Nigral neurons are likely to die of a mechanism other than classical apoptosis in Parkinson's disease

The finding of apoptosis in Parkinson's disease (PD) represents a contentious issue. In fact, there is increasing evidence that an alternative mechanism of cell death is at work in the parkinsonian substantia nigra, which we tentatively term aposklesis. Unlike apoptosis, aposklesis ("withering") lacks the morphological signs of apoptosis and takes a slow course which is in agreement with the predicted rate of dopaminergic cell death in PD. Cells undergoing aposklesis may stain positive in the TUNEL reaction and show a reticular nuclear labeling but lack any significant chromatin condensation and the formation of apoptotic bodies. Not only neurons but also glial cells appear to undergo this form of cell death, which represents a relatively common finding in degenerative diseases of the CNS.

Increased levels of HPV16 E6*I transcripts in high-grade cervical cytology and histology (CIN II+) detected by rapid real-time RT-PCR amplification

OBJECTIVE

As cervical dysplasia may regress to normal cytology or progress to cervical carcinoma, it would be valuable to have a diagnostic tool to help decide whether therapeutic conization should be performed.

METHODS

Cervical samples of 301 HPV16 positive women were collected in RNAlater reagent to prevent RNA degradation. Relative levels of HPV16 DNA and HPV16 E6*I mRNA in the samples were determined using real-time polymerase chain reaction. Findings were correlated with histological diagnoses and cytological follow-up.

RESULTS

HPV16 E6*I mRNA levels were significantly higher in women with cytologically diagnosed severe cervical dysplasia (mean normalized ratio = 0.25) than in those with mild-to-moderate dysplasia (mean norm. ratio = 0.12), atypical squamous cells of uncertain origin (mean norm. ratio = 0.071) or normal cytology (mean norm. ratio = 0.034). Viral DNA levels were not significantly different between severe and mild-to-moderate dysplasia (mean norm. ratios, 55.8 and 63.5, respectively). The PPV for a histological diagnosis of severe cervical dysplasia [cervical intraepithelial neoplasia (CIN) II+] increased with the amounts of E6*I mRNA to more than 90% whereas the sensitivity decreased. The absence of HPV16 E6*I transcripts as well as HPV16 DNA considerably increased the negative predictive value and the specificity. However, low concentrations (or complete absence) of E6*I mRNA did not preclude a CIN II+ diagnosis.

CONCLUSIONS

Although the sensitivity is low, high levels of HPV16 E6*I mRNA are indicative of CIN II+ in cytologically diagnosed cervical dysplasia of individual patients. Thus, quantification of HPV16 E6*I mRNA could be helpful in managing follow-up and treatment in a subset of HPV16 positive women.

Inter-laboratory comparison of DNA preservation in archival paraffin-embedded human brain tissue from participating centres on four continents

DNA extracted from formalin-fixed and paraffin-embedded brain tissue is known to contain as yet ill-characterized inhibitors of the PCR process. As part of a project that aims to clarify the role of mitochondrial DNA sequence variation in human neurodegenerative diseases using DNA from various ethnic backgrounds, we have investigated factors that influence the preservation of archival DNA and its suitability for PCR. In this study, neuropathological tissue samples were analysed that had been routinely processed in 18 international centres on four continents. Following DNA extraction, PCR amplification of mitochondrial and nuclear DNA sequences was performed with and without additional purification of the template DNA. In addition, the DNA used for PCR was analysed by HPLC. Phosphate-buffered formalin proved to be a superior fixative compared with unbuffered aldehyde: DNA extraction resulted in greater yields, the molecular weight of the isolated DNA was higher and PCR was more successful. PCR inhibitors were identified as (1) high concentrations of small (<300 bp) DNA fragments that competitively compete with template DNA and (2) contaminants of the DNA template solution including denatured protein that cannot be completely removed by phenolic extraction. HPLC analysis did not reveal significant qualitative differences between DNA isolated from fresh-frozen tissue samples and DNA recovered from formalin-fixed, paraffin-embedded brain tissue. The fact that DNA could be amplified from the majority of tissue specimens in this study suggests that rare diseases and diseases where ethnic background plays an important role can be sampled for genetic polymorphism analysis on a global scale using archival neuropathological collections.

