Gene expression in profiling in individual cases reveals consistent transcriptional changes in alcoholic human brain

Chronic alcohol exposure induces lasting behavioral changes, tolerance, and dependence. This results, at least partially, from neural adaptations at a cellular level. Previous genome-wide gene expression studies using pooled human brain samples showed that alcohol abuse causes widespread changes in the pattern of gene expression in the frontal and motor cortices of human brain. Because these studies used pooled samples, they could not determine variability between different individuals. In the present study, we profiled gene expression levels of 14 postmortem human brains (seven controls and seven alcoholic cases) using cDNA microarrays (46 448 clones per array). Both frontal cortex and motor cortex brain regions were studied. The list of genes differentially expressed confirms and extends previous studies of alcohol responsive genes. Genes identified as differentially expressed in two brain regions fell generally into similar functional groups, including metabolism, immune response, cell survival, cell communication, signal transduction and energy production. Importantly, hierarchical clustering of differentially expressed genes accurately distinguished between control and alcoholic cases, particularly in the frontal cortex.

Genetic study of alcoholism and novel gene expression in the alcoholic brain

Alcohol dependence may result from neuroadaptation involving alteration of gene expression after long-term alcohol exposure. The systematic study of gene expression profiles of the human alcoholic brain was initiated using the method of polymerase chain reaction (PCR)-differential display and was followed by DNA microarray. To date, more than 100 alcohol-responsive genes have been identified from the frontal cortex, motor cortex and nucleus accumbens of the human brain. These genes have a wide range of functions in the brain and indicate diverse actions of alcohol on neuronal function. This review discusses the current information on the genetic basis of alcoholism and the induction and characterization of these alcohol-responsive genes.

Changes in neuronal protein 22 expression and cytoskeletal association in the alcohol-dependent and withdrawn rat brain

The action of alcohol on neuronal pathways has been an issue of increasing research focus, with numerous findings contradicting the previously accepted idea that its effect is nonspecific. The human NP22 (hNP22) gene was revealed by its elevated expression in the frontal cortex of the human alcoholic. The sequences of hNP22 and the rat orthologue rNP22 contain a number of domains consistent with those of cytoskeletal-interacting proteins. Localization of rNP22 is restricted to the cytoplasm and processes of neurons and it colocalizes with elements of the microfilament and microtubule matrices including filamentous actin (F-actin), alpha-tubulin, tau, and microtubule-associated protein 2 (MAP2). Withdrawal of Wistar rats after alcohol dependence induced by alcohol vapor produced elevated levels of rNP22 mRNA and protein in the cortex, CA2, and dentate gyrus regions of the hippocampus. In contrast, there was decreased rNP22 expression in the striatum after chronic ethanol exposure. Chronic ethanol exposure did not markedly alter rNP22 colocalization with F-actin, alpha-tubulin, or MAP2, although colocalization at the periphery of the neuronal soma with F-actin was observed only after chronic ethanol exposure and withdrawal. Rat NP22 colocalization with MAP2 was reduced during withdrawal, whereas association with alpha-tubulin and actin was maintained. These findings suggest that the effect of chronic ethanol exposure and withdrawal on rNP22 expression is region selective. Rat NP22 may affect microtubule or microfilament function, thereby regulating the neuroplastic changes associated with the development of alcohol dependence and physical withdrawal.

Comparative gene expression in brain regions of human alcoholics

The mesocorticolimbic system is the reward centre of the brain and the major target for drugs of abuse including alcohol. Neuroadaptive changes in this region are thought to underlie the process of tolerance and dependence. Recently, several research groups have searched for alcohol-responsive genes using high-throughput microarrays and well-characterized human post-mortem material. Comparison of data from these studies of cortical regions highlights the differences in experimental approach and selection of cases. However, alcohol-responsive gene sets associated with transcription, oxidative stress and energy production were common to these studies. In marked contrast, alcohol-responsive genes in the nucleus accumbens and the ventral tegmental area are primarily associated with changes in neurotransmission and signal transduction. These data support the concept that, within cortical regions, changes in gene expression are associated with alcoholism-related pathology. In the dopaminergic tract of the mesocorticolimbic system, alcohol-responsive gene sets suggest long-term neuroplastic changes in synaptic transmission.

