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Biomedical subjects

A D Roses

Publications and source records attributed to A D Roses.

At least 91 records · Page 5Linked to original sources
PubMed1997

Oligomerization of expanded-polyglutamine domain fluorescent fusion proteins in cultured mammalian cells.

Six inherited neurologic diseases, including Huntington's disease, result from the expansion of a CAG domain of the disease genes to produce a domain of more than 40 glutamines in the expressed protein. The mechanism by which expansion of this polyglutamine domain causes disease is unknown. Recent studies demonstrated oligomerization of polyglutamine-domain proteins in mammalian neurons. To study oligomerization of polyglutamine proteins and to identify heterologous protein interactions, varying length polyglutamine-green fluorescent protein fusion proteins were expressed in cultured COS-7 cells. The 19- and 35-glutamine fusion proteins (non-pathologic length) distributed diffusely throughout the cytoplasm. In contrast, 56- and 80-glutamine fusion proteins (pathologic length) formed fibrillar arrays resembling those previously observed in neurons in Huntington's disease and in a transgenic mouse model. These aggregates were intranuclear and intracytoplasmic. Intracytoplasmic aggregates were surrounded by collapsed intermediate filaments. The intermediate filament protein vimentin co-immunoisolated with expanded polyglutamine fusion proteins. This cellular model will expedite investigations into oligomerization of polyglutamine proteins and their interactions with other proteins.

Animals↗
PubMed1997

Alzheimer's disease: the genetics of risk.

Each copy of an epsilon 4 allele of the gene encoding the lipid carrier apoE increases the probability of the disease and shifts its onset to lower ages. Yet the gene does not cause the disease. Thus, although genotyping is highly valuable in diagnosis and drug testing, it cannot offer useful predictions about persons whose cognition is unimpaired. After discovery of a second susceptibility gene, predictability will change profoundly.

Age of Onset↗
PubMed1997

Relation of age and apolipoprotein E to cognitive function in Down syndrome adults.

To test the cognitive effects of aging and apolipoprotein E (APOE) in individuals at high risk for Alzheimer's disease (AD), we assessed APOE genotypes and performance on a battery of neuropsychological tests in 41 non-demented, Down syndrome (DS) adults. Old DS subjects (ages 41-61 years) showed poorer memory and orientation scores than young DS adults (ages 22-38 years), but the groups did not differ in other measures after we controlled for intellectual function. Language ability was inversely related to APOE genotype, even after age was controlled for, with the presence of the epsilon 2 allele corresponding to better language skills than epsilon 4. Age-related cognitive changes in non-demented DS adults are consistent with the early effects of AD. The relationship between basic linguistic skills and APOE genotype supports this genetic factor in influencing the development of dementia and AD neuropathology in DS.

Adult↗
PubMed1997

The clinical introduction of genetic testing for Alzheimer disease. An ethical perspective.

OBJECTIVE: Primary caregivers should be aware of recent progress in the genetics of Alzheimer disease (AD) and of the clinical and ethical considerations raised regarding the introduction of genetic testing for purposes of disease prediction and susceptibility (risk) analysis in asymptomatic individuals and diagnosis in patients who present clinically with dementia. This statement addresses arguments for and against clinical genetic testing. PARTICIPANTS: The 20 participants were selected by the investigators (S.G.P., T.H.M., A.B.Z., and P.J.W.) to achieve balance in the areas of genetics, counseling, ethics, and public policy, and to include leadership from related consensus projects. The consensus group met twice in closed meetings and carried on extensive correspondence over 2 years (1995-1997). The project was supported by the National Human Genome Research Institute of the National Institutes of Health. EVIDENCE: All 4 involved chromosomes were discussed in group meetings against a background of information from several focus group sessions with AD-affected families. The focus groups comprised volunteers identified by the Cleveland Area Chapter of the Alzheimer's Disease and Related Disorders Association and represented a variety of ethnic populations. CONSENSUS PROCESS: The first draft was written in April 1996 by the principal investigator (S.G.P.) after the consensus group had met twice. The draft was mailed to all consensus group members 3 times over 6 months for extensive response and redrafting by the principal investigator until all members were satisfied. CONCLUSIONS: Except for autosomal dominant early-onset families, genetic testing in asymptomatic individuals is unwarranted. Use of APOE genetic testing as a diagnostic adjunct in patients already presenting with dementia may prove useful but it remains under investigation. The premature introduction of genetic testing and possible adverse consequences are to be avoided.

Advisory Committees↗
PubMed1997

D2 dopamine receptor A1 allele in Alzheimer disease and aging.

