Synaptic dysfunction and degeneration are central events in Alzheimer’s disease (AD) pathophysiology that are thought to occur early in disease progression. Synaptic pathology may be studied by examining protein biomarkers specific for different synaptic elements. We recently showed that the dendritic protein neurogranin (Ng), including the endogenous Ng peptide 48 to 76 (Ng48–76), is markedly increased in cerebrospinal fluid (CSF) in AD and that Ng48–76 is the dominant peptide in human brain tissue. The aim of this study was to characterize Ng in plasma and CSF using mass spectrometry and to investigate the performance of plasma Ng as an AD biomarker.
Paired plasma and CSF samples from patients with AD (n = 25) and healthy controls (n = 20) were analyzed in parallel using an immunoassay developed in-house on the Meso Scale Discovery platform and hybrid immunoaffinity-mass spectrometry (HI-MS). A second plasma material from patients with AD (n = 13) and healthy controls (n = 17) was also analyzed with HI-MS. High-resolution mass spectrometry was used for identification of endogenous plasma Ng peptides.
Ng in human plasma is present as several endogenous peptides. Of the 16 endogenous Ng peptides identified, seven were unique for plasma and not detectable in CSF. However, Ng48–76 was not present in plasma. CSF Ng was significantly increased in AD compared with controls (P < 0.0001), whereas the plasma Ng levels were similar between the groups in both studies. Plasma and CSF Ng levels showed no correlation. CSF Ng was stable during storage at −20°C for up to 2 days, and no de novo generation of peptides were detected.
For the first time, to our knowledge, we have identified several endogenous Ng peptides in human plasma. In agreement with previous studies, we show that CSF Ng is significantly increased in AD as compared with healthy controls. The origin of Ng in plasma and its possible use as a biomarker need to be further investigated. The results suggest that CSF Ng, in particular Ng48–76, might reflect the neurodegenerative processes within the brain, indicating a role for Ng as a potential novel clinical biomarker for synaptic function in AD.
Electronic supplementary material
The online version of this article (doi:10.1186/s13195-015-0124-3) contains supplementary material, which is available to authorized users.
Loss-of-function mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene are associated with decreased catalytic activity of acid sphingomyelinase (ASM) and are the cause of the autosomal recessive lysosomal storage disorder Niemann-Pick disease (NPD) types A and B. Currently, >100 missense mutations in SMPD1 are listed in the Human Gene Mutation Database. However, not every sequence variation in SMPD1 is detrimental and gives rise to NPD. We have analysed several alleged SMPD1 missense mutations mentioned in a recent publication and found them to be common variants of SMPD1 that give rise to normal in vivo and in vitro ASM activity. (Comment on Manshadi et al. Int. J. Mol. Sci.
2015, 16, 6668–6676).
gene variant; missense mutation; Niemann-Pick disease; polymorphism; sphingomyelin phosphodiesterase
White matter (WM) magnetic resonance imaging (MRI) hyperintensities are common in Alzheimer’s disease (AD), but their pathophysiological relevance and relationship to genetic factors are unclear. In the present study, we investigated potential apolipoprotein E (APOE)-dependent effects on the extent and cognitive impact of WM hyperintensities in patients with AD.
WM hyperintensity volume on fluid-attenuated inversion recovery images of 201 patients with AD (128 carriers and 73 non-carriers of the APOE ε4 risk allele) was determined globally as well as regionally with voxel-based lesion mapping. Clinical, neuropsychological and MRI data were collected from prospective multicenter trials conducted by the German Dementia Competence Network.
WM hyperintensity volume was significantly greater in non-carriers of the APOE ε4 allele. Lesion distribution was similar among ε4 carriers and non-carriers. Only ε4 non-carriers showed a correlation between lesion volume and cognitive performance.
The current findings indicate an increased prevalence of WM hyperintensities in non-carriers compared with carriers of the APOE ε4 allele among patients with AD. This is consistent with a possibly more pronounced contribution of heterogeneous vascular risk factors to WM damage and cognitive impairment in patients with AD without APOE ε4-mediated risk.
Electronic supplementary material
The online version of this article (doi:10.1186/s13195-015-0111-8) contains supplementary material, which is available to authorized users.
