👤 Christian Keller

The emergence of Alzheimer's disease (AD) pathology has been the focus of multiple hypotheses, with amyloid β (Aβ) playing a central role due to its presence in both familial and sporadic AD. Therefore, a crucial aspect of AD research is understanding the generation of different Aβ species. Aβ peptides result from the proteolytic processing of Amyloid Precursor Protein (APP) by β- and γ-secretases, with BACE1 being the most prominent β-secretase. However, BACE1-overexpressing mouse models exhibit disadvantages, making them limited for AD research. Importantly, N-terminally truncated Aβ species, which constitute up to 70 % of Aβ in AD brains, are not generated by BACE1. In recent years, alternative proteases capable of cleaving APP have been identified, bridging the gap between N-terminally truncated Aβ species and BACE1-derived Aβ. Among these novel players, the metalloprotease meprin β has emerged as a risk factor in AD pathology, generating both N-terminally truncated and full-length Aβ species. Our primary objective was to develop a mouse model that more accurately resembles the pathology of AD beyond BACE1-overexpressing models, while simultaneously confirming APP cleavage of meprin β in the hippocampus and cerebral cortex. Overexpression of meprin β led to a marked increase in soluble Aβ levels, particularly in the hippocampus, indicating a higher vulnerability or elevated meprin β activity in this region compared to the cerebral cortex. Notably, this biochemical change occurred without any observable behavioral deficits, suggesting a region-specific role of meprin β in AD pathology that may extend beyond immediate functional impairment. Show less

Nivolumab and nintedanib are both established agents for pre-treated NSCLC of adenocarcinoma histology. Hypothesizing that the combination of immune checkpoint inhibition (nivolumab) and anti-angiogenesis (nintedanib) increases efficacy, we intended to determine a safe and efficacious dose for the combination. Our multi-center, open-label, single arm, phase Ib/II study enrolled patients with histologically confirmed stage IIIB/IV adenocarcinoma NSCLC and one or two previous lines of systemic treatment with platinum-based chemotherapy +/- checkpoint inhibitors (CPI). A traditional 3 + 3 design was used to determine a recommended phase II dose (RP2D) for nintedanib combined with nivolumab. Primary endpoints were safety and tolerability together with 6- and 9-month rates of progression-free survival (PFS). The RP2D was determined as 200 mg nintedanib twice daily (bid) with 240 mg nivolumab biweekly (Q2W). No new safety signals were detected. PFS milestone rates at 6 and 9 months for the 52 patients who received this dose were 25% [95% CI 14.3-37.3%] and 11.5% [4.7-21.8%], respectively. Median overall survival (mOS) was 12.2 months [95% CI: 8.13-18.37]. Central biomarker analysis based on combined positive score (CPS) revealed that high PD-L1 and low PD-L1/low FGFR1 identified patients with prolonged OS at 36 months (70% and 40%, respectively), while low PD-L1/high FGFR1 was associated with shorter OS (p = 0.0195). CPI-rechallenged patients had better OS outcomes than those who were CPI-naïve (mOS 8.13 months [95% CI 2.03-15.2] vs. 14.7 months [95% CI 8.2-NR]; logrank p = 0.0493). Combination of nivolumab and nintedanib was shown to be safe and feasible. Despite missing synergistic effects on efficacy for the overall population, promising OS was observed for patients with high PD-L1 expression and for patients with previous immunotherapy. Therefore, CPI responsiveness may have been restored in some cases. Inhibition of FGFR-mediated tumor progression seems relevant in tumors with lower levels of both PD-L1 and FGFR1 expression and might be effectively inhibited by nintedanib. The combination nivolumab/nintedanib might warrant further exploration in selected patients. Show less

Many membrane proteins, including G protein-coupled receptors (GPCRs), are susceptible to denaturation when extracted from their native membrane by detergents. Therefore, alternative methods have been developed, including amphiphilic copolymers that enable the direct extraction of functional membrane proteins along with their surrounding lipids. Among these amphiphilic copolymers, styrene/maleic acid (SMA) and diisobutylene/maleic acid (DIBMA) polymers have been extensively studied. Despite their many benefits, SMA and DIBMA polymers also have considerable drawbacks limiting their applications. Herein, we describe a series of new amphiphilic copolymers derived from DIBMA via partial amidation of the carboxylate pendant groups with various biocompatible amines. We characterize the new polymer's nanodisc-forming properties and ability to extract the melanocortin 4 receptor (MC Show less

