Filamin A (FLNA) is a cytoplasmic actin binding protein, recently shown to be expressed as a long and short isoform. Mutations in FLNA are associated with a wide spectrum of disorders, including an... Show moreFilamin A (FLNA) is a cytoplasmic actin binding protein, recently shown to be expressed as a long and short isoform. Mutations in FLNA are associated with a wide spectrum of disorders, including an X-linked form of chronic intestinal pseudo-obstruction (CIPO). However, the role of FLNA in intestinal development and function is largely unknown. In this study, we show that FLNA is expressed in the muscle layer of the small intestine from early human fetal stages. Expression of FLNA variants associated with CIPO, blocked expression of the long flna isoform and led to an overall reduction of RNA and protein levels. As a consequence, contractility of human intestinal smooth muscle cells was affected. Lastly, our transgenic zebrafish line showed that the flna long isoform is required for intestinal elongation and peristalsis. Histological analysis revealed structural and architectural changes in the intestinal smooth muscle of homozygous fish, likely triggered by the abnormal expression of intestinal smooth muscle markers. No defect in the localization or numbers of enteric neurons was observed. Taken together, our study demonstrates that the long FLNA isoform contributes to intestinal development and function. Since loss of the long FLNA isoform does not seem to affect the enteric nervous system, it likely results in a myopathic form of CIPO, bringing new insights to disease pathogenesis. Show less
Common single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions... Show moreCommon single-nucleotide polymorphisms (SNPs) are predicted to collectively explain 40-50% of phenotypic variation in human height, but identifying the specific variants and associated regions requires huge sample sizes1. Here, using data from a genome-wide association study of 5.4 million individuals of diverse ancestries, we show that 12,111 independent SNPs that are significantly associated with height account for nearly all of the common SNP-based heritability. These SNPs are clustered within 7,209 non-overlapping genomic segments with a mean size of around 90 kb, covering about 21% of the genome. The density of independent associations varies across the genome and the regions of increased density are enriched for biologically relevant genes. In out-of-sample estimation and prediction, the 12,111 SNPs (or all SNPs in the HapMap 3 panel2) account for 40% (45%) of phenotypic variance in populations of European ancestry but only around 10-20% (14-24%) in populations of other ancestries. Effect sizes, associated regions and gene prioritization are similar across ancestries, indicating that reduced prediction accuracy is likely to be explained by linkage disequilibrium and differences in allele frequency within associated regions. Finally, we show that the relevant biological pathways are detectable with smaller sample sizes than are needed to implicate causal genes and variants. Overall, this study provides a comprehensive map of specific genomic regions that contain the vast majority of common height-associated variants. Although this map is saturated for populations of European ancestry, further research is needed to achieve equivalent saturation in other ancestries. Show less
NNMT wordt beschouwd als een nieuw potentieel farmacologisch doelwit in de behandeling van een verscheidenheid van kankers, stofwisselingsziekten en andere pathologieën. Het toenemend aantal... Show moreNNMT wordt beschouwd als een nieuw potentieel farmacologisch doelwit in de behandeling van een verscheidenheid van kankers, stofwisselingsziekten en andere pathologieën. Het toenemend aantal publicaties waarin de rol van NNMT bij ziekten wordt opgehelderd, heeft op zijn beurt de ontwikkeling van krachtige en selectieve remmers van NNMT gestimuleerd, waarbij in de afgelopen vijf jaar een toenemend aantal verbindingen is onthuld. Hoofdstuk 1 geeft een uitgebreid overzicht van de huidige status van de ontwikkeling van NNMT remmers, relevante in vitro en in vivo studies, en een bespreking van de uitdagingen waar men bij de ontwikkeling van NNMT remmers voor staat. In hoofdstuk 2 werd een gevarieerde bibliotheek van remmers geprepareerd om de verschillende gebieden van de NNMT bindingsplaats te onderzoeken. In hoofdstuk 3 wordt verslag gedaan van een scaffold-hopping strategie om nieuwe en krachtige bisubstraat NNMT remmers te genereren. In hoofdstuk 4 wordt een prodrug strategie beschreven om de polariteit van verbinding 17u te verlagen en de cellulaire activiteit te verbeteren. In hoofdstuk 5 wordt het ontwerp en de synthese beschreven van een bibliotheek van verbindingen die zich richten op de covalente interactie met actieve site cysteïne en serine residuen met behulp van verschillende functionele groepen. Show less
Nicotinamide N-methyltransferase (NNMT) methylates nicotinamide (vitamin B3) to generate 1-methylnicotinamide (MNA). NNMT overexpression has been linked to a variety of diseases, most prominently... Show moreNicotinamide N-methyltransferase (NNMT) methylates nicotinamide (vitamin B3) to generate 1-methylnicotinamide (MNA). NNMT overexpression has been linked to a variety of diseases, most prominently human cancers, indicating its potential as a therapeutic target. The development of small-molecule NNMT inhibitors has gained interest in recent years, with the most potent inhibitors sharing structural features based on elements of the nicotinamide substrate and the S-adenosyl-l-methionine (SAM) cofactor. We here report the development of new bisubstrate inhibitors that include electron-deficient aromatic groups to mimic the nicotinamide moiety. In addition, a trans-alkene linker was found to be optimal for connecting the substrate and cofactor mimics in these inhibitors. The most potent NNMT inhibitor identified exhibits an IC50 value of 3.7 nM, placing it among the most active NNMT inhibitors reported to date. Complementary analytical techniques, modeling studies, and cell-based assays provide insights into the binding mode, affinity, and selectivity of these inhibitors. Show less
