A comprehensive analysis of deletions, multiplications, and copy number variations in PARK2.

OBJECTIVES: To perform a comprehensive population genetic study of PARK2. PARK2 mutations are associated with juvenile parkinsonism, Alzheimer disease, cancer, leprosy, and diabetes mellitus, yet ironically, there has been no comprehensive study of PARK2 in control subjects; and to resolve controversial association of PARK2 heterozygous mutations with Parkinson disease (PD) in a well-powered study. METHODS: We studied 1,686 control subjects (mean age 66.1 ± 13.1 years) and 2,091 patients with PD (mean onset age 58.3 ± 12.1 years). We tested for PARK2 deletions/multiplications/copy number variations (CNV) using semiquantitative PCR and multiplex ligation-dependent probe amplification, and validated the mutations by real-time quantitative PCR. Subjects were tested for point mutations previously. Association with PD was tested as PARK2 main effect, and in combination with known PD risk factors: SNCA, MAPT, APOE, smoking, and coffee intake. RESULTS: A total of 0.95% of control subjects and 0.86% of patients carried a heterozygous CNV mutation. CNV mutations found in 16 control subjects were all in exons 1-4, sparing exons that encode functionally critical protein domains. Thirteen patients had 2 CNV mutations, 5 had 1 CNV and 1 point mutation, and 18 had 1 CNV mutation. Mutations found in patients spanned exons 2-9. In whites, having 1 CNV was not associated with increased risk (odds ratio 1.05, p = 0.89) or earlier onset of PD (64.7 ± 8.6 heterozygous vs 58.5 ± 11.8 normal). CONCLUSIONS: This comprehensive population genetic study in control subjects fills the void for a PARK2 reference dataset. There is no compelling evidence for association of heterozygous PARK2 mutations, by themselves or in combination with known risk factors, with PD.

parkin mutation analysis in clinic patients with early-onset Parkinson [corrected] disease.

parkin Mutations are the most common identified cause of Parkinson's disease (PD). It has been suggested that patients with young-onset PD be screened for parkin mutations as a part of their clinical work-up. The aim of this study was to assess parkin mutation frequency in a clinical setting, correlate genotype with phenotype, and evaluate the current justification for clinical parkin testing. Patients were selected from a movement disorder clinic based on diagnosis of PD and onset age

Impact of DNA testing for early-onset familial Alzheimer disease and frontotemporal dementia.

BACKGROUND: DNA testing of persons at risk for hereditary, degenerative neurologic diseases is relatively new. Only anecdotal reports of such testing in familial Alzheimer disease (FAD) exist, and little is know about the personal and social impact of such testing. METHODS: In a descriptive, observational study, individuals at 50% risk for autosomal dominant, early-onset FAD or frontotemporal dementia with parkinsonism linked to chromosome 17 underwent DNA testing for the genetic mutations previously identified in affected family members. Individuals were followed up for (1/2) to 3 years and were interviewed regarding attitudes toward the testing process and the impact of the results. RESULTS: Twenty-one (8.4%) of 251 persons at risk for FAD or frontotemporal dementia requested genetic testing. The most common reasons for requesting testing were concern about early symptoms of dementia, financial or family planning, and relief from anxiety. Twelve individuals had positive DNA test results, and 6 of these had early symptoms of dementia; 8 had negative results; and 1 has not yet received results. Of 14 asymptomatic individuals completing testing, 13 believed the testing was beneficial. Two persons reported moderate anxiety and 1 reported moderate depression. As expected, persons with negative test results had happier experiences overall, but even they had to deal with ongoing anxiety and depression. Thus far, there have been no psychiatric hospitalizations, suicide attempts, or denials of insurance. CONCLUSIONS: Genetic testing in early-onset FAD and frontotemporal dementia can be completed successfully. Most individuals demonstrate effective coping skills and find the testing to be beneficial, but long-term effects remain unknown.

TAU as a susceptibility gene for amyotropic lateral sclerosis-parkinsonism dementia complex of Guam.

