Fused in Sarcoma (FUS) gene mutations are not a frequent cause of essential tremor in Europeans

FUS/TLS (denoting fused in sarcoma/translocated in liposarcoma [MIM 137070]) codifies an RNA binding protein. Mutations in this gene cause amyotrophic lateral sclerosis (ALS; MIM 608030). Essential tremor (ET [MIM 190300]) is the most frequent movement disorder. Despite its strong familiar aggregation, recently a whole exome sequencing study has identified FUS mutations as a cause of familial ET. To determine whether mutations in FUS are also common in other populations, we sequenced FUS gene in 178 unrelated Spanish subjects with ET. We detected only an intronic single-pair nucleotide deletion (c.1293-37delC), which was predicted to affect mRNA splicing. However, leukocyte mRNA analysis showed no changes in FUS expression. In conclusion, coding or splicing FUS mutations are not a frequent cause of ET in the Spanish population.

A novel mutation in the PSEN1 gene (L286P) associated with familial early-onset dementia of Alzheimer type and lobar haematomas

The aim of this study was to describe a novel mutation in exon 8 of the presenilin gene (L286P) associated with early-onset autosomal dominant Alzheimer's disease (AD) and lobar haematomas. The proband was a woman who developed cognitive decline with predominant memory loss at the age of 35 years. The patient died at the age of 54 years and the neuropathological examination confirmed the diagnosis of AD. Three of her four siblings, one parent and one sibling of her parent had suffered from cognitive decline at ages between 35 and 42 years. Three of them also presented lobar haematomas. The neuropathological examination, available in one of them, disclosed the presence of severe amyloid angiopathy as the cause of the haematoma. The study of PSEN1 gene with single strand conformation polymorphism technique failed to show abnormalities suggestive of mutations. Direct sequencing disclosed the presence of a missense mutation in codon 286 (L286P) in the proband and her already affected descendent, which was absent in the healthy sibling. L286P is a novel mutation in PSEN1 that causes familial early-onset AD and brain haematomas related to amyloid angiopathy.

Increased cerebral activity in Parkinson?s disease patients carrying the DRD2 TaqIA A1 allele during a demanding motor task: a compensatory mechanism?

Previous studies suggest that neuroimaging techniques are useful for detecting the effects of functional genetic polymorphisms on brain function in healthy subjects or in patients presenting with psychiatric or neurodegenerative conditions. Former evidence showed that individuals carrying risk alleles displayed broader patterns of brain activity during behavioural and cognitive tasks, despite being clinically comparable to non-carriers. This suggests the presence of compensatory brain mechanisms. In the present study, we investigated this effect in Parkinson's disease (PD) patients carrying the DRD2 TaqIA A1 allelic variant. This variant may confer an increased risk of developing the disease and/or influence the clinical presentation. During a complex sequential motor task, we evidenced by functional magnetic resonance imaging that A1 allele carriers activated a larger network of bilateral cerebral areas than non-carriers, including cerebellar and premotor regions. Both groups had similar clinical and demographic measures. In addition, their motor performance during the functional magnetic resonance experiment was comparable. Therefore, our conclusions, pending replication in a larger sample, seem to reflect the recruitment of compensatory cerebral resources during motor processing in PD patients carrying the A1 allele.

Brain tau expression and correlation with the H1/H1 tau genotype in frontotemporal lobar degeneration patients

Alterations in tau mRNA splicing and association with H1/H1 tau genotype have been described in some sporadic tauopathies. We evaluated the 4R/3R tau mRNA ratio in 18 patients with frontotemporal lobar degeneration (FTLD), and the effect of the H1/H1 genotype on this ratio. The 4R/3R mRNA ratio in frontal cortex was similar in FTLD patients and controls. The H1/H1 genotype carriers showed a significant increase in 4R/3R mRNA ratio, suggesting that this genotype could modulate the tau mRNA splicing.