Microglia play a critical role in maintaining neural function. While microglial activity follows a circadian rhythm, it is not clear how this intrinsic clock relates to their function, especially... Show moreMicroglia play a critical role in maintaining neural function. While microglial activity follows a circadian rhythm, it is not clear how this intrinsic clock relates to their function, especially in stimulated conditions such as in the control of systemic energy homeostasis or memory formation. In this study, we found that microglia-specific knock-down of the core clock gene, Bmal1, resulted in increased microglial phagocytosis in mice subjected to high-fat diet (HFD)-induced metabolic stress and likewise among mice engaged in critical cognitive processes. Enhanced microglial phagocytosis was associated with significant retention of pro-opiomelanocortin (POMC)-immunoreactivity in the mediobasal hypothalamus in mice on a HFD as well as the formation of mature spines in the hippocampus during the learning process. This response ultimately protected mice from HFD-induced obesity and resulted in improved performance on memory tests. We conclude that loss of the rigorous control implemented by the intrinsic clock machinery increases the extent to which microglial phagocytosis can be triggered by neighboring neurons under metabolic stress or during memory formation. Taken together, microglial responses associated with loss of Bmal1 serve to ensure a healthier microenvironment for neighboring neurons in the setting of an adaptive response. Thus, microglial Bmal1 may be an important therapeutic target for metabolic and cognitive disorders with relevance to psychiatric disease. Show less
Learning to read a second language (L2) can pose a great challenge for children who have already been struggling to read in their first language (L1). Moreover, it is not clear whether, to what... Show moreLearning to read a second language (L2) can pose a great challenge for children who have already been struggling to read in their first language (L1). Moreover, it is not clear whether, to what extent, and under what circumstances L1 reading difficulty increases the risk of L2 reading difficulty. This study investigated Chinese (L1) and English (L2) reading skills in a large representative sample of 1,824 Chinese–English bilingual children in Grades 4 and 5 from both urban and rural schools in Beijing. We examined the prevalence of reading difficulty in Chinese only (poor Chinese readers, PC), English only (poor English readers, PE), and both Chinese and English (poor bilingual readers, PB) and calculated the co-occurrence, that is, the chances of becoming a poor reader in English given that the child was already a poor reader in Chinese. We then conducted a multinomial logistic regression analysis and compared the prevalence of PC, PE, and PB between children in Grade 4 versus Grade 5, in urban versus rural areas, and in boys versus girls. Results showed that compared to girls, boys demonstrated significantly higher risk of PC, PE, and PB. Meanwhile, compared to the 5th graders, the 4th graders demonstrated significantly higher risk of PC and PB. In addition, children enrolled in the urban schools were more likely to become better second language readers, thus leading to a concerning rural–urban gap in the prevalence of L2 reading difficulty. Finally, among these Chinese–English bilingual children, regardless of sex and school location, poor reading skill in Chinese significantly increased the risk of also being a poor English reader, with a considerable and stable co-occurrence of approximately 36%. In sum, this study suggests that despite striking differences between alphabetic and logographic writing systems, L1 reading difficulty still significantly increases the risk of L2 reading difficulty. This indicates the shared meta-linguistic skills in reading different writing systems and the importance of understanding the universality and the interdependent relationship of reading between different writing systems. Furthermore, the male disadvantage (in both L1 and L2) and the urban–rural gap (in L2) found in the prevalence of reading difficulty calls for special attention to disadvantaged populations in educational practice. Show less
Bayer, S.; Zhai, Z.W.; Strumia, M.; Tong, X.G.; Gao, Y.; Staring, M.; ... ; Ravikumar, N. 2019
Purpose Morphological changes to anatomy resulting from invasive surgical procedures or pathology, typically alter the surrounding vasculature. This makes it useful as a descriptor for feature... Show morePurpose Morphological changes to anatomy resulting from invasive surgical procedures or pathology, typically alter the surrounding vasculature. This makes it useful as a descriptor for feature-driven image registration in various clinical applications. However, registration of vasculature remains challenging, as vessels often differ in size and shape, and may even miss branches, due to surgical interventions or pathological changes. Furthermore, existing vessel registration methods are typically designed for a specific application. To address this limitation, we propose a generic vessel registration approach useful for a variety of clinical applications, involving different anatomical regions. Methods A probabilistic registration framework based on a hybrid mixture model, with a refinement mechanism to identify missing branches (denoted as HdMM+) during vasculature matching, is