Nuclear carrier and RNA-binding proteins in frontotemporal lobar degeneration associated with fused in sarcoma (FUS) pathological changes.

AIMS: We aimed to investigate the role of the nuclear carrier and binding proteins, transportin 1 (TRN1) and transportin 2 (TRN2), TATA-binding protein-associated factor 15 (TAF15) and Ewing's sarcoma protein (EWS) in inclusion body formation in cases of frontotemporal lobar degeneration (FTLD) associated with fused in sarcoma protein (FTLD-FUS). METHODS: Eight cases of FTLD-FUS (five cases of atypical FTLD-U, two of neuronal intermediate filament inclusion body disease and one of basophilic inclusion body disease) were immunostained for FUS, TRN1, TRN2, TAF15 and EWS. Ten cases of FTLD associated with TDP-43 inclusions served as reference cases. RESULTS: The inclusion bodies in FTLD-FUS contained TRN1 and TAF15 and, to a lesser extent, EWS, but not TRN2. The patterns of immunostaining for TRN1 and TAF15 were very similar to that of FUS. None of these proteins was associated with tau or TDP-43 aggregations in FTLD. CONCLUSIONS: Data suggest that FUS, TRN1 and TAF15 may participate in a functional pathway in an interdependent way, and imply that the function of TDP-43 may not necessarily be in parallel with, or complementary to, that of FUS, despite each protein sharing many similar structural elements.

Increased neural progenitors in individuals with cerebral small vessel disease.

AIMS: Recent work has highlighted a significant increase of neural stem/progenitor cells after stroke in humans. In this study, we examined neurogenesis in small vessel disease, a key concurrent pathology in Alzheimer's disease. METHODS: We assayed autopsy tissue from 13 vascular dementia patients with small vessel disease and 12 age-matched subjects without cerebrovascular pathology, undertaking immunohistochemistry in the affected brain area and the subventricular zone with a well-characterized battery of antibodies to detect neural stem cells/progenitors and immature neurones, as well as choline acetyltransferase immunoreactivity. RESULTS: We showed significant increases ranging from 33% to 92% (P < 0.05) in neural progenitor cells around the areas of microvascular pathology and in the subventricular zone in patients with small vessel disease compared to individuals without cerebrovascular changes, even in patients with severe cerebrovascular disease, as defined by neuropathological assessment. Some of the progenitor cells give rise to immature neurones in the affected areas. These alterations were associated with vascular changes, but were unrelated to the cholinergic deficit observed in the cortex and subventricular zone in these patients, in contrast to other dementias examined such as dementia with Lewy bodies. CONCLUSIONS: This study provides evidence for neurogenesis in small vessel disease and may have important implications for the development of new therapies for neurodegenerative diseases.

Quantitative neurodegenerative pathology does not explain the degree of hippocampal atrophy on MRI in degenerative dementia.

OBJECTIVE: The purpose of this study was to investigate the neuropathological substrates underlying in vivo hippocampal atrophy on magnetic resonance imaging (MRI) in autopsy confirmed neurodegenerative dementia cases. METHODS: Thirty-one neuropathologically verified cases (23 with Lewy body dementia (LBD) and eight with Alzheimer's disease (AD)) were included who had undergone an MRI scan close to death (mean 1.5 years). Manual volumetric measurements were undertaken for the hippocampus, entorhinal cortex and amygdala on MRI, along with quantitative neuropathological analysis of plaque, tangle and Lewy body pathology in the same regions. The relationship between neuropathology and MRI volumes was assessed using correlations and linear regression. RESULTS: Hippocampal and amygdala volumes were significantly smaller in cases with AD than with LBD, but there was no difference in entorhinal cortex volume. Analysing all cases together, a significant positive correlation was observed between normalised hippocampal volume and percent area of Lewy bodies in the hippocampus (r=0.449, p=0.017) but not with tangles (r=0.059, p=0.766) or plaques (r=-0.361, p=0.119). There were no other significant correlations between regional MRI volume and measures of neuropathology. Regression analysis showed that overall diagnosis of AD rather than burden of individual pathological changes was the most significant predictor of hippocampal volume loss in autopsy confirmed cases. CONCLUSION: Our results suggest that (i) hippocampal and amygdala but not entorhinal cortex, volumes differ between AD and LBD and (ii) factors other than current markers of neurodegenerative pathological change are responsible for atrophy of medial temporal lobe structures in AD and LBD.