BACKGROUND: A Guam variant of amyotrophic lateral sclerosis (ALS-G) and parkinsonism dementia complex (PDC-G) are found in the Chamorro people of Guam. Both disorders have overlapping neuropathologic findings, with neurofibrillary tangles in spinal cord and brain. The cause of ALS-G-PDC-G is unknown, although inheritance and environment appear important. Because neurofibrillary tangles containing tau protein are present in ALS-G-PDC-G, and because mutations in the tau gene (TAU) cause autosomal dominant frontotemporal dementia, TAU was examined as a candidate gene for ALS-G-PDC-G. METHODS: TAU was evaluated by DNA sequence analysis in subjects with ALS-G-PDC-G, by linkage analysis of TAU polymorphisms in an extended pedigree from the village of Umatac, and by evaluation of linkage disequilibrium with polymorphic markers flanking and within TAU. RESULTS: Linkage disequilibrium between ALS-G-PDC-G and the TAU polymorphism CA3662 was observed. For this 2-allele system, PDC and ALS cases were significantly less likely than Guamanian controls to have the 1 allele (4.9% and 2% vs 11.5%, respectively; Fisher exact P =.007). DNA sequence analysis of TAU coding regions did not demonstrate a mutation responsible for ALS-G-PDC-G. Analysis of TAU genotypes in an extended pedigree of subjects from Umatac showed obligate recombinants between TAU and ALS-G-PDC-G. Linkage analysis of the Umatac pedigree indicates that TAU is not the major gene for ALS-G-PDC-G. CONCLUSIONS: The genetic association between ALS-G-PDC-G implicates TAU in the genetic susceptibility to ALS-G-PDC-G. TAU may be a modifying gene increasing risk for ALS-G-PDC-G in the presence of another, as yet, unidentified gene.

A genomic sequence analysis of the mouse and human microtubule-associated protein tau.

Microtubule associated protein tau (MAPT) encodes the microtubule associated protein tau, the primary component of neurofibrillary tangles found in Alzheimer's disease and other neurodegenerative disorders. Mutations in the coding and intronic sequences of MAPT cause autosomal dominant frontotemporal dementia (FTDP-17). MAPT is also a candidate gene for progressive supranuclear palsy and hereditary dysphagic dementia. A human PAC (201 kb) and a mouse BAC (161 kb) containing the entire MAPT and Mtapt genes, respectively, were identified and sequenced. Comparative DNA sequence analysis revealed over 100 conserved non-repeat potential cis-acting regulatory sequences in or close to MAPT. Those islands with greater than 67% nucleotide identity range in size from 20 to greater than 1700 nucleotides. Over 90 single nucleotide polymorphisms were identified in MAPT that are candidate susceptibility alleles for neurodegenerative disease. The 5' and 3' flanking genes for MAPT are the corticotrophin-releasing factor receptor (CRFR) gene and KIAA1267, a gene of unknown function expressed in brain.

Frequency of tau gene mutations in familial and sporadic cases of non-Alzheimer dementia.

BACKGROUND: Mutations in the tau gene have been reported in families with frontotemporal dementia (FTD) linked to chromosome 17. It remains uncertain how commonly such mutations are found in patients with FTD or non-Alzheimer dementia with or without a positive family history. OBJECTIVE: To determine the frequency of tau mutations in patients with non-Alzheimer dementia. PATIENTS AND METHODS: One hundred one patients with non-Alzheimer, nonvascular dementia, most thought to have FTD. Of these, 57 had a positive family history of dementia. Neuropathologic findings were available in 32. The tau gene was sequenced for all exons including flanking intronic DNA, portions of the 3' and 5' untranslated regions, and at least 146 base pairs in the intron following exon 10. RESULTS: Overall, the frequency of the tau mutations was low, being 5.9% (6/101) in the entire group. No mutations were found in the 44 sporadic cases. However, 6 (10.5%) of the 57 familial cases and 4 (33%) of the 12 familial cases with tau pathologic findings had mutations in the tau gene. The most common mutation was P301L. CONCLUSIONS: We conclude that tau mutations are uncommon in a neurology referral population with non-Alzheimer dementia, even in those with a clinical diagnosis of FTD. However, a positive family history and/or tau pathologic findings increase the likelihood of a tau mutation. There must be other genetic and nongenetic causes of FTD and non-Alzheimer dementia, similar to the etiologic heterogeneity present in Alzheimer disease.