Expression of alpha-synuclein in non-apoptotic, slowly degenerating facial motoneurones

The discovery that missense mutations in the alpha-synuclein gene represent a rare genetic cause of Parkinson's disease (PD) has had significant impact on the development of research into neurodegenerative disorders. It is becoming increasingly clear that alpha-synuclein plays a central role in the pathological process, which causes Lewy body formation and neurodegeneration in PD. Importantly, there is evidence to suggest that mutated alpha-synuclein is toxic to both nerve cells and glia. However, the regulation and function of wild-type alpha-synuclein are as yet ill defined. Using the facial nerve axotomy model, we have addressed the question whether the expression of alpha-synuclein in nerve cells may change in response to injury. We were particularly interested in testing the hypothesis that the severity of neuronal injury had an effect on alpha-synuclein metabolism. Facial nerve cut and crush, respectively, were performed in adult rats where normal facial motoneurones do not express alpha-synuclein. Following axotomy, a subset of facial motoneurones newly expressed high levels of alpha-synuclein immunoreactivity in their cell body and, occasionally, their nucleus. Significantly more nerve cells were labelled following facial nerve transection than following facial nerve crush. Confocal microscopy revealed a granular pattern of alpha-synuclein aggregation in degenerating nerve cells. Interestingly, the observed cell death phenotype was clearly non-apoptotic and developed over days or weeks rather than hours. Thus, axotomy of adult rat facial motoneurones triggers de novo expression of alpha-synuclein and this expression is associated with a non-apoptotic, slow form a neurodegeneration. In addition, the extent of alpha-synuclein expression is related to the severity of neuronal injury.

Genotype-phenotype correlation in gemistocytic astrocytomas

OBJECTIVE

Gemistocytic astrocytomas often behave aggressively and carry the least favorable prognosis among diffuse astrocytomas. The frequency of p53 mutations has been reported to be significantly higher in the gemistocytic variant as compared with other astrocytomas.

METHODS

Between 1985 and 1998, we selected 25 tumor samples from among 201 samples from patients with gemistocytic astrocytomas operated on at the Mayo Clinic. Exons 5 to 8 of the p53 gene were sequenced using an automated deoxyribonucleic acid sequencer. Morphometric characterization of individual gemistocytes was performed using an image analysis program.

RESULTS

Of 25 tissue samples analyzed, 16 were found to carry a p53 missense mutation (three in exon 5, three in exon 6, one in exon 7, and nine in exon 8), and one sequence variant was synonymous. Mutations were clustered at codons 151 (2 of 17 mutations), 193 (3 of 17 mutations), and 273 (5 of 17 mutations) of the p53 gene. Patients whose tumors carried a p53 mutation were significantly younger than other patients, and their tumors tended to accumulate more p53 protein than those of other patients. Phenotype analysis of gemistocytes revealed that the sizes of tumor cell nuclei and of entire tumor cells in the same tissue area were positively correlated. Smaller tumor cell nuclei tended to be less circular or more atypical. In addition, more atypical gemistocytes were found in tumors lacking a wild-type p53 allele as well as in tissue from patients whose postoperative survival was shorter.

CONCLUSION

Our data confirm that the frequency of p53 mutations is significantly higher (approximately twofold) in gemistocytic astrocytomas as compared with other astrocytoma subtypes. Whether the high frequency of p53 mutations contributes to the more aggressive behavior of gemistocytic astrocytomas, however, remains unclear.

The alpha1-antichymotrypsin A-allele in German Parkinson disease patients

An increased frequency of the A-allele of the alpha-antichymotrypsin (ACT) gene has been recently described in Japanese patients suffering from Parkinson disease (PD). In the present study, we have analyzed 62 German PD patients with regard to their ACT and APOE genotypes and compared them to 53 controls without clinical or pathological evidence of neurodegenerative disease. The A-allele frequency was 47% in PD patients compared to 54% in control cases excluding ACT as a major susceptibility factor for PD in the Caucasian population. Yet, ACT-A allele frequencies were significantly different (p < 0.001) between Japanese and German controls. Therefore, although our data do not suggest that the alpha1-ACT polymorphism is a significant risk factor for the development of PD, a consideration of differences in genetic background seems warranted when evaluating susceptibility factors for neurodegenerative disease.

Parkinson disease: analysis of mitochondrial DNA in monozygotic twins

We have sequenced all mitochondrial complex I and tRNA genes in five pairs of monozygotic twins with a longitudinal diagnosis of idiopathic Parkinson disease (PD). At the time of molecular genetic analysis, four of the pairs were discordant for PD. Five novel homoplasmic sequence variants, including two missense mutations (ND2 4924 G/A, ND3 10192 C/T), were detected in mitochondrial genes of complex I in four of the pairs. In addition, a total of 20 known polymorphisms affecting both complex I and tRNA genes was found. Importantly, mitochondrial DNA sequences were identical in diseased and non-affected siblings of each pair. Our results demonstrate that missense mutations of mitochondrial complex I may occur in clinically discordant parkinsonian twins, questioning the direct pathogenic relevance of at least some of these mutations.