Medial temporal lobe atrophy on MRI differentiates Alzheimer's disease from dementia with Lewy bodies and vascular cognitive impairment: a prospective study with pathological verification of diagnosis.

The purpose of this study was to determine the diagnostic accuracy of medial temporal lobe atrophy (MTA) on MRI for distinguishing Alzheimer's disease from other dementias in autopsy confirmed cases, and to determine pathological correlates of MTA in Alzheimer's disease, dementia with Lewy bodies (DLB) and vascular cognitive impairment (VCI). We studied 46 individuals who had both antemortem MRI and an autopsy. Subjects were clinicopathologically classified as having Alzheimer's disease (n = 11), DLB (n = 23) or VCI (n = 12). MTA was rated visually using a standardized (Scheltens) scale blind to clinical or autopsy diagnosis. Neuropathological analysis included Braak staging as well as quantitative analysis of plaques, tangles and alpha-synuclein Lewy body-associated pathology in the hippocampus. Correlations between MTA and pathological measures were carried out using Spearman's rho, linear regression to assess the contributions of local pathologic changes to MTA. Receiver operator curve analysis was used to assess the diagnostic specificity of MTA for Alzheimer's disease among individuals with Alzheimer's disease, DLB and VCI. MTA was a highly accurate diagnostic marker for autopsy confirmed Alzheimer's disease (sensitivity of 91% and specificity of 94%) compared with DLB and VCI. Across the entire sample, correlations were observed between MTA and Braak stage (rho = 0.50, P < 0.001), per cent area of plaques in the hippocampus (rho = 0.37, P = 0.014) and per cent area of tangles in the hippocampus (rho = 0.49, P = 0.001). Linear regression showed Braak stage (P = 0.022) to be a significant predictor of MTA but not percent area of plaques (P = 0.375), percent area of tangles (P = 0.330) or percent area of Lewy bodies (P = 0.086). MTA on MRI had robust discriminatory power for distinguishing Alzheimer's disease from DLB and VCI in pathologically confirmed cases. Pathologically, it is more strongly related to tangle rather than plaque or Lewy body pathology in the temporal lobe. It may have utility as a means for stratifying samples in vivo on the basis of putative differences in pathology.

Prognostic significance of HER2 and HER4 coexpression in childhood medulloblastoma.

Recent in vitro studies of the epidermal growth factor receptor (EGFR) family have revealed complex signaling interactions involving the production of ligand-mediated heterodimers synergistic for the transformation of cells in vitro. In a series of 70 patients with childhood medulloblastoma, we have used immunohistochemistry and Western blotting analysis to investigate the expression patterns of all four EGFR family members (EGFR, HER2, HER3, and HER4) and heregulin-alpha, a ligand for the HER3 and HER4 receptors. The majority of cases expressed two or more receptor proteins; coexpression of the HER2 and HER4 receptors occurred in 54%. Expression of the ligand heregulin-alpha was detected in 31% of tumors. To investigate whether coexpression results in receptor heterodimerization, we have also performed immunoprecipitation analysis of protein extracts from primary tumors, and we demonstrate various patterns of receptor interaction including between HER2 and HER4. In multivariate 25-year survival analysis with clinicopathological disease features, no individual receptor or heregulin-alpha achieved significance. In contrast, when considered together in the multivariate model, coexpression of HER2 and HER4 demonstrated independent prognostic significance (P = 0.006). These data suggest the hypothesis that HER2-HER4 receptor heterodimerization is of particular biological significance in this disease, and this report is the first to demonstrate potential clinical significance of EGFR family heterodimerization in human cancer. Finally, we have also analyzed expression of the AP-2 transcription factor implicated in the positive regulation of HER2 and HER3 gene transcription in malignant cells and reveal an association between AP-2 expression and not only HER2 and HER3, but also HER4 levels in medulloblastoma primary tumors.