The genetics of Alzheimer's disease.

Alzheimer's disease (AD) is a genetically complex disorder. Mutations in the amyloid precursor protein and presenilin 1 (PS1) genes are fully penetrant and cause early-onset AD. Mutations in presenilin 2, a PS1 homologue, cause partially penetrant autosomal dominant AD with onset age beginning at 40 years and extending past 75 years. A fourth gene, apolipoprotein E (ApoE) is a risk-factor for late-onset AD. Over 40 genes have been tested as AD candidate genes, yet none has been clearly established as an AD risk factor. Linkage studies have implicated a number of chromosome regions as possible sites for late-onset AD loci with the strongest evidence being for chromosome 12. Candidate genes in this region include alpha2-macroglobulin (A2M) and low-density lipoprotein receptor-related gene (LRP), although neither has been clearly established as an AD gene. Identification of additional late-onset genes will require larger samples, more sophisticated analysis methods, and large-scale positional cloning efforts.

Single-step conversion of P1 and P1 artificial chromosome clones into yeast artificial chromosomes.

Large insert genomic clones are useful for generating transgenic animals, particularly when specific mutations are introduced. To facilitate manipulation of large genomic sequences, we developed a method of converting Escherichia coli P1 artificial chromosomes (PACs) into yeast artificial chromosomes (YACs). A shuttle vector, pMAX-121, was generated that contains elements needed to generate a YAC (cen4, ars, ura3, his, and two telomere segments) along with approximately 1.3 kb of sequence homologous to P1 and PAC vector sequences. Cotransformation of yeast with the target PAC or P1 clone and pMAX-121 results in two homologous recombination events. The first, between the target clone and pMAX-121, results in a circular molecule. The second is an intramolecular recombination event between the two pMAX-121 telomere sequences, resulting in a linear molecule. The resulting YAC is stably maintained in yeast and can be further modified using homologous recombination. The method was used to convert a 201-kb PAC containing the human tau gene into a stable linear YAC. A second vector, pLys2-neo, was developed to retrofit the YAC with the yeast lys2 gene, a selectable marker replacing the yeast ura3 gene, and a Pgk-neo cassette that confers G418 resistance to mammalian cells. The resulting YAC can be used for generating transgenic animals and stably transfected cell lines. Also, the lys2 marker facilitates introduction of mutations by homologous recombination.

A novel mutation at position +12 in the intron following exon 10 of the tau gene in familial frontotemporal dementia (FTD-Kumamoto)

Exonic and intronic mutations in the tau gene cause familial frontotemporal dementia and parkinsonism linked to chromosome 17. Here, we describe a new mutation, consisting of a C-to-T transition at position +12 of the intron following exon 10 of the tau gene in the Kumamoto pedigree, showing frontotemporal dementia. The mutation caused a marked reduction in melting temperature of the tau exon 10-splicing regulatory element RNA and a large increase in exon 10-containing transcripts. Brain tissue from affected individuals showed an abnormal preponderance of exon 10-containing transcripts that was reflected at the protein level by an overproduction of tau isoforms with four microtubule-binding repeats. Immunostaining revealed the presence of tau aggregates in degenerating neurons and glial cells. Isolated tau filaments had a twisted ribbon-like morphology and were made of hyperphosphorylated four-repeat tau isoforms. The additional mutation located dose to the splice-donor site of the intron following exon 10 of the tau gene supports the view that intronic mutations exercize their pathogenic effect by destabilizing RNA secondary structure.

Familial frontotemporal dementia with ubiquitin-positive, tau-negative inclusions.

