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.

Effects of saline, mannitol, and furosemide on acute decreases in renal function induced by radiocontrast agents

BACKGROUND

Injections of radiocontrast agents are a frequent cause of acute decreases in renal function, occurring most often in patients with chronic renal insufficiency and diabetes mellitus.

METHODS

We prospectively studied 78 patients with chronic renal insufficiency (mean [+/- SD] serum creatinine concentration, 2.1 +/- 0.6 mg per deciliter [186 +/- 53 mumol per liter]) who underwent cardiac angiography. The patients were randomly assigned to receive 0.45 percent saline alone for 12 hours before and 12 hours after angiography, saline plus mannitol, or saline plus furosemide. The mannitol and furosemide were given just before angiography. Serum creatinine was measured before and for 48 hours after angiography, and urine was collected for 24 hours after angiography. An acute radiocontrast-induced decrease in renal function was defined as an increase in the base-line serum creatinine concentration of at least 0.5 mg per deciliter (44 mumol per liter) within 48 hours after the injection of radiocontrast agents.

RESULTS

Twenty of the 78 patients (26 percent) had an increase in the serum creatinine concentration of at least 0.5 mg per deciliter after angiography. Among the 28 patients in the saline group, 3 (11 percent) had such an increase in serum creatinine, as compared with 7 of 25 in the mannitol group (28 percent) and 10 of 25 in the furosemide group (40 percent) (P = 0.05). The mean increase in serum creatinine 48 hours after angiography was significantly greater in the furosemide group (P = 0.01) than in the saline group.

CONCLUSIONS

In patients with chronic renal insufficiency who are undergoing cardiac angiography, hydration with 0.45 percent saline provides better protection against acute decreases in renal function induced by radiocontrast agents than does hydration with 0.45 percent saline plus mannitol or furosemide.

Isolation of human T-cell leukemia virus in acquired immune deficiency syndrome (AIDS)

Several isolates of a human type-C retrovirus belonging to one group, known as human T-cell leukemia virus (HTLV), have previously been obtained from patients with adult T-cell leukemia or lymphoma. The T-cell tropism of HTLV and its prevalence in the Caribbean basin prompted a search for it in patients with the epidemic T-cell immune deficiency disorder known as AIDS. Peripheral blood lymphocytes from one patient in the United States and two in France were cultured with T-cell growth factor (TCGF) an shown to express HTLV antigens. Virus from the U.S. patient was isolated and characterized and shown to be related to HTLV subgroup I. The virus was also transmitted into normal human T cells from umbilical cord blood of a newborn. Whether or not HTLV-I or other retroviruses of this family with T-cell tropism cause AIDS, it is possible that patients from whom the virus can be isolated can also transmit it to others. If the target cell of AIDS is the mature T cell as suspected, the methods used in these studies may prove useful for the long-term growth of these cells and for the identification of antigens specific for the etiological agent of AIDS.

Isolation and transmission of human retrovirus (human t-cell leukemia virus)

Nine new isolates of human T-cell leukemia-lymphoma virus (HTLV) were obtained from cells of seven patients with malignancies of mature T cells and from two clinically normal relatives of a T-cell leukemia patient. These people were from the United States, Israel, the West Indies, and Japan. The virus was detected in the fresh T cells and was isolated from the established T-cell lines. Each isolate is closely related to the first HTLV isolate, and all the new HTLV isolates were transmitted into normal human T cells obtained from the umbilical cord blood of newborns.

Corticobasal degeneration and progressive supranuclear palsy share a common tau haplotype

OBJECTIVE

To analyze the association of polymorphisms in the tau gene with pathologically confirmed corticobasal degeneration (CBD).

BACKGROUND

The authors previously described an extended tau haplotype (H1) that covers the human tau gene and is associated with the development of progressive supranuclear palsy (PSP). The authors now extend this analysis to CBD, a neurodegenerative condition with clinical and neuropathologic similarities to PSP. Like PSP, CBD is associated with accumulation of aggregates containing the 4-repeat isoforms of tau. Because of difficulty in diagnosis of CBD, the authors only analyzed cases with pathologically confirmed CBD.

METHODS

The authors collected 57 unrelated, neuropathologically confirmed cases of CBD. Tau sequencing in these cases failed to show the presence of pathogenic mutations. Polymorphisms that spanned the tau gene were analyzed in all CBD cases and controls.