introduced. Vascular structures are represented as 6-dimensional hybrid point sets comprising spatial positions and centerline orientations, using Student's t-distributions to model the former and Watson distributions for the latter. Results The proposed framework is evaluated for intraoperative brain shift compensation, and monitoring changes in pulmonary vasculature resulting from chronic lung disease. Registration accuracy is validated using both synthetic and patient data. Our results demonstrate, HdMM+ is able to reduce more than 85% of the initial error for both applications, and outperforms the state-of-the-art point-based registration methods such as coherent point drift and Student's t-distribution mixture model, in terms of mean surface distance, modified Hausdorff distance, Dice and Jaccard scores. Conclusion The proposed registration framework models complex vascular structures using a hybrid representation of vessel centerlines, and accommodates intricate variations in vascular morphology. Furthermore, it is generic and flexible in its design, enabling its use in a variety of clinical applications. Show less
Nicotinamide N-methyltransferase (NNMT) catalyzes the methylation of nicotinamide to form N-methylnicotinamide. Overexpression of NNMT is associated with a variety of diseases, including a number... Show moreNicotinamide N-methyltransferase (NNMT) catalyzes the methylation of nicotinamide to form N-methylnicotinamide. Overexpression of NNMT is associated with a variety of diseases, including a number of cancers and metabolic disorders, suggesting a role for NNMT as a potential therapeutic target. By structural modification of a lead NNMT inhibitor previously developed in our group, we prepared a diverse library of inhibitors to probe the different regions of the enzyme’s active site. This investigation revealed that incorporation of a naphthalene moiety, intended to bind the hydrophobic nicotinamide binding pocket via π–π stacking interactions, significantly increases the activity of bisubstrate-like NNMT inhibitors (half-maximal inhibitory concentration 1.41 μM). These findings are further supported by isothermal titration calorimetry binding assays as well as modeling studies. The most active NNMT inhibitor identified in the present study demonstrated a dose-dependent inhibitory effect on the cell proliferation of the HSC-2 human oral cancer cell line. Show less
Background: The potential survival benefits of adding radiotherapy to systemic therapy for esophageal cancer patients with oligometastases are unknown.Methods: In this retrospective analysis,... Show moreBackground: The potential survival benefits of adding radiotherapy to systemic therapy for esophageal cancer patients with oligometastases are unknown.Methods: In this retrospective analysis, patients with stage IV esophageal cancer (according to the American Joint Committee on Cancer Seventh edition staging system) with <= 3 metastases who underwent chemotherapy with cisplatin/paclitaxel between 2012 and 2015 were identified. Patients received chemotherapy (CT) alone vs. concurrent chemoradiotherapy (CCRT) to all metastases.Results: Of 461 patients, 97% had squamous cell cancer. One hundred and ninety-six patients (42.5%) received CCRT and 265 (57.5%) underwent CT alone. At week 8, there were 3 (1.5%) complete responses (CR) and 95 (48.5%) partial responses (PR) in the CCRT group, compared to 3 (1.1%) CR and 102 (38.5%) PR in the CT alone group. The overall rate of improvement in dysphagia score was noted in 78.5% of patients in the CCRT group versus 61.5% in the CT alone group (P=0.014). A statistically significant difference was demonstrated in disease control rate between the two groups (81.6% vs. 64.5%, P<0.001). Patients who underwent CCRT had superior median PFS and a trend toward longer median OS compared to those receiving CT alone (8.7 vs. 7.3 months, P=0.002 and 16.8 vs. 14.8 months, P=0.056, respectively). The median OS was 19.3 months in patients who achieved CR/PR, compared to 14.9 months and 9.6 months for patients who had stable disease and progressive disease, respectively (P<0.001).Conclusions: Compared to chemotherapy alone, chemoradiation to all sites in patients with esophageal cancer with <= 3 metastases may lead to a modest increase in PFS and a trend toward longer OS. Further investigation of optimal integration of radiotherapy and chemotherapy in these patients is warranted. Show less
This thesis describes the design, characterization and application of dextran based crosslinked network. Dextran, a neutral and hydrophilic polysaccharide, was functionalized with maleimide or... Show moreThis thesis describes the design, characterization and application of dextran based crosslinked network. Dextran, a neutral and hydrophilic polysaccharide, was functionalized with maleimide or vinyl sulfone groups which are able to form covalent bonds with nucleophilic thiols via a thiol-Michael addition reaction. The functionalized dextran polymers are liable to be crosslinked to generate 3D networks. Novel drug delivery platforms, including dextran-albumin hydrogels and dextran-poly(ethylene glycol)-albumin hydrogels, were established in which human serum albumin acts simultaneously as an affinity-based drug carrier and crosslinker. The obtained drug delivery platforms showed high drug loading efficiency and demonstrated sustained release of drug molecules. This thesis also explores emerging applications of hydrogels. New method to form giant unilamellar vesicles was established by assisting the hydration process of a lipid film with a dextran-poly(ethylene glycol) hydrogel film. Using this approach, polymer and additive-free GUVs can be prepared rapidly in high yield under physiological ionic strength conditions. Show less
Tu, J.; Bussmann, J.; Du, G.; Gao, Y.; Bouwstra, J.A.; Kros, A. 2018
