Cloning of a gene bearing missense mutations in early-onset familial Alzheimer's disease

Some cases of Alzheimer's disease are inherited as an autosomal dominant trait. Genetic linkage studies have mapped a locus (AD3) associated with susceptibility to a very aggressive form of Alzheimer's disease to chromosome 14q24.3. We have defined a minimal cosegregating region containing the AD3 gene, and isolated at least 19 different transcripts encoded within this region. One of these transcripts (S182) corresponds to a novel gene whose product is predicted to contain multiple transmembrane domains and resembles an integral membrane protein. Five different missense mutations have been found that cosegregate with early-onset familial Alzheimer's disease. Because these changes occurred in conserved domains of this gene, and are not present in normal controls, they are likely to be causative of AD3.

Familial Alzheimer's disease in kindreds with missense mutations in a gene on chromosome 1 related to the Alzheimer's disease type 3 gene

We report the cloning of a novel gene (E5-1) encoded on chromosome 1 which has substantial nucleotide and amino-acid sequence similarity to the S182 gene on chromosome 14q24.3. Mutations, including three new missense mutations in the S182 gene, are associated with the AD3 subtype of early-onset familial Alzheimer's disease (AD). Both the E5-1 and the S182 proteins are predicted to be integral membrane proteins with seven membrane-spanning domains, and a large exposed loop between the sixth and seventh transmembrane domains. Analysis of the nucleotide sequence of the open reading frame (ORF) of the E5-1 gene led to the discovery of two missense substitutions at conserved amino-acid residues in affected members of pedigrees with a form of familial AD that has a later age of onset than the AD3 subtype (50-70 years versus 30-60 years for AD3). These observations imply that the E5-1 gene on chromosome 1 and the S182 gene on chromosome 14q24.3 are members of a family of genes (presenilins) with related functions, and indicates that mutations in conserved residues of E5-1 could also play a role in the genesis of AD. Our results also indicate that still other AD susceptibility genes exist.

Alzheimer's disease associated with mutations in presenilin 2 is rare and variably penetrant

Missense mutations in the presenilin 2 (PS-2) gene on chromosome 1 were sought by direct nucleotide sequence analysis of the open reading frame of 60 pedigrees with familial Alzheimer's disease (FAD). In the majority of these pedigrees, PS-1 and beta-amyloid precursor protein (beta APP) gene mutations had been excluded. While no additional PS-2 pathogenic mutations were detected, four silent nucleotide substitutions and alternative splicing of nucleotides 1338-1340 (Glu325) were observed. Analysis of additional members of a pedigree known to segregate a Met239Val mutation in PS-2 revealed that the age of onset of symptoms is highly variable (range 45-88 years). This variability is not attributable to differences in ApoE genotypes. These results suggest (i) that, in contrast to mutations in PS-1, mutations in PS-2 are a relatively rare cause of FAD; (ii) that other genetic or environmental factor modify the AD phenotype associated with PS-2 mutations; and (iii) that still other FAD susceptibility genes remain to be identified.

A prospective study of the clinical utility of ApoE genotype in the prediction of outcome in patients with memory impairment

Given the relationship between the presence of ApoE epsilon 4 and Alzheimer's disease (AD), were studied whether knowledge of epsilon 4 status would predict which memory-impaired patients would develop AD over time. One hundred seven patients who presented with memory impairment but not dementia were referred to the study by their family physicians. These patients were followed prospectively over a 2-year period. Twenty-nine patients developed AD, while 78 did not develop dementia. We found that ApoE genotype was a reliable prognostic indicator of who developed AD in this group only when memory test performance was included in the predictive model. These findings indicate that limitations of ApoE genotyping in isolation as a prognostic indicator of AD. Because this study included prospectively selected patients who were followed longitudinally, our findings are likely to have more relevance in the clinical setting than those obtained from currently available retrospective studies.