RESULTS

Analyzing tau polymorphisms in CBD cases showed that the frequency of H1 and H1/H1 was significantly increased when analyzing all cases and when separating by country of origin. H1 frequency in all CBD cases was 0.921, compared with a control frequency of 0.766 (X(2) = 9.1, p = 0.00255 [1df], OR 3.56 [8.43 > CI 95% > 1.53]). The H1/H1 frequency was also significantly higher at 0.842 compared with 0.596 in age-matched controls (X(2) = 17.42, p = 0.00016, 2df), OR 3.61 [7.05 > CI 95% > 1.85]).

CONCLUSIONS

The CBD tau association described here suggests that PSP and CBD share a similar cause, although the pathogenic mechanism behind the two diseases leads to a different clinical and pathologic phenotype.

Transformation of human umbilical cord blood T cells by human T-cell leukemia/lymphoma virus

Several isolates of human T-cell leukemia/lymphoma virus (HTLV) were transmitted to normal human T cells obtained from the umbilical cord blood of newborns. T cells from seven specimens were immortalized by infection with different HTLV isolates and their properties were compared with those of activated uninfected normal T cells grown in the presence of T-cell growth factor (TCGF) and with those of HTLV-positive neoplastic T-cell lines derived from patients with T-cell malignancies. The HTLV-infected cells generally belonged to a class of mature T cells (OKT4+ and Leu 3A+) and differed from the normal uninfected cells in that they could be propagated in culture indefinitely; possessed altered morphology, including convoluted nuclei and some bi- and multinucleated giant cells; formed large clumps in culture; demonstrated a diminished requirement for TCGF; had an increased density of TCGF receptors; often became completely independent of exogenous TCGF; and expressed HLA-DR determinants. These properties of the HTLV-infected cord blood T cells contrasted to those of uncultured cord blood T cells and of cord blood cells stimulated with mitogen and grown with TCGF but resembled the characteristics of T-cell lines established previously from patients with HTLV-associated T-cell malignancies. This in vitro system offers a unique opportunity to study the basic mechanism involved in abnormal growth and neoplastic transformation of a specific class of human T cells.

Organochlorine insecticides in substantia nigra in Parkinson's disease

The concentrations of organochlorine (OC) compounds in the substantia nigra (SN) were compared in Parkinson's disease (PD) with concentrations in brain from cortical Lewy body dementia (CLBD), Alzheimer's disease (AD), and nondemented nonparkinsonian controls (CON). The levels of the gamma isomer of hexachlorocyclohexane (gammaHCH, lindane) were significantly higher in PD tissues (mean +/- SD: 0.56 +/- 0.434 microg/g lipid) than in the other three groups (CLBD 0.052 +/- 0.101 microg/g lipid; AD none detected; CON 0.125 +/- 0.195; all differences from PD significant at p < .05, Mann-Whitney U-test). Dieldrin (HEOD) was higher in PD brain than in AD or control brain, while 1,1'-(2,2-dichloroethenyl diene)-bis(4-chlorobenzene) (p,p-DDE) and total Aroclor-matched polychlorinated biphenyls (matched PCBs) were only higher in PD substantia nigra when these concentrations were compared with those of CLBD. These findings are not inconsistent with the hypothesis derived from epidemiological work and animal studies that organochlorine insecticides produce a direct toxic action on the dopaminergic tracts of the substantia nigra and may contribute to the development of PD in those rendered susceptible by virtue of cytochrome P-450 polymorphism, excessive exposure, or other factors.

Transcriptomic and genetic studies identify IL-33 as a candidate gene for Alzheimer's disease

The only recognized genetic determinant of the common forms of Alzheimer's disease (AD) is the epsilon 4 allele of the apolipoprotein E gene (APOE). To identify new candidate genes, we recently performed transcriptomic analysis of 2741 genes in chromosomal regions of interest using brain tissue of AD cases and controls. From 82 differentially expressed genes, 1156 polymorphisms were genotyped in two independent discovery subsamples (n=945). Seventeen genes exhibited at least one polymorphism associated with AD risk, and following correction for multiple testing, we retained the interleukin (IL)-33 gene. We first confirmed that the IL-33 expression was decreased in the brain of AD cases compared with that of controls. Further genetic analysis led us to select three polymorphisms within this gene, which we analyzed in three independent case-control studies. These polymorphisms and a resulting protective haplotype were systematically associated with AD risk in non-APOE epsilon 4 carriers. Using a large prospective study, these associations were also detected when analyzing the prevalent and incident AD cases together or the incident AD cases alone. These polymorphisms were also associated with less cerebral amyloid angiopathy (CAA) in the brain of non-APOE epsilon 4 AD cases. Immunohistochemistry experiments finally indicated that the IL-33 expression was consistently restricted to vascular capillaries in the brain. Moreover, IL-33 overexpression in cellular models led to a specific decrease in secretion of the A beta(40) peptides, the main CAA component. In conclusion, our data suggest that genetic variants in IL-33 gene may be associated with a decrease in AD risk potentially in modulating CAA formation.