The internet age bears new challenges that include health risks. It is agreed that excessive internet use may reach pathological levels. However, the concept of internet addiction lacks specificity and, therefore, warrants studies on its diagnostic and etiologic classification. This study was conducted to characterize the novel DSM-5 criteria for internet gaming disorder and the adapted criteria for the “social network disorder”. Based on the established association of handedness and substance use disorders, we also explored whether internet use related to laterality. For this study, 3,287 volunteers participated in the online survey and gave particulars concerning their internet use in general, internet gaming and use of social networks, laterality markers (hand, foot, eye, ear, rotational preference in gymnastics, and head turning asymmetry) and health status. Of the participants, 1.1 % fulfilled the criteria for internet gaming disorder, and 1.8 % fulfilled the criteria for social network disorder. The applied criteria were highly correlated with the time spent on the respective internet activities (p < 4 × 10−56). The analyses of comorbidity and working hours support the thresholds of 5/9 criteria and ≥30 h/week spent on the internet for the classification as pathological (p < 5 × 10−2). Moreover, we found that left-handedness related to more affirmed criteria and longer times spent on social networks (p ≤ 4 × 10−2). The provided criteria proved to be user-friendly, comprehensible and well accepted. The results contribute to a better understanding of pathological internet gaming and social network use and provide evidence that biological markers of substance use disorders are involved in internet addiction.
Internet addiction; Internet gaming disorder; Social network; Laterality; Handedness
Originally developed for the treatment of epilepsy, pregabalin has become a compound with a wide spectrum of indications comprising anxiety disorders and chronic pain and is therefore largely prescribed. Thus, it is important for clinicians to be aware of rare, but serious adverse effects. The following report illustrates the case of a 20-year-old male with a severe depressive syndrome following pregabalin medication which even led to a suicide attempt.
Depression; Anticonvulsants; Suicide; Pregabalin
Rare mutations in AβPP, PSEN1, and PSEN2 cause uncommon early onset forms of Alzheimer’s disease (AD), and common variants in MAPT are associated with risk of other neurodegenerative disorders. We sought to establish whether common genetic variation in these genes confer risk to the common form of AD which occurs later in life (>65 years). We therefore tested single-nucleotide polymorphisms at these loci for association with late-onset AD (LOAD) in a large case-control sample consisting of 3,940 cases and 13,373 controls. Single-marker analysis did not identify any variants that reached genome-wide significance, a result which is supported by other recent genome-wide association studies. However, we did observe a significant association at the MAPT locus using a gene-wide approach (p = 0.009). We also observed suggestive association between AD and the marker rs9468, which defines the H1 haplotype, an extended haplotype that spans the MAPT gene and has previously been implicated in other neurodegenerative disorders including Parkinson’s disease, progressive supranuclear palsy, and corticobasal degeneration. In summary common variants at AβPP, PSEN1, and PSEN2 and MAPT are unlikely to make strong contributions to susceptibility for LOAD. However, the gene-wide effect observed at MAPT indicates a possible contribution to disease risk which requires further study.
Alzheimer’s disease; amyloid-β protein precursor; genetics; human; MAPT protein; PSEN1 protein; PSEN2 protein
The α-Ca2+/calmodulin-dependent protein kinase II (αCaMKII) is a crucial enzyme controlling plasticity in the brain. The autophosphorylation of αCaMKII works as a ‘molecular memory' for a transient calcium activation, thereby accelerating learning. We investigated the role of αCaMKII autophosphorylation in the establishment of alcohol drinking as an addiction-related behavior in mice. We found that alcohol drinking was initially diminished in αCaMKII autophosphorylation-deficient αCaMKIIT286A mice, but could be established at wild-type level after repeated withdrawals. The locomotor activating effects of a low-dose alcohol (2 g/kg) were absent in αCaMKIIT286A mice, whereas the sedating effects of high-dose (3.5 g/kg) were preserved after acute and subchronic administration. The in vivo microdialysis revealed that αCaMKIIT286A mice showed no dopamine (DA) response in the nucleus accumbens to acute or subchronic alcohol administration, but enhanced serotonin (5-HT) responses in the prefrontal cortex. The attenuated DA response in αCaMKIIT286A mice was in line with altered c-Fos activation in the ventral tegmental area after acute and subchronic alcohol administration. In order to compare findings in mice with the human condition, we tested 23 single-nucleotide polymorphisms (SNPs) in the CAMK2A gene for their association with alcohol dependence in a population of 1333 male patients with severe alcohol dependence and 939 controls. We found seven significant associations between CAMK2A SNPs and alcohol dependence, one of which in an autophosphorylation-related area of the gene. Together, our data suggest αCaMKII autophosphorylation as a facilitating mechanism in the establishment of alcohol drinking behavior with changing the DA–5-HT balance as a putative mechanism.
