Apolipoprotein E gene promoter polymorphisms in Alzheimer's disease

The Impact of Apolipoprotein E (APOE) Epigenetics on Aging and Sporadic Alzheimer's Disease

Sporadic Alzheimer's disease (AD) derives from an interplay among environmental factors and genetic variants, while epigenetic modifications have been expected to affect the onset and progression of its complex etiopathology. Carriers of one copy of the apolipoprotein E gene (APOE) ε4 allele have a 4-fold increased AD risk, while APOE ε4/ε4-carriers have a 12-fold increased risk of developing AD in comparison with the APOE ε3-carriers. The main longevity factor is the homozygous APOE ε3/ε3 genotype. In the present narrative review article, we summarized and described the role of APOE epigenetics in aging and AD pathophysiology. It is not fully understood how APOE variants may increase or decrease AD risk, but this gene may affect tau- and amyloid-mediated neurodegeneration directly or indirectly, also by affecting lipid metabolism and inflammation. For sporadic AD, epigenetic regulatory mechanisms may control and influence APOE expression in response to external insults. Diet, a major environmental factor, has been significantly associated with physical exercise, cognitive function, and the methylation level of several cytosine-phosphate-guanine (CpG) dinucleotide sites of APOE.

APOEε4 and risk of Alzheimer's disease - time to move forward

The inheritance of Apolipoprotein E4 (APOEε4) brings the highest genetic risk of Alzheimer's disease (AD), arguably the highest genetic risk in human pathology. Since the discovery of the association, APOE protein isoforms have been at the center of tens of thousands of studies and reports. While, without a doubt, our knowledge about the normal physiological function of APOE isoforms in the brain has increased tremendously, the questions of how the inheritance of the APOEε4 allele translates into a risk of AD, and the risk is materialized, remain unanswered. Moreover, the knowledge about the risk associated with APOEε4 has not helped design a meaningful preventative or therapeutic strategy. Animal models with targeted replacement of Apoe have been generated and, thanks to the recent NIH/NIA/Alzheimer's disease Association initiative, are now freely available to AD researchers. While helpful in many aspects, none of the available models recapitulates normal physiological transcriptional regulation of the human APOE gene cluster. Changes in epigenetic regulation of APOE alleles in animal models in response to external insults have rarely been if ever, addressed. However, these animal models provide a useful tool to handle questions and investigate protein-protein interactions with proteins expressed by other recently discovered genes and gene variants considered genetic risk factors of AD, like Triggering Receptor expressed on Myeloid cells 2 (TREM2). In this review, we discuss genetic and epigenetic regulatory mechanisms controlling and influencing APOE expression and focus on interactions of APOE and TREM2 in the context of microglia and astrocytes' role in AD-like pathology in animal models.

Cognitive impairment in patients with multiple sclerosis: association with the APOE gene and promoter polymorphisms

Background Studies examining the ε4 allele of the APOE gene as a factor affecting the severity of multiple sclerosis (MS) have yielded conflicting results. The focus of these studies on physical disability to the neglect of cognitive impairment is surprising in light of the associations between the ε4 allele and other dementia conditions. Only two studies examine the relationship between the ε4 allele and cognitive impairment.

Methods A neuropsychological test battery was administered to 263 MS patients, and their current disability status was evaluated. Genotypes were determined for APOE epsilon and for two promoter region polymorphisms (-219 G/T and -491 A/T).

Results Although effects were generally weak, female patients with the -491 AA genotype had a later age of disease onset, lower disability scores, and somewhat higher scores on the cognitive battery. Male patients with the ε2 allele had lower disability and higher scores on the cognitive battery. The ε4 allele was not related to physical disability, and there was no difference between ε4+and ε4– patients in overall cognitive performance. However, when patients with severe cognitive impairment were identified, a greater proportion (52%) of these patients had the ε4 allele than those in the unimpaired group (27%).

Conclusion An association with the ε4 allele was evident in this study, but only in cases of severe cognitive impairment.

Transcriptional regulation and its misregulation in Alzheimer's disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder characterized by loss of memory and cognitive function. A key neuropathological event in AD is the accumulation of amyloid-β (Aβ) peptide. The production and clearance of Aβ in the brain are regulated by a large group of genes. The expression levels of these genes must be fine-tuned in the brain to keep Aβ at a balanced amount under physiological condition. Misregulation of AD genes has been found to either increase AD risk or accelerate the disease progression. In recent years, important progress has been made in uncovering the regulatory elements and transcriptional factors that guide the expression of these genes. In this review, we describe the mechanisms of transcriptional regulation for the known AD genes and the misregualtion that leads to AD susceptibility.