Hippocampal and neocortical ubiquitin-immunoreactive inclusions in amyotrophic lateral sclerosis with dementia

Amyotrophic lateral sclerosis (ALS) patients with dementia were found to have ubiquitin-immunoreactive (IR) inclusions in the dentate granule cells of the hippocampus. These inclusions were also present in some patients with minor cognitive changes but otherwise typical ALS. Ubiquitin-IR inclusions were also found in neurons of superficial layers of the frontal and temporal cortex and in the entorhinal cortex in patients with ALS and dementia. These ubiquitin-IR inclusions were non-argyrophilic, and were not labelled by antibodies which identify Alzheimer's neurofibrillary tangles and Pick bodies, nor were they typical of cortical Lewy bodies. Our findings indicate that ubiquitin-IR inclusions in small neurons of the hippocampus, entorhinal area and neocortex are a characteristic feature of degeneration of non-motor cortex in ALS, and are particularly associated with cognitive impairment and dementia of frontal lobe type.

Progranulin gene mutations associated with frontotemporal dementia and progressive non-fluent aphasia

Frontotemporal lobar degeneration (FTLD) refers to a focal, non-Alzheimer form of cerebral degeneration that encompasses the distinct clinical syndromes of frontotemporal dementia (FTD), progressive non-fluent aphasia (PNFA) and semantic dementia. Some patients show tau-based pathological changes and in familial cases mutations have been identified in the microtubule-associated protein tau gene (MAPT) on chromosome 17q21. However, many cases are tau-negative, showing instead ubiquitin-immunoreactive (UBQ-ir) neuronal cytoplasmic inclusions and neurites, and in some familial cases UBQ-ir neuronal intranuclear inclusions of a lentiform appearance. Very recently, mutations have been identified in familial cases in the progranulin (PGRN) gene, also on chromosome 17q21. Clinical, pathological and molecular diversity within FTLD highlights the importance of careful examination of clinical-pathological-genetic relationships. This paper reports, for the first time, a clinico-pathological investigation of two FTLD families with PGRN mutations, and compares the clinical characteristics with those of patients studied in the department with MAPT mutations. The clinical profile associated with PGRN mutations constituted, in some patients, a prototypical picture of FTD and in others one of PNFA, both profiles occurring within the same family. Patients with PGRN mutations exhibited phonological deficits, whereas in patients with MAPT mutations language abnormalities, when present in addition to the prominent behavioural disorder, take the form of semantic disturbance. The findings provide compelling evidence for the link between FTD and PNFA, while raising the possibility of identifiable clinical differences between FTLD patients with MAPT and PGRN mutations.

Distribution of lipids in 8,500 men with coronary artery disease. Department of Veterans Affairs HDL Intervention Trial Study Group

In the present study we measured fasting lipid profiles in over 8,500 community-living men with coronary artery disease (CAD) to determine the distribution of lipid abnormalities in this population: 81% were white and 16% black; mean age 62.9 +/- 8 years; mean total cholesterol 214 +/- 41 mg/dl; low-density lipoprotein (LDL) cholesterol 140 +/- 37 mg/dl; high-density lipoprotein (HDL) cholesterol 39 +/- 11 mg/dl; and triglycerides 190 +/- 142 mg/dl. After adjusting for age, the only significant difference between blacks and whites was a higher HDL cholesterol in blacks (45 vs 38 mg/dl, p < 0.003). With use of cut points established by the National Cholesterol Education Program, 87% of subjects had high LDL cholesterol (> or = 100 mg/dl), 38% had low HDL cholesterol (< 35 mg/dl), and 33% had high triglycerides (> 200 mg/dl). We estimated that 42% of men with CAD would be definite candidates for cholesterol-lowering medication according to the National Cholesterol Education Program guidelines and that 41% of those in whom cholesterol-lowering medication would not be definitely indicated had low levels of HDL cholesterol. We conclude that (1) black men with CAD have substantially higher HDL cholesterol than white men, (2) almost 90% of male patients with CAD are candidates for dietary intervention and > 40% may need medications to lower LDL cholesterol, and (3) 40% of patients without a definite indication for cholesterol-lowering medications have low levels of HDL cholesterol.