Role of mitochondria in Parkinson disease

The cause of the selective degeneration of nigrostriatal neurons in Parkinson disease (PD) has remained largely unknown. Exceptions include rare missense mutations in the alpha-synuclein gene on chromosome 4, a potentially pathogenic mutation affecting the ubiquitin pathway, and mutations in the parkin gene on chromosome 6. However, unlike classical PD, the latter syndrome is not associated with the formation of typical Lewy bodies. In contrast, a biochemical defect of complex I of the mitochondrial respiratory chain has been described in a relatively large group of confirmed PD cases. Recent cybrid studies indicate that the complex I defect in PD has a genetic cause and that it may arise from mutations in the mitochondrial DNA. Sequence analysis of the mitochondrial genome supports the view that mitochondrial point mutations are involved in PD pathogenesis. However, although mitochondria function as regulators in several known forms of cell death, their exact involvement in PD has remained unresolved. This is of relevance because classical apoptosis does not appear to play a major role in the degeneration of the parkinsonian nigra.

Two novel point mutations of mitochondrial tRNA genes in histologically confirmed Parkinson disease

Mutations in mitochondrially encoded tRNA genes have been described in a variety of neurological disorders. One such mutation, the A to G transition at nucleotide position 4336 of the mitochondrial tRNA(Gln) gene, has been associated with both Alzheimer and Parkinson disease. We have now performed a complete sequence analysis of all 22 mitochondrially encoded tRNA genes in 20 cases of histologically proven idiopathic Parkinson disease. Genomic DNA extracted from the substantia nigra of frozen or formalin-fixed and paraffin-embedded brains was used for amplification by polymerase chain reaction followed by automated sequencing. Two new homoplasmic point mutations were detected in the genes for tRNA(Thr) (15950 G/A) and tRNA(Pro) (15965 T/C) in 1 patient each. Restriction enzyme digestion revealed absence of the 15950 G/A mutation in 96 controls and in 40 cases of neuropathologically confirmed Alzheimer disease. The 15965 T/C mutation was shown to be absent from 100 control subjects and 47 Alzheimer cases. In addition to the two novel mutations, six known sequence variants were detected in a total of 6 different patients in the genes for tRNA(Asp) (G7521A, 1), tRNA(Arg) (T10463C, 1), tRNA(LeuCUN) (A12308G, 2), and tRNA(Thr) (A15924G, 1; G15928A, 2), including 1 patient carrying the tRNA(Gln) (A4336G) mutation. The G15950A transition affects position 70 of the aminoacyl acceptor stem of tRNA(Thr), which has been implicated as a recognition element for threonyl-tRNA synthetase and, at least in some tRNAs, in the processing of primary mitochondrial transcripts. The T15965C point mutation in the mitochondrial tRNA(Pro) gene alters position 64 of the TpsiC stem. The corresponding nucleotide in bacterial aminoacyl-tRNAs is involved in the interaction with elongation factor Tu. Thus, the two novel mutations are likely to be of functional relevance and could contribute to dopaminergic nerve cell death in affected individuals.

Analysis of mitochondrial targeting sequence and coding region polymorphisms of the manganese superoxide dismutase gene in German Parkinson disease patients

Two polymorphisms of the MnSOD gene, Ile58Thr and Ala9Val, have been associated with Parkinson disease (PD). The Ile58Thr amino acid exchange affects the stability at the tetrameric interface of the enzyme and reduces the enzymatic activity of MnSOD while the Ala/Val substitution at position -9 of the mitochondrial targeting sequence (MTS) may lead to misdirected intracellular trafficking. We have analyzed 63 German Caucasian PD patients for possible sequence variation in the MTS as well as in exon 3 of the MnSOD gene. All 63 PD patients analyzed exhibited a T at nucleotide position 5777 in exon 3 of the MnSOD gene corresponding to ATA, or Ile at the peptide level, and no other sequence variants were found. In addition, both alleles of the Ala9Val polymorphism in the MTS of MnSOD were equally distributed between German PD patients and controls excluding this gene variant as a risk factor for PD in Caucasian subjects.