BACKGROUND: The apolipoprotein E4 (APOE*4) allele is a major risk factor for the common forms of late-onset Alzheimer disease (AD), but does not account for all the genetic variation in late-onset AD; hence, other genetic markers must be examined. The D2 dopamine receptor (DRD2) A1 allele is associated with abnormal brain function and decreased DRD2s. These receptors are decreased in hippocampus and amygdala in AD, and allele frequencies may vary with age. OBJECTIVE: To study APOE and DRD2 genotypes in patients with AD and cognitively intact controls of varying ages. DESIGN: The DRD2 and APOE genotypes were examined in 832 unrelated white subjects, including 554 patients with AD (486 sporadic; 68 familial) and 278 controls. Logistic regressions tested A1 allele effects on disease status and age, and DRD2 linkage with AD was investigated in 60 families with late-onset AD. SETTING: University medical centers. SUBJECTS: Patients (mean +/- SD age, 74.6 +/- 8.1 years; range, 52-98 years) had probable AD, according to standard consensus diagnostic criteria; controls (mean +/- SD age, 69.2 +/- 8.6 years; range, 50-93 years) were cognitively intact. MAIN OUTCOME MEASURES: Disease status, age, and DRD2 linkage with AD. RESULTS: No association between the DRD2 and APOE alleles was found, and the presence of the A1 allele did not increase the risk for AD. There was also no evidence of linkage between DRD2 and AD. Age analyses, including both patients and controls, indicated a decrease in A1 allele frequency with age. CONCLUSIONS: The A1 allele does not contribute to AD risk, alone or in combination with the APOE*4 allele. The DRD2 A1 allele frequencies decrease with age in both patients and controls. Thus, studies of DRD2 disease association need to control for age.

Aged↗
PubMed1997

Genetic testing for Alzheimer disease. Practical and ethical issues.

The dissection of the heterogeneous genetics of the Alzheimer diseases (ADs) is currently more advanced than in any other common disease. Not only are 3 uncommon autosomal dominant mutation loci identified, but universally inherited susceptibility polymorphisms associated with risk and age of onset distributions for familial and "sporadic" AD are also confirmed. The utility of testing for mutations of the amyloid precursor protein and the presenilin 1 and presenilin 2 genes conforms to strategies in common use for rare mutations. The selection of patients with very early-onset AD, especially those with family histories of the disease, will increase the possibility of diagnosis. All testing should be performed using recommended counseling procedures. Apolipoprotein E (ApoE) susceptibility polymorphisms are genetic risk factors but do not allow prediction of the age of onset of AD for cognitively normal individuals. Recent large, collaborative studies have found that when ApoE genotyping is used sequentially in diagnosis following criteria-based evaluations, the specificity of early diagnosis is significantly increased. For patients clinically diagnosed with AD who carried an ApoE epsilon 4 allele, the positive predictive value was 94% and 97% in 2 multicenter collaborative series. The utility of ApoE genotyping is reviewed and recommendations for early use in diagnosis are explained. There are ethical, social, actuarial, and legal problems currently associated with genetic testing and these concerns are also discussed.

Alzheimer Disease↗
PubMed1997

No association or linkage between an intronic polymorphism of presenilin-1 and sporadic or late-onset familial Alzheimer disease.

Recent reports have shown an association between an intronic polymorphism of the presenilin-1 (PSEN1) gene and late-onset (age at onset > 65) familial and sporadic (no family history) Alzheimer disease (AD). The reported association was independent of the effect of the only previously identified gene associated with late-onset AD, APOE. Blood samples were obtained from members of 122 multiplex AD families, 42 unrelated cases of AD with positive family histories of dementia, 456 sporadic cases of AD, and 317 controls of similar ages at examination to the cases. These samples were genotyped for an intronic polymorphism of the PSEN1 gene, located 3' to exon 8, and the data analyzed for evidence of association or linkage. The samples were also genotyped for APOE and the data analyzed to see if the association or linkage changed when controlling for APOE genotype. There was no statistically significant increase (at alpha = .01) in allele 1 (199 bp) or genotype 1/1 in the sporadic AD cases, or in a random sample of one affected from each multiplex family, compared to controls. When examining the effect of the PSEN1 polymorphism while controlling for APOE genotype, APOE genotype was strongly associated with AD, but the PSEN1 polymorphism genotype was not. Model-trait dependent (lod score) and independent (Sim1BD) methods detected no evidence of linkage between PSEN1 and AD. In this independent dataset, the previously reported association between the intronic PSEN1 polymorphism and AD cannot be confirmed, and the conclusion that PSEN1 is a major susceptibility gene for late-onset AD is not supported.