Expression of the ErbB-neuregulin signaling network during human cerebellar development: implications for the biology of medulloblastoma.

The four receptor tyrosine kinase I receptors, ErbB-1, ErbB-2, ErbB-3, and ErbB-4, which have been implicated in the development of a variety of normal and malignant tissues, are activated through ligand mediated homo- and heterodimerization. We have previously reported the frequent coexpression, heterodimerzation, and prognostic significance of ErbB-2 and ErbB-4 in childhood medulloblastoma, an embryonal tumor of the cerebellar external granule cell layer (EGL). In the present study, we have used immunohistochemistry and Western blotting analysis to analyze the expression of the ErbB receptors and neuregulin (NRG) 1-alpha and NRG1-beta ligands during normal human cerebellar development. We demonstrate that ErbB-1, ErbB-3, ErbB-4, and NRG1-beta display specific temporal and topographical distribution in the cerebellum during intrauterine and postnatal life, and that normal ErbB-NRG signaling in the EGL multiplying zone is likely to be mediated by ErbB-4 and NRG1-beta. In contrast, ErbB-2, which is expressed in 86% of medulloblastomas, could not be detected at any stage of cerebellar development. Therefore, we propose that positive deregulation of ErbB-2 expression in the cerebellar EGL, leading to the formation of a NRG41-beta-driven ErbB-2/ErbB-4 autocrine loop, is an important factor in medulloblastoma tumorigenesis. In further support of this hypothesis, we provide evidence using reverse transcription-PCR analysis that expression of the ErbB-2 and ErbB-4 receptors, but not ErbB-1 or ErbB-3, is deregulated in medulloblastoma compared with normal developing cerebellum. We also demonstrate NRG1-beta expression in 87% (n = 46 of 48) of medulloblastoma primary tumors, with the greatest expression levels occurring in tumors with high ErbB-2 and ErbB-4 receptor coexpression. Furthermore, the expression of all three components of the proposed autocrine loop (ie., ErbB-2, ErbB-4, and NRG1-beta) was significantly related to the presence of metastases at diagnosis (P < 0.05).

D2 dopamine receptor gene (DRD2) Taq1 A polymorphism: reduced dopamine D2 receptor binding in the human striatum associated with the A1 allele.

The relationship between a dopamine D2 receptor genetic polymorphism at the Taq1 A locus and the level of D2 receptor binding was investigated in normal, middle aged to elderly subjects with no psychiatric or neurological disorders. D2 receptor binding was measured by autoradiography in the caudate, putamen and nucleus accumbens, using the specific D2 receptor ligand [3H]-raclopride. In a sample of 44 individuals, only one was homozygous for the A1 allele, 25 were homozygous for A2 and 18 were heterozygotes. The presence of one or two A1 alleles was associated with reduced D2 receptor binding in all areas of the striatum, reaching statistical significance in the ventral caudate and putamen (p = 0.01 and p = 0.044, respectively). This reduction was more marked in males than females, particularly in the putamen. A genetic predisposition to lower D2 receptor expression may increase susceptibility to neuroleptic medication or clinical symptoms that are associated with diseases involving dopaminergic pathology.

CYP2D6 is associated with Parkinson's disease but not with dementia with Lewy Bodies or Alzheimer's disease.