Tumor cells release extracellular vesicles (EVs) that contribute to the polarization of macrophages towards tumor-associated macrophages (TAMs). High expression levels of the RNA binding protein IGF2BP2/IMP2 are correlated with increased tumor cell proliferation, invasion, and poor prognosis in the clinic. However, there is a lack of understanding of whether IMP2 affects the cargo of cancer cell-derived EVs, thereby modulating macrophage polarization. EVs were isolated from IMP2-expressing HCT116 parental cells (WT) and CRISPR/Cas9 IMP2 knockout (KO) cells. EVs were characterized according to MISEV guidelines, microRNA cargo was assessed by microRNA-Seq, and the protein cargo was analyzed by proteomics. Primary human monocyte-derived macrophages (HMDMs) were polarized by EVs, and the expression of genes and surface markers was assessed using qPCR and flow cytometry, respectively. Morphological changes of macrophages, as well as the migratory potential of cancer cells, were assessed by the Incucyte EVs from WT and KO cells had a similar size and concentration and were positive for 25 vesicle markers. The expression of tumor-promoting genes was higher in macrophages polarized with WT EVs than KO EVs, while the expression of TNF and IL6 was reduced. A similar pattern was observed in macrophages from zebrafish larvae treated in vivo. WT EV-polarized macrophages showed a higher abundance of TAM-like surface markers, higher matrix degrading activity, as well as a higher promotion of cancer cell migration. MicroRNA-Seq revealed a significant difference in the microRNA composition of WT and KO EVs, particularly a high abundance of miR-181a-5p in WT EVs, which was absent in KO EVs. Inhibitors of macropinocytosis and phagocytosis antagonized the delivery of miR-181a-5p into macrophages and the downregulation of the miR-181a-5p target DUSP6. Proteomics data showed differences in protein cargo in KO vs. WT EVs, with the differentially abundant proteins mainly involved in metabolic pathways. WT EV-treated macrophages exhibited a higher basal oxygen consumption rate and a lower extracellular acidification rate than KO EV-treated cells. Our results show that IMP2 determines the cargo of EVs released by cancer cells, thereby modulating the EVs' actions on macrophages. Expression of IMP2 is linked to the secretion of EVs that polarize macrophages towards a tumor-promoting phenotype. Show less

Acute respiratory distress syndrome (ARDS) in corona virus disease 19 (COVID-19) is triggered by hyperinflammation, thus providing a rationale for immunosuppressive treatments. The Janus kinase inhibitor Ruxolitinib (Ruxo) has shown efficacy in severe and critical COVID-19. In this study, we hypothesized that Ruxo's mode of action in this condition is reflected by changes in the peripheral blood proteome. This study included 11 COVID-19 patients, who were treated at our center's Intensive Care Unit (ICU). All patients received standard-of-care treatment and Linear modeling of MS data yielded 27 significantly differentially regulated proteins on day 1, 69 on day 6 and 72 on day 10. Only five factors (IGLV10-54, PSMB1, PGLYRP1, APOA5, WARS1) were regulated both concordantly and significantly over time. Overrepresentation analysis revealed biological processes involving T-cells only on day 1, while a humoral immune response and complement activation were detected at day 6 and day 10. Pathway enrichment analysis identified the Our results indicate that the mechanism of action of Ruxo in COVID-19-ARDS can be related to both known effects of this drug as a modulator of T-cells and the SARS-CoV-2-infection. Show less

Fibroblast growth factors (FGFs) are key regulators of the remarkable regenerative capacity of the liver. Mice lacking FGF receptors 1 and 2 (Fgfr1 and Fgfr2) in hepatocytes are hypersensitive to cytotoxic injury during liver regeneration. Using these mice as a model for impaired liver regeneration, we identified a critical role for the ubiquitin ligase Uhrf2 in protecting hepatocytes from bile acid accumulation during liver regeneration. During regeneration after partial hepatectomy, Show less

In adult males, spermatogonia maintain lifelong spermatozoa production for oocyte fertilization. To understand spermatogonial metabolism we compared gene profiles in rat spermatogonia to publicly available mouse, monkey, and human spermatogonial gene profiles. Interestingly, rat spermatogonia expressed metabolic control factors Show less