Alcohol & Alcoholism; alphaCaMKII; Animal models; autophosphorylation; c-Fos; Dopamine; microdialysis; Serotonin; αCaMKII; autophosphorylation; alcohol; reinforcement; dopamine; serotonin
In compensatory endocytosis, scission of vesicles from the plasma membrane to the cytoplasm is a prerequisite for intravesicular reacidification and accumulation of neurotransmitter molecules. Here, we provide time-resolved measurements of the dynamics of the alkaline vesicle population which appears upon endocytic retrieval. Using fast perfusion pH-cycling in live-cell microscopy, synapto-pHluorin expressing rat hippocampal neurons were electrically stimulated. We found that the relative size of the alkaline vesicle population depended significantly on the electrical stimulus size: With increasing number of action potentials the relative size of the alkaline vesicle population expanded. In contrast to that, increasing the stimulus frequency reduced the relative size of the population of alkaline vesicles. Measurement of the time constant for reacification and calculation of the time constant for endocytosis revealed that both time constants were variable with regard to the stimulus condition. Furthermore, we show that the dynamics of the alkaline vesicle population can be predicted by a simple mathematical model. In conclusion, here a novel methodical approach to analyze dynamic properties of alkaline vesicles is presented and validated as a convenient method for the detection of intracellular events. Using this method we show that the population of alkaline vesicles is highly dynamic and depends both on stimulus strength and frequency. Our results implicate that determination of the alkaline vesicle population size may provide new insights into the kinetics of endocytic retrieval.
Concerns about worsening memory (“memory concerns”; MC) and impairment in memory performance are both predictors of Alzheimer's dementia (AD). The relationship of both in dementia prediction at the pre-dementia disease stage, however, is not well explored. Refined understanding of the contribution of both MC and memory performance in dementia prediction is crucial for defining at-risk populations. We examined the risk of incident AD by MC and memory performance in patients with mild cognitive impairment (MCI).
We analyzed data of 417 MCI patients from a longitudinal multicenter observational study. Patients were classified based on presence (n = 305) vs. absence (n = 112) of MC. Risk of incident AD was estimated with Cox Proportional-Hazards regression models.
Risk of incident AD was increased by MC (HR = 2.55, 95%CI: 1.33–4.89), lower memory performance (HR = 0.63, 95%CI: 0.56–0.71) and ApoE4-genotype (HR = 1.89, 95%CI: 1.18–3.02). An interaction effect between MC and memory performance was observed. The predictive power of MC was greatest for patients with very mild memory impairment and decreased with increasing memory impairment.
Our data suggest that the power of MC as a predictor of future dementia at the MCI stage varies with the patients' level of cognitive impairment. While MC are predictive at early stage MCI, their predictive value at more advanced stages of MCI is reduced. This suggests that loss of insight related to AD may occur at the late stage of MCI.
Various computer-based methods exist for the detection and quantification of protein spots in two dimensional gel electrophoresis images. Area-based methods are commonly used for spot quantification: an area is assigned to each spot and the sum of the pixel intensities in that area, the so-called volume, is used a measure for spot signal. Other methods use the optical density, i.e. the intensity of the most intense pixel of a spot, or calculate the volume from the parameters of a fitted function.
In this study we compare the performance of different spot quantification methods using synthetic and real data. We propose a ready-to-use algorithm for spot detection and quantification that uses fitting of two dimensional Gaussian function curves for the extraction of data from two dimensional gel electrophoresis (2-DE) images. The algorithm implements fitting using logical compounds and is computationally efficient. The applicability of the compound fitting algorithm was evaluated for various simulated data and compared with other quantification approaches. We provide evidence that even if an incorrect bell-shaped function is used, the fitting method is superior to other approaches, especially when spots overlap. Finally, we validated the method with experimental data of urea-based 2-DE of Aβ peptides andre-analyzed published data sets. Our methods showed higher precision and accuracy than other approaches when applied to exposure time series and standard gels.