The similarities between the clinical and pathological findings of dementia with Lewy Bodies (DLB) with Alzheimer's disease and Parkinson's disease are complex, and their significance for pathogenesis is unresolved. It is likely that DLB shares common disease determinants with both Alzheimer's disease and Parkinson's disease. Clinically DLB shows the presence of dementia similar, though not identical, to that found in Alzheimer's disease. A parkinsonian movement disorder is present in a proportion of DLB cases. Pathologically DLB shows senile plaques, as with Alzheimer's disease, and also substantia nigra neurone loss and Lewy bodies, as with Parkinson's disease. At a genetic level, DLB shows an elevated Apolipoprotein E epsilon4 frequency as described in Alzheimer's disease, but this is absent in Parkinson's disease. An elevated frequency of the CYP2D6*4 allele has been found in Parkinson's disease and we have therefore genotyped a large series of clinically and neuropathologically confirmed cases of DLB, Alzheimer's disease, Parkinson's disease and age-matched control individuals for the CYP2D6*4 allele. Whilst an elevated frequency of the CYP2D6*4 allele was found in Parkinson's disease, no such elevations were found in DLB or Alzheimer's disease. Stratification of the CYP2D6*4 allele with respect to the Apolipoprotein E epsilon4 also did not show any significant associations with the CYP2D6*4 allele. The CYP2D6*4 allele is not a major genetic determinant of DLB and the results place DLB with Alzheimer's disease rather than Parkinson's disease on a genetic level.

Cortical concentrations of corticotropin-releasing hormone and its receptor in Alzheimer type dementia and major depression.

Corticotropin-releasing hormone-immunoreactivity (CRH-IR) and CRH receptors (binding capacity and affinity) were measured in postmortem cortical areas from depressed subjects, two groups of senile dementia of the Alzheimer type (SDAT), and age-, sex-, and postmortem-delay-matched controls. No difference in CRH-IR and CRH receptor status between depressed subjects and controls was noted. CRH-IR was decreased in all cortical areas in SDAT, with a corresponding increase in CRH receptor binding capacity (with no change in affinity) in occipital cortex. No effects of postmortem delay were seen. It is suggested that the increase in CRH receptor numbers in SDAT is related to the degree of distribution of pathological involvement in specific regions.

Neocortical concentrations of neuropeptides in senile dementia of the Alzheimer and Lewy body type: comparison with Parkinson's disease and severity correlations.

Corticotropin releasing hormone (CRH), somatostatin (SRIF), and arginine vasopressin (AVP) concentrations were estimated using radioimmunoassay in the temporal and occipital cortices in postmortem brain from patients clinically and neuropathologically diagnosed as senile dementia of the Lewy body type (SDLT), senile dementia of the Alzheimer type (SDAT), and Parkinson's disease (PD) and from neurologically normal controls. The concentration of temporal and occipital neocortical CRH was diminished in both SDAT and SDLT compared to control values, whereas SRIF was reduced only in temporal cortex in both these conditions. In contrast, the concentrations of both CRH and SRIF were unaltered in PD. The concentrations of AVP in SDLT, SDAT, and PD were similar to those found in the control groups. The decrement in SRIF, but not CRH, was found to be correlated with some indices of severity of illness in SDAT; a similar but nonsignificant trend for SRIF was observed in SDLT.

Nigrostriatal dopaminergic activities in dementia with Lewy bodies in relation to neuroleptic sensitivity: comparisons with Parkinson's disease.