Neurodegenerative Genes Polymorphisms of the -491A/T APOE, the -877T/C APP and the Risk of Primary Open-angle Glaucoma in the Polish Population

BACKGROUND

Glaucoma is characterized by optic neuropathy of the retinal ganglion cell. It may be possible that β-amyloid (Aβ) and apolipoprotein E (APOE), the main proteins of the pathogenesis of AD, play a role in glaucoma development. The aim of this study was to evaluate a relationship between the APP and APOE gene polymorphisms and the risk of primary open-angle glaucoma (POAG) occurrence.

MATERIALS AND METHODS

The study consisted of 183 patients with POAG and 209 healthy subjects. Genomic DNA was extracted from peripheral blood. Analysis of the gene polymorphisms was performed using PCR-RFLP.

RESULTS

We found a statistically significant increase of the -491 T allele frequency (p=0.02; OR=1.48; 95% CI=1.06-2.08) of APOE in POAG compared to healthy controls. There were no differences in the genotype and allele distributions and odds ratios of the APP polymorphism between patients and controls group. We also found an association between APOE polymorphic variant and retinal nerve fiber layer (RNFL). There was a statistically significant difference in the APOE gene A/T genotype frequency in the early POAG stage and middle-advanced POAG stage in comparison to the advanced POAG stage (p=0.04; OR=3.38; 95% CI=1.04-10.97).

CONCLUSIONS

The -491 T allele of APOE polymorphism may be associated with a risk of POAG occurrence in the Polish population.

Molecular neuropathogenesis of Alzheimer's disease: an interaction model stressing the central role of oxidative stress

Alzheimer's disease (AD) exhibits a complex etiology that simultaneously manifests as a complex cellular, neurobiological, molecular, anatomic-physiological and clinical entity. Other significant psychiatric conditions, such as depression and schizophrenia, may also present with complex and concurrent clinical and/or molecular phenotypes. These neuropsychiatric pathologies also originate from both environmental and genetic factors. We analyzed the molecular phenotypes of AD and discuss them with respect to the classical theories, which we integrated into mechanisms that share molecular and/or anatomical connections. Based on these mechanisms, we propose an interaction model and discuss the model in light of studies that refute or support it. Given the spectrum of AD phenotypes, we limit the scope of our discussion to a few, which facilitates concrete analysis. In addition, the study of specific, individual pathogenic phenotypes may be critical to defining the complex mechanisms leading to AD, thereby improving strategies for developing novel therapies.

Genetic variation in APOE cluster region and Alzheimer's disease risk

We report the fine mapping/sequencing results of promoter and regulatory regions of APOE cluster genes (APOE, APOC1, APOC4, APOC2, and TOMM40) in Alzheimer's disease (AD) risk as well as in the progression from mild cognitive impairment (MCI) to AD. Long-range sequencing in 29 MCI subjects who progressed to dementia revealed 7 novel variants. Two potentially relevant novel variants and 34 single nucleotide polymorphisms (SNPs) were genotyped in a large sample of AD, MCI, and control subjects (n = 1453). Globally, very little association signal was observed in our sample in the absence of APOE ε4. Rs5158 (APOC4 intron 1) and rs10413089 (3' to APOC2) showed a trend toward an increase in AD risk independently from APOE ε4 associated risk though it did not survive multiple test correction (uncorrected p = 0.0099 and 0.01, respectively). Interestingly, rs10413089 showed a similar effect in an independent series. The analysis of the discovery sample showed an association of TOMM40 single nucleotide polymorphisms with progression from MCI stage to AD (rs59007384 and rs11556510), as well as with a shorter time to progression from MCI status to AD (rs10119), though these results could not be replicated in independent series. Further studies are needed to investigate the role of APOE cluster variants in AD risk.

Association between an intronic apolipoprotein E polymorphism and bone mineral density in Singaporean Chinese females

INTRODUCTION

Apolipoprotein E (ApoE) is implicated in the pathogenesis of osteoporosis.

