Elevated plasma ferritin in elderly individuals with high neocortical amyloid-ß load.

Ferritin, an iron storage and regulation protein, has been associated with Alzheimer's disease (AD); however, it has not been investigated in preclinical AD, detected by neocortical amyloid-ß load (NAL), before cognitive impairment. Cross-sectional analyses were carried out for plasma and serum ferritin in participants in the Kerr Anglican Retirement Village Initiative in Aging Health cohort. Subjects were aged 65-90 years and were categorized into high and low NAL groups via positron emission tomography using a standard uptake value ratio cutoff=1.35. Ferritin was significantly elevated in participants with high NAL compared with those with low NAL, adjusted for covariates age, sex, apolipoprotein E ɛ4 carriage and levels of C-reactive protein (an inflammation marker). Ferritin was also observed to correlate positively with NAL. A receiver operating characteristic curve based on a logistic regression of the same covariates, the base model, distinguished high from low NAL (area under the curve (AUC)=0.766), but was outperformed when plasma ferritin was added to the base model (AUC=0.810), such that at 75% sensitivity, the specificity increased from 62 to 71% on adding ferritin to the base model, indicating that ferritin is a statistically significant additional predictor of NAL over and above the base model. However, ferritin's contribution alone is relatively minor compared with the base model. The current findings suggest that impaired iron mobilization is an early event in AD pathogenesis. Observations from the present study highlight ferritin's potential to contribute to a blood biomarker panel for preclinical AD.

Clinical and genetic predictors of paclitaxel neurotoxicity based on patient- versus clinician-reported incidence and severity of neurotoxicity in the ICON7 trial.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting toxicity of paclitaxel, with no reliable method to identify at-risk patients. We investigated the incidence and risk factors including genetic polymorphisms associated with the development of CIPN based on clinician and patient reporting of neuropathic symptoms. PATIENTS AND METHODS: Risk factors for the development of CIPN were examined in 454 patients treated with paclitaxel/carboplatin from the International Collaboration on Ovarian Neoplasms 7 (ICON7) trial. Neuropathy was graded by clinicians by standard adverse event reporting and by patients utilising OV28 questionnaire. Genetic risk factors were examined by selecting six single nucleotide polymorphisms in genes associated with microtubule function. Risk factors were assessed via dose-to-event cox regression models. RESULTS: Grade >2 neuropathy was reported by clinicians in 28% of patients, while 67% of patients reported 'quite a bit' or 'very much' tingling or numbness. Agreement between clinicians and patients was poor (κ = 0.236, 95% confidence interval, 0.177-0.296, P < 0.001). Older age, bevacizumab treatment and bowel resection were associated with clinician reported CIPN, while older age and volume of residual disease were associated with patient-reported neuropathy. There were no significant associations between clinician-reported neuropathy or patient-reported neuropathy and TUBB2, CEP72 or individual MAPT or GSK3B SNPs, however MAPT additive polymorphisms were associated with patient-reported neuropathy and GSK3B additive polymorphisms were associated with clinician reported CIPN. CONCLUSIONS: There was significant discordance between patient- and clinician-reported neurotoxicity. The lack of consensus regarding optimal outcome measures and whose opinion with regard to CIPN takes precedence is a limitation in the investigation of risk factors for CIPN. Care must be taken to select and include patient-reported outcome measures in CIPN assessment to enable accurate identification of genetic and other risk factors for neuropathy.

Clinical heterogeneity of the C9orf72 genetic mutation in frontotemporal dementia.

The C9orf72 genetic mutation represents the most common cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Studies over the last 2 years have revealed a number of key features of this mutation in the fields of clinical neurology, imaging, pathology, and genetics. Despite these efforts, the clinical phenotype appears to extend beyond FTD and ALS into the realm of psychiatric disease, and while highly variable survival rates have been reported, the clinical course of carriers remains relatively unexplored. This report describes two contrasting C9orf72 cases, one with a protracted indolent course dominated by neuropsychiatric features and the other with a rapidly progressive dementia. In both cases, initial structural brain imaging was relatively normal.

Positional cloning, association analysis and expression studies provide convergent evidence that the cadherin gene FAT contains a bipolar disorder susceptibility allele.