Differential expression of MHC class II molecules by microglia and neoplastic astroglia: relevance for the escape of astrocytoma cells from immune surveillance

There is increasing evidence that microglia serve as antigen presenters in the human CNS. Although the occurrence of MHC class II immunoreactive cells has been reported in astrocytic gliomas, the relative contribution of microglia to this cell population has not been studied in detail. Using computer-assisted image analysis, we have investigated the expression of MHC class II molecules and of the microglia/macrophage markers Ki-MIP, RCA-1, KP1 and iba1, in 97 astrocytic gliomas comprising all WHO grades to answer the question whether there is a correlation between tumour grade and the number of MHC class II positive microglia/macrophage profiles. Microglia expressing MHC class II were common in astrocytomas and anaplastic astrocytomas but rare in pilocytic tumours although there was significant variation within each group. MHC class II immunoreactivity was reduced in highly cellular areas of glioblastomas where large numbers of cells expressing macrophage markers were still present. Thus, there was no simple relationship between tumour grade and microglial/macrophage MHC class II expression. In addition, up to 55% of astrocytic gliomas contained MHC class II immunoreactive tumour cells. Microglia but not tumour cells were found to express the BB1/B7 costimulator. We conclude that microglia in astrocytic gliomas are well equipped to function as antigen presenting cells. Yet, neoplastic astroglia appear to acquire the capacity to downregulate microglial MHC class II expression and, at the same time, may induce T-cell clonal anergy through aberrant expression of MHC class II molecules.

Neurodegeneration and aging: role of the second genome

The latest Health Report of the World Health Organization predicts a significant increase in the age of human populations over the next two decades. In the developed world, at least 20% of the population will be older than 65 years. This development together with the as yet unknown etiology of many neurodegenerative disorders has caused an increased interest in the biology and pathophysiology of mitochondria. Dysfunction of mitochondria has been linked to both normal aging and neurodegenerative disorders, with the latter occurring much more frequently at higher age. Specifically, genetic defects in mitochondria have been shown to accumulate during life, and certain mutations of mitochondrial genes have been implicated in the etiology of Parkinson's and Alzheimer's diseases. In addition, a large number of new mitochondrial diseases have been identified following the first description of mitochondrial mutations 10 years ago. While there can be little doubt that DNA defects of mitochondria play a role in aging, specific mutations of mitochondrial genes underlying Parkinson's or Alzheimer's diseases remain to be identified. There is evidence, however, that mutations of the mitochondrial genome may increase the susceptibility to neurodegeneration.

Microglia and the development of spongiform change in Creutzfeldt-Jakob disease

Recent in vitro experiments suggest that neurotoxicity of the prion protein is dependent on the presence of microglia. We have studied 11 cases of Creutzfeldt-Jakob disease (CJD) using immunocytochemistry in combination with computerized image analysis to clarify the relationship between spongiform change and microglial activation. MHC class II-positive microglia were almost exclusively confined to cortical gray matter where the neuropil area occupied by these cells exceeded that of controls more than 350-fold. In cortical regions with a bimodal distribution of spongiform degeneration, the presence of class II-positive microglia correlated well with the presence of vacuolation in layer V, but significantly less with spongiform change in layers II and III. In areas where spongiform degeneration affected the entire depth of the cortex, activated microglia were predominantly located in the inner one-half of the cortex or were evenly distributed throughout all cortical laminae. Here, microglia exhibited atypical, tortuous cell processes and occasionally intracytoplasmic vacuoles, suggesting that microglia themselves may become a disease target. Taken together, our results provide indirect evidence against an early causative involvement of microglia in the development of spongiform change. At later stages, however, diseased microglia could produce harmful factors which mediate both astrogliosis and neuronal injury.

Histopathology and APOE genotype of the first Alzheimer disease patient, Auguste D

Alois Alzheimer published two papers on the disease which was named after him by Emil Kraepelin in 1910. Each of these papers contains clinical and pathological data on a patient Alzheimer had seen at the hospital. We have previously reported on the rediscovery of tissue sections from Alzheimer's second published case of Alzheimer disease, Johann F., which probably gave the disease its name (Neurogenetics 1997; 1:73-80). Here, we describe the histopathology and APOE genotype of Alois Alzheimer's first patient, Auguste D. As in the case of Johann F., a large number of tissue sections belonging to Alzheimer's laboratory, which was later headed by Spielmeyer, were found among material kept at the Institute of Neuropathology of the University of Munich. As described by Alzheimer in his original report (Allg Zeitschr Psychiatr 1907; 64:146-148), there were numerous neurofibrillary tangles and many amyloid plaques, especially in the upper cortical layers of this patient. Yet, there was no microscopic evidence for vascular, i.e., arteriosclerotic, lesions. Interestingly, Alzheimer's histological preparations did not include the hippocampus or entorhinal region. The APOE genotype of this patient was shown to be epsilon3/epsilon3 by PCR-based restriction enzyme analysis, indicating that mutational screening of the tissue is feasible. The historical importance of the case of Auguste D. lies in the fact that it marks the beginning of research into Alzheimer disease. In addition, neurofibrillary tangles were first described in this brain.

