How Do Different Forms of Vascular Brain Injury Relate to Cognition in a Memory Clinic Population: The TRACE-VCI Study

Background: Memory clinic patients frequently present with different forms of vascular brain injury due to different etiologies, often co-occurring with Alzheimer’s disease (AD) pathology. / Objective: We studied how cognition was affected by different forms of vascular brain injury, possibly in interplay with AD pathology. / Methods: We included 860 memory clinic patients with vascular brain injury on magnetic resonance imaging (MRI), receiving a standardized evaluation including cerebrospinal fluid (CSF) biomarker analyses (n = 541). The cognitive profile of patients with different forms of vascular brain injury on MRI (moderate/severe white matter hyperintensities (WMH) (n = 398), microbleeds (n = 368), lacunar (n = 188) and non-lacunar (n = 96) infarct(s), macrobleeds (n = 16)) was assessed by: 1) comparison of all these different forms of vascular brain injury with a reference group (patients with only mild WMH (n = 205) without other forms of vascular brain injury), using linear regression analyses also stratified for CSF biomarker AD profile and 2) multivariate linear regression analysis. / Results: The cognitive profile was remarkably similar across groups. Compared to the reference group effect sizes on all domains were <0.2 with narrow 95% confidence intervals, except for non-lacunar infarcts on information processing speed (age, sex, and education adjusted mean difference from reference group (β: – 0.26, p = 0.05). Results were similar in the presence (n = 300) or absence (n = 241) of biomarker co-occurring AD pathology. In multivariate linear regression analysis, higher WMH burden was related to a slightly worse performance on attention and executive functioning (β: – 0.08, p = 0.02) and working memory (β: – 0.08, p = 0.04). / Conclusion: Although different forms of vascular brain injury have different etiologies and different patterns of cerebral damage, they show a largely similar cognitive profile in memory clinic patients regardless of co-occurring AD pathology

Identification of regulatory variants associated with genetic susceptibility to meningococcal disease

Non-coding genetic variants play an important role in driving susceptibility to complex diseases but their characterization remains challenging. Here, we employed a novel approach to interrogate the genetic risk of such polymorphisms in a more systematic way by targeting specific regulatory regions relevant for the phenotype studied. We applied this method to meningococcal disease susceptibility, using the DNA binding pattern of RELA - a NF-kB subunit, master regulator of the response to infection - under bacterial stimuli in nasopharyngeal epithelial cells. We designed a custom panel to cover these RELA binding sites and used it for targeted sequencing in cases and controls. Variant calling and association analysis were performed followed by validation of candidate polymorphisms by genotyping in three independent cohorts. We identified two new polymorphisms, rs4823231 and rs11913168, showing signs of association with meningococcal disease susceptibility. In addition, using our genomic data as well as publicly available resources, we found evidences for these SNPs to have potential regulatory effects on ATXN10 and LIF genes respectively. The variants and related candidate genes are relevant for infectious diseases and may have important contribution for meningococcal disease pathology. Finally, we described a novel genetic association approach that could be applied to other phenotypes

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Plasma lipid profiles discriminate bacterial from viral infection in febrile children

Fever is the most common reason that children present to Emergency Departments. Clinical signs and symptoms suggestive of bacterial infection ar