Improved learning algorithms for mixture of experts in multiclass classification

Mixture of experts (ME) is a modular neural network architecture for supervised learning. A double-loop Expectation-Maximization (EM) algorithm has been introduced to the ME architecture for adjusting the parameters and the iteratively reweighted least squares (IRLS) algorithm is used to perform maximization in the inner loop [Jordan, M.I., Jacobs, R.A. (1994). Hierarchical mixture of experts and the EM algorithm, Neural Computation, 6(2), 181-214]. However, it is reported in literature that the IRLS algorithm is of instability and the ME architecture trained by the EM algorithm, where IRLS algorithm is used in the inner loop, often produces the poor performance in multiclass classification. In this paper, the reason of this instability is explored. We find out that due to an implicitly imposed incorrect assumption on parameter independence in multiclass classification, an incomplete Hessian matrix is used in that IRLS algorithm. Based on this finding, we apply the Newton-Raphson method to the inner loop of the EM algorithm in the case of multiclass classification, where the exact Hessian matrix is adopted. To tackle the expensive computation of the Hessian matrix and its inverse, we propose an approximation to the Newton-Raphson algorithm based on a so-called generalized Bernoulli density. The Newton-Raphson algorithm and its approximation have been applied to synthetic data, benchmark, and real-world multiclass classification tasks. For comparison, the IRLS algorithm and a quasi-Newton algorithm called BFGS have also been applied to the same tasks. Simulation results have shown that the use of the proposed learning algorithms avoids the instability problem and makes the ME architecture produce good performance in multiclass classification. In particular, our approximation algorithm leads to fast learning. In addition, the limitation of our approximation algorithm is also empirically investigated in this paper.

Reduced risk of relapse after long-term nucleos(t)ide analogue consolidation therapy for chronic hepatitis B

BACKGROUND

Before stopping nucleos(t)ide analogue (NA) treatment in chronic hepatitis B (CHB), 6-12 months of consolidation therapy is recommended.

AIM

To investigate the effect of consolidation therapy on off-treatment outcomes in CHB patients.

METHODS

We included 94 patients who stopped NA after at least 1 year of therapy. Patients could be HBeAg-positive or HBeAg-negative at start-of-treatment, but were HBeAg-negative and had undetectable HBV DNA at time of discontinuation. Consolidation therapy was defined as treatment after the first undetectable HBV DNA (and HBeAg loss for HBeAg-positive patients) until NA cessation.

RESULTS

At 3 years, 74% of the start-of-treatment HBeAg-positive and 75% of the start-of-treatment HBeAg-negative patients developed HBV DNA >2000 IU/mL at a single time point, whereas a persistent virological relapse (≥2 tests of HBV DNA >2000 IU/mL 6 months apart within 1 year) developed in 49% of the start-of-treatment HBeAg-positive and 53% of the start-of-treatment HBeAg-negative patients. For both HBeAg-positive and HBeAg-negative patients, consolidation therapy of ≥3 years was associated with lower persistent virological relapse rates compared to <1 year (1-year relapse rate: 25% vs. 54%; P = 0.063 and 24% vs. 57%; P = 0.036, respectively). At 3 years, 9% of the HBeAg-positive and 14% of the HBeAg-negative patients became HBsAg-negative. Prolonged consolidation therapy increased the likelihood of HBsAg loss. Two cirrhotic patients developed hepatic decompensation but both recovered.

CONCLUSIONS

After nucleos(t)ide analogue discontinuation, relapse was common in patients with chronic hepatitis B. Prolongation of consolidation therapy beyond 3 years decreased the risk of persistent virological relapse and increased the likelihood of HBsAg loss.

Impact of glyphosate on the development, fertility and demography of Chrysoperla externa (Neuroptera: Chrysopidae): ecological approach

Few ecotoxicological studies have used life table analysis to evaluate the toxicity of pesticides on beneficial organisms. This study is the first report of the effect of the herbicide glyphosate on a predator insect, Chrysoperla externa, using a demographic approach. This predator is associated to soybean pests and has a potential role as a biological control agent in the Neotropical Region. The objective of this work was to evaluate the side-effects of glyphosate on the development, fertility and demography of C. externa, treated orally by ingestion of glyphosate-dipped eggs of Sitotroga cerealella in laboratory conditions. The data were analyzed using the age-stage, two-sex life table. Development from third larval instar to pupae and adult longevity were shorter in glyphosate-treatment than in the control. Adult pre-reproductive period was longer in glyphosate-treatment than in the control. Fecundity and fertility were deeply reduced, as well, being fertility greater affected. A high important reduction was registered in all population parameters. Most eggs from glyphosate-treated cohort looked abnormal, smaller than control, dehydrated and became black 2d after oviposition. In addition, adults developed tumours in the abdomen region at 20d after emergence, being the effect more drastic in females than males. It is beyond the scope of our study to speculate on the effects of this herbicide on C. externa field populations. However, it seems likely that populations under continuous use of glyphosate would be exposed at greater detrimental effects in the long term.