Novel mutations of mitochondrial complex I in pathologically proven Parkinson disease

Complete sequence analysis of all mitochondrial complex I genes was performed in 22 cases of neuropathologically confirmed idiopathic Parkinson disease (PD). DNA from the substantia nigra was used as a template for polymerase chain reaction-based genomic sequencing. Seven novel mutations causing the exchange of amino acids were detected in subunit genes ND1 (3992 C/ T, 4024 A/G), ND4 (11253 T/C, 12084 C/T), ND5 (13711 G/A, 13768 T/C), and ND6 (14582 T/C). In addition, five known missense mutations affecting the ND1 (3335 T/C, 3338 T/C), ND2 (5460 G/A), ND3 (10398 A/G), and ND5 (13966 A/G) genes as well as three secondary LHON mutations (4216 T/C, 4917 A/ G, 13708 G/A) were found in the PD group. Among the novel mutations, the 11253 T/C transition which changes a conserved isoleucine residue into threonine is most likely to be of functional relevance. Furthermore, 43 synonymous polymorphisms were detected in PD brains, including 20 novel sequence variants. Haplogroup analysis revealed that most unique missense mutations were found in PD cases belonging to the D(c) haplogroup. Our data are in line with the view that PD is not a single disease entity but comprises a genetically heterogeneous group of disorders. The results of our study further suggest that 90% or more of all idiopathic PD cases are not due to sequence variation of mitochondrial complex I, but that mitochondrial mutations may play a pathogenic role in a subset of PD patients.

Low prevalence of apolipoprotein E epsilon 4 allele in the neurofibrillary tangle predominant form of senile dementia

Apolipoprotein E (apoE) genotypes were analyzed in a subset of demented very old patients who share a uniform neuropathological picture consisting of various numbers of neurofibrillary tangles (NFT) in allocortical areas of the inferomedial temporal lobe without significant numbers of either diffuse amyloid or neuritic plaques. Among 18 patients with this condition referred to as NFT-predominant senile dementia (average age at death 87 +/- 4.7 years), we found allele frequencies of 0.11 epsilon 2, 0.86 epsilon 3 and 0.03 epsilon 4, which are significantly different from allele frequencies reported in Alzheimer's disease (0.04 epsilon 2, 0.59 epsilon 3 and 0.38 epsilon 4). The low prevalence of the apoE epsilon 4 allele in this subset of patients is striking and suggests that NFT-predominant senile dementia is a dementing neurodegenerative disease in which the deposition of A beta-amyloid did not occur, possibly due to protective effects of epsilon 2 and/or epsilon 3 alleles or lack of a promoting effect of apoE epsilon 4 on amyloidogenesis. We propose that NFT-predominant dementia is a variant of Alzheimer's disease occurring in the very old.

The 'common deletion' is not increased in parkinsonian substantia nigra as shown by competitive polymerase chain reaction

Previous studies have estimated levels of mitochondrial DNA (mtDNA) carrying the 4,977-base-pair 'common deletion' in tissues from patients with Parkinson's disease (PD) by using semiquantitative techniques. The role of this deleted mtDNA species in the pathogenesis of PD has remained controversial. We have applied competitive polymerase chain reaction to achieve exact quantitation of deleted mtDNA in the substantia nigra and additional brain regions of cases with neuropathologically confirmed Lewy-body parkinsonism. In addition, genotyping was carried out for CYP2D6G1,934A and CYP2D6C2,938T alleles and the mitochondrial ND2 (nucleotide 5,460) and transfer RNA for glutamine (nucleotide 4,336) sequence variants. Parkinsonian brains showed 1-3% deleted mtDNA in the substantia nigra, that is, deletion levels were not higher than in age-matched controls. Our findings suggest that the defect in complex I of the respiratory chain observed in PD is not primarily due to the 'common deletion.'

Association of the mitochondrial tRNA(A4336G) mutation with Alzheimer's and Parkinson's diseases

Alzheimer's and Parkinson's diseases (AD, PD) are among the most common neurodegenerative disorders in adults. Both AD and PD have a complex aetiology, and it is widely considered that genetic factors, acting independently or in concert with other genetic and/or environmental factors, modify the risk of developing them. While the apolipoprotein E (ApoE) epsilon 4 allele represents an established risk factor for familial and sporadic late-onset AD, it has been suggested that a common polymorphism in the alpha 1-antichymotrypsin gene modifies the ApoE epsilon 4 dosage effect in AD. Moreover, it has been proposed that a mitochondrial tRNA(Gln) sequence variant (A4336G transition) confers an increased risk for both AD and PD. This finding is of particular interest as the A4336G mutation seems to predispose to two clinically and neuropathologically distinct neurodegenerative disorders. We have examined the allelic frequencies of these putative susceptibility genes in 28 neuropathologically confirmed cases of AD, 23 cases with Lewy-body PD and 100 age-matched controls without clinical or histological evidence of neurodegenerative disease. The ApoE epsilon 4 allele frequency was significantly overrepresented in AD patients vs controls (0.35 vs 0.11) but we could not find evidence for an association between the alpha 1-antichymotrypsin AA genotype, the ApoE epsilon 4 allele and AD. In contrast, the mtDNA(A4336G) mutation was present in one of AD cases and in two of 23 PD patients, whereas no mutation was found in 100 age-matched controls (P < 0.05). Our data therefore support the hypothesis that the mitochondrial A4336G mutation represents a risk factor for AD and PD.