Wnt target gene analysis in colorectal cancer and intestinal stem cells

The intestinal epithelium is a specialized simple epithelium that lines the gut and performs primary functions of digestion, absorption and forms a barrier against luminal pathogens. It is organized in invaginations called crypts and finger-like protrusions called villi. The crypts harbor proliferating stem cells and their transit amplifying daughter cells, while villi are covered with terminally differentiated cell types with specialized functions. Malignant transformation of intestinal epithelium is almost invariably initiated by activating Wnt pathway mutations. As a common result, ?-catenin accumulates in the nucleus, and constitutively binds to the transcription factor TCF4, resulting in transcriptional activation of Wnt/TCF4 target genes. This in turn initiates transformation of intestinal epithelial cells. Physiologically, the Wnt pathway is essential for the maintenance of crypt progenitor proliferation. Because of the intimate connection between Wnt signaling and intestinal biology, we have attempted to unravel the TCF4 target gene program activated by this pathway in crypts and colorectal tumors. In chapter 2 and 3 we performed expression profiling studies of colorectal cancer cell lines carrying an inducible block of the Wnt signaling pathway. The differentially expressed, ?-catenin/TCF responsive, genes were compared with genes up-regulated in prospectively collected colorectal adenomas and/or carcinomas compared with normal mucosa from the same individuals. This resulted in the “intestinal Wnt signature”. The Wnt target genes identified through this approach can be either direct regulated by the TCF/ ?-catenin complex or through intermediate transcription factor(s). In chapter 4, we identify direct Wnt targets based on chromatin immunoprecipitation (ChIP)-coupled DNA microarray analysis (ChIP-on-chip). We immunoprecipitated chromatin-bound TCF4 from LS174T colorectal cancer cells, and identified the bound DNA sequences through hybridization on DNA microarrays. Testing of these TCF4-bound regions in luciferase-based reporter gene assays demonstrated that these DNA sequences often behave as Wnt-controlled enhancers or promoters. In chapter 5, we have determined a gene signature for intestinal stem cells. One of the genes was the Wnt target gene Ascl2. The Ascl2 gene encodes a bHLH transcription factor with an unusually restricted expression pattern, i.e. its expression is predominantly detected in extraembryonic tissues and in intestinal epithelium. Transgenic expression of the Ascl2 transcription factor throughout the intestinal epithelium induces crypt hyperplasia and de novo crypt formation on villi. Induced deletion of the Ascl2 gene in adult small intestine leads to disappearance of CBC stem cells within days. The combined results from these gain- and loss-of-function experiments imply that Ascl2 plays an essential role in the maintenance of adult intestinal stem cells. In chapter 6 and 7 we describe the generation of various new mouse models that will be used for further characterization of the intestinal epithelium. Two of the generated models will be used for characterization of intestinal stem cells. The others will be used to study the function of the Regenerating (Reg) gene family in the intestine

Correcting for the Absence of a Gold Standard Improves Diagnostic Accuracy of Biomarkers in Alzheimer's Disease

Background: Studies investigating the diagnostic accuracy of biomarkers for Alzheimer's disease (AD) are typically performed using the clinical diagnosis or amyloid-β positron emission tomography as the reference test. However, neither can be considered a gold standard or a perfect reference test for AD. Not accounting for errors in the reference test is known to cause bias in the diagnostic accuracy of biomarkers. Objective: To determine the diagnostic accuracy of AD biomarkers while taking the imperfectness of the reference test into account. Methods: To determine the diagnostic accuracy ofADbiomarkers and taking the imperfectness of the reference test into account, we have developed a Bayesian method. This method establishes the biomarkers' true value in predicting the AD-pathology status by combining the reference test and the biomarker data with available information on the reliability of the reference test. The new methodology was applied to two clinical datasets to establish the joint accuracy of three cerebrospinal fluid biomarkers (amyloid-

Ascl2 acts as an R-spondin/Wnt-responsive switch to control stemness in intestinal crypts

The Wnt signaling pathway controls stem cell identity in the intestinal epithelium and in many other adult organs. The transcription factor Ascl2 (a Wnt target gene) is a master regulator of intestinal stem cell identity. It is unclear how the continuous Wnt gradient along the crypt axis is translated into discrete expression of Ascl2 and discrete specification of stem cells at crypt bottoms. We show that (1) Ascl2 is regulated in a direct autoactivatory loop, leading to a distinct on/off expression pattern, and (2) Wnt/R-spondin can activate this regulatory loop. This mechanism interprets the Wnt levels in the intestinal crypt and translates the continuous Wnt signal into a discrete Ascl2 "on" or "off" decision. In turn, Ascl2, together with {beta}-catenin/Tcf, activates the genes fundamental to the stem cell state. In this manner, Ascl2 forms a transcriptional switch that is both Wnt responsive and Wnt dependent to define stem cell identity