Early changes in extracellular matrix in Alzheimer's disease

AIMS

Although changes in extracellular matrix (ECM) scaffold have been reported previously in Alzheimer's disease (AD) compared to normal ageing, it is not known how alterations in the numerous components of the perivascular ECM might occur at different stages of AD. This study therefore investigates potential changes in basement membrane-associated ECM molecules in relation to increasing Braak stages.

METHODS

Thirty patients were divided into three groups (control subject, subclinical AD and AD patients). ECM levels of collagen IV, perlecan and fibronectin as well as human platelet endothelial cell adhesion molecule (hPECAM) were quantified by immunohistochemistry. Von Willebrand factor staining was measured to assess vessel density. Expression levels were correlated with the presence of amyloid plaques.

RESULTS

Collagen IV, perlecan and fibronectin expression was increased in subclinical AD and AD patients when compared to controls, in frontal and temporal cortex, whilst no further increase was detected between subclinical AD and AD. These changes were not associated with an increase in vessel density, which was instead decreased in the temporal cortex of AD patients. In contrast, hPECAM levels remained unchanged. Finally, we found similar pattern in levels of amyloid deposition between the different Braak stages and showed that changes in ECM components correlated with amyloid deposition.

CONCLUSION

Present data support the hypothesis that significant ECM changes occur during the early stages of AD. ECM changes affecting brain microvascular functions could therefore drive disease progression and provide potential new early investigational biomarkers in AD.

Amyloid phenotype characterization of transgenic mice overexpressing both mutant amyloid precursor protein and mutant presenilin 1 transgenes

Doubly transgenic mice (PSAPP) overexpressing mutant APP and PS1 transgenes were examined using antibodies to Abeta subtypes and glial fibrillary acidic protein (GFAP). Visible Abeta deposition began primarily in the cingulate cortex of PSAPP mice at approximately 10 weeks of age. By 6 months, the mice had extensive amyloid deposition throughout the hippocampus and cortex as well as other regions of the brain. Highly congophilic deposits consisting of N-terminal normal and modified forms of Abeta were identified, reminiscent of those found in human AD brain. Both immunohistochemistry and mass spectrometry showed that Abeta42 forms were underrepresented relative to Abeta40, and Abeta43 was undetectable. Deposits were associated with prominent gliosis which increased with age, but in 14-month-old PSAPP mice, GFAP immunoreactivity in the vicinity of amyloid deposits was substantially reduced compared to APP littermates. These mice have considerable utility in the study of the amyloid phenotype of AD.

Alteration of T-cell functions by infection with HTLV-I or HTLV-II

Two functionally different types of human T-cell clones, one with helper function and two with specific activity, were infected with different isolates of HTLV-I and HLTV-II. Both types of human T cells showed alterations in specific function after infection with either of the HTLV subgroups. Before HTLV infection, the T-cell clone with helper function proliferates and provides help to B cells only in the presence of both a specific soluble antigen (keyhole limpet hemocyanin) and histocompatible antigen-presenting cells. After HTLV infection, these cells respond with increased proliferation and indiscriminant stimulation of polyclonal immunoglobulin production by B cells, regardless of the histocompatibility of the antigen-presenting cells or the presence of the soluble antigen. Infection of the normal cytotoxic T-cell clones led to a dimunition or loss of the cytotoxic function. The results of these studies suggest some possible mechanisms for induction of immune deficiency and of polyclonal B-cell activation by viruses of the HTLV family.