Numerical solution of a nonlinear advance-delay-differential equation from nerve conduction theory

A functional differential equation which is nonlinear and involves forward and backward deviating arguments is solved numerically. The equation models conduction in a myelinated nerve axon in which the myelin completely insulates the membrane, so that the potential change jumps from node to node. The equation is of first order with boundary values given at t = +/- infinity. The problem is approximated via a difference scheme which solves the problem on a finite interval by utilizing an asymptotic representation at the endpoints, cubic interpolation and iterative techniques to approximate the delays, and a continuation method to start the procedure. The procedure is tested on a class of problems which are solvable analytically to access the scheme's accuracy and stability, then applied to the problem that models propagation in a myelinated axon. The solution's dependence on various model parameters of physical interest is studied. This is the first numerical study of myelinated nerve conduction in which the advance and delay terms are treated explicitly.

Targeted deletion of Minpp1 provides new insight into the activity of multiple inositol polyphosphate phosphatase in vivo

Multiple inositol polyphosphate phosphatase (Minpp1) metabolizes inositol 1,3,4,5,6-pentakisphosphate (InsP(5)) and inositol hexakisphosphate (InsP(6)) with high affinity in vitro. However, Minpp1 is compartmentalized in the endoplasmic reticulum (ER) lumen, where access of enzyme to these predominantly cytosolic substrates in vivo has not previously been demonstrated. To gain insight into the physiological activity of Minpp1, Minpp1-deficient mice were generated by homologous recombination. Tissue extracts from Minpp1-deficient mice lacked detectable Minpp1 mRNA expression and Minpp1 enzyme activity. Unexpectedly, Minpp1-deficient mice were viable, fertile, and without obvious defects. Although Minpp1 expression is upregulated during chondrocyte hypertrophy, normal chondrocyte differentiation and bone development were observed in Minpp1-deficient mice. Biochemical analyses demonstrate that InsP(5) and InsP(6) are in vivo substrates for ER-based Minpp1, as levels of these polyphosphates in Minpp1-deficient embryonic fibroblasts were 30 to 45% higher than in wild-type cells. This increase was reversed by reintroducing exogenous Minpp1 into the ER. Thus, ER-based Minpp1 plays a significant role in the maintenance of steady-state levels of InsP(5) and InsP(6). These polyphosphates could be reduced below their natural levels by aberrant expression in the cytosol of a truncated Minpp1 lacking its ER-targeting N terminus. This was accompanied by slowed cellular proliferation, indicating that maintenance of cellular InsP(5) and InsP(6) is essential to normal cell growth. Yet, depletion of cellular inositol polyphosphates during erythropoiesis emerges as an additional physiological activity of Minpp1; loss of this enzyme activity in erythrocytes from Minpp1-deficient mice was accompanied by upregulation of a novel, substitutive inositol polyphosphate phosphatase.

NGF enhances neurite regeneration from nerve-transected terminals of young adult and aged mouse dorsal root ganglia in vitro

Dorsal root ganglia with nerve fibers, dissected from 3-month-old young adult mice and 26-month-old aged mice, were embedded in collagen gel. In the young adult mice regenerating neurites appeared from nerve-transected terminals after 12-24 h in culture, regardless of the length of fibers, but in the aged mice, regenerating neurites were first seen after 12-48 h. Administration of nerve growth factor to the explants markedly enhanced the growth of regenerating neurites from both the young adult and aged mice.

Multiple inositol polyphosphate phosphatase: evolution as a distinct group within the histidine phosphatase family and chromosomal localization of the human and mouse genes to chromosomes 10q23 and 19

