and in quiescence. Hypothesizing that conserved genes are important, we used an integrated analysis, based on congruent transcriptome analysis, CEC-tailored genome-scale metabolic modeling, and gene expression meta-analysis in cross-species datasets, followed by in vitro and in vivo validation, to identify SQLE and ALDH18A1 as previously unknown metabolic angiogenic targets.Stemcel biology/Regenerative medicine (incl. bloodtransfusion