Compound fitting as a quantification method for 2-DE spots shows several advantages over other approaches and could be combined with various spot detection methods.
The algorithm was scripted in MATLAB (Mathworks) and is available as a supplemental file.
Two dimensional gel electrophoresis; Beta amyloid; Image analysis; Spot quantification
Odorant pens are used by medical practitioners and researchers to assess olfactory dysfunction. Despite their routine use, there are currently no data on the gas-phase odorant concentrations released from the pen tips or whether these concentrations scale linearly with the aqueous-phase concentrations inside the pens. The commercially available Sniffin’ Sticks odor threshold test containing n-butanol was chosen for evaluation. The gas-phase concentration of n-butanol at the tip of each pen was measured directly in a new set of pens via proton-transfer-reaction mass spectrometry (PTR-MS). Measurements were additionally made on the same pens after 6 months and two older pen sets, namely a 3-year-old (used) and 4-year-old (new) set. Furthermore, application-related tests were made to determine the performance of the pens during routine use and under stress. These data demonstrate that the gas-phase n-butanol concentrations of the threshold pens are linear over the entire set, both for brand-new pens and 6 months later; this reflects the expected performance that was previously only assumed. Furthermore, the application–simulation tests demonstrated a good performance of the pens when used according to their intended protocol. Measurements of the older pen sets suggest that storage conditions are more critical than usage for pen stability. The present findings confirm that the n-butanol odorant pens are an appropriate tool for threshold testing, provided they are stored and handled correctly.
n-Butanol; Olfaction; PTR-MS; Sniffin’ Sticks; Odor threshold test
In neuropsychiatric diseases with basal ganglia involvement, higher cognitive functions are often impaired. In this exploratory study, we examined healthy young adults to gain detailed insight into the relationship between basal ganglia volume and cognitive abilities under non-pathological conditions.
We investigated 137 healthy adults that were between the ages of 21 and 35 years with similar educational backgrounds. Magnetic resonance imaging (MRI) was performed, and volumes of basal ganglia nuclei in both hemispheres were calculated using FreeSurfer software. The cognitive assessment consisted of verbal, numeric and figural aspects of intelligence for either the fluid or the crystallised intelligence factor using the intelligence test Intelligenz-Struktur-Test (I-S-T 2000 R). Our data revealed significant correlations of the caudate nucleus and pallidum volumes with figural and numeric aspects of intelligence, but not with verbal intelligence. Interestingly, figural intelligence associations were dependent on sex and intelligence factor; in females, the pallidum volumes were correlated with crystallised figural intelligence (r = 0.372, p = 0.01), whereas in males, the caudate volumes were correlated with fluid figural intelligence (r = 0.507, p = 0.01). Numeric intelligence was correlated with right-lateralised caudate nucleus volumes for both females and males, but only for crystallised intelligence (r = 0.306, p = 0.04 and r = 0.459, p = 0.04, respectively). The associations were not mediated by prefrontal cortical subfield volumes when controlling with partial correlation analyses.
The findings of our exploratory analysis indicate that figural and numeric intelligence aspects, but not verbal aspects, are strongly associated with basal ganglia volumes. Unlike numeric intelligence, the type of figural intelligence appears to be related to distinct basal ganglia nuclei in a sex-specific manner. Subcortical brain structures thus may contribute substantially to cognitive performance.
Different pools and functions have recently been attributed to spontaneous and evoked vesicle release. Despite the well-established function of evoked release, the neuronal information transmission, the origin as well as the function of spontaneously fusing synaptic vesicles have remained elusive. Recently spontaneous release was found to e.g. regulate postsynaptic protein synthesis or has been linked to depressive disorder. Nevertheless the strength and cellular localization of this release form was neglected so far, which are both essential parameters in neuronal information processing.
Here we show that the complete recycling pool can be turned over by spontaneous trafficking and that spontaneous fusion rates critically depend on the neuronal localization of the releasing synapse. Thereby, the distribution equals that of evoked release so that both findings demonstrate a uniform regulation of these fusion modes.