Late-onset frontotemporal dementia associated with a novel PGRN mutation

We describe a new mutation in the PGRN gene (A303AfsX57) associated with late-onset frontotemporal dementia and with "cat's eye" shaped intranuclear and cytoplasmatic ubiquitin immunoreactive inclusions in the neuropathological exam. The A303AfsX57 mutation is consistent with a nucleotide deletion in exon 8 (c908delC). This deletion causes a frameshift at codon 303 that introduces a premature termination codon (A303AfsX57).

Sequence analysis of tau 3'untranslated region and saitohin gene in sporadic progressive supranuclear palsy

BACKGROUND

The extended tau H1 haplotype has previously been described in association with progressive supranuclear palsy (PSP). Recently, a new gene called saitohin (STH), nested within an intron of tau, has been discovered. The Q7R polymorphism of STH appears to be related to late onset Alzheimer's disease.

OBJECTIVES

To search for genetic changes in the 3'untranslated region (3'UTR) of tau and adjacent sequence LOC147077, and in the coding region of STH in PSP patients.

METHODS

The study included 57 PSP patients and 83 healthy controls. The genetic analysis of each region was performed through sequencing. The Q7R polymorphism was studied through restriction enzyme and electrophoresis analysis.

RESULTS

No mutations were found in the regions analysed. The QQ genotype of the STH polymorphism was over-represented in participants with PSP (91.5%) compared with control subjects (47%) (p< or =0.00001). This genotype co-segregated with the H1/H1 haplotype in our PSP cases.

CONCLUSIONS

Our results do not support a major role for the tau 3'UTR in PSP genetics. The QQ genotype of STH confers susceptibility for PSP and is in linkage disequilibrium with the H1/H1 haplotype.

Primary progressive aphasia as the initial manifestation of corticobasal degeneration and unusual tauopathies

The clinical, neuroradiological, neuropathological and biochemical findings in four patients with primary progressive aphasia and tauopathy are described. The aphasic syndrome preceded by several years the appearance of other symptoms in every case. Asymmetrical apraxia with alien hand phenomenon occurred in one case. Frontotemporal symptoms occurred in three cases, but progressed to dramatic cognitive devastation in only one of these. Generalized dementia consistent with probable Alzheimer's disease (AD) developed with time in another. Cerebral computer tomography scans, magnetic resonance imaging and SPECT studies revealed marked asymmetries in one case, and showed nonspecific cerebral atrophy in the remaining ones. The neuropathological examination revealed typical corticobasal degeneration (CBD) in one case; CBD and AD in another; and atypical CBD, argyrophilic grain disease (AGD) and alpha-synucleinopathy consistent with Parkinson's disease in a third. Unique neuropathological findings were found in the remaining case. This was characterized by severe cerebral atrophy, marked neuronal loss in the cerebral cortex and abnormal tau deposition in neurons of the cerebral cortex, diencephalon and brain stem. Ballooned neurons, Pick bodies, generalized cortical neurofibrillary tangles and astrocytic plaques were absent. However, massive globular inclusions, containing phospho-tau, occurred in glial cells, mainly oligodendrocytes, in the white matter. Biochemical studies of frontal homogenates revealed four bands of 73/74, 68, 64 and 60 kDa of phosphorylated tau (using antibodies recognizing phospho-tau Thr181, Ser262 and Ser422) in the patient with AD and CBD, suggesting a predominant AD pattern in this case. Two bands of 68 and 64 kDa of phospho-tau were recovered in the sarkosyl-insoluble fraction in the other three cases. This pattern is similar to that found in CBD, progressive supranuclear palsy and AGD. Taken together, the present series further supports pure and combined CBD as causes of primary progressive aphasia, and they extend the hypothesis that primary progressive aphasia may be the initial symptom of distinct tauopathies.