A susceptibility locus for bipolar disorder was previously localized to chromosome 4q35 by genetic linkage analysis. We have applied a positional cloning strategy, combined with association analysis and provide evidence that a cadherin gene, FAT, confers susceptibility to bipolar disorder in four independent cohorts (allelic P-values range from 0.003 to 0.024). In two case-control cohorts, association was identified among bipolar cases with a family history of psychiatric illness, whereas in two cohorts of parent-proband trios, association was identified among bipolar cases who had exhibited psychosis. Pooled analysis of the case-control cohort data further supported association (P=0.0002, summary odds ratio=2.31, 95% CI: 1.49-3.59). We localized the bipolar-associated region of the FAT gene to an interval that encodes an intracellular EVH1 domain, a domain that interacts with Ena/VASP proteins, as well as putative beta-catenin binding sites. Expression of Fat, Catnb (beta-catenin), and the three genes (Enah, Evl and Vasp) encoding the Ena/VASP proteins, were investigated in mice following administration of the mood-stabilizing drugs, lithium and valproate. Fat was shown to be significantly downregulated (P=0.027), and Catnb and Enah were significantly upregulated (P=0.0003 and 0.005, respectively), in response to therapeutic doses of lithium. Using a protein interaction map, the expression of genes encoding murine homologs of the FAT (ft)-interacting proteins was investigated. Of 14 interacting molecules that showed expression following microarray analysis (including several members of the Wnt signaling pathway), eight showed significantly altered expression in response to therapeutic doses of lithium (binomial P=0.004). Together, these data provide convergent evidence that FAT and its protein partners may be components of a molecular pathway involved in susceptibility to bipolar disorder.

Hemorrhage is uncommon in new Alzheimer family with Flemish amyloid precursor protein mutation.

BACKGROUND: Most mutations in the amyloid precursor protein (APP) gene have been associated with familial Alzheimer disease (AD); however, some mutations within the Abeta-coding sequence have been described in families with recurrent cerebral hemorrhage. The APPAla692Gly (Flemish) mutation was reported in a family in which affected members developed hemorrhagic stroke, progressive dementia, or both. OBJECTIVE: To describe clinical, neuropathologic, and genetic features of a family of British origin with the Flemish APP mutation. METHODS: Clinical features of the proband and two affected relatives were obtained by history, examination, and medical record review. Some information on deceased affected relatives was obtained by informant interview. Neuropathologic examination was carried out on one case. DNA studies were carried out on three affected and three unaffected individuals. RESULTS: Presenile dementia was present in a pattern consistent with dominant inheritance, with the APP692 mutation being found in all affecteds and no unaffecteds. The proband also had a cerebral hemorrhage, but was the only one of five affecteds to have this complication. Neuropathologic examination confirmed AD, congophilic angiopathy, and hemorrhagic infarction. CONCLUSIONS: This expands the number of families reported with mutations in the coding region of the amyloid precursor protein gene. Cerebral hemorrhage appears to be less frequent in this family than in the previously reported Flemish pedigree with the same mutation.

Similar early clinical presentations in familial and non-familial frontotemporal dementia.

BACKGROUND: It is unclear whether there are early clinical features that can distinguish between patients with familial and non-familial frontotemporal dementia (FTD). OBJECTIVE: To compare the clinical features of FTD cases who have tau gene mutations with those of cases with a family history of FTD but no tau gene mutation, and with sporadic cases with neither feature. METHODS AND RESULTS: Comparisons of the behavioural, cognitive, and motor features in 32 FTD patients (five positive for tau gene mutations, nine familial but tau negative, and 18 tau negative sporadic) showed that age of onset and duration to diagnosis did not differ between the groups. Apathy was not observed in tau mutation positive cases, and dysexecutive signs were more frequent in familial tau mutation negative cases. Memory deficits and behavioural changes were common in all groups. CONCLUSIONS: In comparison with other neurodegenerative conditions such as Alzheimer's disease and Parkinson's disease, neither tau gene mutations nor strong familial associations confer earlier disease susceptibility.

Baculoviruses expressing the human familial Alzheimer's disease presenilin 1 mutation lacking exon 9 increase levels of an amyloid beta-like protein in Sf9 cells.