In contrast to recent works, our results strengthen the assumption that identical vesicles are used for evoked and spontaneous release and extended the knowledge about spontaneous fusion with respect to its amount and cellular localization. Therefore our data supported the hypothesis of a regulatory role of spontaneous release in neuronal outgrowth and plasticity as neurites secrete neurotransmitters to initiate process outgrowth of a possible postsynaptic neuron to form a new synaptic connection.
Aim. Identification of women with moderate alcohol abuse during pregnancy is difficult. We correlated self-reported alcohol consumption during pregnancy and patient characteristics with objective alcohol indicators measured in fetal meconium. Methods. A total of 557 women singleton births and available psychological tests, obstetric data and meconium samples were included in statistical analysis. Alcohol metabolites (fatty acid ethyl esters (FAEEs) and ethyl glucuronide (EtG)), were determined from meconium and correlated with patient characteristics.
Results. We found that 21.2% of the 557 participants admitted low-to-moderate alcohol consumption during pregnancy. Of the parameters analyzed from meconium, only EtG showed an association with alcohol history (P < 0.01). This association was inverse in cases with EtG value above 120 ng/g. These values indicate women with most severe alcohol consumption, who obviously denied having consumed alcohol during pregnancy. No other associations between socioeconomic or psychological characteristics and the drinking status (via meconium alcohol metabolites) could be found. Conclusion. Women who drink higher doses of ethanol during pregnancy, according to metabolite measures in meconium, might be less likely to admit alcohol consumption. No profile of socioeconomic or psychological characteristics of those women positively tested via meconium could be established.
Purpose. The aim of this study was to investigate whether single nucleotide polymorphisms (SNPs) in genes of the stress hormone signaling pathway, specifically FKBP5, NR3C1, and CRHR1, are associated with depressive symptoms during and after pregnancy. Methods. The Franconian Maternal Health Evaluation Study (FRAMES) recruited healthy pregnant women prospectively for the assessment of maternal and fetal health including the assessment of depressiveness. The German version of the 10-item Edinburgh Postnatal Depression Scale (EPDS) was completed at three time points in this prospective cohort study. Visit 1 was at study entry in the third trimester of the pregnancy, visit 2 was shortly after birth, and visit 3 was 6–8 months after birth. Germline DNA was collected from 361 pregnant women. Nine SNPs in the above mentioned genes were genotyped. After construction of haplotypes for each gene, a multifactorial linear mixed model was performed to analyse the depression values over time. Results. EPDS values were within expected ranges and comparable to previously published studies. Neither did the depression scores differ for comparisons among haplotypes at fixed time points nor did the change over time differ among haplotypes for the examined genes. No haplotype showed significant associations with depressive symptoms severity during pregnancy or the postpartum period. Conclusion. The analysed candidate haplotypes in FKBP5, NR3C1, and CRHR1 did not show an association with depression scores as assessed by EPDS in this cohort of healthy unselected pregnant women.
Conversion of soluble α-synuclein into insoluble and fibrillar inclusions is a
hallmark of Parkinson’s disease and other synucleinopathies. Accumulating evidence
points towards a relationship between its generation at nerve terminals and structural
synaptic pathology. Little is known about the pathogenic impact of α-synuclein
conversion and deposition at nigrostriatal dopaminergic synapses in transgenic mice,
mainly owing to expression limitations of the α-synuclein construct. Here, we
explore whether both the rat as a model and expression of the bacterial artificial
chromosome construct consisting of human full-length wild-type α-synuclein could
exert dopaminergic neuropathological effects. We found that the human promoter induced a
pan-neuronal expression, matching the rodent α-synuclein expression pattern,
however, with prominent C-terminally truncated fragments. Ageing promoted conversion of
both full-length and C-terminally truncated α-synuclein species into insolube and
proteinase K-resistant fibres, with strongest accumulation in the striatum, resembling
biochemical changes seen in human Parkinson’s disease. Transgenic rats develop early
changes in novelty-seeking, avoidance and smell before the progressive motor deficit.
Importantly, the observed pathological changes were associated with severe loss of the
dopaminergic integrity, thus resembling more closely the human pathology.