A novel mutation (V89L) in the presenilin 1 gene in a family with early onset Alzheimer's disease and marked behavioural disturbances

A novel mutation (V89L) in the presenilin 1 (PSEN1) gene is described in a family with pathologically confirmed Alzheimer's disease. The mutation was identified in two affected members with early onset Alzheimer's disease characterised by early and marked behavioural disturbances. The mutation is located on the same side of the helix as other described mutations in the first transmembrane domain and its relation to other mutations in this helix suggests that they share a common pathogenic mechanism.

Alzheimer disease is not associated with polymorphisms in the angiotensinogen and renin genes

Hypertension has been implicated as a risk factor for Alzheimer disease (AD) and dementia in epidemiological studies of humans. It is thus possible that there are common genetic determinants for hypertension and AD. Epidemiological, clinical, and experimental data suggest that the renin-angiotensin-aldosterone system is a critical regulator of blood pressure. The presence of an MboI site in an RFLP in the renin gene and the Thr at the Met/Thr polymorphism at codon 235 (M235T) of the angiotensinogen gene have been reported to be associated with hypertension. These variants were studied in autopsy-confirmed AD cases and matched controls from the U.K. While no association was detected with the renin polymorphism, a weak deleterious effect was observed in cases homozygous for the angiotensinogen Thr allele. However, this association was not observed in a French cohort of clinically diagnosed AD cases and controls, suggesting that the initial observation was a type I error. Thus, these polymorphisms are unlikely to be associated with AD risk.

Analysis of the coding and the 5' flanking regions of the alpha-synuclein gene in patients with Parkinson's disease

Missense mutations of the alpha-synuclein gene have been reported to explain a few kindreds with autosomal dominant Parkinson's disease (PD). In order to identify mutations in our PD patients, we have screened the coding region and 5'flanking region of the gene. DNA samples from 50 patients with familial PD were screened via single-strand conformation polymorphism (SSCP) for mutations in the alpha-synuclein gene. The 5' flanking region was examined in 117 additional PD patients (27 patients with unclear family history for PD, and 90 patients without family history) and in 169 control subjects. We found one change (G199A) in exon 4 in one family with a pattern of autosomal dominant PD. However, this mutation did not result in an amino acid substitution (valine) and did not segregate completely with PD. The analysis of the 5' flanking region also showed a new polymorphism, a nucleotide insertion (- 164insA) linked to a nucleotide substitution (C-116G), in patients and in controls. The -164insA/C-116G allele was present in 52.3% of the patients and in 47.6% of the controls. We did not find significant differences regarding the allelic and genotype frequencies between PD and control groups. These results suggest that mutations in the alpha-synuclein gene are a very rare cause of familial PD and that the novel -164insA/C-116G polymorphism in the 5' flanking region does not confer susceptibility to develop PD.

Detection of the presenilin 1 gene mutation (M139T) in early-onset familial Alzheimer disease in Spain

In a family with early-onset Alzheimer disease (EOAD) from Spain we found a mutation in the presenilin 1 (PS1) gene that predicts a methionine-to-threonine change at the PS1 residue 139 (M139T). This mutation was previously reported in a independent French family. The age of onset of the disease was similar in the affected members from both families, suggesting a specific age of expression (range 47-50 years). The detection of the M139T mutation in an independent EOAD family strongly supports the pathogenicity of this mutation in familial Alzheimer disease (AD).

A novel presenilin 1 mutation (Leu166Arg) associated with early-onset Alzheimer disease

BACKGROUND

Pathogenic mutations in the presenilin 1 (PS1) gene leading to early-onset Alzheimer disease have been described in various populations. The different mutations are not distributed randomly in the PS1 protein but are clustered in some PS1 exons.

OBJECTIVE

To screen the PS1 gene in search of a potential mutation in a Spanish family with early-onset Alzheimer disease.

METHODS

Single-stranded conformational polymorphism and heteroduplex analyses of all exons were used to search for a potential mutation. Subsequent sequencing of the DNA samples with an abnormal heteroduplex pattern was performed to identity the mutation in the sense strand and in the complementary strand.