Presenilin 1 (PS1) plays a pivotal role in the production of the amyloid-beta protein (Abeta) that is central to the pathogenesis of Alzheimer's disease. PS1 regulates the intramembranous proteolysis of a 99-amino-acid C-terminal fragment of the amyloid precursor protein (APP-C99), a cleavage event that releases Abeta following a reaction catalyzed by an enzyme termed 'gamma-secretase'. The molecular mechanism of PS1-mediated, gamma-secretase cleavage remains largely unresolved. In particular, controversy surrounds whether PS1 includes the catalytic site of the gamma-secretase protease or whether instead PS1 mediates gamma-secretase activity indirectly, perhaps by regulating the trafficking or presentation of substrates to the 'authentic' protease, which may be a molecule distinct from PS1. To address this issue, the baculovirus expression system was used to co-express: (i) APP-C99; (ii) a pathogenic, constitutively active mutant form of PS1 lacking exon 9 (PS1DeltaE9); (iii) nicastrin and (iv) tropomyosin in Spodoptera frugiperda (Sf9) cells. Cells infected with APP-C99 alone produced an Abeta-like species, and levels of this species were enhanced by the addition of baculoviruses bearing the PS1DeltaE9 mutation. The addition to APP-C99-infected cells of baculoviruses bearing nicastrin, also a transmembrane protein, had a neutral or inhibitory effect on the reaction; tropomyosin viruses had the same effect as nicastrin viruses. These results suggest that PS1DeltaE9 molecules expressed in Sf9 cells retain the ability to modulate Abeta levels. Baculoviral-expressed PS1DeltaE9 provides a source of microgram quantities of bioactive molecules for use as starting material for purifying and reconstituting gamma-secretase activity from its individual purified component parts.

Variable phenotype of Alzheimer's disease with spastic paraparesis.

A variant form of Alzheimer's disease (AD), in which spastic paraparesis (SP) precedes dementia, is characterised by large, noncored, weakly neuritic Abeta-amyloid plaques resembling cotton wool balls and is caused by genomic deletion of presenilin 1 exon 9. A pedigree with a 5.9 kb exon 9 deletion shows a phenotypic spectrum including subjects with typical AD or with SP and numerous cotton wool plaques. In SP subjects, dementia onset is delayed and modified. This phenotypic variation suggests that modifying factors are associated with exon 9 deletions.

Progressive supranuclear palsy pathology caused by a novel silent mutation in exon 10 of the tau gene: expansion of the disease phenotype caused by tau gene mutations.

Genetic mutations in the tau gene on chromosome 17 are known to cause frontotemporal dementias. We have identified a novel silent mutation (S305S) in the tau gene in a subject without significant atrophy or cellular degeneration of the frontal and temporal cortices. Rather the cellular pathology was characteristic of progressive supranuclear palsy, with neurofibrillary tangles concentrating within the subcortical regions of the basal ganglia. Two affected family members presented with symptoms of dementia and later developed neurological deficits including abnormality of vertical gaze and extrapyramidal signs. The third presented with dystonia of the left arm and dysarthria, and later developed a supranuclear gaze palsy and falls. The mutation is located in exon 10 of the tau gene and forms part of a stem-loop structure at the 5' splice donor site. Although the mutation does not give rise to an amino acid change in the tau protein, functional exon-trapping experiments show that it results in a significant 4.8-fold increase in the splicing of exon 10, resulting in the presence of tau containing four microtubule-binding repeats. This study provides direct molecular evidence for a functional mutation that causes progressive supranuclear palsy pathology and demonstrates that mutations in the tau gene are pleiotropic.

Novel Leu723Pro amyloid precursor protein mutation increases amyloid beta42(43) peptide levels and induces apoptosis.

A novel missense mutation, Leu723Pro, in the amyloid precursor protein (APP) gene was discovered in an early-onset Alzheimer's disease family. Expression of L723P mutant APP complementary DNA in CHO cells resulted in a 1.4- to 1.9-fold increased production of the 42(43)-amino acid length amyloid beta peptide compared with the wild-type sequence and was capable of causing apoptosis. The mutation is predicted to alter the luminal transmembrane length and helical arrangement of the APP molecule and thus affect the gamma-secretase cleavage site.

Nonparametric simulation-based statistical analyses for bipolar affective disorder locus on chromosome 21q22.3.