Interactions between serotonergic genotype and amino acid transmitter receptor expression in human alcoholics

Serotonin can modulate the activity of neural reward pathways that are strongly implicated in mediating the effects of chronic alcohol misuse, and its treatment, in human subjects. In previous work and as discussed elsewhere at this meeting, we and others have found consistent differences in the parameters of GABA and glutamate receptors, and the expression of their component subunit transcripts and proteins, in areas of the alcoholic brain that are altered by alcoholism. We did not fi nd clear changes in GABA and glutamate transport function in such samples, but a series of microarray analyses showed consistent upregulation of the presynaptic GABA/betaine transporter SLC6A12. Microarray studies showed no signifi cant differences in the expression of transcripts associated with 5HT transmission; however, only a small number of such elements were present on the arrays. Here we partitioned GABAA and NMDA pharmacology, and subunit mRNA and protein expression, measured in samples of frontal and motor cortex obtained at autopsy from alcoholics without comorbid disease, alcoholics with liver cirrhosis, and controls, according to 5HTTLPR (SLC6A4) and 5HT1B (HTR1B) polymorphisms. We found no effect of these genotypes on the expression of GABAA receptor gene products, but there was a signifi cant mRNA Transcript X Area X Group X 5HTTLPR Interaction with NMDA subunit isoform expression measured by Real Time PCR with GAPDH normalization. Further analysis showed the effect to be selective for alcoholics with cirrhosis, to be most marked in the pathologically vulnerable frontal cortex, and to vary with subunit transcript (F2,76 = 6.545, P = 0.002). NR1 expression was most affected, followed by NR2A, with NR2B expression least altered. Pilot data suggest 5HT1B genotype may also modulate NMDA subunit expression. Interactions between amino acid and serotonin transmission may infl uence susceptibility to alcohol dependence or pathogenesis

Spatial correlations between beta-amyloid (Abeta) deposits and blood vessels in early-onset Alzheimer's disease

In cases of late-onset Alzheimer’s disease (AD), there is a spatial correlation between the classsic ‘cored’ type of Beta-amyloid (Abeta) deposit and the large vertically penetrating arterioles in the cerebral cortex suggesting that blood vessels are involved in the pathogenesis of the classic deposits. In this chapter, the spatial correlations between the diffuse, primitive, and classic Abeta deposits and blood vessels were studied in 10 cases of early-onset AD in the age range 40 – 65 years. Sections of frontal cortex were immunostained with antibodies against Abeta?and with collagen IV to reveal the Abeta deposits and blood vessel profiles. In the early-onset cases as a whole, all types of Abeta? deposit and blood vessel profiles were distributed in clusters. There was a positive spatial correlation between the clusters of the diffuse Abeta deposits and the larger (>10µm) and smaller diameter (<10?m) blood vessel profiles in one and three cases respectively. The primitive and classic Abeta deposits were spatially correlated with larger and smaller blood vessels both in three and four cases respectively. Spatial correlations between the Abeta deposits and blood vessels may be more prevalent in cases expressing amyloid precursor protein (APP) than presenilin 1 (PSEN1) mutations. Apolipoprotein E (Apo E) genotype of the patient did not appear to influence the spatial correlation with blood vessel profiles. The data suggest that the larger diameter blood vessels are less important in the pathogenesis of the classic Abeta deposits in early-onset compared with late-onset AD.

Spatial correlations between beta-amyloid (A beta) deposits and blood vessels in familial Alzheimer's disease

In sporadic Alzheimer’s disease (SAD), the classic (‘dense-cored’) ß-amyloid (Aß) deposits are aggregated around the larger blood vessels in the upper laminae of the cerebral cortex. To determine whether a similar relationship exists in familial AD (FAD), the spatial correlations between the diffuse, primitive, and classic ß-amyloid (Aß deposits and blood vessels were studied in ten FAD cases including cases linked to amyloid precursor protein (APP) and presenilin (PSEN) gene mutations and expressing apolipoprotein E (apo E) allele E4. Sections of frontal cortex were immunolabelled with antibodies against Aß and with collagen IV to reveal the Aß deposits and blood vessel profiles. In the FAD cases as a whole, Aßdeposits were distributed in clusters. There was a positive spatial correlation between the clusters of the diffuse Aßdeposits and the larger (>10 µm) and smaller diameter (<10 µm) blood vessels in one and three cases respectively. The primitive Aß deposits were spatially correlated with larger and smaller blood vessels each in four cases and the classic deposits in three and four cases respectively. Apo E genotype of the patient did not influence spatial correlation with blood vessels. Hence, spatial correlations between the classic deposits and larger diameter blood vessels were significantly less frequent in FAD compared with SAD. It was concluded that both Aß deposit morphology and AD subtype determine spatial correlations with blood vessels in AD.