Rediscovery of the case described by Alois Alzheimer in 1911: historical, histological and molecular genetic analysis

In 1911, Alois Alzheimer published a detailed report (Zbl. ges. Neurol. Psych. 4: 356-385) on a peculiar case of the disease that had been named after him by Emil Kraepelin in 1910. Alzheimer describes a 56-year-old male patient (Johann F.) who suffered from presenile dementia and who was hospitalized in Kraepelin's clinic for more than 3 years. Post-mortem examination of the patient's brain revealed numerous amyloid plaques but no neurofibrillary tangles in the cerebral cortex, corresponding to a less common form of Alzheimer disease which may be referred to as 'plaque only'. We have identified well-preserved histological sections of this case and performed mutational screening of exon 17 of the amyloid precursor protein gene and genotyping for apolipoprotein E alleles. The patient was shown to be homozygous for apolipoprotein allele epsilon3 and lacked APP mutations at codons 692, 693, 713 and 717. This case is of historical importance as it may have convinced Kraepelin to name the disease after his co-worker, Alois Alzheimer.

On the question of apoptosis in the parkinsonian substantia nigra

Apoptosis has been postulated as a mechanism of nerve cell death in Parkinson's disease. In the present study, the substantia nigra of 22 neuropathologically confirmed Parkinson cases and 8 control brains was studied using the in situ end-labeling (TUNEL) method. About 50% of parkinsonian brains showed a small number of TUNEL-positive glial cells in the substantia nigra, whereas no neurons showed convincing TUNEL positivity or any morphological signs of apoptosis. No correlation was observed between the number of TUNEL-positive glial cells and microglial activation. Our results fail to demonstrate apoptosis as a mechanism of cell death in Parkinson's disease.

Long-lasting perivascular accumulation of major histocompatibility complex class II-positive lipophages in the spinal cord of stroke patients: possible relevance for the immune privilege of the brain

Six cases of middle cerebral artery occlusion are presented in which the cellular changes accompanying descending degeneration of the lateral corticospinal tract were studied at different time points (5 days-10 years) following the insult. Microglia and perivascular cells were found to ingest large amounts of myelin degradation products, while expressing high levels of major histocompatibility complex (MHC) class II molecules. Activation of perivascular macrophages, as indicated by increased class II expression, lasted for many years and appeared to follow down-regulation of both phagocytic activity and class II expression on parenchymal microglia. TUNEL labeling was absent from both microglia and perivascular cells at all time points investigated. Indirect evidence is presented that microglia may transfer myelin degradation products to the perivascular space. Perivascular cells which express MHC class II molecules constitutively do not appear to leave the perivascular compartment in large numbers and could release myelin degradation products into the cerebrospinal fluid. The possible immunological consequences of these findings are discussed with respect to their possible relevance for antigen presentation and autoimmune central nervous system disease.

Regional heterogeneity of mtDNA heteroplasmy in parkinsonian brain

There is increasing evidence for a role of defects of mitochondrial DNA in the etiology of neurodegenerative disorders such as Parkinson's and Alzheimer's disease as well as in normal aging. In several studies a biochemical defect of complex I of the respiratory chain (NADH dehydrogenase, EC 1.6.5.3) has been found in the substantia nigra of Parkinsonian brains. Thus, mutations of mitochondrial genes encoding subunits of complex I could contribute to the pathogenesis of Parkinson's disease. A heteroplasmic G5460A mutation affecting the ND2 subunit of NADH dehydrogenase was detected in several brains of patients with idiopathic Parkinson's disease. Since this mutation is heteroplasmic we were interested in the distribution of mutated and wild-type mitochondrial DNA in different brain areas. Relative levels of mutated DNA were quantified in a large number of anatomical regions using DNA extracted from formalin-fixed and paraffin-embedded brain tissue. DNA was amplified by the polymerase chain reaction and digested employing the restriction enzyme Hphl. The proportion of mutated DNA was determined by laser densitometry. In addition, genotype-phenotype analyses were performed on sections of the substantia nigra with the aid of an automated image analysis system. Ratios of mutant to wild-type DNA varied between 44% and 98%. However, there was no systematic relationship between mutated DNA ratios and ontogenetically related brain areas suggesting that the observed regional heterogeneity of mitochondrial DNA heteroplasmy is most likely due to random segregation during development. Therefore, tissue-specific differences in the sensitivity to pathogenic effects of the ND2(5460) mutation or the influence of additional susceptibility genes may be envisioned.