OBJECTIVE

To investigate possible association of the non-classical APOE gene +113C/G (rs440446) intron 1 enhancer polymorphism with bone mineral density (BMD) in a homogeneous Chinese population in Singapore.

METHODS

A total of 655 volunteers, males and females, aged between 31 and 72 years, from the public participated. BMD was measured using dual-energy X-ray absorptiometry and APOE +113C/G (rs440446) genotypes were determined by Sequenom MassARRAY system. To adjust for potential confounders, anthropometric, demographic, and lifestyle determinants were obtained, and serum lipids and E(2) were measured.

RESULTS

The +113C/G (rs440446) polymorphism within the APOE gene was associated with BMD in Chinese Singaporean females only. Females with the heterozygous CG genotype were significantly associated with reduced total, lumbar spine, and femoral neck of hip BMD, after multilevel adjustment of confounders. The association was stronger in the spine than in the hip. When females were stratified according to WHO classification for osteoporosis, those with CG and GG genotypes had increased risk (OR 3.50 and 2.22, respectively) of developing osteopenia/osteoporosis in the lumbar spine. Serum lipids did not explain the influence of APOE +113 C/G (rs440446) on BMD.

CONCLUSION

This study demonstrated an association between APOE +113C/G (rs440446) polymorphism with measures of BMD in Singaporean Chinese females.

The complex interaction between APOE promoter and AD: an Italian case-control study

The single nucleotide polymorphisms (SNPs) rs449647, rs769446 and rs405509 in the promoter region of the APOE gene have been variously suggested to be epsilon 4-independent risk factors for Alzheimer's disease (AD). A previous Italian study found that the rs449647 was significantly associated with late-onset AD. The aim of this study was to verify whether these APOE promoter SNPs are genetic risk factors for AD and to investigate their interaction with the common APOE polymorphism. A total of 169 clinically diagnosed AD patients and 99 cognitively intact age-matched controls were included in the study. Significant associations with AD independent from sex, age and APOE/epsilon 4 status were found for rs449647 A/A and rs405509 G/G genotypes (positive), and rs449647 A/T and rs405509 T/T genotypes (negative). Haplotype frequency estimation at the APOE locus showed significant associations for the ATG4, ATT4 and ACG3 (positive) and ATT2, ATT3 and TCG3 (negative) haplotypes. Therefore this study confirms the role of the rs449647 A/A genotype as risk factor for AD in Italy and suggests that promoter genotypes and APOE haplotypes might have a complex function in AD-associated genetic risk factors.

Interactions of functional apolipoprotein E gene promoter polymorphisms with smoking on aortic atherosclerosis

BACKGROUND

Apolipoprotein E gene (APOE) interacts with environmental factors in defining risk for atherosclerosis. We studied whether the APOE epsilon2/epsilon3/epsilon4 genotype or APOE promoter polymorphisms -219G/T and +113G/C might interact with smoking on the development of fatty streaks. We also studied the previously unknown effects of +113G/C on transcriptional activity.

METHODS AND RESULTS

The fatty streak areas of aorta were measured morphometrically in subjects of the Helsinki Sudden Death Study. Within APOE epsilon3/epsilon3 subjects, there was a strong interaction between smoking and both -219G/T (P=0.009) and +113G/C (P=0.003) promoter polymorphisms on abdominal aorta fatty streak area: the -219T- and +113C-allele carriers had larger lesion areas compared with G/G (12.7% versus 5.9%, P=0.007; 12.9% versus 6.3%, P=0.010, respectively) within nonsmokers. Within smokers, the associations were inverse. Moreover, smoking increased the fatty streak area within -219G/G or +113G/G genotypes and -219G/+113G/epsilon3 haplotype carriers. Functional studies in reporter assay showed that in comparison with the +113G allele, the +113C allele had higher transcriptional activity and bound transcription factors from liver cell nuclear extract with significantly lower affinity.

CONCLUSIONS

In middle-aged Finnish men with APOE epsilon3/epsilon3 genotype, the APOE promoter polymorphisms -219G/T and +113G/C interact with smoking in modulating aortic atherosclerosis. The +113G/C polymorphism has an effect on transcriptional activity.