Multiple inositol polyphosphate phosphatase is the only enzyme known to hydrolyze the abundant metabolites inositol pentakisphosphate and inositol hexakisphosphate. We have previously demonstrated that the chick homolog of multiple inositol polyphosphate phosphatase, designated HiPER1, has a role in growth plate chondrocyte differentiation. The relationship of these enzymes to intracellular signaling is obscure, and as part of our investigation we have examined the murine ((MMU)Minpp1) and human ((HSA)MINPP1) homologs. Northern blot analysis demonstrated expression of ((MMU)Minpp1 in a variety of mouse tissues, comparable to the expression of other mammalian homologs, but less restricted than the expression of HiPER1 in chick. A purified (MMU)Minpp1 fusion protein cleaved phosphate from inositol (1,3,4,5)-tetrakisphosphate and para-nitrophenyl phosphate. When the presumptive active site histidine was altered to alanine by site-directed mutagenesis, enzyme activity was abolished, confirming the classification of (MMU)Minpp1 as a histidine phosphatase. The amino acid sequences of the murine and human MINPP proteins share >80% identity with the rat enzyme and >56% identity with HiPER1, with conservation of the C-terminal consensus sequence that retains proteins in the endoplasmic reticulum. The intron/exon structure of the mammalian (MMU)Minpp1 and (HSA)MINPP1 genes is also conserved compared to the chick HiPER1 gene. Sequence analysis of plant and fruit fly MINPP homologs supports the hypothesis that the MINPP enzymes constitute a distinct evolutionary group within the histidine phosphatase family. We have mapped (HSA)MINPP1 to human chromosome 10q23 by fluorescence in situ hybridization, YAC screening, and radiation hybrid mapping. This assignment places (HSA)MINPP1 in a region of chromosome 10 that is frequently mutated in human cancers and places (HSA)MINPP1 proximal to the tumor suppressor PTEN, which maps to 10q23.3. Using a radiation hybrid panel, we localized (MMU)Minpp1 to a region of mouse chromosome 19 that includes the murine homolog of Pten. The evolutionary conservation of this novel enzyme within the inositol polyphosphate pathway suggests a significant role for multiple inositol polyphosphate phosphatase throughout higher eukaryotes.

Substance P and neurokinin A metabolism by cultured human skeletal muscle myocytes and fibroblasts

A recent study determined that cultured human skeletal muscle adult myoblasts, myotubes, and fibroblasts degraded angiotensins and kinins via neutral endopeptidase-24.11 (NEP-24.11: EC 3.4.24.11) and aminopeptidase N (APN: EC 3.4.11.2). Due to the possible importance of other peptides to skeletal muscle blood flow and function, the present study looked specifically at the metabolism of the neurokinins substance P (SP) and neurokinin A (NKA) by skeletal muscle peptidases. The results show that SP is degraded not only by NEP-24.11, but also sequentially by dipeptidyl(amino)peptidase IV (DAP IV: EC 3.4.14.5)/APN. NKA is unaffected by DAP IV but is metabolized by NEP-24.11 and APN. NEP-24.11 was inhibited by phosphoramidon (IC50 = 80 nM), thiorphan and ZINCOV, DAP IV by diprotin A (IC50 = 8 microM), and APN by amastatin (IC50 = 50 nM) and bestatin (IC50 = 100 microM). Skeletal muscle myocyte and fibroblast metabolism of SP and NKA may regulate local skeletal muscle vascular and extravascular functions including SP- and NKA-mediated nerve-induced vasodilation. Inhibition of both NEP-24.11 and DAP IV/APN may increase skeletal muscle blood flow and decrease peripheral vascular resistance via potentiation of local neurokinin levels.

Determination of serum aluminium using an ion-pair reversed-phase high-performance liquid chromatographic-fluorimetric system with lumogallion

An ion-pair reversed-phase high-performance liquid chromatographic method with fluorimetric detection, using lumogallion [4-chloro-3-(2,4-dihydroxyphenylazo)-2-hydroxybenzene-1-sulphonic acid] as a ligand, has been successfully applied to the determination of aluminium in human serum. The highly fluorescent aluminium-lumogallion complex (lambda ex 505 nm, lambda em 574 nm) was separated on a LiChrosorb RP-18 column with an eluent consisting of 30% acetonitrile, 70% 0.02 M potassium hydrogen phthalate and 10 microM lumogallion. The proposed system offers a simple, rapid, selective and sensitive method for the determination of aluminium in serum. The detection limit for aluminium was 0.05 microgram/l in aqueous solution and the limit of determination was 2.2 micrograms/l in serum. The recovery of the method is generally over 90%.

Interaction of prostaglandin E1 with alpha-cyclodextrin in aqueous systems: stability of the inclusion complex

Prostavasin, an inclusion complex of prostaglandin E1 (PGE1) with alpha-cyclodextrin (alpha-CD), is used in the therapy of thrombosis. Nuclear magnetic resonance measurements have been made to study the interaction of PGE1 with alpha-CD. The observed interaction (chemical shift) and the derived dissociation constant prove that only weak interaction forces are operative and that complete dissociation occurs upon dilution.

