Candidate gene analysis of semaphorins in patients with Alzheimer's disease.

Semaphorins of the SemaIV family are expressed in neurons and decreased in brains from patients with Alzheimer's disease (AD). Accumulation of an internalized form of Sema3A is associated with degeneration of neurons, making these molecules candidates for the development of AD. Single nucleotide polymorphisms (SNPs) rs36026860 and rs28469467 in Sema3A as well as rs13284404 and rs11526468 in Sema4D were analyzed in a population of 240 patients with AD compared with 222 age-matched controls. None of SNPs in Sema3A were present, either in patients or controls. The distribution of the Sema4D rs11526468 and rs13284404 SNPs was not significantly different between patients and controls, even stratifying for gender or age at onset. In silico analysis predicted that rs11526468 and rs28469467 are probably damaging. This high degree of conservation of Sema3A suggests a very important role for this protein. However, neither Sema3A nor Sema4D likely influence the susceptibility to AD.

MCP-1 A-2518G polymorphism: effect on susceptibility for frontotemporal lobar degeneration and on cerebrospinal fluid MCP-1 levels.

The distribution of the MCP-1 A-2518G single nucleotide polymorphisms (SNP) was analyzed in a population of 212 patients with frontotemporal lobar degeneration (FTLD) compared with 203 age-matched controls. A significantly decreased allelic frequency of the G allele in patients compared with controls was observed (21.1 versus 29.3%, P = 0.011, OR: 0.59, CI: 0.40-0.87). Stratifying according to gender, the association was maintained in male patients versus male controls (17.8 versus 29.4%, P = 0.016, OR = 0.46, 95% CI: 0.25-0.84), but not in female patients compared with female controls (23.5 versus 29.2%, P > 0.05). The frequency of apolipoprotein E epsilon4 carriers was increased in patients (26.4 versus 13.8%, P = 0.0015, OR: 2.24, 95% CI: 1.37-3.67). Apolipoprotein E status did not influence the distribution of the A-2518G SNP. Monocyte chemotactic protein (MCP)-1 levels were determined in cerebrospinal fluid (CSF) collected from 23 patients and 17 controls. MCP-1 CSF levels were increased in patients compared with controls (449.01 +/- 27.57 versus 364.19 +/- 23.75 pg/ml, P = 0.011). Stratifying patients according to the presence of the polymorphic allele, significantly increased CSF MCP-1 levels were observed in carriers of the G allele compared with non-carriers (502.21 +/- 44.57 versus 395.87 +/- 21.92 pg/ml, P = 0.045). The MCP-1 A-2518G SNP acts as protective factor for sporadic FTLD, possibly by influencing MCP-1 production.

Analysis of the genes coding for subunit 10 and 15 of cytochrome c oxidase in Alzheimer's disease.

Decay of mitochondria and oxidative stress are associated with normal aging, but many neurodegenerative diseases, and particularly Alzheimer's disease (AD), are characterized by a significant increase in the intensity of these traits. Recent data suggest the possible contribution of heme deficiency to the progressive derangement of mitochondria in AD brain; shortage of heme, and particularly of heme-a, actually leads to loss of mitochondrial cytochrome c oxidase (COX), abnormal production of reactive oxygen species and altered amyloid precursor protein metabolism. We reasoned that differences in the amount and/or functioning of COX assembly subunit 10 (COX10) and 15 (COX15), the key enzymes involved in heme-a biosynthesis, could be linked to variations of the individual risk to develop AD. We analyzed their mRNA expression in the hippocampus from AD patients and controls, investigated the existence of nucleotide variations in their DNA sequences and analyzed their distribution in large groups of AD and control individuals. COX 15 mRNA was significantly more abundant in the cerebral tissue of AD patients (3.18 +/- 1.70 vs. 1.22 +/- 0.66 microg, normalized dose, P = 0.01). The IVS-178G>A SNP in COX10 and the c+1120C>T SNP in COX15 were significantly less represented in the patient group (P < 0.001 and P = 0.017, respectively) with respective odd ratios of 0.22 and 0.59, suggesting a possible protective role toward the risk for AD.

Absence of TARDBP gene mutations in an italian series of patients with frontotemporal lobar degeneration.