VLA-1: a T cell surface antigen which defines a novel late stage of human T cell activation

The VLA-1 protein complex defines a previously undescribed very late stage of activated T cell differentiation, following either alloantigen or mitogen activation. This protein appears after 2-3 weeks of activation, considerably later than the early T cell activation antigens such as the interleukin 2 (IL 2) receptor, transferrin receptor, 4F2 antigen, T10 and HLA-DR, and has therefore been termed very late antigen-1 (VLA-1). Unlike the IL 2 receptor, VLA-1 expression does not require restimulation with antigen, and in fact, VLA-1 expression was high on T cells that had lost their IL 2 receptors. Expression of VLA-1 was found on all or nearly all long-term-activated T cells including T4+ and T8+ clones, bulk cultures, long-term T cells from adults and newborns and long-term T cells maintained in pure or crude IL 2 preparations. VLA-1 was also found on HTLV-1 infected T cell populations. Immunoprecipitation experiments confirmed that the VLA-1 protein complex (210 000/130 000 Mr) can be co-expressed with another protein complex called VLA-2 (165 000/130 000 Mr) on the same T cell clones. However, co-expression was not obligatory because in some long-term cultures little or no VLA-2 was present relative to VLA-1. Because VLA-1 defines a novel late stage of T cell activation, being present on all or most all types of long-term activated T cells, and not on any other cell types in peripheral blood, it has unique potential as a marker for activated T cells in vivo and may provide a clue towards elucidating novel long-term T cell functions or growth requirements of this late stage of T cell differentiation.

Human T-cell leukemia-lymphoma virus (HTLV) is in T but not B lymphocytes from a patient with cutaneous T-cell lymphoma

A human type C retrovirus, designated HTLV, previously was isolated from or identified in some patients with leukemias and lymphomas of mature T lymphocytes. HTLV is genetically and serologically distinct from any known animal retroviruses. The absence of HTLV proviral sequences in DNA from normal humans showed that HTLV is not a ubiquitous endogenous (germ-line transmitted) virus of humans. Antibodies to HTLV core proteins have been identified in some people with T-cell neoplasias and are particularly prevalent in Japanese with adult T-cell leukemia, suggesting that HTLV is acquired horizontally. However, it was possible that HTLV is transmitted through the germ line of some (possibly rare) families and is then expressed in the HTLV- positive malignancies. An opportunity to study this question was provided by the development of several T-cell lines and a B-cell provided by the development of several T-cell lines and a B-cell line from one HTLV-positive patient with a cutaneous T-cell lymphoma. Here we report that HTLV proteins or nucleic acids (or both) are found in three independently derived T-cell lines, all shown by HLA typing to have originated from the patient. In contrast, the B-cell line, the identity of which was also ascertained by HLA typing, contained no detectable HTLV protein, RNA, or proviral DNA. Because the sensitivity of the latter assay is more than sufficient to detect one proviral equivalent per haploid genome, the results indicate that HTLV was not transmitted to this patient through the germ line but rather was acquired by infection.

Location of lesions in Korsakoff's syndrome: neuropsychological and neuropathological data on two patients

Psychometric and neuropathological findings on two Korsakoff amnesics are described. Both patients showed anterograde and retrograde amnesia, poor performance on the Peterson short-term memory task, on the Wisconsin card sort test and on certain visuo-spatial tasks. Patient J.W. performed consistently worse on tests of anterograde, but not retrograde amnesia, whereas patient B.C. showed more perseverative difficulties and, unlike J.W., his measured intelligence seemed to have declined from its premorbid level. Both patients showed marked neuronal loss from the medial mammillary bodies and a narrow band of gliosis in the medial thalamus, adjacent to the wall of the third ventricle, a region known as the paratenial nucleus. Only B.C. showed visible signs of cortical atrophy. Morphometric measures did, however, reveal reduced nucleolar volumes in layers III and V of the frontal cortex, with B.C. also showing more marked neuronal loss from these layers. B.C. also showed neuronal loss from the CA1 region of the hippocampus and reduced nucleolar volumes in the septum. Significantly, both patients had normal neuronal numbers and nucleolar volumes in the nucleus basalis of Meynert. J.W. only showed greater dysfunction than B.C. in one region: the locus caeruleus. This finding was related to his more severe amnesia.