Isolation and age-related characterization of mouse Schwann cells from dorsal root ganglion explants in type I collagen gels

A technique for isolation of adult Schwann cells (ScC) from dorsal root ganglia (DRG) is described. Decapsulated DRG explants embedded into type I collagen gels were cultured for 3 days in serum-free medium during which ScC migrated from the explant. These explants were then grown in serum-supplemented medium to allow ScC proliferation. On day 10 the number of ScC isolated from DRG explants per mouse was about 2.5 x 10(5), and the purity was greater than 95%. This culture system provided sufficient numbers of highly purified adult ScC in a shorter culture period (2-3 times) than other methods. We used ScC from this method to determine the age-related changes in attachment, growth, and survival of ScC cultured in serum-free medium. The attachment capacity of adult ScC on type I collagen or polylysine was similar to that of newborn ScC. However, the collagen promoted growth and survival of adult ScC but not that of neonatal ScC, indicating age-related differences of ScC properties in vitro.

Speaker identification using time-delay HMEs

In this paper, we extend the Hierarchical Mixture of Experts (HME) to temporal processing and explore it for a substantial problem, that of text-dependent speaker identification. For a specific multiway classification, we propose a generalized Bernoulli density instead of the multinomial logit density to avoid the instability during training. Time-delay technique is applied for spatio-temporal processing in the HME and a combining scheme is presented for combining multiple time-delay HMEs in order to complete a multi-scale analysis for the temporal data. Using the time-delay HME along with the EM algorithm as well as the combination of multiple time-delay HMEs, the speaker identification system has a good performance and yields significantly fast training. We have also addressed some issues about the time-delay techniques in the HME.

Somatic mutation and germline variants of MINPP1, a phosphatase gene located in proximity to PTEN on 10q23.3, in follicular thyroid carcinomas

Various genes have been identified to play a role in the pathogenesis of follicular thyroid tumors. Cowden syndrome is the only known familial syndrome with an increased risk of both follicular thyroid adenoma (FA) and carcinoma (FTC). Germline mutations in the tumor suppressor gene PTEN, which encodes a dual-specificity phosphatase, have been found in up to 80% of patients with Cowden syndrome suggesting a role of PTEN in the pathogenesis of follicular thyroid tumors. Although somatic intragenic mutations in PTEN, which maps to 10q23.3, are rarely found in follicular tumors, loss of heterozygosity (LOH) of markers within 10q22-24 occurs in about 25%. Recently, another phosphatase gene, MINPP1, has been localized to 10q23.3. MINPP1 has the ability to remove 3-phosphate from inositol phosphate substrates, a function that overlaps that of PTEN. Because of this overlapping function with PTEN and the physical location of MINPP1 to a region with frequent LOH in follicular thyroid tumors, we considered it to be an excellent candidate gene that could contribute to the pathogenesis of follicular thyroid tumors. We analyzed DNA from tumor and corresponding normal tissue from 23 patients with FA and 15 patients with FTC for LOH and mutations at the MINPP1 locus. LOH was identified in four malignant and three benign tumors. One of these FTCs with LOH was found to harbor a somatic c.122C > T or S41L mutation. We also found two germline sequence variants, c.809A > G (Q270R) and IVS3 + 34T > A. The c.809A > G variant was found in only one patient with FA but not in patients with FTC or normal controls. More interestingly, IVS3 + 34T > A was found in about 15% of FA cases and normal controls but not in patients with FTC. These results suggest a role for MINPP1 in the pathogenesis of at least a subset of malignant follicular thyroid tumors, and MINPP1 might act as a low penetrance predisposition allele for FTC.

Xeroderma pigmentosum variant: DNA ploidy analysis of various skin tumors and normal-appearing skin in a patient

BACKGROUND

The patient with xeroderma pigmentosum provides an appropriate human model for the evaluation of tumor development and progression.

METHODS

We describe a patient with variant-type xeroderma pigmentosum who developed actinic keratoses, a squamous cell carcinoma, and its metastasis into a lymph node. DNA ploidy was measured and analyzed in cells of these tumors and the patient's sun-exposed as well as sun-shielded skin.

RESULTS

The sun-shielded skin showed a normal diploid DNA distribution pattern, while the sun-exposed skin had an increased number of hyperdiploid cells. The actinic keratosis showed further increased hyperdiploid cells. The squamous cell carcinoma showed a large number of hyperdiploid cells and formed an aneuploid cell fraction. Histographically, the aneuploid cell fraction became more apparent and was revealed to be a major fraction in the metastatic squamous cell carcinoma.

CONCLUSIONS

The changes in the DNA ploidy pattern well reflect the clinical and histologic characteristics of the respective skin conditions and likely provide the cellular basis for the sequential or stepwise carcinogenic process in the patient's xeroderma pigmentosum skin. Further studies are necessary to determine whether the present results explain the similar carcinogenic process in sun-damaged skin of the nonpredisposed general population.