Recent analyses in Greenlandic Inuit identified six genetic polymorphisms (rs74771917, rs3168072, rs12577276, rs7115739, rs174602 and rs174570) in the fatty acid desaturase gene cluster (FADS1-FADS2-FADS3) that are associated with multiple metabolic and anthropometric traits. Our objectives were to systematically assess whether dietary polyunsaturated fatty acid (PUFA) intake modifies the associations between genetic variants in the FADS gene cluster and cardiometabolic traits, and to functionally annotate top-ranking candidates to estimate their regulatory potential. Data analyses consisted of the following: interaction analyses between the 6 candidate genetic variants and dietary PUFA intake; gene-centric joint analyses to detect interaction signals in the FADS region; haplotype-centric joint tests across 30 haplotype blocks in the FADS region to refine interaction signals; and functional annotation of top-ranking loci from the previous steps. These analyses were undertaken in Swedish adults from the GLACIER Study (N = 5,160); data on genetic variation and eight cardiometabolic traits were used. Interactions were observed between rs174570 and n-6 PUFA intake on fasting glucose (P The association between FADS variants and triglycerides may be modified by PUFA intake. The intronic FADS2 rs5792235 variant is a potential causal variant in the region, having the highest regulatory potential. However, our results suggest that multiple haplotypes may harbour functional variants in a region, rather than a single causal variant. Show less

In this study, we aimed to clinically and genetically characterize LVNC patients and investigate the prevalence of variants in known and novel LVNC disease genes. Left ventricular non-compaction cardiomyopathy (LVNC) is an increasingly recognized cause of heart failure, arrhythmia, thromboembolism, and sudden cardiac death. We sought here to dissect its genetic causes, phenotypic presentation and outcome. In our registry with follow-up of in the median 61 months, we analysed 95 LVNC patients (68 unrelated index patients and 27 affected relatives; definite familial LVNC = 23.5%) by cardiac phenotyping, molecular biomarkers and exome sequencing. Cardiovascular events were significantly more frequent in LVNC patients compared with an age-matched group of patients with non-ischaemic dilated cardiomyopathy (hazard ratio = 2.481, P = 0.002). Stringent genetic classification according to ACMG guidelines revealed that TTN, LMNA, and MYBPC3 are the most prevalent disease genes (13 patients are carrying a pathogenic truncating TTN variant, odds ratio = 40.7, Confidence interval = 21.6-76.6, P < 0.0001, percent spliced in 76-100%). We also identified novel candidate genes for LVNC. For RBM20, we were able to perform detailed familial, molecular and functional studies. We show that the novel variant p.R634L in the RS domain of RBM20 co-segregates with LVNC, leading to titin mis-splicing as revealed by RNA sequencing of heart tissue in mutation carriers, protein analysis, and functional splice-reporter assays. Our data demonstrate that the clinical course of symptomatic LVNC can be severe. The identified pathogenic variants and distribution of disease genes-a titin-related pathomechanism is found in every fourth patient-should be considered in genetic counselling of patients. Pathogenic variants in the nuclear proteins Lamin A/C and RBM20 were associated with worse outcome. Show less

Routine genetic testing in Dilated Cardiomyopathy (DCM) has recently become reality using Next-Generation Sequencing. Several studies have explored the relationship between genotypes and clinical phenotypes to support risk estimation and therapeutic decisions, however, most studies are small or restricted to a few genes. This study provides to our knowledge the first systematic meta-analysis on genotype-phenotype associations in DCM. We retrieved PubMed/Medline literature on genotype-phenotype associations in patients with DCM and mutations in LMNA, PLN, RBM20, MYBPC3, MYH7, TNNT2 and TNNI3. We summarized and extensively reviewed all studies that passed selection criteria and performed a meta-analysis on key phenotypic parameters. Together, 48 studies with 8097 patients were included. Furthermore, we reviewed recent studies investigating genotype-phenotype associations in DCM patients with TTN mutations. The average frequency of mutations in the investigated genes was between 1 and 5 %. The mean age of DCM onset was the beginning of the fifth decade for all genes. Heart transplantation (HTx) rate was highest in LMNA mutation carriers (27 %), while RBM20 mutation carriers were transplanted at a markedly younger age (mean 28.5 years). While 73 % of DCM patients with LMNA mutations showed cardiac conduction diseases, low voltage was the reported ECG hallmark in PLN mutation carriers. The frequency of ventricular arrhythmia in DCM patients with LMNA (50 %) and PLN (43 %) mutations was significantly higher. The penetrance of DCM phenotype in subjects with TTN truncating variants increased with age and reached 100 % by age of 70. A pooled analysis of available genotype-phenotype data shows a higher prevalence of sudden cardiac death (SCD), cardiac transplantation, or ventricular arrhythmias in LMNA and PLN mutation carriers compared to sarcomeric gene mutations. This study will further support the clinical interpretation of genetic findings. Show less