RESULTS

We found a novel mutation in exon 6 of the PS1 gene at a site that, so far, had not been described as a cluster of mutations. The mutation (an A to C change) causes a substitution of leucine for arginine at position 166 of the PS1 protein and is located adjacent to the transmembrane domain III, where few mutations have been found. In this family, the disease follows an autosomal inheritance pattern with early onset (range, 32-44 years).

CONCLUSION

A novel missense mutation (Leu166Arg) at an atypical site associated with early-onset Alzheimer disease has been identified in a Spanish family.

Significant association between the tau gene A0/A0 genotype and Parkinson's disease

A significant association between the tau gene A0/A0 genotype and progressive supranuclear palsy has been reported recently. To determine if the presence of a tau polymorphism could constitute a risk factor for the development of sporadic and familial Parkinson's disease, a dinucleotide repeat marker at intron 11 was genotyped in 152 patients with PD, 52 patients with Alzheimer's disease, and 150 healthy controls. We detected a significant difference in A0 allelic frequency in the Parkinson's disease group (79.27%) compared with the control group (71%) and the Alzheimer's disease group (73.07%). Individuals homozygous for the A0 allele were also detected significantly more frequently in the Parkinson's disease group (63.8%) compared with the control group (52.66%) and the Alzheimer's disease group (48.07%). These results suggest a possible involvement of the tau gene in the pathogenesis of some cases of Parkinson's disease.

Identification of a novel polymorphism in the promoter region of the tau gene highly associated to progressive supranuclear palsy in humans

An intronic polymorphism and other changes in the transcribed region of the tau gene forming a haplotype have been previously described associated to progressive supranuclear palsy (PSP). These results raised the possibility that a change at or near the tau gene could be responsible for an increased risk to develop PSP. We initiated the present work in research for potential changes in the promoter region of the tau gene that could further extend the previously described haplotype. The tau promoter region was analyzed through single strand conformation polymorphism followed by direct sequencing in PSP patients (n = 35), in controls (n = 195) and in Alzheimer's disease (AD; n = 74) patients. We have been able to identify a G to C change at position -221 of the tau gene promoter region. The CC genotype has been detected to be present with a significantly higher frequency in PSP patients (91.4%; P < 0.00001; OR = 11.8), but not in AD patients, as compared with controls (49.74%). Subsequently we have detected that the CC -221 tau promoter genotype is significantly associated to the tau intronic A0/A0 genotype (P < 0.00001). The detected -221 tau G to C change occurs within a potential c-myb proto-oncogene element present in the promoter region. Thus, in addition to extending the previously described haplotype associated to PSP, this -221 G to C change is an interesting candidate that could provide a potential explanation for the association of the haplotype to increased risk for developing PSP.

Parental origin and meiotic stage of non-disjunction in 139 cases of trisomy 21

The parental origin and the meiotic stage of non-disjunction have been determined in 139 Down syndrome patients with regular trisomy 21 and in their parents through the analysis of DNA polymorphism. The meiotic error is maternal in 91.60% cases and paternal in 8.39% of cases. Of the maternal cases, 72.41% were due to meiosis I errors (MMI) and 27.58% were due to meiosis II errors (MMII). Of the paternal cases, 45.45% were due to meiosis I (PMI) and 54.54% were due to meiosis II (PMII). The mean maternal ages were 31.6 +/- 5.3 (+/- SD) years in errors from MMI, 32.3 +/- 6.4 years in errors from MMII, 31.4 +/- 4.6 years in errors from PMI and 29.5 +/- 2.7 years in errors from PMII. No significant statistical differences were observed between maternal and paternal errors, further supporting the presence of a constant chromosome 21 non-disjunction error type.

A presenilin 1 mutation (Ser169Pro) associated with early-onset AD and myoclonic seizures

OBJECTIVE

To characterize the mutation responsible for early-onset AD in a large Spanish kindred.