Pronounced impact of Th1/E47cs mutation compared with -491 AT mutation on neural APOE gene expression and risk of developing Alzheimer's disease

Possession of the apolipoprotein E (APOE) epsilon4 allele is the most frequently associated genetic susceptibility factor for Alzheimer's disease (AD). Recently, new polymorphisms in the regulatory region of the APOE gene have been described. We analysed the effects of three of these mutations (-491 AT, -427 CT and Th1/E47cs) on disease risk in a large case-control study, and tested their impacts on APOE allelic expression in brain tissues. The Th1/E47cs T allele was associated with an increased risk of occurrence of AD, while the -491 T allele was associated with a decreased risk, independently of the APOE epsilon2/epsilon3/epsilon4 polymorphism effect. However, the impact of the Th1/E47cs mutation was the strongest. The -427 CT polymorphism was not associated with the disease. In AD subjects heterozygous for the epsilon4 allele, analysis of allelic expression showed that the relative expression levels of the epsilon4 allele were higher than those of the corresponding controls. Consistent with epidemiological data, the relative level of expression of the epsilon4 allele was modified accordingly to the presence or absence of the two main promoter polymorphisms, indicating, in vivo, the deleterious effect of the Th1/E47cs T allele and the protective effect of the -491 T allele in population. These data indicate that in addition to the qualitative effect of the APOE epsilon2/epsilon3/epsilon4 polymorphisms on the AD occurrence, the quantitative variation of expression of these alleles due to functional APOE promoter mutations, is a key determinant of AD development.

Hydrogenation of single-walled carbon nanotubes

Towards the development of a useful mechanism for hydrogen storage, we have studied the hydrogenation of single-walled carbon nanotubes with atomic hydrogen using core-level photoelectron spectroscopy and x-ray absorption spectroscopy. We find that atomic hydrogen creates C-H bonds with the carbon atoms in the nanotube walls, and such C-H bonds can be completely broken by heating to 600 degrees C. We demonstrate approximately 65 +/- 15 at % hydrogenation of carbon atoms in the single-walled carbon nanotubes, which is equivalent to 5.1 +/- 1.2 wt % hydrogen capacity. We also show that the hydrogenation is a reversible process.

Inherited frontotemporal dementia in nine British families associated with intronic mutations in the tau gene

Genetic screening of 171 patients with frontotemporal lobar degeneration disclosed 14 patients, across nine pedigrees, with mutations in the intron to exon 10 in the tau gene, a region regulating the splicing of exon 10 via a stem loop mechanism. Thirteen of these patients had the +16 splice site mutation and one had the +13 splice site mutation. Affected members of all nine families presented with changes in behaviour and social conduct that were prototypical of frontotemporal dementia (FTD). In all patients with the +16 splice site mutation, the behavioural profile was characterized by disinhibition, restless overactivity, a fatuous affect, puerile behaviour and verbal and motor stereotypies. The single patient with the +13 mutation presented a contrasting picture of apathy and inertia. In addition, all patients had evidence of semantic loss. Pathologically, five of the six patients so far autopsied shared frontotemporal atrophy with involvement of the substantia nigra. The underlying histology was that of microvacuolar-type cortical degeneration with a few swollen cells. Tau pathology was widespread throughout the brain and present in neurones and glial cells, mostly in the frontal and temporal cortical regions. This was in the form of neurofibrillary tangles and amorphous tau deposits (pre-tangles); Pick bodies were not observed. Ultrastructurally, the tau filaments had a twisted, ribbon-like morphology distinct from the paired helical filaments of Alzheimer's disease. One patient died from an unrelated illness whilst in the early clinical stages of FTD. In this patient, cortical microvacuolar and astrocytic changes were absent, though there were scattered neurones and glial cells, immunoreactive to tau, throughout the cortical and subcortical regions. The disease process underlying the neurodegeneration within these inherited forms of FTD may therefore stem directly from early, primary alterations in the function of tau. All eight families with the +16 mutation seem to be part of a common extended pedigree, possibly originating from a founder member residing within the North Wales region of Great Britain.

Recombination rates across the HLA complex: use of microsatellites as a rapid screen for recombinant chromosomes

Meiotic recombination does not appear to occur randomly across chromosomes, but rather seems to be restricted to specific regions. A striking example of this phenomenon is illustrated by the HLA class II region. No recombination within the 100 kb encompassing the DRB1-DQA1-DQB1 loci has been reported, whereas the random association of TAP1 with TAP2 alleles suggests the presence of a hotspot for recombination within the 15 kb separating the closest variant sites of these two loci. Recombination rates between loci may provide clues to the functional properties of haplotypes. Absence of recombination may suggest the necessity to keep alleles of certain genes in phase and, alternatively, high recombination rates may suggest selective pressure to diversify haplotypes within the population. To address this issue, recombination rates across the HLA complex were determined using the 59 Centre d'Etude Polymorphisme Humain (CEPH) pedigrees. The allele frequencies of four microsatellite markers which map at sites ranging from the telomeric to centromeric ends of the complex were determined and the markers were used as a rapid means for identification of recombinant chromosomes. Typing these as well as other polymorphic loci within the HLA class I, II and III regions allowed assignment of the segments where recombination occurred. Recombination rates within the class II region (defined here as DRB1 to DPB1) and class III region (defined here as HLA-B to DRB1) regions were 0.74% and 0.94%, respectively, both of which are within an expected range given the standard of 1% recombination rate per megabase of DNA per meiosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Consistent associations of HLA class I and II and transporter gene products with progression of human immunodeficiency virus type 1 infection in homosexual men