OBJECTIVE: To describe the clinical features, neuropathology, and genetic studies in a family with autosomal dominant frontotemporal dementia (FTD). BACKGROUND: Clinical Pick's disease, or FTD with parkinsonism, has been described in several families linked to chromosome 17 (FTDP-17). Most of these have shown tau protein mutations. The clinical and pathologic variations in these families resemble the spectrum of sporadic FTD or "Pick complex." METHODS: Clinical and behavioral analysis of the affected members with extensive histochemical and neuropathologic description of three cases, genetic analysis of three clinically affected members and seven at risk members to assess linkage to chromosome 17, and sequencing of the tau gene in two patients were performed. RESULTS: The clinical pattern shows a highly stereotypic disinhibition dementia with late extrapyramidal features, progressive mutism, and terminal dysphagia in three generations of affected individuals. Neuropathology showed frontotemporal atrophy, and microscopically tau- and synuclein-negative and ubiquitin-positive neuronal inclusions, in the background of superficial cortical spongiosis, neuronal loss, and gliosis. Tau expression was restricted to oligodendroglia. All exons and surrounding introns of the tau gene were sequenced, and no mutation or disease-related polymorphisms were detected in either of two affected pedigree members. CONCLUSION: This family with autosomal dominant frontotemporal dementia (FTD) shows no tau expression in neurons. The ubiquitin-positive, tau-negative inclusions have been described before in FTD with and without motor neuron disease, but not in a familial form. The clinical and some pathologic features are similar to those of several of the families included in descriptions of FTD with parkinsonism linked to chromosome 17, but the linkage to tau has been excluded. The defect in this family, however, could be functionally related to tau mutations.

Pro-apoptotic effects of tau mutations in chromosome 17 frontotemporal dementia and parkinsonism.

It was recently discovered that mutations of tau cause hereditary frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Here we report that cultured SH-SY5Y human neuroblastoma cells transfected with mutated tau genes are more vulnerable to apoptotic stimulus. Two kinds of mutations of tau causing FTDP-17 were examined in the present study: one was in exon 10 (N279K) and the other was in exon 12 (V337M). SH-SY5Y cells transfected with either mutated tau were more vulnerable to serum withdrawal, whereas cells transfected with the wild-type tau or vector alone showed no significant change in apoptotic vulnerability. The increase in the intracellular calcium concentration by the serum withdrawal was significantly greater in the SH-SY5Y cells transfected with mutated tau genes than in cells transfected with the wild-type tau or vector alone. These results suggest that mutations of tau might cause FTDP-17 by these pro-apoptotic functions by disrupting the intracellular calcium homeostasis.

A mutation in the microtubule-associated protein tau in pallido-nigro-luysian degeneration.

We detected a missense mutation in exon 10 of tau that causes a substitution at codon 279 (N279K) in a Japanese patient with a familial background of parkinsonism and dementia originally described as pallido-nigro-luysian degeneration. This mutation is the same as one seen in a Caucasian family with pallido-ponto-nigral degeneration. The similarities between these two families suggest a common genetic mechanism that may account for the peculiar distribution of neuroglial degeneration with tauopathy.

Missense and silent tau gene mutations cause frontotemporal dementia with parkinsonism-chromosome 17 type, by affecting multiple alternative RNA splicing regulatory elements.

Frontotemporal dementia with parkinsonism, chromosome 17 type (FTDP-17) is caused by mutations in the tau gene, and the signature lesions of FTDP-17 are filamentous tau inclusions. Tau mutations may be pathogenic either by altering protein function or gene regulation. Here we show that missense, silent, and intronic tau mutations can increase or decrease splicing of tau exon 10 (E10) by acting on 3 different cis-acting regulatory elements. These elements include an exon splicing enhancer that can either be strengthened (mutation N279(K)) or destroyed (mutation Delta280(K)), resulting in either constitutive E10 inclusion or the exclusion of E10 from tau transcripts. E10 contains a second regulatory element that is an exon splicing silencer, the function of which is abolished by a silent FTDP-17 mutation (L284(L)), resulting in excess E10 inclusion. A third element inhibiting E10 splicing is contained in the intronic sequences directly flanking the 5' splice site of E10 and intronic FTDP-17 mutations in this element enhance E10 inclusion. Thus, tau mutations cause FTDP-17 by multiple pathological mechanisms, which may explain the phenotypic heterogeneity observed in FTDP-17, as exemplified by an unusual family described here with tau pathology as well as amyloid and neuritic plaques.