BACKGROUND: In dementia with Lewy bodies (DLB) mild extrapyramidal symptoms are associated with moderate reductions in substantia nigra neuron density and concentration of striatal dopamine. Many DLB patients treated with typical neuroleptics suffer severe adverse reactions, which result in decreased survival. METHODS: In a series of DLB cases, with and without neuroleptic sensitivity, substantia nigra neuron densities, striatal dopamine and homovanillic acid concentrations, and autoradiographic [3H]mazindol and [3H]raclopride binding (to the dopamine transporter and D2 receptor, respectively) were analyzed and compared to control and idiopathic Parkinson's disease cases. RESULTS: D2 receptors were up-regulated in neuroleptictolerant DLB and Parkinson's disease compared to DLB without neuroleptic exposure and controls. D2 receptors were not up-regulated in DLB cases with severe neuroleptic reactions. Dopamine uptake sites were reduced concomitantly with substantia nigra neuron density in Parkinson's disease compared to controls, but there was no significant correlation between substantia nigra neuron density and [3H]mazindol binding in DLB groups. There was no significant difference in substantia nigra neuron density, [3H]mazindol binding, and dopamine or homovanillic acid concentration between neuroleptic-tolerant and -sensitive groups. CONCLUSIONS: Failure to up-regulate D2 receptors in response to neuroleptic blockade or reduced dopaminergic innervation may be the critical factor responsible for neuroleptic sensitivity.

Glutamate receptor binding in the human hippocampus and adjacent cortex during development and aging.

Distinct patterns of age-related alterations in NMDA (MK801 binding) and non-NMDA, AMPA (CNQX), and kainate binding have been identified in human hippocampus and parahippocampal gyrus in normal individuals with no evidence of degenerative brain disease ranging in age from 24 gestational weeks to 94 years. Whereas MK801 binding did not alter substantially over this age range, CNQX binding rose from low levels in the fetus to maximum levels between neonate and middle age, and kainate binding declined extensively from the perinatal to adult stage. Following maturity, there were no significant changes in kainate binding, although MK801 binding increased in CA1 and CA3 and CNQX binding declined in several regions, particularly CA2 and subiculum. For each receptor binding the timing of these fluctuations ocurring during development and aging varied within different regions of the dentate gyrus, hippocampus proper, subicular complex, and entorhinal cortex examined. The transient peaks of receptor binding are likely to reflect processes of synaptogenesis and pruning and may provide clues regarding the role of the different glutamate receptor subtypes in various pathologies of the hippocampus and adjacent cortex associated with developmental disorders (of genetic origin or due to perinatal trauma or insult). The absence of substantial changes in any subtype examined from middle to old age suggests alterations in transmitter binding to these glutamate receptors are not involved in senescent neurodegeneration.

Convergent cholinergic activities in aging and Alzheimer's disease.

Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities have been examined postmortem in a series of 66 individuals with no evidence of CNS disease, ranging in age from 24 gestational weeks to 95 years and in 33 cases of Alzheimer's disease (AD) aged 57-89 years. In the normal human hippocampus a striking and highly significant age-related decline in ChAT occurred from middle to old age (between 40 and 100 years); a trend apparent at a later stage and to a lesser extent in the hippocampal gyrus. In both areas enzyme activity in AD was inversely related to age at death; reductions compared with the normal were on average 70-80% in the 60-70 year old groups compared with 30-40% in the 80-90 year old group. A similar trend was apparent with respect to acetylcholinesterase (AchE) histochemical activity associated with fibers and terminals (predominantly cholinergic and concentrated in CA3 and 4 of the hippocampus) but not with reactive perikarya (considered to be noncholinergic) present in both hippocampus and cortex. These data indicate that the normal aging human hippocampus may constitute a useful model for investigating the dysfunction or degeneration of basal forebrain cholinergic neurons in AD.

Neurochemical activities in human temporal lobe related to aging and Alzheimer-type changes.

