Eva Bagyinszky

The genetics of Alzheimer’s disease

Alzheimer’s disease (AD) is a complex and heterogeneous neurodegenerative disorder, classified as either early onset (under 65 years of age), or late onset (over 65 years of age). Three main genes are involved in early onset AD: amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2). The apolipoprotein E (APOE) E4 allele has been found to be a main risk factor for late-onset Alzheimer’s disease. Additionally, genome-wide association studies (GWASs) have identified several genes that might be potential risk factors for AD, including clusterin (CLU), complement receptor 1 (CR1), phosphatidylinositol binding clathrin assembly protein (PICALM), and sortilin-related receptor (SORL1). Recent studies have discovered additional novel genes that might be involved in late-onset AD, such as triggering receptor expressed on myeloid cells 2 (TREM2) and cluster of differentiation 33 (CD33). Identification of new AD-related genes is important for better understanding of the pathomechanisms leading to neurodegeneration. Since the differential diagnoses of neurodegenerative disorders are difficult, especially in the early stages, genetic testing is essential for diagnostic processes. Next-generation sequencing studies have been successfully used for detecting mutations, monitoring the epigenetic changes, and analyzing transcriptomes. These studies may be a promising approach toward understanding the complete genetic mechanisms of diverse genetic disorders such as AD.

Role of inflammatory molecules in the Alzheimer's disease progression and diagnosis

Alzheimers disease (AD) is a complex disorder and the most common form of neurodegenerative dementia. Several genetic, environmental, and physiological factors, including inflammations and metabolic influences, are involved in the progression of AD. Inflammations are composed of complicated networks of many chemokines and cytokines with diverse cells. Inflammatory molecules are needed for the protection against pathogens, and maintaining their balances is important for normal physiological function. Recent studies demonstrated that inflammation may be involved in neurodegenerative dementia. Cellular immune components, such as microglia or astrocytes, mediate the release of inflammatory molecules, including tumor necrosis factor, growth factors, adhesion molecules, or chemokines. Over- and underexpression of pro- and anti-inflammatory molecules, respectively, may result in neuroinflammation and thus disease initiation and progression. In addition, levels of several inflammatory factors were reported to be altered in the brain or bodily fluids of patients with AD, reflecting their neuropathological changes. Therefore, simultaneous detection of several inflammatory molecules in the early or pre-symptomatic stage may improve the early diagnosis of AD. Further studies are needed to determine, how induction or inhibition of inflammatory factors could be used for AD therapies. This review summarizes the role or possible role of immune cells and inflammatory molecules in disease progression or prevention.

Role of apolipoprotein E in neurodegenerative diseases.

Apolipoprotein E (APOE) is a lipid-transport protein abundantly expressed in most neurons in the central nervous system. APOE-dependent alterations of the endocytic pathway can affect different functions. APOE binds to cell-surface receptors to deliver lipids and to the hydrophobic amyloid-β peptide, regulating amyloid-β aggregations and clearances in the brain. Several APOE isoforms with major structural differences were discovered and shown to influence the brain lipid transport, glucose metabolism, neuronal signaling, neuroinflammation, and mitochondrial function. This review will summarize the updated research progress on APOE functions and its role in Alzheimer’s disease, Parkinson’s disease, cardiovascular diseases, multiple sclerosis, type 2 diabetes mellitus, Type III hyperlipoproteinemia, vascular dementia, and ischemic stroke. Understanding the mutations in APOE, their structural properties, and their isoforms is important to determine its role in various diseases and to advance the development of therapeutic strategies. Targeting APOE may be a potential approach for diagnosis, risk assessment, prevention, and treatment of various neurodegenerative and cardiovascular diseases in humans.

A novel PSEN1 H163P mutation in a patient with early-onset Alzheimer's disease: Clinical, neuroimaging, and neuropathological findings

We report a novel presenilin 1 gene (PSEN1) mutation (H163P) in a patient with sporadic early-onset Alzheimers disease. Clinical, molecular, and neuropathological examinations were performed on an index patient, who presented at the age of 34 years with depression and memory disturbances. At the age of 36 years, she exhibited seizures and myoclonus, cerebellar ataxia, and Parkinsonism. A novel mutation at codon 163 was found in PSEN1, which was changed from histidine to proline. Severe atrophy was noted in the frontal and temporal lobes of the brain. A histopathological examination of the frontal cortex revealed senile plaques and severe neurofibrillary tangles. PSEN1 codon 163 could be a mutational hot spot in early-onset Alzheimers disease, and may result in a homogeneous phenotype similar to that of other patients with codon-163 mutations; thus, widening the spectrum of PSEN1 codon-163-linked phenotypes.