A clinical pathological comparison of three families with frontotemporal dementia and identical mutations in the tau gene (P301L)

We investigated three separate families (designated D, F and G) with frontotemporal dementia that have the same molecular mutation in exon 10 of the tau gene (P301L). The families share many clinical characteristics, including behavioural aberrations, defective executive functions, language deficits, relatively preserved constructional abilities and frontotemporal atrophy on imaging studies. However, Family D has an earlier mean age of onset and shorter duration of disease than Families F and G (49.0 and 5.1 years versus 61-64 and 7.3-8.0 years, respectively). Two members of Families D and F had neuropathological studies demonstrating lobar atrophy, but the brain from Family D had prominent and diffuse circular, intraneuronal, neurofibrillary tangles not seen in Family F. The brain from Family F had ballooned neurons typical of Pick's disease type B not found in Family D. A second autopsy from Family D showed neurofibrillary tangles in the brainstem with a distribution similar to that found in progressive supranuclear palsy. These three families demonstrate that a missense mutation in the exon 10 microtubule-binding domain of the tau protein gene can produce severe behavioural abnormalities with frontotemporal lobar atrophy and microscopic tau pathology. However, the findings in these families also emphasize that additional unidentified environmental and/or genetic factors must be producing important phenotypic variability on the background of an identical mutation. Apolipoprotein E genotype does not appear to be such a factor influencing age of onset in this disease.

A distinct familial presenile dementia with a novel missense mutation in the tau gene.

We report a Japanese family with early onset hereditary frontotemporal dementia and a novel missense mutation (Ser305Asn) in the tau gene. The patients presented with personality changes followed by impaired cognition and memory as well as disorientation, but minimal Parkinsonism. Imaging studies showed fronto-temporal atrophy with ventricular dilatation more on the left, and postmortem examination of the brain revealed numerous neurofibrillary tangles (NFTs) with an unusual morphology and distribution. Silver-stained sections showed ring-shaped NFTs partially surrounding the nucleus that were most prominent in frontal, temporal, insular and postcentral cortices, as well as in dentate gyrus. Cortical NFTs were restricted primarily to layer II, and were composed of straight tubules. Numerous glial cells containing coiled bodies and abundant neuropil threads were detected in cerebral white matter, hippocampus, basal ganglia, diencephalon and brain stem, but no senile plaques or other diagnostic lesions were seen. Both the glial and neuronal tangles were stained by antibodies to phosphorylation-independent and phosphorylation-dependent epitopes in tau. Thus, this novel mutation causes a distinct familial tauopathy.

Pathogenic implications of mutations in the tau gene in pallido-ponto-nigral degeneration and related neurodegenerative disorders linked to chromosome 17.

Pallido-ponto-nigral degeneration (PPND) is one of the most well characterized familial neurodegenerative disorders linked to chromosome 17q21-22. These hereditary disorders are known collectively as frontotemporal dementia (FTD) and parkinsonism linked to chromosome 17 (FTDP-17). Although the clinical features and associated regional variations in the neuronal loss observed in different FTDP-17 kindreds are diverse, the diagnostic lesions of FTDP-17 brains are tau-rich filaments in the cytoplasm of specific subpopulations of neurons and glial cells. The microtubule associated protein (tau) gene is located on chromosome 17q21-22. For these reasons, we investigated the possibility that PPND and other FTDP-17 syndromes might be caused by mutations in the tau gene. Two missense mutations in exon 10 of the tau gene that segregate with disease, Asn279(Lys) in the PPND kindred and Pro301(Leu) in four other FTDP-17 kindreds, were found. A third mutation was found in the intron adjacent to the 3' splice site of exon 10 in patients from another FTDP-17 family. Transcripts that contain exon 10 encode tau isoforms with four microtubule (MT)-binding repeats (4Rtau) as opposed to tau isoforms with three MT-binding repeats (3Rtau). The insoluble tau aggregates isolated from brains of patients with each mutation were analyzed by immunoblotting using tau-specific antibodies. For each of three mutations, abnormal tau with an apparent Mr of 64 and 69 was observed. The dephosphorylated material comigrated with tau isoforms containing exon 10 having four MT-binding repeats but not with 3Rtau. Thus, the brains of patients with both the missense mutations and the splice junction mutation contain aggregates of insoluble 4Rtau in filamentous inclusions, which may lead to neurodegeneration.

Tau is a candidate gene for chromosome 17 frontotemporal dementia.