BACKGROUND/AIM: Recent studies showed that TAR DNA-binding protein 43 (TDP-43), encoded by the TARDBP gene, is a major pathological protein in both sporadic and familial frontotemporal lobar degeneration (FTLD). The aim of this study was to search for mutations of the TARDBP gene in the disease. METHODS: We sequenced the TARDBP gene in 172 unrelated FTLD patients recruited from 2 Italian memory clinics. RESULTS: We identified 3 different variants of the TARDBP gene in 12 FTLD patients. Three patients showed a silent variant, Ala66Ala (c.332T --> C) in exon 2. A novel heterozygous mutation was found in intron 4 (c.543 + 51A --> G) in 1 patient, which is not located at the splicing site. Finally, a c.208C --> T variant in the 3' untranslated region was detected in 8 probands. None of the aforementioned variants were predicted to affect TDP-43. Hence, pathogenic mutations were not identified in any of the FTLD cases. CONCLUSION: Our study, in accord with previous studies in different populations, found no evidence for a major genetic role of the TARDBP gene in FTLD.

Intrathecal levels of IL-6, IL-11 and LIF in Alzheimer's disease and frontotemporal lobar degeneration.

Cerebrospinal fluid (CSF) levels of interleukin (IL)-6, IL-11 and leukaemia inhibitory factor (LIF) were evaluated in 43 patients with Alzheimer's disease (AD) and 24 patients with frontotemporal lobar degeneration (FTLD) as compared with 30 agematched controls (CON), and correlated with clinical and demographic data and with CSF biomarkers amyloid beta (A beta)42, total tau and tau phosphorylated at position 181 (P-tau). CSF IL-11 mean levels were significantly increased in AD and FTLD as compared with CON (6.5 +/- 4.6 and 6.6 +/- 5.1 versus 3.1 +/- 3.3 pg/ml, P = 0.009). IL-6 mean levels did not differ between patients and CON (P > 0.05),whereas LIF levels were not detectable in patients or in CON. In AD patients, a significantly positive correlation between MMSE scores and IL-11 CSF concentration was observed (r = 0.344, P = 0.028). No correlations with CSF A beta 42, total tau and P-tau were found. IL-11, but not IL-6 levels are increased in AD and FTLD, and the highest peaks were observed in patients with a less severe degree of cognitive deterioration, therefore suggesting a role of this cytokine in early phases of neurodegeneration.

Gender-specific influence of the chromosome 16 chemokine gene cluster on the susceptibility to Multiple Sclerosis.

Macrophage-derived chemokine (MDC/CCL22) plays a role in Experimental Autoimmune Encephalomyelitis (EAE), the animal model of Multiple Sclerosis (MS). MDC/CCL22 gene is part of a chemokine cluster, which includes also thymus and Activation-Regulated Chemokine (TARC/CCL17). The frequency of the C/T and C/A Single Nucleotide Polymorphisms (SNPs) in the promoter and coding sequence of CCL22 as well as the C/T SNP in the promoter of CCL17 were determined in 370 patients with Multiple Sclerosis (MS) compared with 380 controls. A trend towards a decreased allelic frequency of the A allele of the CCL22 C/A SNP as well as of the T allele of the CCL17 C/T SNP was found in patients compared with controls. The frequency of the AT haplotype was significantly decreased in MS patients (P=0.017, OR: 0.49, CI: 0.28-0.87). Stratifying patients according to gender, the observed association was even more pronounced in male patients compared with male controls (P=0.004, OR=0.18, 95% CI: 0.06-0.50), whereas no significant differences were observed in females. Therefore, the presence of the AT haplotype in chromosome 16 chemokine cluster is likely to confer a decreased risk of developing MS, particularly in males.

Polymorphisms in the LOC387715/ARMS2 putative gene and the risk for Alzheimer's disease.

BACKGROUND: Age-related macular degeneration (ARMD) and Alzheimer's disease (AD) are neurodegenerative disorders that share a high prevalence among elderly people, the extracellular deposition of beta-amyloid and the involvement of genetic factors in their aetiology. Genetic linkage with the chromosome regions 10q26 and 10q24-25 have been shown for ARMD and AD, respectively. The rs10490924 polymorphism, the major determinant of the 10q26 association with ARMD, determines the A69S substitution in the LOC387715/ARMS2 gene. Little information is available about the expression of the gene in humans. METHODS: We analysed the expression of the gene by RT-PCR in the brain and we looked for nucleotide variations in the gene sequence by DHPLC. RESULTS: We found specific gene transcripts in the hippocampus, cortex and cerebellum. The genetic analysis identified two other common variations, which determine the R3H change (rs10490923) and a premature stop codon (rs2736911), respectively. The analysis of their distribution in 213 AD patients and 149 controls revealed a trend for a reduced frequency of the variant allele of rs2736911 in AD patients (p = 0.038), with an odds ratio of 0.631. CONCLUSION: The LOC387715/ARMS2 gene is expressed in the human brain, and it may concur to the individual risk for AD.