Activities relating to 3 neurotransmitter and 4 neuropeptide systems have been examined in human temporal lobe (post mortem) for their relationships with age and Alzheimer-type changes (senile plaques and cognitive function). Significant alterations with increasing age (from 61 to 92 years) in a series of non-demented cases included a reduction of the cholinergic enzyme, choline acetyltransferase, and an increase in vasoactive intestinal peptide immunoreactivity. In cases of alzheimer's disease the only neurochemical activity investigated which correlated significantly with cognitive impairment (assessed from a Mental Test Score obtained shortly before death) and with the severity of Alzheimer-type abnormalities (senile plaques density) was choline acetyltransferase. Further analyses of the data in relation to the severity of plaque formation suggest that alterations in other neurochemical activities including reductions in dopamine-beta-hydroxylase activity, cholecystokinin octapeptide (aqueous extracted) and somatostatin immunoreactivities and an increase in substance P immunoreactivity, may occur at later stages of the disease process. These comparative data suggest that biochemical changes in this brain area associated with age and earlier stages of Alzheimer's disease may be relatively selective.

Elevation in late-life depression of intercellular adhesion molecule-1 expression in the dorsolateral prefrontal cortex.

OBJECTIVE: Late-life depression may be associated with vascular disease. The authors investigated this association by determining whether intercellular adhesion molecule-1 (ICAM-1), a marker of ischemia-induced inflammation, is elevated in the dorsolateral prefrontal cortex in depression. METHOD: The authors studied postmortem tissue from 20 depressed subjects and a matched comparison group of 20 nondepressed subjects. They used immunocytochemistry to stain ICAM-1 in blood vessels on sections of the dorsolateral prefrontal cortex and occipital cortex and quantitative true color image analysis to measure the proportion of vessels expressing ICAM-1. RESULTS: ICAM-1 was significantly higher in both the gray and white matter of the depressed subjects' dorsolateral prefrontal cortex than the comparison subjects' dorsolateral prefrontal cortex. The difference between these groups was much smaller in the gray and white matter of the occipital cortex. CONCLUSIONS: These findings support the vascular depression hypothesis, which has important implications for the understanding and management of late-life depression.

Cholinergic activity in autism: abnormalities in the cerebral cortex and basal forebrain.

OBJECTIVE: Measures of cholinergic transmitter activity were investigated in patients with autism because of reported neuropathological abnormalities in cholinergic nuclei in the basal forebrain. METHOD: Levels of cholinergic enzyme and receptor activity were measured in the frontal and parietal cerebral cortex of deceased autistic adults, similarly aged normal adults without mental retardation, and nonautistic mentally retarded adults. The immunoreactivity levels of brain-derived neurotrophic factor and nerve growth factor were measured in the basal forebrain. RESULTS: There were no differences between the autistic and comparison groups in choline acetyltransferase or acetylcholinesterase activity in the cerebral cortex and basal forebrain or in muscarinic M(2) receptor or alpha-bungarotoxin binding within the cortex. Cortical M(1) receptor binding was up to 30% lower than normal in the autistic subjects, and the difference reached significance in the parietal cortex. In both the parietal and frontal cortices, differences in nicotinic receptors assessed by [(3)H]epibatidine binding were significant and extensive (65%-73% lower in the autistic group than in the normal subjects); there were no differences in nicotine binding in the basal forebrain. Immunochemical analysis indicated lower levels of both the alpha(4) and beta(2) nicotinic receptor subunits in the parietal cortex. The M(1) receptor abnormality was not evident in the nonautistic group with mental retardation, although the lower [(3)H]epibatidine binding was apparent. In the basal forebrain, the level of brain-derived neurotrophic factor in the autistic group was three times as high as the level of the normal group. CONCLUSIONS: These neurochemical abnormalities implicate the cholinergic system in developmental disorders such as autism and suggest the potential for intervention based on cholinergic receptor modulation.

Report of the second dementia with Lewy body international workshop: diagnosis and treatment. Consortium on Dementia with Lewy Bodies.