Frontotemporal dementia with parkinsonism, chromosome 17 type (FTDP-17), a recently defined disease entity, is clinically characterized by personality changes sometimes associated with psychosis, hyperorality, and diminished speech output, disturbed executive function and nonfluent aphasia, bradykinesia, and rigidity. Neuropathological changes include frontotemporal atrophy often associated with atrophy of the basal ganglia, substantia nigra, and amygdala. Neurofibrillary tangles (NFTs) are seen in some but not all families. Inheritance is autosomal dominant and the gene has been regionally localized to 17q21-22 in a 2- to 4-centimorgan (cM) region flanked by markers D17S800 and D17S791. The gene for tau, the primary component of NFTs, is located in the same region of chromosome 17. Tau was evaluated as a candidate gene. Physical mapping studies place tau within 2 megabases or less of D17S791, but it is probably outside the D17S800-D17S791 FTDP-17 interval. DNA sequence analysis of tau coding regions in affected subjects from two FTDP-17 families revealed nine DNA sequence variants, eight of which were also identified in controls and are thus polymorphisms. A ninth variant (Val279Met) was found in one FTDP-17 family but not in the second FTDP-17 family. Three lines of evidence indicate that the Val279Met change is an FTDP-17 causative mutation. First, the mutation site is highly conserved, and a normal valine is found at this position in all three tau interrepeat sequences and in other microtubule associated protein tau homologues. Second, the mutation co-segregates with the disease in family A. Third, the mutation is not found in normal controls.

Missense mutations in the chromosome 14 familial Alzheimer's disease presenilin 1 gene.

Mutations in the presenilin genes (PS-1 and PS-2) cause early onset autosomal dominant Alzheimer's disease (AD). Eight early-onset, autopsy-documented familial AD kindreds were screened for mutations in PS-1, and seven different mutations were identified. Three of these were new mutations (G209V, A426P, and E120D), two were previously reported mutations in new families, and three mutations were confirmed in previously published families. Two of these new mutations are found within predicted transmembrane domains (TMDs 4, 7, and 8). The A426P mutation is the most C-terminal PS-1 mutation identified to date.

An expression map from human chromosome 14q24.3.

We have constructed an expression map of chromosome 14q24.3 between markers D14S42 and D14S63. cDNA selection with YACs from 14q24.3 was used to generate expressed sequence tags (ESTs). The localization of ESTs was confirmed on a YAC contig. PCR products of ESTs were used as probes to screen cDNA libraries leading to the isolation of transcripts for known and unknown genes. In total, the expression map contains 7 known genes previously mapped to 14q24.3, 6 cDNA transcripts, and 15 anonymous ESTs. The addition of 21 unique transcribed loci from an approximately 5- to 7-Mb region of chromosome 14q24.3 will facilitate future efforts to identify human disease genes from this region.

Chromosome 17 and hereditary dementia: linkage studies in three non-Alzheimer families and kindreds with late-onset FAD.

Several previous families with differing clinical and pathologic characteristics have demonstrated linkage to the 17q21-22 region. We have performed a linkage analysis with chromosome 17 markers on three families showing autosomal dominant inheritance of non-Alzheimer dementia and 60 kindreds with late-onset familial Alzheimer's disease (FAD). Family A shows unequivocal evidence of linkage with a maximum lod score of 5.0 for marker D17S934 (theta = 0.001). This family has an unusual syndrome of a schizophrenia-like psychosis beginning in the fifth or sixth decade followed by severe dementia with an average disease duration of 13.8 years. Neuropathology from five autopsies in this family has shown marked neurofibrillary tangle formation (NFT), degeneration of the amygdala, and no amyloid plaques. This confirms the presence of a gene associated with dementia on 17q and extends the related phenotype to include schizophrenia-like symptoms and classic NFT pathology. A second family with early aphasia progressing to dementia and cortical-basal ganglion-like degeneration also has suggestive evidence for linkage to 17q. A third family with very early-onset dementia (mean, 31 years) and nonspecific pathology can be excluded from the 17q region and emphasizes additional genetic heterogeneity in non-Alzheimer hereditary dementia. Finally, we also present evidence against linkage to D17S579 in the set of 60 families with late-onset FAD, providing further evidence that the chromosome 17 gene is unlikely to be involved in the pathogenesis of typical AD.