A quantitative study of the pathological changes in white matter in multiple system atrophy

The density and spatial distribution of the vacuoles, glial cell nuclei and glial cytoplasmic inclusions (GCI) were studied in the white matter of various cortical and subcortical areas in 10 cases of multiple system atrophy (MSA). Vacuolation was more prevalent in subcortical than cortical areas and especially in the central tegmental tract. Glial cell nuclei widespread in all areas of the white matter studied; overall densities of glial cell nuclei being significantly greater in the central tegmental tract and frontal cortex compared with areas of the pons. The GCI were present most consistently in the external and internal capsules, the central tegmental tract and the white matter of the cerebellar cortex. The density of the vacuoles was greater in the MSA brains than in the control brains but glial cell density was similar in both groups. In the majority of areas, the pathological changes were distributed across the white matter randomly, uniformly, or in large diffuse clusters. In most areas, there were no spatial correlations between the vacuoles, glial cell nuclei and GCI. These results suggest: (i) there is significant degeneration of the white matter in MSA characterized by vacuolation and GCI; (ii) the central tegmental tract is affected significantly more than the cortical tracts; (iii) pathological changes are diffusely rather than topographically distributed across the white matter; and (iv) the development of the vacuoles and GCI appear to be unrelated phenomena. © 2007 Japanese Society of Neuropathology.

A quantitative study of the pathological changes in ten patients with multiple system atrophy (MSA)

The densities of the glial cytoplasmic inclusions (GCI), neuronal inclusions (NI), and abnormal neurons were studied in the frontal cortex, hippocampus, cerebellum, basal ganglia and areas of the pons and medulla in 10 cases of multiple system atrophy (MSA). GCI density was greater in the substantia nigra and globus pallidus compared with the frontal cortex and hippocampus. Abnormal neurons were most abundant in the frontal cortex, substantia nigra, and inferior olivary nucleus. NI and abnormal neuron densities were positively correlated in the globus pallidus but negatively correlated in the hippocampus. The NI and GCI were only positively correlated in the pons. GCI in the pons and inferior olivary nucleus, NI in the substantia nigra, and abnormal neurons in the frontal cortex varied significantly between cases. The MSA cases did not cluster according to disease subtype. The data suggest that: 1) the greatest densities of pathological changes occur in the substantia nigra and globus pallidus, 2) density of the GCI is unrelated to that of the NI, and 3) there is overlapping pathology between the various subtypes of MSA.

Quantification of vacuolation ('spongiform change'), surviving neurones and prion protein deposition in eleven cases of variant Creutzfeldt-Jakob disease

Vacuolation ('spongiform change') and prion protein (PrP) deposition were quantified in the cerebral cortex, hippocampus, dentate gyrus and molecular layer of the cerebellum in 11 cases of variant Creutzfeldt-Jakob disease (vCJD). The density of vacuoles was greater in the cerebral cortex compared to the hippocampus, dentate gyrus and cerebellum. Within the cortex, vacuole density was significantly greater in the occipital compared to the temporal lobe and the density of surviving neurones was greatest in the occipital lobe. The density of the non-florid PrP plaques was greater in the cerebellum compared to the other brain areas. There were significantly more florid-type PrP plaques in the cerebral cortex compared to the hippocampus and the molecular layer of the cerebellum. No significant correlations were observed between the densities of the vacuoles and the PrP plaques. The densities of vacuoles in the parietal cortex and the non-florid plaques in the frontal cortex were positively correlated with the density of surviving neurones. The densities of the florid and the non-florid plaques were positively correlated in the parietal cortex, occipital cortex, inferior temporal gyrus and dentate gyrus. The data suggest: (i) vacuolation throughout the cerebral cortex, especially in the occipital lobe, but less evident in the hippocampus and molecular layer of the cerebellum; (ii) the non-florid plaques are more common than the florid plaques and predominate in the molecular layer of the cerebellum; and (iii) either the florid plaques develop from the non-florid plaques or both types are morphological variants resulting from the same degenerative process.

Dissociating the spatio-temporal characteristics of cortical neuronal activity associated with human volitional swallowing in the healthy adult brain

Human swallowing represents a complex highly coordinated sensorimotor function whose functional neuroanatomy remains incompletely understood. Specifically, previous studies have failed to delineate the temporo-spatial sequence of those cerebral loci active during the differing phases of swallowing. We therefore sought to define the temporal characteristics of cortical activity associated with human swallowing behaviour using a novel application of magnetoencephalography (MEG). In healthy volunteers (n = 8, aged 28-45), 151-channel whole cortex MEG was recorded during the conditions of oral water infusion, volitional wet swallowing (5 ml bolus), tongue thrust or rest. Each condition lasted for 5 s and was repeated 20 times. Synthetic aperture magnetometry (SAM) analysis was performed on each active epoch and compared to rest. Temporal sequencing of brain activations utilised time-frequency wavelet plots of regions selected using virtual electrodes. Following SAM analysis, water infusion preferentially activated the caudolateral sensorimotor cortex, whereas during volitional swallowing and tongue movement, the superior sensorimotor cortex was more strongly active. Time-frequency wavelet analysis indicated that sensory input from the tongue simultaneously activated caudolateral sensorimotor and primary gustatory cortex, which appeared to prime the superior sensory and motor cortical areas, involved in the volitional phase of swallowing. Our data support the existence of a temporal synchrony across the whole cortical swallowing network, with sensory input from the tongue being critical. Thus, the ability to non-invasively image this network, with intra-individual and high temporal resolution, provides new insights into the brain processing of human swallowing. © 2004 Elsevier Inc. All rights reserved.