BACKGROUND/OBJECTIVE: The second International Workshop of the Consortium on Dementia with Lewy Bodies (DLB) met to review developments since publication of consensus guidelines for the clinical and pathologic diagnosis of DLB in 1996. The specificity of a clinical diagnosis of probable DLB, made using consensus criteria, is generally high (>85%), but sensitivity of case detection is lower and more variable. Inter-rater reliability for the core clinical features-recurrent visual hallucinations and spontaneous motor features of parkinsonism-is acceptable, but reliable identification of fluctuating cognition remains problematic. Depression and REM sleep behavior disorder may be additional features supportive of a diagnosis of DLB that were not included in the original guideline. RESULTS: It is recommended that the clinical consensus criteria continue to be used in their current format with research efforts focused on increasing sensitivity of case detection. Antiubiquitin immunocytochemistry is the method of choice for routine detection of Lewy bodies for diagnostic purposes in research and clinical practice. The use of alpha-synuclein antibodies to label Lewy bodies and Lewy neurites represents a major methodologic advance since the first DLB workshop. alpha-Synuclein-based methods are likely to be most useful in research laboratories, particularly for clinicopathologic correlative studies. CONCLUSION: Clinical management of DLB patients usually centers on the treatment of noncognitive features. There is now a pressing need to establish appropriately designed randomized controlled trials in DLB. Collaboration between dementia and movement disorder specialists is essential for rapid progress in research and clinical management protocols.

An evaluation of the predictive validity and inter-rater reliability of clinical diagnostic criteria for senile dementia of Lewy body type.

Several recent autopsy studies suggest that senile dementia of Lewy body type (SDLT) may be the second most common neuropathologic cause of dementia in the elderly, accounting for 7 to 30% of all cases. Operational criteria for the antemortem clinical diagnosis of SDLT have already been proposed by our group. The performance of these is now examined by randomizing the case notes from a new series of SDLT, Alzheimer, and multi-infarct dementia patients for psychiatric assessment by four raters of varying clinical experience and blind to pathologic diagnosis. Using the SDLT criteria, the two most experienced raters agreed in 94% of cases (kappa = 0.87), with the least experienced rater agreeing in 78% (kappa = 0.50). Diagnostic specificity for SDLT was uniformly high (90.0 to 97.0%), with a mean sensitivity of detection of 74%, and was greater by the experienced (90.0%) than the least experienced (55%) clinician. The antemortem identification of SDLT patients can therefore be achieved with a high degree of diagnostic specificity using such operationalized criteria, although there remains a minority of patients who present with either "typical" Alzheimer-type symptoms or with paranoid or delusional symptoms in the absence of substantial cognitive impairment. Sensitivity to neuroleptics may be a useful diagnostic pointer in these patients.

Lack of association of the alpha2-macroglobulin locus on chromosome 12 in AD.

OBJECTIVE: Analysis of AD has revealed that the apolipoprotein E locus (APOE) cannot account for all of the genetic risk associated with AD. Whole genome scanning in AD families suggests that a chromosome 12 locus may contribute significantly to disease development. The alpha2-macroglobulin gene (A2M) has been suggested as a candidate locus for AD based on analysis of familial AD. METHOD: We determined, in 195 neuropathologically verified AD cases and 107 age-matched control subjects, the association of two common polymorphisms in A2M (a pentanucleotide deletion 5' to the bait domain exon, and a valine-1000-isoleucine polymorphism in the thiolester site of the protein). RESULTS: Evidence was observed for linkage disequilibrium between the deletion and Ile1000 polymorphisms. No evidence was observed for an association between the thiolester polymorphism and AD alone or when accounting for the APOE-epsilon4 allele. No alteration in the frequency of the bait domain deletion was observed, although a small excess (4%) of deletion homozygotes was found in the AD group, which were absent in the control population. CONCLUSIONS: The A2M deletion polymorphism at most accounts for a small fraction of the genetic contribution toward AD, and this is small compared with APOE. Furthermore, reverse transcriptase PCR of A2M RNA from the brains of patients homozygous for the deletion polymorphism showed that the bait domain exon still is present in the RNA. This suggests that the A2M deletion polymorphism may be nonfunctional and that the chromosome 12 AD locus is situated elsewhere.