Bladder outlet obstruction (BOO) induces significant organ remodeling, leading to lower urinary tract symptoms accompanied by urodynamic changes in bladder function. Here, we report mRNA and miRNA transcriptome sequencing of bladder samples from human patients with different urodynamically defined states of BOO. Patients' miRNA and mRNA expression profiles correlated with urodynamic findings. Validation of RNA sequencing results in an independent patient cohort identified combinations of 3 mRNAs (NRXN3, BMP7, UPK1A) and 3 miRNAs (miR-103a-3p, miR-10a-5p, miR-199a-3p) sufficient to discriminate between bladder functional states. All BOO patients shared cytokine and immune response pathways, TGF-β and NO signaling pathways, and hypertrophic PI3K/AKT signaling pathways. AP-1 and NFkB were dominant transcription factors, and TNF-α was the top upstream regulator. Integrated miRNA-mRNA expression analysis identified pathways and molecules targeted by differentially expressed miRNAs. Molecular changes in BOO suggest an increasing involvement of miRNAs in the control of bladder function from the overactive to underactive/acontractile states. Show less

Most genome-wide association studies are confined to middle-aged populations. It is unclear whether associations between single nucleotide polymorphisms (SNPs) and obesity persist in old age. We aimed to relate 10 body mass index (BMI)-associated SNPs to weight, BMI, % fat, visceral and subcutaneous adipose tissue in Health ABC and AGES-Reykjavik comprising 4,846 individuals of European Ancestry, and 1,139 African Americans over age 65. SNPs were scaled using effect estimates from candidate SNPs. In Health ABC, a SNP near GNPDA2 was modestly associated with weight and SAT area (p = .008, p = .001). Risk score (sum of scaled SNPs) was associated with weight, BMI, and SAT area (p < .0001 for all), but neither GNPDA2 nor risk score was associated with weight, BMI, visceral adippose tissue, subcutaneous adipose tissue, or % fat in AGES-Reykjavik. In African Americans, a SNP near SEC16B was weakly associated with weight (p = .04). In this sample of older adults, no BMI-associated SNPs were associated with weight or adiposity. Show less

The molecular mechanisms that guide heart valve formation are not well understood. However, elucidation of the genetic basis of congenital heart disease is one of the prerequisites for the development of tissue-engineered heart valves. We isolated here a mutation in zebrafish, bungee (bng(jh177)), which selectively perturbs valve formation in the embryonic heart by abrogating endocardial Notch signaling in cardiac cushions. We found by positional cloning that the bng phenotype is caused by a missense mutation (Y849N) in zebrafish protein kinase D2 (pkd2). The bng mutation selectively impairs PKD2 kinase activity and hence Histone deacetylase 5 phosphorylation, nuclear export, and inactivation. As a result, the expression of Histone deacetylase 5 target genes Krüppel-like factor 2a and 4a, transcription factors known to be pivotal for heart valve formation and to act upstream of Notch signaling, is severely downregulated in bungee (bng) mutant embryos. Accordingly, the expression of Notch target genes, such as Hey1, Hey2, and HeyL, is severely decreased in bng mutant embryos. Remarkably, downregulation of Histone deacetylase 5 activity in homozygous bng mutant embryos can rescue the mutant phenotype and reconstitutes notch1b expression in atrioventricular endocardial cells. We demonstrate for the first time that proper heart valve formation critically depends on Protein kinase D2-Histone deacetylase 5-Krüppel-like factor signaling. Show less

Aberrant mitogen/extracellular signal-regulated kinase 5 (MEK5)-extracellular signal-regulated protein kinase 5 (ERK5)-mediated signalling has been implicated in a number of tumour types including prostate cancer (PCa). The molecular basis of ERK5-driven carcinogenesis and its clinical relevance remain to be fully characterised. Modulation of ERK5 expression or function in human PCa PC3 and PC3-ERK5 (stably transfected with ERK5) cells was performed using siRNA-mediated knockdown or the MEK inhibitor PD18435 respectively. In vitro significance of ERK5 signalling was assessed by assays for proliferation, motility, invasion and invadopodia. Expression of matrix metalloproteinases/tissue inhibitors of metalloproteases was determined by Q-RT-PCR. Extracellular signal-regulated protein kinase 5 expression in primary and metastatic PCa was examined using immunohistochemistry. Reduction of ERK5 expression or signalling significantly inhibited the motility and invasive capability of PC3 cells. Extracellular signal-regulated protein kinase 5-mediated signalling significantly promoted formation of in vivo metastasis in an orthotopic PCa model (P<0.05). Invadopodia formation was also enhanced by forced ERK5 expression in PC3 cells. Furthermore, in metastatic PCa, nuclear ERK5 immunoreactivity was significantly upregulated when compared with benign prostatic hyperplasia and primary PCa (P=0.013 and P<0.0001, respectively). Our in vitro, in vivo and clinical data support an important role for the MEK5-ERK5 signalling pathway in invasive PCa, which represents a potential target for therapy in primary and metastatic PCa. Show less