Age of Onset↗
PubMed1997

Endoglin gene polymorphism as a risk factor for sporadic intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) is a common and serious type of stroke. Recent studies have shown that inherited factors that affect the development of the vessel wall can increase the risk of ICH. We studied endoglin as a candidate gene in patients with sporadic ICH, since mutations in this gene can cause telangiectasia formation. One hundred three patients with sporadic ICH and 202 controls were studied. The polymerase chain reaction and single-strand conformational polymorphism analysis were used to screen for mutations in exon 7 of the endoglin gene. No coding mutations in exon 7 were identified in the ICH patients or controls. A 6-base intronic insertion was found 26 bases beyond the 3' end of exon 7. The homozygous form of the insertion was present in 9 of 103 (8.7%) ICH patients compared with 4 of 202 (2.0%) controls, p = 0.012 (odds ratio 4.8 [95% confidence interval, 1.28, 21.60]). Analysis of the endoglin transcript around the insertion did not reveal any changes in the RNA sequence. There were no obvious clinical features that distinguished the ICH patients with the homozygous insertion from the other patients. The pathophysiologic mechanism underlying this association remains to be determined.

Adult↗
PubMed1997

Apolipoprotein E genotypes in a neuropathological series from the Consortium to Establish a Registry for Alzheimer's Disease.

We evaluated the sensitivity, specificity, and predictive value of the apolipoprotein E (ApoE) epsilon4 allele for the neuropathological diagnosis of Alzheimer disease (AD) in a clinical series of well-characterized AD patients and controls followed longitudinally in the multicenter study of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD). In the 162 patients for whom autopsy and ApoE genotype data were available, the clinical diagnosis of AD was verified as the primary cause of dementia in 139 cases (139 of 162, or 86%). The sensitivity and specificity of the epsilon4 allele for AD were both 83%. The positive predictive value of the epsilon4 allele was very high at 97% (115 of 119); whereas, the negative predictive value was 44% (19 of 43), providing no useful information for diagnosis of AD when the epsilon4 allele is not present. Of the cases where AD was not considered the primary or sole cause of dementia (n = 23), 6 cases exhibited concomitant neuropathological findings of definite or probable AD and 2 of these 6 cases had at least one epsilon4 allele. These multicenter data extend previous observations reported from smaller case series of single laboratories and demonstrate that once the clinical diagnosis of AD is established, the presence of an epsilon4 allele reliably predicts the ultimate CERAD neuropathological diagnosis of AD. The findings also suggest that ApoE genotype information is useful clinically in bolstering diagnostic confidence when an epsilon4 allele is present and in identifying a group of patients for whom additional diagnostic evaluations may be warranted when the epsilon4 allele is absent.

Aged↗
PubMed1997

Apolipoprotein E epsilon2 does not increase risk of early-onset sporadic Alzheimer's disease.

We examined the association of apolipoprotein E (ApoE) genotype and the risk of early-onset Alzheimer's disease (AD) in 209 white early-onset sporadic cases (43% male) and 303 white controls (48% male) of similar age distribution. The risk of AD was significantly increased, relative to the 3/3 genotype, in people with the 4/4, 3/4, and 2/4 genotypes, controlling for age at time of examination and sex. The 2/3 genotype reduced slightly the risk of AD, although the effect was not statistically significant. We conclude, contrary to some previous reports, that the ApoE epsilon2 allele does not increase the risk of early-onset sporadic AD.

Adult↗
PubMed1997

Apolipoprotein E uptake and low-density lipoprotein receptor-related protein expression by the NTera2/D1 cell line: a cell culture model of relevance for late-onset Alzheimer's disease.

Apolipoprotein E has been shown to be a risk factor for late-onset Alzheimer's disease, with the apolipoprotein epsilon 4 allele conferring the risk. Apolipoprotein E is found in neurofibrillary tangles and senile plaques, the pathological characteristics of Alzheimer's disease. To date there is no direct evidence that human neurons can take up exogenous apolipoprotein E, which is necessary if apolipoprotein E is involved in the formation of neurofibrillary tangles. To examine apolipoprotein E uptake we employed the human NTera2/D1 cell line, which can be induced by retinoic acid to differentiate into postmitotic NTera2-N neurons, which have the characteristics and morphology of human central nervous system neurons. We defined the cell line as genotype apolipoprotein epsilon 3/3 and demonstrated that the cells do not synthesize apolipoprotein E but can take up and internalize exogenous recombinant apolipoprotein E3. We also confirmed the expression of the low-density lipoprotein receptor-related protein, a known receptor for apolipoprotein E. The NTera2/D1 cell line therefore provides a useful human cell model for examining the effects of other apolipoprotein E isoforms with a view to defining intraneuronal interactions of apolipoprotein E.

Alzheimer Disease↗
PubMed1997

Apolipoprotein E, a gene with complex biological interactions in the aging brain.