Apolipoprotein E promoter polymorphisms (-491A/T and -427T/C) and Alzheimer's disease: no evidence of association in the Irish population

BACKGROUND

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder with as yet poorly understood aetiology. Both environmental and genetic factors have been implicated as predisposing factors. The APOE e4 allele is an established genetic susceptibility factor for AD for several populations including the Irish. Polymorphisms (-491A/T and -427T/C) at the promoter region of the APOE gene are postulated to affect the expression of the gene through differential binding of transcription factors.

AIMS

Two APOE promoter polymorphisms (-491A/T and -427T/C) are examined for possible association with AD.

METHODS

Using a case-control study design, a sample of 112 Irish late onset Alzheimer's (LOAD) patients and 107 ethnically matched controls were investigated for association with the above polymorphisms.

CONCLUSIONS

No evidence of association between any of the examined markers and AD was observed. Haplotype analysis using markers -491A/T and -427T/C in conjunction with the APOE (Hha I) polymorphism revealed significant associations of three haplotypes with AD. However, this association was mainly due to the highly significant association of the APOE e4 allele with AD and not of the promoter variants.

Influencia de los factores genéticos y ambientales en el metabolismo lipídico y riesgo cardiovascular asociado al gen apoE

The apolipoprotein E (ApoE) plays an important role in lipid metabolism. This apoprotein presents three major isoforms (apoE2, apoE3 and apoE4) that modulate lipid levels. Carriers of the apoE4 allele have higher total and LDL-cholesterol plasma concentration and a greater coronary risk, particularly for myocardial infarction. Nevertheless, not all the people with this allele develop the disease, which suggests that other genetic or environmental factors are necessary for its total expression. In this review, we will analyze the importance of several polymorphisms in the apoE gene promoter region, as well as various environmental factors, including diet, in the association of this gene with lipid metabolism and cardiovascular risk.

Lipid homeostasis and apolipoprotein E in the development and progression of Alzheimer's disease

Extracellular amyloid plaques, intracellular neurofibrillary tangles, and loss of basal forebrain cholinergic neurons in the brains of Alzheimer's disease (AD) patients may be the end result of abnormalities in lipid metabolism and peroxidation that may be caused, or exacerbated, by beta-amyloid peptide (Abeta). Apolipoprotein E (apoE) is a major apolipoprotein in the brain, mediating the transport and clearance of lipids and Abeta. ApoE-dependent dendritic and synaptic regeneration may be less efficient with apoE4, and this may result in, or unmask, age-related neurodegenerative changes. The increased risk of AD associated with apoE4 may be modulated by diet, vascular risk factors, and genetic polymorphisms that affect the function of other transporter proteins and enzymes involved in brain lipid homeostasis. Diet and apoE lipoproteins influence membrane lipid raft composition and the properties of enzymes, transporter proteins, and receptors mediating Abeta production and degradation, tau phosphorylation, glutamate and glucose uptake, and neuronal signal transduction. The level and isoform of apoE may influence whether Abeta is likely to be metabolized or deposited. This review examines the current evidence for diet, lipid homeostasis, and apoE in the pathogenesis of AD. Effects on the cholinergic system and response to cholinesterase inhibitors by APOE allele carrier status are discussed briefly.

Comprehensive association analysis of APOE regulatory region polymorphisms in Alzheimer disease

Several recent case-control studies have examined the association between single nucleotide polymorphisms (SNPs) in the promoter region of the apolipoprotein E gene (APOE) and risk of Alzheimer disease (AD), with conflicting results. We assessed the relation between five APOE region SNPs and risk of AD in both case-control and family-based analyses. We observed a statistically significant association with the +5361T allele in the overall case-control analysis (P value=0.04) after adjusting for the known effect of the APOE-4 allele. Further analysis revealed this association to be limited to carriers of the APOE-4 allele. Age-stratified analyses in the patients with age at onset of 80 years or greater and age-matched controls showed that the -219T allele (P value=0.009) and the +113C allele (P value=0.03) are associated with increased risk of AD. Despite these findings, haplotype and family-based association analyses were unable to provide evidence that the APOE region SNPs influenced risk of AD independent of the APOE-4 allele. In addition to risk, we tested for association between the SNPs and age at onset of AD, but found no association in the case-control or family based analyses. In conclusion, SNPs +5361, or a SNP in strong linkage disequilibrium, may confer some additional risk for developing AD beyond the risk due to APOE-4; however, the effect independent of APOE-4 is likely to be small.