Diagnostic methods and biomarkers for Alzheimer’s disease

Alzheimer’s disease (AD) is the most frequently occurring and intensively investigated neurodegenerative disorder, which is associated with extracellular senile plaques and intracellular neurofibrillary tangles. In this review, AD related diagnostic strategies and the potential biomarkers of AD will be discussed. Several proteomics methods were developed for disease diagnosis, such as ELISA, MALDI-TOF, SELDI-TOF, and 2 D-electrophoresis. Imaging technologies, such as MRI and PET analyses, are also important, since they could directly show the changes in the brain, associated with dementia progression. MRI technologies might estimate the presence and degree of neurodegeneration by identification and quantification of atrophy. PET could reflect the metabolic changes in the brain by various radioactive molecules (tracers). Along with neuropsycoanalysis of behavioral changes, the progression of dementia can be characterized with biochemical changes in brain metabolisms, in addition to fluctuations in many inflammatory mediators in the cerebral spinal fluid (CSF), blood and in other bodily fluids. These biochemical changes in the brain and other body fluids can be initiated before the appearance of AD symptoms. There is no specific marker for AD along with other dementia, but the combination of different markers may predict the disease progression more accurately. Monitoring the changes in their levels in brain, CSF, blood and body fluids with biomarkers in early disease stages might improve the diagnosis and therapies. Several molecules were established as successful biomarkers for AD diagnosis. Ratio of Abeta42/40 became an important AD marker, which could reflect the disease-associated changes in the blood plasma and CSF. Additional markers were available in blood, such as apolipoprotein E or inflammatory molecules. In CSF, the Abeta42, Tau or phospho-tau could be the most successful biomarker for AD progression. Several new biomarkers and diagnostic approaches were developed for differentiating AD from other forms of dementia. It should be important to predict the AD progression prior to the development of clinical symptoms. Above all, the improvement of above strategies, especially with diverse biomarkers, should support the precise diagnosis of AD, greatly enhancing both AD therapies and preventative measures.

Gene panels and primers for next generation sequencing studies on neurodegenerative disorders

Several types of neurodegenerative diseases were described, including Alzheimer’s disease (AD), frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), prion disease, and Parkinson’s disease (PD). Since the potential treatment strategies of these disorders might be more successful in the pre-clinical stages than in the actual clinical setup, new diagnostic methods were needed. The involvement of heredity in neurodegenerative disorders was established, but several neurodegenerative disorders such as AD, PD, ALS, FTD and Huntington’s disease (HD) are highly complex. Sanger sequencing was used to detect mutations that are causative or risk factors for diseases. The problem with standard sequencing is its high cost and low speed. Recently, next generation sequencing (NGS) strategies were developed, which could provide a more complex genetic analysis of patients with neurodegenerative diseases. In this study, 50 genes were selected, which were established as causative genes for neurodegenerative diseases, but we also included several risk factor genes and candidate genes. Primers (maximum 400-bp length) were designed to screen for mutations and variants in them. We plan to use these primers for NGS screening to create a more detailed genetic profile for these patients. This study could enhance disease diagnosis and would be also helpful in estimating the risk for disease onset in the future.

Analysis of Cerebrospinal Fluid and [11C]PIB PET Biomarkers for Alzheimer’s Disease with Updated Protocols

BACKGROUND Recently, a Korean research group suggested a consensus protocol, based on the Alzheimers Disease Neuroimaging Initiative study protocol but with modifications for minimizing the confounding factors, for the evaluation of cerebrospinal fluid (CSF) biomarkers. OBJECTIVE Here, we analyzed fluid and imaging biomarkers of Alzheimers disease (AD) in Korean population. We used the updated protocol to propose a more accurate CSF biomarker value for the diagnosis of AD. METHODS Twenty-seven patients with AD and 30 cognitively normal controls (NC) were enrolled. CSF was collected from 55 subjects (patients with AD = 26, NC = 29) following the Korea consensus protocol. CSF biomarkers were measured using the INNO-BIA AlzBio3 immunoassay, and Pittsburgh compound B (PIB) positron emission tomography (PET) scans were also performed. RESULTS The cutoff values of CSF amyloid beta 1-42 (Aβ42), total tau (t-Tau), and phosphorylated tau (p-Tau) proteins were 357.1 pg/ml, 83.35 pg/ml, and 38.00 pg/ml, respectively. The cutoff values of CSF t-Tau/Aβ42 and p-Tau/Aβ42 ratio- were 0.210 (sensitivity 100%, specificity 86.21%) and 0.1350 (sensitivity 88.46%, specificity of 92.86%). The concordance rate with PIB-PET was higher using the CSF t-Tau/Aβ42 ratio (κ= 0.849, CI 0.71-0.99) than CSF Aβ42 alone (κ= 0.703, CI 0.51-0.89). CONCLUSIONS Here, we improved controversial factors associated with the previous CSF study protocol and suggested a new cutoff value for the diagnosis of AD. Our results showed good diagnostic performance for differentiation of AD. Thus, we expect our findings could be a cornerstone in the establishment and clinical application of biomarkers for AD diagnosis.