Parkinson’s disease; dopamine; animal models; alpha-synuclein; synapse function
Case. We report a case of catatonia with elevated CK, elevated temperature, and hypoferritinemia after abrupt discontinuation of clozapine in a patient with known proneness to catatonic symptoms. Reinstatement of clozapine therapy was contraindicated due to leukopenia. Neuroleptic malign syndrome could not be ruled out by the administration of quetiapine; this prevented the quick use of other potent D2 antagonists. Some improvement was achieved through supportive therapy, high dose of lorazepam, and a series of 10 ECT sessions. Returning to baseline condition was achieved by a very careful increase of olanzapine. Discussion. Catatonic symptoms in schizophrenia as well as in NMS might be caused by a lack of striatal dopamine (CS) or dopamine D2 antagonism (NMS). CS might be a “special” kind of schizophrenia featuring both hypo- and hyperactivity of dopaminergic transmission. ECT has been described as a “psychic rectifier” or a “reset for the system.” The desirable effect of ECT in cases of CS might be dopaminergic stimulation in the striatum and decrease of both the dopaminergic activity in the limbic system and the serotonergic activity on 5-HT2 receptors. The desirable effect of ECT in NMS would be explained by activation of dopaminergic transmission and/or liberation of dopaminergic receptors from the causative neuroleptics.
Androgen-dependent signaling regulates the growth of the fingers on the human hand during embryogenesis. A higher androgen load results in lower 2D:4D (second digit to fourth digit) ratio values. Prenatal androgen exposure also impacts brain development. 2D:4D values are usually lower in males and are viewed as a proxy of male brain organization. Here, we quantified video gaming behavior in young males. We found lower mean 2D:4D values in subjects who were classified according to the CSAS-II as having at-risk/addicted behavior (n = 27) compared with individuals with unproblematic video gaming behavior (n = 27). Thus, prenatal androgen exposure and a hyper-male brain organization, as represented by low 2D:4D values, are associated with problematic video gaming behavior. These results may be used to improve the diagnosis, prediction, and prevention of video game addiction.
Although several studies have described an association between Alzheimer disease (AD) and genetic variation of mitochondrial DNA (mtDNA), each has implicated different mtDNA variants, so the role of mtDNA in the etiology of AD remains uncertain.
We tested 138 mtDNA variants for association with AD in a powerful sample of 4,133 AD case patients and 1,602 matched controls from 3 Caucasian populations. Of the total population, 3,250 case patients and 1,221 elderly controls met the quality control criteria and were included in the analysis.
In the largest study to date, we failed to replicate the published findings. Meta-analysis of the available data showed no evidence of an association with AD.
The current evidence linking common mtDNA variations with AD is not compelling.
To maintain neurotransmission in central neurons, several mechanisms are employed to retrieve synaptically exocytosed membrane. The two major modes of synaptic vesicle (SV) retrieval are clathrin-mediated endocytosis and activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mode during intense stimulation, however the precise physiological conditions that trigger this mode are not resolved. To determine these parameters we manipulated rat hippocampal neurons using a wide spectrum of stimuli by varying both the pattern and duration of stimulation. Using live-cell fluorescence imaging and electron microscopy approaches, we established that stimulation frequency, rather than the stimulation load, was critical in the triggering of ADBE. Thus two hundred action potentials, when delivered at high frequency, were sufficient to induce near maximal bulk formation. Furthermore we observed a strong correlation between SV pool size and ability to perform ADBE. We also identified that inhibitory nerve terminals were more likely to utilize ADBE and had a larger SV recycling pool. Thus ADBE in hippocampal synaptic terminals is tightly coupled to stimulation frequency and is more likely to occur in terminals with large SV pools. These results implicate ADBE as a key modulator of both hippocampal neurotransmission and plasticity.
Brain-derived neurotrophic factor (BDNF) and apolipoprotein E (ApoE) are thought to be implicated in a variety of neuronal processes, including cell growth, resilience to noxious stimuli and synaptic plasticity. A Val to Met substitution at codon 66 in the BDNF protein has been associated with a variety of neuropsychiatric conditions. The ApoE4 allele is considered a risk factor for late-onset Alzheimer’s disease, but its effects on young adults are less clear. We sought to investigate the effects of those two polymorphisms on hemispheric and lateral ventricular volumes of young healthy adults.