Education modifies the effect of alcohol on memory impairment: the third national health and nutrition examination survey

We examined whether the relation of alcohol consumption to prevalence of verbal memory impairment was modified by education among 4,804 elderly subjects in the Third National Health and Nutrition Examination Survey. Verbal memory was assessed using delayed recall, with impairment defined as a combined score <4. Alcohol consumption over the previous month prior to the interview was assessed using a food frequency questionnaire. Prevalence of verbal memory impairment decreased from 11.3 to 7.2, 5.7, 5.1 and 4.4% in increasing categories of alcohol consumption (none, 1-4, 5-14, 15-30 and >30 drinks per month) in men, and from 7.2 to 3.5 and 2.8% (for none, 1-14, and >14 per month) in women, respectively. Adjusting for age, race, and other factors, prevalence ratios of verbal memory impairment decreased with each increasing alcohol category, but the effect was attenuated when further adjusted for education. There was a much stronger protection from alcohol among subjects with more education: prevalence ratios were reduced from 1.0 to 0.2 to 0.1 for non-drinkers, 1-14, and >14 drinks/month, respectively (p for trend = 0.007). Our results suggest that alcohol intake is associated with a greater decrease in the prevalence of verbal memory impairment among more educated subjects than among those with less education, possibly related to differences in drinking patterns.

The allelic modulation of apolipoprotein E expression by oestrogen: potential relevance for Alzheimer's disease

BACKGROUND

The epsilon4 allele of the apolipoprotein E (APOE) gene is a major genetic risk factor for Alzheimer's disease but appears to be associated with greater risk in women than in men. Some studies suggest that the level of APOE may of its own modulate the risk for Alzheimer's disease. Sex differences and an apparent benefit of oestrogen therapy suggest a role for oestrogen. APOE expression is influenced by oestrogen and oestrogen therapy may not benefit women bearing an APOE epsilon4 allele. These findings suggest an interaction between oestrogen and APOE in the Alzheimer's disease process.

AIM

To explore the hypothesis that APOE expression is regulated by a genomic mechanism and is modified by the polymorphisms in APOE associated with risk for Alzheimer's disease.

METHODS

In vitro binding studies were undertaken between oestrogen receptors and fragments of the human APOE gene. APOE gene expression was studied to investigate a possible functional interaction.

RESULTS

APOE epsilon2/epsilon3/epsilon4 coding and -219 G/T promoter polymorphisms influenced binding to the oestrogen receptor and altered transcriptional activity in response to oestrogen.

CONCLUSIONS

An allele dependent modulation of oestrogen induced regulation of APOE might be involved in the increased risk for Alzheimer's disease in women bearing an epsilon4 allele.

Genetic variation of the APOE promoter and outcome after head injury

The APOE-epsilon4 allele is associated with risk for Alzheimer's disease (AD) and poorer outcome after head injury. Several studies show that polymorphisms in the promoter that influence APOE expression also increase risk for AD. The authors' data from a study of 92 patients are consistent with a possible influence of the G-219T promoter polymorphism on outcome after head injury. The group with unfavorable outcome had a genotype frequency distribution similar to that found in AD.

Biogerontology research in Spain

The article describes the features of biogerontology research in Spain and outlines the research in the biology of ageing, covering a wide spectrum of areas and topics. Research in biogerontology has expanded notably in quality and quantity in the last decades with the development of internationally recognized research groups actively working in the analysis of the complex process of ageing. In the last few years research in ageing has become a priority area in the National Program of Research which has substantially increased funds specifically allocated to biogerontology and biological research on senescence. Despite these improvements, special efforts have to be made not only to consolidate the existing groups but also to facilitate the initiation and development of new research groups in Universities, Hospitals and research institutions with capacity to incorporate trained researchers in this area. It would promote the continuous incorporation of technical and scientific advances in other disciplines to the understanding the biology of ageing and the molecular basis of cellular senescence, that will benefit actual and future ageing population.