Ten non-synonymous single nucleotide polymorphisms (nsSNPs), which were recently associated with colorectal cancer risk in a comprehensive, array based study (AKAP9 M463I, DKK3 G335R, AMPD1 Q12X, LIPC L356F, PSMB9 V32I, THBS1 N700S, CA6 S90G, ASCC3 C1995S, DHX36 S416C and CPA4 G303C) were re-evaluated in the present study based on 626 German familial non-HNPCC colorectal cancer patients and 736 healthy controls. No associations of any of the 10 nsSNPs with colorectal cancer could be replicated. The combined analyses indicated that further research based on additional independent samples is required. Show less

Familial hypertrophic cardiomyopathy (HCM) is a leading cause of sudden cardiac death among young and apparently healthy people. Autosomal dominant mutations within genes encoding sarcomeric proteins have been identified. An autosomal recessive form of HCM has been discovered in a group of Amish children that is associated with poor prognosis and death within the first year of life. Affected patients experienced progressive cardiac failure despite maximal medical treatment. Postmortem histology showed myofibre disarray and myocyte loss consistent with refractory clinical deterioration in affected infants. To conduct a genome-wide screen for linkage and try to identify an autozygous region which cosegregates with the infant cardiac phenotype An autozygous region of chromosome 11 which cosegregates with the infant cardiac phenotype was identified. This region contained the MYBPC3 gene, which has previously been associated with autosomal dominant adult-onset HCM. Sequence analysis of the MYBPC3 gene identified a splice site mutation in intron 30 which was homozygous in all affected infants. All surviving patients with the homozygous MYBPC3 gene mutations (3330+2T>G) underwent an orthotopic heart transplantation. Homozygous mutations in the MYBPC3 gene have been identified as the cause of severe infantile HCM among the Amish population. Show less

When differentiated in the presence of activin A in serum-free conditions, mouse embryonic stem cells efficiently generate an endoderm progenitor population defined by the coexpression of either Brachyury, Foxa2 and c-Kit, or c-Kit and Cxcr4. Specification of these progenitors with bone morphogenetic protein-4 in combination with basic fibroblast growth factor and activin A results in the development of hepatic populations highly enriched (45-70%) for cells that express the alpha-fetoprotein and albumin proteins. These cells also express transcripts of Afp, Alb1, Tat, Cps1, Cyp7a1 and Cyp3a11; they secrete albumin, store glycogen, show ultrastructural characteristics of mature hepatocytes, and are able to integrate into and proliferate in injured livers in vivo and mature into hepatocytes expressing dipeptidyl peptidase IV or fumarylacetoacetate hydrolase. Together, these findings establish a developmental pathway in embryonic stem cell differentiation cultures that leads to efficient generation of cells with an immature hepatocytic phenotype. Show less

Familial hypertrophic cardiomyopathy (FHC) is associated with mutations in 11 genes encoding sarcomeric proteins. Most families present mutations in MYBPC3 and MYH7 encoding cardiac myosin-binding protein C and beta-myosin heavy chain. The consequences of MYH7 mutations have been extensively studied at the molecular level, but controversial results have been obtained with either reduced or augmented myosin motor function depending on the type or homogeneity of myosin studied. In the present study, we took advantage of the accessibility to an explanted heart to analyze for the first time the properties of human homozygous mutant myosin. The patient exhibited eccentric hypertrophy with severely impaired ejection fraction leading to heart transplantation, and carries a homozygous mutation in MYH7 (R403W) and a heterozygous variant in MYBPC3 (V896M). In situ analysis of the left ventricular tissue showed myocyte disarray and hypertrophy plus interstitial fibrosis. In vitro motility assays showed a small, but significant increase in sliding velocity of fluorescent-labeled actin filaments over human mutant cardiac myosin-coated surface compared to control (+18%; P<0.001). Mutant myosin exhibited a large increase in maximal actin-activated ATPase activity (+114%; P<0.05) and Km for actin (+87%; P<0.05) when compared to control. These data show disproportionate enhancement of mechanical and enzymatic properties of human mutant myosin. This suggests inefficient ATP utilization and reduced mechanical efficiency in the myocardial tissue of the patient, which could play an important role in the development of FHC phenotype. Show less