Hemispheric and lateral ventricular volumes of 144 healthy individuals, aged 19–35 years, were measured using high resolution magnetic resonance imaging and data were correlated with BDNF and ApoE genotypes.
There were no correlations between BDNF or ApoE genotype and hemispheric or lateral ventricular volumes.
These findings indicate that it is unlikely that either the BDNF Val66Met or ApoE polymorphisms exert any significant effect on hemispheric or lateral ventricular volume. However, confounding epistatic genetic effects as well as relative insensitivity of the volumetric methods used cannot be ruled out. Further imaging analyses are warranted to better define any genetic influence of the BDNF Val6Met and ApoE polymorphism on brain structure of young healthy adults.
apolipoprotein E; brain-derived neurotrophic factor; magnetic resonance imaging; polymorphism; volumetry
Rare loss-of-function mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene are known to dramatically decrease the catalytic activity of acid sphingomyelinase (ASM), resulting in an autosomal recessive lysosomal storage disorder known as Niemann-Pick disease (NPD) type A and B. In contrast to the general low frequency of those deleterious mutations, we found a relatively high frequency for the proposed type B NPD variant c.1460C>T (p.A487V) in our sample of 58 patients suffering from Major Depressive Disorder. We therefore investigated the biochemical consequences of this variant more closely. Our in vivo data derived from blood cell analyses indicated cellular ASM activity levels in the normal range. The secreted ASM activity levels in blood plasma were slightly lower, but still above those levels reported for type B NPD patients. In vitro expression studies of this ASM variant in different cell lines confirmed these results, showing cellular and secreted enzymatic activities equivalent to those of wild-type ASM and similar expression levels. Thus, we conclude that the ASM variant c.1460C>T (p.A487V) is not a rare missense mutation but an SMPD1 sequence variant that yields a protein with functional catalytic characteristics.
Acid sphingomyelinase (ASM) hydrolyses sphingomyelin and generates the lipid messenger ceramide, which mediates a variety of stress-related cellular processes. The pathological effects of dysregulated ASM activity are evident in several human diseases and indicate an important functional role for ASM regulation. We investigated alternative splicing as a possible mechanism for regulating cellular ASM activity.
We identified three novel ASM splice variants in human cells, termed ASM-5, -6 and -7, which lack portions of the catalytic- and/or carboxy-terminal domains in comparison to full-length ASM-1. Differential expression patterns in primary blood cells indicated that ASM splicing might be subject to regulatory processes. The newly identified ASM splice variants were catalytically inactive in biochemical in vitro assays, but they decreased the relative cellular ceramide content in overexpression studies and exerted a dominant-negative effect on ASM activity in physiological cell models.
These findings indicate that alternative splicing of ASM is of functional significance for the cellular stress response, possibly representing a mechanism for maintaining constant levels of cellular ASM enzyme activity.
Multivariate image analysis has shown potential for classification between Alzheimer's disease (AD) patients and healthy controls with a high-diagnostic performance. As image analysis of positron emission tomography (PET) and single photon emission computed tomography (SPECT) data critically depends on appropriate data preprocessing, the focus of this work is to investigate the impact of data preprocessing on the outcome of the analysis, and to identify an optimal data preprocessing method. In this work, technetium-99methylcysteinatedimer (99mTc-ECD) SPECT data sets of 28 AD patients and 28 asymptomatic controls were used for the analysis. For a series of different data preprocessing methods, which includes methods for spatial normalization, smoothing, and intensity normalization, multivariate image analysis based on principal component analysis (PCA) and Fisher discriminant analysis (FDA) was applied. Bootstrap resampling was used to investigate the robustness of the analysis and the classification accuracy, depending on the data preprocessing method. Depending on the combination of preprocessing methods, significant differences regarding the classification accuracy were observed. For 99mTc-ECD SPECT data, the optimal data preprocessing method in terms of robustness and classification accuracy is based on affine registration, smoothing with a Gaussian of 12 mm full width half maximum, and intensity normalization based on the 25% brightest voxels within the whole-brain region.
Alzheimer's disease (AD); intensity normalization; multivariate analysis; principal component analysis (PCA); single photon emission computed tomography (SPECT); spatial normalization