Straub et al. [1994: Nat Genet 8:291-296] reported a candidate bipolar affective disorder (BAD) locus on chromosome 21q22.3. As a replication study, we analyzed 12 Australian BAD pedigrees for the presence of excess allele sharing and cosegregation with the putative chromosome 21q22.3 BAD locus, using six microsatellite markers. The nonparametric simulation-based statistic SimAPM produced positive results for the marker PFKL (P < 0.001) and D21S198 (P = 0.007). PFKL also demonstrated linkage (P < 0.001) when analyzed using the more conservative statistic, SimIBD. Comparable results were obtained when using the original APM statistic (P = 0.02 for D21S198). However, other nonparametric analyses such as GENEHUNTER and model-free linkage (MFLINK) analysis did not yield significant results. Combined LOD scores for the 12 families were strongly negative for all six markers under six genetic models. Two-point and multipoint analyses of individual families revealed one family, family 17, with maximal LOD scores greater than 1.41 for the 10.5-cM region between PFKL and D21S198. This report provides additional support for the suggestive linkage of a susceptibility locus for BAD on chromosome 21q22.3.

Two novel presenilin-1 mutations (Ser169Leu and Pro436Gln) associated with very early onset Alzheimer's disease.

Mutations in the presenilin-1 (PS-1) gene account for the majority of early onset autosomal-dominant familial Alzheimer's disease (FAD) cases. We identified three missense mutations in the coding sequence of the PS-1 gene in three early onset (EO), FAD pedigrees. Alzheimer's disease was confirmed in one pedigree by autopsy. Mutation analysis of PCR products amplified from genomic DNA templates of affected individuals showed two novel mutations resulting in Ser169Leu and Pro436Gln and one known mutation resulting in Glu318Gly. The two new mutations are located within predicted transmembrane domains three (TM-3) and seven (TM-7), and are associated with a very early age of onset which is consistent with a marked loss of function of the protein. The age of onset in the pedigree with Glu318Gly mutation was similar to that reported previously in a separate pedigree with this mutation.

Association of missense and 5'-splice-site mutations in tau with the inherited dementia FTDP-17.

Thirteen families have been described with an autosomal dominantly inherited dementia named frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), historically termed Pick's disease. Most FTDP-17 cases show neuronal and/or glial inclusions that stain positively with antibodies raised against the microtubule-associated protein Tau, although the Tau pathology varies considerably in both its quantity (or severity) and characteristics. Previous studies have mapped the FTDP-17 locus to a 2-centimorgan region on chromosome 17q21.11; the tau gene also lies within this region. We have now sequenced tau in FTDP-17 families and identified three missense mutations (G272V, P301L and R406W) and three mutations in the 5' splice site of exon 10. The splice-site mutations all destabilize a potential stem-loop structure which is probably involved in regulating the alternative splicing of exon10. This causes more frequent usage of the 5' splice site and an increased proportion of tau transcripts that include exon 10. The increase in exon 10+ messenger RNA will increase the proportion of Tau containing four microtubule-binding repeats, which is consistent with the neuropathology described in several families with FTDP-17.

Localization of frontotemporal dementia with parkinsonism in an Australian kindred to chromosome 17q21-22.

An Australian family with autosomal dominant presenile nonspecific dementia was recently described. The disease results in behavioral changes, usually disinhibition, followed by the onset of dementia accompanied occasionally by parkinsonism. Twenty-eight affected individuals were identified with an age of onset of 39 to 66 years (mean, 53 +/- 8.9 years). We mapped the disease locus to an approximately 26-cM region of chromosome 17q21-22 with a maximum two-point LOD score of 2.87. Affected individuals share a common haplotype between markers D17S783 and D17S808. This region of chromosome 17 contains the loci for several neurodegenerative diseases that lack distinctive pathological features, suggesting that these dementias, collectively referred to as frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17), are caused by mutations in the same gene. The entire coding region of five genes, mapped to the FTDP-17 candidate region, were also sequenced. This analysis included the microtubule-associated protein tau that is the major component of the paired helical filaments observed in Alzheimer's disease. No pathogenic mutations were identified in either the tau gene or in any of the other genes analyzed.

Exclusion of linkage between bipolar affective disorder and chromosome 16 in 12 Australian pedigrees.