The apolipoprotein E epsilon 4 allele in Parkinson's disease with Alzheimer lesions

The association between the apolipoprotein E (ApoE) epsilon 4 allele and Parkinson's disease (PD) with coexistent dementia has remained controversial. We determined ApoE allele frequencies in 35 subjects with neuropathologically confirmed Lewy body Parkinsonism with and without concomitant Alzheimer lesions, 27 patients with Alzheimer's disease (AD), and 54 controls without neurodegenerative disease. We hypothesized that if AD lesions in PD evolve by the same pathomechanism as in "pure AD," the ApoE epsilon 4 allele frequency in PD with AD lesions (PD+AD) and pure AD should be similar. The frequency of the ApoE epsilon 4 allele differed significantly between PD+AD (13.3%) and AD cases (35.2%), but not between PD+AD and PD without AD pathology (12.5%) or controls (11.1%). We conclude that the ApoE epsilon 4 allele does not function as a risk factor which influences the development of AD lesions in PD. Our data suggest that Parkinson's disease with Alzheimer lesions and Alzheimer's disease with coexistent Parkinsonian features represent two distinct entities at both the clinicopathological and molecular genetic levels.

Mitochondrial NADH dehydrogenase and CYP2D6 genotypes in Lewy-body parkinsonism

The cause of nerve-cell death in sporadic Parkinson's disease remains unknown. Although environmental factors have been traditionally implicated in the etiology of Parkinson's disease, recent studies strongly suggest that there is a genetic contribution to this multifactorial disorder. We studied archival brain tissue from clinically and neuropathologically verified cases of Parkinson's disease, using nonradioactive cycle sequencing and restriction enzymatic analysis of polymerase chain reaction products. Twenty-one Parkinsonian brains with brain stem Lewy-bodies and 77 control brains were genotyped at two mitochondrial loci previously implicated in the etiology of neurodegenerative disease. In addition, genotyping was performed for two alleles of the debrisoquine 4-hydroxylase gene (CYP2D6). A heteroplasmic mtDNAG5460A missense mutation in the ND2 subunit gene of NADH dehydrogenase was three times more frequent in Parkinson cases (4/21) compared to controls (5/77). A homoplasmic mtDNAA4336G transition which alters the mitochondrial tRNAGln gene product was found in one Parkinson case. Frequencies of the CYP2D6G1934A and CYP2D6C2938T alleles were not significantly different between Parkinson cases and controls. Two Parkinsonian brains with high degrees of heteroplasmy for the ND2G5460A mutation and one CYP2D6C2938T homozygous case showed very high numbers of Lewy-bodies in the substantia nigra. The results of this study are in line with the concept that different genetic loci may be involved in Parkinson's disease susceptibility. They provide a hint that the ND2(5460) mutation, in combination with other factors, could play a role in disease pathogenesis in a subset of patients.

Apolipoprotein E genotype and neuropathological phenotype in two members of a German family with chromosome 14-linked early onset Alzheimer's disease

Molecular genetic analysis was performed in two autopsy-confirmed cases of early-onset Alzheimer's disease belonging to a large German pedigree [FAD2, according to the nomenclature of St. George-Hyslop, et al. (1987) Science 235:885-890]. The disease in this family has been linked to chromosome 14. As gene interactions are considered to influence the age of onset and tissue pathology in Alzheimer's disease, we have studied three candidate genes that could modify disease progression. In this study a new polymerase chain reaction (PCR) assay was established for apolipoprotein E genotyping in archival neuropathological tissue, exon 17 of the amyloid precursor protein gene was directly sequenced, and a candidate mutation site at nucleotide (nt) 5460 of the mitochondrial NADH dehydrogenase subunit gene ND2 was analyzed employing PCR followed by HphI digestion. Whereas no sequence variations were detected in exon 17APP or at nt5460 of mitochondrial DNA, the apolipoprotein E genotypes of the two cases differed. Neuropathological examination revealed a higher number of beta A4-positive amyloid plaques and a larger total tissue area covered by beta A4 deposits in the epsilon 3/epsilon 3 homozygote. In contrast, the number of cortical neurofibrillary tangles and the number of plaques with tau-positive neurites appeared to be higher in the epsilon 3/epsilon 4 heterozygote. Our findings support the view that the chromosome 14 genetic defect, rather than apolipoprotein E genotype, is the preeminent factor determining Alzheimer's disease pathology in this family.