BACKGROUND

Mutations in the presenilin 1 (PS1) gene have been identified and are known to be responsible for 18 to 50% of familial early-onset AD cases.

METHODS

Patients were characterized clinically. The proband was further studied with EEG, CSF analysis, CT, brain biopsy, and histology. Other members were studied using EEG, CT, MRI, and SPECT. Genetic analysis of PS1 was performed using PCR amplification of PS1 exons and direct sequencing followed by PS1 modeling of the normal and mutant PS1 proteins.

RESULTS

A novel mutation (Ser169Pro) in exon 6 of the PS1 gene was identified in different affected members. The Ser169Pro mutation is located at a site of the PS1 protein that is not a cluster of mutations. The mutation was not present in 100 general population controls and in 50 unrelated sporadic AD cases. The Ser169Pro mutation is associated with generalized myoclonic seizures several years after the initial symptoms of AD, a very early AD onset (< or =35 years), and a rapidly progressive cognitive decline.

CONCLUSIONS

The absence of the PS1 Ser169Pro mutation in the general population and in sporadic AD cases together with its detection in the affected members of this kindred suggests that it is a pathogenic mutation. The serine to proline change predicts a kink in the alpha-helix of the transmembrane domain of the PS1 protein that could radically disrupt its normal structure. Further characterization of the effect of this mutation could help identify the function of the PS1 protein and the pathogenic mechanisms of AD.

Alpha1-antichymotrypsin gene polymorphism and susceptibility to Parkinson's disease

OBJECTIVE

To determine whether the alpha1-antichymotrypsin AA genotype (ACT-AA) confers susceptibility for developing Parkinson's disease (PD) in the Spanish population.

BACKGROUND

A correlation between the ACT-AA genotype and the risk of developing PD has been recently reported in the Japanese population.

METHODS

The ACT genotypes of 71 patients diagnosed with clinically definite PD were compared with those of 109 age-matched healthy control subjects.

RESULTS

The authors found that the ACT-AA polymorphism frequency was not increased significantly in the PD group (31%) compared with the control group (28.4%). The ACT allelic distribution was also similar for familial and sporadic PD, for female and male patients, and for the different clinical subtypes of PD. The age at onset of PD was significantly lower in the ACT-AA patients compared with non-ACT-AA patients. When the actual age was considered, the ACT-AA frequency was higher in PD patients < or =50 years old (50%) compared with that present in patients >50 years old (26.8%), but the same effect was found in control subjects.

CONCLUSIONS

The ACT-AA polymorphism is not related to an increased risk of developing PD in the Spanish population. The ACT-AA overrepresentation in PD and control subjects < or =50 years old suggests that this polymorphism could be associated with life-threatening conditions other than PD.

Significant changes in the tau A0 and A3 alleles in progressive supranuclear palsy and improved genotyping by silver detection

BACKGROUND

Progressive supranuclear palsy (PSP) is characterized by intraneuronal inclusions of neurofibrillary tangles formed by aggregated tau protein. A significant association between the tau gene A0/A0 genotype and PSP recently has been reported.

OBJECTIVES

To determine if a significant association between the tau gene A0/A0 genotype and PSP could be found in an independent population with a genetic background different from that in which the initial association was reported, and to standardize a nonradioactive method for tau gene genotyping.

SETTING

Hospital and university research laboratories.

SUBJECTS AND METHODS

To facilitate genotyping of the tau gene, we standardized the conditions for silver-based detection of the tau gene dinucleotide polymorphism. Thirty patients from Spain clinically diagnosed as having probable PSP were included in the study and compared with different control groups.

RESULTS

A highly significant overrepresentation of the A0/A0 genotype (P<.001) and a decrease in the frequency of the A0/A3 genotype were found in the Spanish patients with PSP compared with the control group. A method based on silver detection was standardized for the genotyping of the tau gene.