Specific interaction of heterogeneous nuclear ribonucleoprotein A1 with the -219T allelic form modulates APOE promoter activity

The polymorphic -219T/G variant in the APOE promoter has been associated with variations in basal transcriptional activity as well as with the risk of developing Alzheimer's disease, myocardial infarction and early-onset coronary heart disease. The molecular mechanisms underlying these effects are presently unknown. In this report, we show that nuclear extracts from Jurkat cells form a T-specific complex with a motif including the -219 site within the APOE promoter. By DNA-affinity chromatography and mass spectrometry, the human heterogeneous nuclear ribonucleoprotein hnRNPA1(A1) was identified as one component of the complex. In vitro binding analysis indicated that a fragment of A1 had a marked binding specificity for the T form. Interaction of A1 with this region is driven by an adjacent telomeric-like sequence; however, the presence of G, but not T, at -219 position inhibited this interaction. The differences in transcriptional activity between the -219T and -219G promoter allelic forms correlated with the expression levels of A1 in several cell lines; also, over-expression of A1 increased the activity of the T form relative to that of the G form. These results indicate that A1 transactivates APOE promoter activity by direct and specific interaction with the -219T site.

Expanding the association between the APOE gene and the risk of Alzheimer's disease: possible roles for APOE promoter polymorphisms and alterations in APOE transcription

Alzheimer's disease (AD) is the most commonly diagnosed form of dementia in the elderly. Predominantly this disease is sporadic in nature with only a small percentage of patients exhibiting a familial trait. Early-onset AD may be explained by single gene defects; however, most AD cases are late onset (> 65 years) and, although there is no known definite cause for this form of the disease, there are several known risk factors. Of these, the epsilon4 allele of the apolipoprotein E (apoE) gene (APOE) is a major risk factor. The epsilon4 allele of APOE is one of three (epsilon2 epsilon3 and epsilon4) common alleles generated by cysteine/arginine substitutions at two polymorphic sites. The possession of the epsilon 4 allele is recognized as the most common identifiable genetic risk factor for late-onset AD across most populations. Unlike the pathogenic mutations in the amyloid precursor or those in the presenilins, APOE epsilon4 alleles increase the risk for AD but do not guarantee disease, even when present in homozygosity. In addition to the cysteine/arginine polymorphisms at the epsilon2/epsilon3/epsilon4 locus, polymorphisms within the proximal promoter of the APOE gene may lead to increased apoE levels by altering transcription of the APOE gene. Here we review the genetic and biochemical evidence supporting the hypothesis that regulation of apoE protein levels may contribute to the risk of AD, distinct from the well known polymorphisms at the epsilon2/epsilon3/epsilon4 locus.

Genotype-related differences of hippocampal apolipoprotein E levels only in early stages of neuropathological changes in Alzheimer's disease

Inheritance of the epsilon4 allele of apolipoprotein E (APOE, gene; apoE, protein) represents the most common genetic risk factor for developing Alzheimer's disease (AD), but the role of apoE in AD pathogenesis is yet to be clarified. A number of studies investigating apoE expression and protein levels in AD brain in correlation to its genetic polymorphism has yielded controversial results. We designed our approach based on neuropathological characteristics of AD to investigate apoE levels in relation to the APOE genotype and AD-related neurofibrillary changes, and amyloid deposits. We determined hippocampal apoE levels by reducing sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting in 70 Braak-staged and APOE-genotyped autopsy brains. In our stage-, age- and gender-matched case sample, we found a significant increase of hippocampal apoE in the APOE epsilon3 homozygotes with beginning AD-related pathology (Braak stages I and II) compared with brain samples free of neurofibrillary changes and amyloid deposits. In the APOE epsilon4 allele carriers no such increase was found. In both genotype groups, severely affected brain samples with widespread neurofibrillary changes (Braak stages V and VI) and amyloid deposits (Braak stage C) showed low apoE levels comparable to those found in unaffected brain samples (Braak stage 0). Our data suggests that the isoform-specific impact of apoE on the development of AD may be of crucial importance only in the early stages of the disease. These stages are believed to represent phases of the disease in which the beginning neurodegeneration can be compensated by plastic reorganization.