Characterization of inflammatory biomarkers and candidates for diagnosis of Alzheimer’s disease

Alzheimer’s disease (AD) is the most common form of neurodegenerative dementia, several genetic, non-genetic, and environmental factors could be involved in disease progression. Association was suggested between inflammation and AD progression. Since neuroinflammation can be involved in neurodegeneration, studies suggested that several inflammatory molecules (cytokines) might enhance the inflammation or suppress the immune system. Altered cytokine levels might reflect the neuropathological changes in patients. This review summarizes the validated and potential inflammatory biomarkers in AD, and it is focusing on interleukins (ILs), interferons (IFNs) and tumor necrosis factors (TNFs). Interleukins have dual role in the AD progression: Several ILs (such as IL1, IL6 or IL8) can promote the disease-associated inflammatory pathways, while the others (such as IL1ra, IL4 or IL10) might be involved in the neuroprotection and dementia prevention. Conflicting reports are available on the role of IFNs (IFNα, IFNβ and IFNγ) in AD progression. Several studies reported that they might have neuroprotective effects, but the others suggested that they can contribute to neurotoxiciy by inducing the pro-inflammatory cytokines. TNFα can be expressed with other pro-inflammatory cytokines and induce the neurodegeneration. Both TNFα and TNFR were suggested as successful markers for AD and dementia. Several cytokines can be used to distinguish the AD patients from the healthy individuals, since their expression might be up-or down-regulated in the brain of AD patients. Some cytokines might be useful to measure the severity of the disorder. Overproduction of pro-inflammatory molecules could result neuroinflammation and enhance the neurotoxicity. Inhibiting the pro-inflammatory- and/ or inducing the anti-inflammatory molecules might improve the therapies for AD.

Probable novel PSEN2 Val214Leu mutation in Alzheimer’s disease supported by structural prediction

BackgroundPSEN2 mutations are rare variants, and fewer than 30 different PSEN2 mutations have been found. So far, it has not been reported in Asia.Case presentationPSEN2 mutation at codon 214 for predicting a valine to leucine substitution was found in a 70-year-old woman, who showed a dementia of the Alzheimer type. We did not find the mutation in 614 control chromosomes. We also predicted the structures of presenilin 2 protein with native Val 214 residue and Leu 214 mutation, which revealed significant structural changes in the region.ConclusionIt could be a novel mutation verified with structural prediction in a patient with Alzheimer’s disease.

A genetic screen of the mutations in the Korean patients with early-onset Alzheimer’s disease

Early-onset Alzheimer’s disease (EOAD) has distinct clinical characteristics in comparison to late-onset Alzheimer’s disease (LOAD). The genetic contribution is suggested to be more potent in EOAD. However, the frequency of causative mutations in EOAD could be variable depending on studies. Moreover, no mutation screening study has been performed yet employing large population in Korea. Previously, we reported that the rate of family history of dementia in EOAD patients was 18.7% in a nationwide hospital-based cohort study, the Clinical Research Center for Dementia of South Korea (CREDOS) study. This rate is much lower than in other countries and is even comparable to the frequency of LOAD patients in our country. To understand the genetic characteristics of EOAD in Korea, we screened the common Alzheimer’s disease (AD) mutations in the consecutive EOAD subjects from the CREDOS study from April 2012 to February 2014. We checked the sequence of APP (exons 16–17), PSEN1 (exons 3–12), and PSEN2 (exons 3–12) genes. We identified different causative or probable pathogenic AD mutations, PSEN1 T116I, PSEN1 L226F, and PSEN2 V214L, employing 24 EOAD subjects with a family history and 80 without a family history of dementia. PSEN1 T116I case demonstrated autosomal dominant trait of inheritance, with at least 11 affected individuals over 2 generations. However, there was no family history of dementia within first-degree relation in PSEN1 L226F and PSEN2 V214L cases. Approximately, 55.7% of the EOAD subjects had APOE ε4 allele, while none of the mutation-carrying subjects had the allele. The frequency of genetic mutation in this study is lower compared to the studies from other countries. The study design that was based on nationwide cohort, which minimizes selection bias, is thought to be one of the contributors to the lower frequency of genetic mutation. However, the possibility of the greater likeliness of earlier onset of sporadic AD in Korea cannot be excluded. We suggest early AD onset and not carrying APOE ε4 allele are more reliable factors for predicting an induced genetic mutation than the presence of the family history in Korean EOAD population.