Polymorphic products of genes in the HLA region contributing to variability in the course of human immunodeficiency virus type 1 (HIV-1) infection were identified by screening 375 Caucasian seroconverters who were aggregated from 3 cohorts. AIDS-free time was related to numerous (15) class I alleles, alone or in conjunction with transporter protein variants, to homozygosity at the A or B locus, and to alleles of two class II haplotypes. A prognostic scoring algorithm derived from the 3 cohorts captured multiple HLA contributions to protection or to risk (relative hazard=0.57-60 per unit increase in score, all P<<.001). The impact of HLA was strong and appeared independent of the effects of chemokine receptor/ligand polymorphisms and antiretroviral treatment. The algorithm also predicted divergent rates of CD4+ cell decline in 2 other groups, totaling 227 seropositive persons (P=.06 - <.001). Confirmation of these relationships should encourage investigation of HIV-1 antigen processing and presentation mediated by polymorphisms in the HLA region.

Frequency of tau mutations in three series of non-Alzheimer's degenerative dementia

Splice-site and missense mutations have been identified in tau associated with frontotemporal dementia with parkinsonism linked to chromosome 17. In this study we assessed the genetic contribution of tau mutations to three patient series with non-Alzheimer's (non-AD) degenerative dementia. The groups included (1) a community-based dementia series from Minnesota, MN; (2) a referral series with clinicopathological tauopathy; and (3) a pathologically confirmed familial frontotemporal dementia series from Manchester, UK. Comparing the three clinical series: in the stringently diagnosed Manchester frontotemporal dementia series, tau mutations were present in 13.6% of cases (three splice-site mutations); in the clinicopathological referral series that used more general inclusion criteria, 3 cases with P301L mutations were observed, which represents a lower mutation frequency of 3.6% (9.4% in familial cases); in contrast, tau mutations were not detected in the Minnesota community-based dementia series, suggesting the occurrence of these mutations in dementia generally is rare (<0.2%). These data identify the prevalence of mutations in three different clinical settings and indicate that this figure is sensitive to the diagnostic criteria used in each patient series.

Partial purification of detergent-soluble HL-A antigen and its cleavage by papain

HL-A antigen solubilized with the non-ionic detergent, Brij 99, has been purified to about 50% of homogeneity from a cultured human lymphoblast line. It consists of two nonidentical subunits of 44,000 and 12,000 molecular weight (MW). Upon papain proteolysis the 44,000 MW peptide is converted by at least two cleavages to a 34,000 MW peptide, but the 12,000 MW peptide appears to be unchanged. Concomitantly, the apparent molecular weight in gel filtration chromatography under nondenaturing conditions in the presence of Brij 99 is reduced from 460,000 to 45,000. HL-A molecules produced by direct papain proteolysis of membranes and by papain treatment of purified detergent-soluble HL-A are identical.

Apolipoprotein E epsilon 2 allele promotes longevity and protects patients with Down's syndrome from dementia

Although individuals with Down's syndrome nearly always develop the clinical and pathological features of Alzheimer's disease, some clearly do not become demented despite living into their sixth and seventh decades. Genetic variation at the apolipoprotein E locus has recently been shown to be an important determinant of Alzheimer's disease, with the epsilon 4 allele having been shown to be associated with the disease and, at least in some cases, the epsilon 2 allele being negatively associated with the disease. Here we show, in a series of clinically assessed individuals with Down's syndrome, that the epsilon 2 allele of ApoE is associated with both longevity and the absence of clinical evidence of dementia. These data show that the clinical phenotype of Down's syndrome can be modulated by genes on chromosomes other than chromosome 21. The importance of this observation to the pathogenesis of Alzheimer's disease, both in Down's syndrome and in general, is discussed.