The spatial distribution and temporal dynamics of brain regions activated during the perception of object and non-object patterns

Both animal and human studies suggest that the efficiency with which we are able to grasp objects is attributable to a repertoire of motor signals derived directly from vision. This is in general agreement with the long-held belief that the automatic generation of motor signals by the perception of objects is based on the actions they afford. In this study, we used magnetoencephalography (MEG) to determine the spatial distribution and temporal dynamics of brain regions activated during passive viewing of object and non-object targets that varied in the extent to which they afforded a grasping action. Synthetic Aperture Magnetometry (SAM) was used to localize task-related oscillatory power changes within specific frequency bands, and the time course of activity within given regions-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. Both single subject and group-averaged data on the spatial distribution of brain activity are presented. We show that: (i) significant reductions in 10-25 Hz activity within extrastriate cortex, occipito-temporal cortex, sensori-motor cortex and cerebellum were evident with passive viewing of both objects and non-objects; and (ii) reductions in oscillatory activity within the posterior part of the superior parietal cortex (area Ba7) were only evident with the perception of objects. Assuming that focal reductions in low-frequency oscillations (< 30 Hz) reflect areas of heightened neural activity, we conclude that: (i) activity within a network of brain areas, including the sensori-motor cortex, is not critically dependent on stimulus type and may reflect general changes in visual attention; and (ii) the posterior part of the superior parietal cortex, area Ba7, is activated preferentially by objects and may play a role in computations related to grasping. © 2006 Elsevier Inc. All rights reserved.

The spatial patterns of Pick bodies, Pick cells and Alzheimer’s disease pathology in Pick’s disease

The spatial patterns of Pick bodies (PB), Pick cells (PC), senile plaques (SP) and neurofibrillary tangles (NFT) were studied in the frontal and temporal lobe in nine cases of Pick’s disease (PD). Pick bodies exhibited clustering in 41/44 (93%) of analyses and clusters of PB were regularly distributed parallel to the tissue boundary in 24/41 (58%) of analyses. Pick cells exhibited clustering with regular periodicity of clusters in 14/16 (88%) analyses, SP in three out of four (75%) analyses and NFT in 21/27 (78%) analyses. The largest clusters of PB were observed in the dentate gyrus and PC in the frontal cortex. In 10/17 (59%) brain areas studied, a positive or negative correlation was observed between the densities of PB and PC. The densities of PB and NFT were not significantly correlated in the majority of brain areas but a negative correlation was observed in 7/29 (24%) brain areas. The data suggest that PB and PC in patients with PD exhibit essentially the same spatial patterns as SP and NFT in Alzheimer’s disease (AD) and Lewy bodies (LB) in dementia with Lewy bodies (DLB). In addition, there was a spatial correlation between the clusters of PB and PC, suggesting a pathogenic relationship between the two lesions. However, in the majority of tissues examined there was no spatial correlation between the clusters of PB and NFT, suggesting that the two lesions develop in association with different populations of neurons.

Is neuropathological heterogeneity in Alzheimer’s disease related to apolipoprotein genotype?

The abundance of senile plaques (SP) and neurofibrillary tangles (NFT) was studied in cortical and subcortical regions from 30 patients with Alzheimer’s disease (AD) expressing different apolipoprotein E (apoE) genotypes. Principal components analysis (PCA) was used to identify the most important neuropathological variations between individual patients and to determine whether these variations were related to apoE genotype. The first two principal components (PC) accounted for 60% and 40% of the total variance of the SP and NFT data respectively. The abundance of SP in the frontal and occipital cortex and NFT in the frontal cortex, amygdala and substantia nigra were positively correlated with the first principal component (PC1). Analysis of the SP data revealed that the apoE score of the patient (the sum of the two alleles) was positively correlated with PC1 while analysis of the NFT data revealed no significant correlations between apoE score and the PC. The data suggest that apoE genotype was more closely related to variations in the distribution and abundance of SP than of NFT. In addition, a more rapid spread of SP into the frontal and occipital cortex may occur in patients with a high apoE score.