Several recent reports of possible susceptibility loci for bipolar affective disorder (BAD) have identified sites on a number of chromosomes. Specifically, two Danish studies have suggested the presence of a susceptibility locus for BAD on chromosome 16p13. As the first step of a whole genome scan, we screened 12 Australian families with markers at 16p13 and also a number of markers spanning the entirety of chromosome 16. Linkage analysis was undertaken using both the parametric lod score method (two- and multipoint) with different models and diagnostic thresholds, and the nonparametric affected pedigree member (APM) method. Results of lod score analysis convincingly excluded the 16p13 region from linkage to BAD in these families, while APM provided no support for linkage. Furthermore, using the broad definition of BAD, with individuals affected by bipolar I and II and recurrent unipolar disorders included, the entire chromosome was excluded from linkage to BAD with autosomal-dominant transmission at a maximum age-specific penetrance of 60%, and with autosomal-dominant and recessive modes of transmission at a maximum age-specific penetrance level of 90%. Diagnostic thresholds which did not include unipolar affected individuals were somewhat less informative. However, a majority (between 63-96%, depending upon the model) of the chromosome was clearly excluded using narrow diagnostic thresholds. Moreover, no positive lod scores were obtained at theta = 0.00 for any tested model or diagnostic threshold. Our results indicate that no linkage exists between BAD and chromosome 16 markers in this group of Australian families.

Two novel (M233T and R278T) presenilin-1 mutations in early-onset Alzheimer's disease pedigrees and preliminary evidence for association of presenilin-1 mutations with a novel phenotype.

Eleven early-onset dementia families, all with affected individuals who have either presented clinical symptoms of early onset familial Alzheimer's disease (EOFAD) or have been confirmed to have EOFAD by autopsy, and two early onset cases with biopsy-confirmed AD pathology, were screened for missense mutations in the entire coding region of presenilin-1 (PS-1) and -2 (PS-2) genes. Missense mutations were detected by direct sequence analysis of PCR products amplified from genomic DNA templates of affected individuals. Three pedigrees were attributable to known mutations in the PS-1 gene: P264L, E280A and the splice acceptor site (G to T) mutation, which results in the deletion of residues 290-319 of PS-1 (PS-1 delta 290-319). In a fourth pedigree, a novel PS-1 mutation was identified in exon 7 (M233T), which is homologous to a pathogenic PS-2 mutation (M239V), and is characterized by a very early average age of onset (before the age of 35). In one early onset case, another novel PS-1 mutation was identified in exon 8 (R278T). Of the five remaining families and the other early onset case, none have missense mutations in the PS-1 or PS-2 genes, or in exon 16 and 17 of the APP gene. Moreover, two of the PS-1 mutations, PS-1 delta 290-319 and R278T, are associated with the co-presentation of familial spastic paraparesis (FSP) in some of the affected family members. Our data raise the possibility that the phenotypic spectrum associated with PS-1 mutations may extend beyond typical FAD to include FSP, a disease heretofore unsuspected to bear any relationship to FAD. In addition, our data suggest that other novel EOFAD loci, in addition to APP and the presenilin genes, are involved in the aetiology of up to 50% of EOFAD cases.

A mutation in codon 717 of the amyloid precursor protein gene in an Australian family with Alzheimer's disease.

DNA from the probands of seven Australian families with hereditary Alzheimer's disease was screened for the presence of known mutations in the amyloid precursor protein (APP) gene on chromosome 21 using single stranded conformational polymorphism (SSCP) analysis [14]. One subject was found to have a mutation causing a Val-->Ile substitution at position 717. This was confirmed by restriction enzyme digestion and sequencing. The mutation has been found in both the other affected family members available for study and in two at-risk relatives. It was not present in the only living unaffected relative who has passed the usual age of onset in this family. There is so far no evidence that apolipoprotein E (APOE) genotype influences age of onset in this family, though numbers are small. Two other families with autopsy confirmation and age of onset in the fifth decade had no APP mutation and are thought likely to have a mutation on chromosome 14 on the basis of their earlier onset age.

Haplotype analysis of MEN 2 mutations.

Multiple endocrine neoplasia type 2 (MEN 2) is a dominantly inherited cancer syndrome which affects thyroid C cells, and with variable frequency, the adrenal medulla, parathyroid and enteric autonomic ganglia. The syndrome is due to germline mutation in the receptor tyrosine kinase gene, RET. We have recently shown an unexpected correlation between one particular RET mutation, cys634-->arg, and the probability of parathyroid involvement in families with MEN 2A. Here we use haplotype analysis in the families to show that this correlation is not explained by a single founder chromosome which carries both the cys634-->arg mutation and a separate allele conferring susceptibility to parathyroid abnormality, but is probably due to the cys634-->arg mutation itself. The results also indicate that new mutations to MEN 2 are not infrequent.