CONCLUSIONS

The detection of a significant association between the tau gene A0/A0 genotype and PSP in 2 independent populations rules out genetic stratification as an explanation for the association and indicates that the presence of the tau A0/A0 genotype is a risk factor for developing PSP independent of genetic background. Alternatively, the results could be interpreted as a protective effect of the A3 allele.

Apolipoprotein E epsilon 4 alleles and meiotic origin of non-disjunction in Down syndrome children and in their corresponding fathers and mothers

An increased risk of Alzheimer disease (AD) has been reported in young mothers of Down syndrome (DS) probands. Subsequently, an increased frequency of the apolipoprotein E (apoE) allele epsilon 4 has been found in mothers (< or = 32 years) of DS children due to meiosis II (MII) errors providing a potential explanation for the increased risk of AD in DS mothers. In the present study we genotyped apoE and determined the origin of non-disjunction of 132 mothers and the corresponding fathers and DS children from Spain. Unexpectedly no epsilon 4 alleles have been detected in MII mothers of < or = 32 years of age (P = 0.02). Thus our study not only fails to find the effect previously reported, but it detects an opposite correlation. An increase in the epsilon 4 frequency (0.227) is detected in MI mothers <28 as compared to the epsilon 4 frequency present in MI mothers >28 years of age (0.089), although the differences are not significant if correction for multiple comparisons is applied. The simplest overall interpretation of the previously reported and present findings is that the detected associations are due to random statistical variation rather than to some real effect of the epsilon 4 allele. However the important potential implications of alternative explanations imply that this issue deserves further clarification in independent studies in other populations.

Alpha-antichymotrypsin gene polymorphism and risk for Alzheimer's disease in the Spanish population

The alpha-antichymotrypsin (ACT) and the ApoE polymorphisms have been determined in 136 Alzheimer's disease (AD) patients and in 92 age-matched controls. Only a borderline significant difference is found when comparing the overall ACT/AA genotype frequency between AD patients and controls (chi2, P = 0.08). However this difference is attributable entirely and significantly to the ApoE epsilon4 non-carrier AD group (chi2, P = 0.004). No differences are found in the ACT/AA genotype frequency of the ApoE epsilon4 AD carrier group as compared controls (chi2, P = 0.98) in contrast with previous works. These findings support that the presence of the ACT/AA genotype is a genetic risk factor for developing AD in non-ApoE epsilon4 carriers subjects in our population.

Low apolipoprotein E epsilon4 allele frequency in the population of Catalonia (Spain) determined by PCR-RFLP and Laser fluorescent sequencer

Specific apolipoprotein E alleles have been associated in the last few years with several diseases using appropriate controls. However, these control groups are rarely representative of the general population since they correspond either to aged or healthy control groups (and thus depleted of pathological alleles). For this reason it is difficult at present to compare population allelic frequencies in different countries. In order to provide this essential basic data representative of the general population, in this work we have determined the distribution of apolipoprotein E alleles in 226 individuals from the population of Catalonia (Spain) sampled with the main purpose of paternity testing. The allelic frequencies are: epsilon2 = 0.064, epsilon3 = 0.810 and epsilon4 = 0.126, predicting a lower incidence of Alzheimer disease and possibly also of other pathologies where this allele is a risk factor.

The genotype 2/2 of the presenilin-1 polymorphism is decreased in Spanish early-onset Alzheimer's disease

We have found a significantly lower frequency of the presenilin-1 (PS-1) intronic polymorphism 2/2 genotype in early-onset Alzheimer's disease (AD) patients without APOE epsilon4 alleles (2/2 = 0.054; P = 0.009) as compared to age matched non-epsilon4 controls (2/2 = 0.227). Moreover the average age of onset in AD patients with the PS-1 2/2 genotype is older than that in AD patients with a 1/2 genotype or with a 1/1 genotype. This data suggest a protective effect of the 2/2 genotype which would delay the age of onset in AD. Our results do not support an association between the 1/1 genotype and AD. However, a non-significant increase of the 1/1 genotype is found in non-epsilon4 AD patients (P = 0.20).