Genomic studies of the spleen protein tyrosine kinase locus reveal a complex promoter structure and several genetic variants

Here we show that the gene of the cytoplasmic tyrosine kinase SYK spans a region of 90kb with 13 coding exons, an alternative exon 14 and at least two 5' untranslated regions exons 1a and 1b. 5' RACE (Rapid amplification of cDNA ends) of human Syk cDNAs demonstrated a complex promoter usage and splicing pattern. We identified three common single nucleotide polymorphisms in the exon la promoter region of the Syk gene as well as a variant Syk cDNA haplotype. This haplotype was characterized by a constellation of 5 silent mutations in the Syk cDNA: 1065(C-T), 1302(G-C), 1338(G-A), 1521(C-T) and 1545(T-C). A hypervariable CATATA(n) repeat polymorphism was also localized to the intron between exons 11 and 12. These novel insights into the genomic organization, promoter structure and genetic variability of Syk will serve as a foundation for detailed molecular epidemiological investigation of its potential role in human cancer biology.

ApoE epsilon3-haplotype modulates Alzheimer beta-amyloid deposition in the brain

ApoE epsilon4 allele increases the risk of late-onset Alzheimer disease (AD) as well as the amount of beta-amyloid deposition in the brain. Because half of AD patients do not have ApoE epsilon4, it is important to search for other determinants of ApoE that modify AD risk. We tested whether the haplotype background of the most common ApoE allele, epsilon3, influences brain amyloid deposition or the risk of neuropathologically verified AD in a population-based sample of elderly Finns. To exclude the effects of ApoE protein polymorphism we focused these analyses on subjects homozygous for epsilon3. Haplotypes were defined using polymorphisms at positions - 491 and -219 of the ApoE promoter and at position +113 of intron-1. We found that epsilon3-haplotypes containing the promoter allele -219T were associated with reduced amyloid deposition and reduced risk of neuropathologically verified AD as compared to epsilon3-haplotypes containing -219G. The functional polymorphism(s) responsible for the haplotypic difference remains to be identified. These results indicate that there is significant allelic variation in the ApoE gene region, which modulates brain amyloid deposition and AD risk, independent of the ApoE protein polymorphism.

Regional and hormone-dependent effects of apolipoprotein E genotype on changes in bone mineral in perimenopausal women

We studied 479 perimenopausal Danish women aged 45-58 years to examine differences between APOE genotypes with respect to (1) baseline total body bone mineral density (BMD) and densities measured in five different regions (ultradistal forearm, proximal forearm, lumbar spine, femoral neck, and total hip region); (2) serum levels of alkaline phosphatase, bone isoenzyme alkaline phosphatase, osteocalcin, parathyroid hormone (PTH), 25-hydroxyvitamin D, and urine hydroxyproline/creatinine excretion ratio; and (3) changes in bone mineral during 5 years of follow-up. Baseline BMDs were identical, whereas serum levels of alkaline phosphatase and its bone isoenzyme were higher in women with APOE 2-2 and APOE 2-3 than in women with APOE 3-3 and APOE 3-4 and lower in women with APOE 4-4. Among women not receiving hormonal-replacement therapy (HRT; n = 262), those with APOE 2-2 and APOE 2-3 had 30-40% lower rates of femoral neck and total hip bone mineral loss than women with APOE 3-3 and APOE 3-4, whereas the rates of mineral loss in other skeletal regions did not differ between these APOE genotypes. Women with APOE 4-4 appeared to have lower rates of bone mineral loss in all regions. Women treated with hormones throughout the follow-up period (n = 113) gained bone mineral, and women with APOE 3-4 and APOE 4-4 gained relatively more mineral than other women. A comparison of untreated and treated women with APOE 2-3, APOE 3-3, and APOE 3-4 suggests a possible modification of the effect of APOE genotype by HRT. In conclusion, the common APOE polymorphism has a complex effect on bone metabolism in perimenopausal Danish women including possible modification by hormone use: (1) among women not receiving HRT, those with APOE*2 have lower bone mineral losses in the femoral neck and hip region than other women, and (2) among women receiving HRT, those with APOE*4 gain more bone mineral than other women.

Alzheimer's risk associated with human apolipoprotein E, alpha-2 macroglobulin and lipoprotein receptor related protein polymorphisms: absence of genetic interactions, and modulation by gender

Apolipoprotein E (apoE), the lipoprotein receptor related protein (LRP) and alpha-2 macroglobulin (alpha2M) have been proposed as a functional complex involved in amyloid clearance, a crucial event for Alzheimer's disease development. In this work, we present an epidemiological approach aimed to study the interactions among these genes, age and gender. This approach did not reveal significant associations between the genes; however, the present study indicated that the risk associated with APOE promoter and LRP gene polymorphisms is modulated by gender.