Age-dependent neurodegeneration in Alzheimer disease (AD) may be viewed as a complex interaction among: (i) susceptibility polymorphisms, (ii) somatic mutations or alterations that occur over extended periods of time, and (iii) environmental interactions. Putative "sporadic" diseases appear to have a much stronger genetic component than had been considered previously. For example, in Alzheimer disease, apolipoprotein E is a major susceptibility locus that accounts for approximately half the heritability. Specific APOE genotypes are associated with different relative risks and age of onset distributions. Disease may be expressed as a confluence of several genetic risk factors, superimposed upon the age-dependent increments of somatic mitochondrial mutations, and environmental determinants such as head injury, stroke, or hypoxia. A matrix involving each of these complex factors may influence the age of onset of AD in a particular individual. With careful clinically based family and epidemiological studies, it is now possible to tease out the relevant genetic contributions from the confluence of other factors leading to complex disease affecting specific sets of neurons. The highly intricate maze of contributing factors provides many potential unanticipated opportunities to design rational therapeutic and preventative strategies.

Aging↗
PubMed1997

A model for susceptibility polymorphisms for complex diseases: apolipoprotein E and Alzheimer disease.

Apolipoprotein E (APOE) polymorphisms are associated with variable risk and age of onset distributions for the common form of Alzheimer disease. Clinical genetic applications of APOE genotyping differ from those of family-specific mutations because the APOE genotypes are universally distributed in all populations, with ethnic and racial variations in relative allele frequencies. The association of a common disease affecting millions of people with genetic risk factors provides a new paradigm for understanding disease pathogenesis and an opportunity to focus on relevant genetic mechanisms. Clinical applications of APOE genotype information are based on epidemiological principles, rather than family-specific genetic counselling. At the present time it is not possible to predict when or if any individual will develop AD. Likewise, no APOE genotype provides escape from risk. However, an impending ethical and social dilemma is on the near horizon. When additional susceptibility polymorphisms are found, for example within a recently reported linkage to a chromosome 12 region, disease prediction may be possible for millions of unaffected individuals at a time when preventive therapies are not yet available. This impending capability should be a wake-up call for anticipating social, ethical, and legal problems. It differs from the current model of family specific mutations because, rather than affecting a relatively small population at risk, millions of people will be capable of receiving favorable or unfavorable prognostic information. The association of common polymorphisms with complex diseases finds its first example in APOE and AD. Just as the linkage search for other susceptibility genes can be modelled after AD, the medical, ethical, social, and legal implications of this paradigm can serve as a template for other complex disease loci being actively sought by industry and in academic laboratories.

Age Factors↗
PubMed1997

Further exclusion of FSHD1B from the telomeric region of 10q.

The localization of the gene for the majority of cases of facioscapulohumeral muscular dystrophy is established as 4q35-qter (FSHD1A), although locus heterogeneity has been demonstrated with a minority of families unlinked to 4q. In FSHD1A, the disease is associated with a deletion of 3.3 kb repeats from a tandem repeat located near the as-yet-unidentified gene. This repeat cross-hybridizes with a telomeric region on 10q, making this cross-hybridizing region a feasible candidate gene for FSHD1B. We have tested the most telomeric marker on 10q (sAVA4) and excluded approximately 17 cM on either side of this marker as harboring the FSHD1B gene.

Alleles↗
PubMed1997

Preliminary report of a genetic basis for cognitive decline after cardiac operations. The Neurologic Outcome Research Group of the Duke Heart Center.

BACKGROUND: Changes in memory and cognition frequently follow cardiac operations. We hypothesized that patients with the apolipoprotein E-epsilon 4 allele are genetically predisposed to cognitive dysfunction after cardiac operations. METHODS: The apolipoprotein E-epsilon 4 allele was evaluated as a predictor variable for postoperative cognitive dysfunction in 65 patients undergoing cardiac bypass grafting at Duke University Medical Center. The primary outcome measure was performance on a cognitive battery administered preoperatively and at 6 weeks postoperatively. RESULTS: In a multivariable logistic regression analysis including apolipoprotein E-epsilon 4, preoperative score, age, and years of education, a significant association was found between apolipoprotein E-epsilon 4 and change in cognitive test score in measures of short-term memory at 6 weeks postoperatively. Patients with lower educational levels were more likely to show a decline in cognitive function associated with the apolipoprotein E-epsilon 4 allele. CONCLUSIONS: This study suggests that apolipoprotein E genotype is related to cognitive dysfunction after cardiopulmonary bypass. Cardiac surgical patients may be susceptible to deterioration after physiologic stress as a result of impaired genetically determined neuronal mechanisms of maintenance and repair.

Age Factors↗