Absence of the mitochondrial A7237T mutation in Parkinson's disease

In recent years much has been speculated about a pathogenic role of mitochondrial defects in Parkinson's disease. Ozawa et al. (BBRC 176, 938-946, 1991) have described an A/T transversion at nucleotide 7237 of mitochondrial DNA affecting cytochrome-c-oxidase (complex IV) of the respiratory chain that could contribute to the pathogenesis of PD. Employing PCR based genomic sequencing and restriction enzyme analysis on 19 cases of Lewy-body parkinsonism, we exclude this mutation as a common cause of Parkinson's disease. This demonstrates the need for systematic sequencing of the mitochondrial genome in a large number of histologically verified cases of Parkinson's disease.

No association of mutations at nucleotide 5460 of mitochondrial NADH dehydrogenase with Alzheimer's disease

NADH dehydrogenase (EC 1.6.99.3) mutations at nucleotide 5460 of mitochondrial DNA (codon 331 of the ND2 subunit gene) have been associated with Alzheimer's disease (BBRC 182, 238-246, 1992; BBRC 189, 1202-1206, 1992). We have sequenced codons 304-347 of this gene in 15 neuropathologically confirmed cases of Alzheimer's disease. In addition, restriction enzyme analysis was performed on the same cases and on 28 control brains. No mutations were detected in the Alzheimer brains but heteroplasmy for a G-->A transition at nucleotide 5460 of mtDNA was found in the frontal cortex of a single control. Thus, our findings do not confirm reports of a significant association between mutations at nucleotide 5460 of mitochondrial DNA and Alzheimer's disease.

Use of neuropathological tissue for molecular genetic studies: parameters affecting DNA extraction and polymerase chain reaction

Nuclear and mitochondrial DNA were extracted from gray matter of human cerebral cortex which had either been formalin-fixed and embedded into paraffin or stored in formalin for up to 26 years. Extraction conditions were optimized for proteinase K digestion, i.e., enzyme concentration, digestion temperature and incubation time. Using the polymerase chain reaction (PCR), DNA was successfully amplified from archival material and sequenced employing a direct nonradioactive cycle sequencing protocol. In general, tissue embedded into paraffin following brief fixation in formalin gave good quantitative results, i.e., up to 1 microgram DNA/mg tissue were extracted. This yield was at least one order of magnitude higher than that obtained with tissue stored in formalin. However, paraffin-embedded neuropathological material was found to contain an as-yet-unidentified PCR inhibitor, and a deleterious effect of long-term fixation in unbuffered low-grade formalin was clearly detectable. Importantly, both paraffin-embedded tissue blocks and human brain that had been stored in formalin for many years yielded DNA sufficient for qualitative analysis. The implications of these findings for the use of neuropathological material in molecular genetic studies are discussed.

Non-radioactive direct sequencing of PCR products amplified from neuropathological specimens

We have developed a simple, rapid and relatively inexpensive protocol for direct non-isotopic cycle sequencing of DNA amplified using the polymerase chain reaction (PCR). PCR is performed on routine and archival neuropathological tissue. For sequencing, a 5'-digoxigenin end-labelled oligonucleotide primer is annealed and extended during thermal cycling, sequencing reactions are separated on a standard sequencing gel and the gel is contact-blotted to a nylon membrane. Sequenced DNA is visualized using immunological detection of digoxigenin.

Purification of human microsomal liver glucose-6-phosphatase system by affinity chromatography and immunodetection

A multiple purification of phosphohydrolase (PH) and phosphotranslocase (PT) of the human liver microsomal glucose-6-phosphatase system has been obtained by a rapid two-step procedure using affinity chromatography. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of the final products showed one major band each at 63 and 37 kDa for PH and PT respectively. The immunoblot analysis of SDS-PAGE of various purification steps for human liver using rabbit antibodies raised against the enzyme preparations also showed major bands at 63 and 37 kDa for PH and PT respectively. A major band at 260 kDa was observed by the Western blot of native PAGE of the enzyme preparation for PH. Cross-reacting materials at the positions of 63 and 37 kDa were detected only in liver, kidney and intestine. From five liver samples of patients suffering from type Ia glycogenosis there were diminished amounts of crossreacting materials at 63 kDa only in two samples. The uptake of glucose-6-phosphate has taken place in liposomes of Sepharose affinity purified products suggesting that this preparation may be a complex of PH and glucose-6-phosphate translocase.