Absence of TREM2 polymorphisms in patients with Alzheimer's disease and Frontotemporal Lobar Degeneration.

Triggering Receptor Expressed on Myeloid cells (TREM)2 deficiency originates a genetic syndrome characterized by bone cysts and presenile dementia, named Nasu-Hakola disease (NHD). Early onset dementia and marked involvement of frontal regions are features characterizing both NHD and other kinds of neurodegenerative disorders, such as Frontotemporal Lobar Degeneration (FTLD), and, in some cases, Alzheimer's disease (AD). Three Single Nucleotide Polymorphisms (SNPs) in TREM2 coding region were screened by allelic discrimination in a population of probable AD patients as well as FTLD patients as compared with age-matched controls. In addition, mutation scanning of the coding region of TREM2 gene was carried out in 7 patients with early onset AD (EOAD), 16 FTLD, and 20 controls. None of the SNPs analyzed was present, either in patients or controls. Moreover, mutation scanning of the five exons of TREM2 failed to detect the presence of novel polymorphisms. These data demonstrate that TREM2 coding region is highly conserved, implying a crucial role of this receptor. Further studies, including a functional analysis, are certainly required to clarify the role of TREM2 in neurodegenerative processes.

Candidate gene analysis of SPARCL1 gene in patients with multiple sclerosis.

Recently, proteomic analysis in cerebrospinal fluid (CSF) from patients with MS identified four proteins which are present in MS but not in normal human CSF, including SPARCL1, an extracellular matrix-associated protein member of the SPARC family. One hundred eighty-six patients with MS and 185 age-matched controls were genotyped for A/G single nucleotide polymorphism (SNP) in exon 1 (rs1049539), C/G SNP in exon 4 (rs1049544), resulting in a substitution of an aspartate with an histidine, and A/G substitution in the exon 5 (rs1130643), leading to the substitution of alanine with threonine. No significant differences in either allelic or genotypic frequency of the three SNPs were found (P>0.05), even in stratifying MS patients according to the course of the disease. Stratifying according to gender, a trend towards a decreased frequency of the C/C genotype of the rs1049544 was observed in male patients as compared with male controls (30.2% versus 44.0%; P=0.217). Despite proteomic studies in CSF from MS patients suggested an important role for SPARCL1 in the development of the disease, SPARCL1 gene does not appear to act as susceptibility factor for MS in the population investigated here. However, the frequency of the C/C genotype of rs1049544 was decreased in male patients, possibly conferring a lower risk of developing MS in male population. Further studies are needed to clarify this issue.

Oxidative imbalance in patients with mild cognitive impairment and Alzheimer's disease.

Increasing evidence supports a role of oxidative imbalance, characterized by impaired antioxidant enzymatic activity and increased reactive oxygen species (ROS) production, in mild cognitive impairment (MCI) and Alzheimer's disease (AD) pathogenesis. Hyperhomocysteinemia, another risk factor for AD, also contributes to oxidative damage. Plasma total homocysteine (tHcy) and ROS levels, and total antioxidant capacity (TAC) were determined in 71 AD, 36 MCI and 28 vascular dementia (VaD) patients as well as in 44 age-matched controls. tHcy levels were significantly increased in patients with AD and VaD an a trend towards an increase in multiple domain MCI was observed. TAC was significantly decreased in AD as well as MCI, but not in VaD patients. In AD patients, a negative correlation was found between TAC and disease duration. ROS levels did not differ among groups, but were correlated with age. In conclusion, a pattern characterized by increased tHcy levels and decreased TAC is present in AD as well as MCI patients. While increased tHcy levels were also found in VaD, TAC modifications occur specifically in AD. ROS levels appear to be correlated with age rather than with a specific dementing disorder, thus leading to the hypothesis that oxidative imbalance observed in AD could be due to a decreased TAC.

Intrathecal chemokine synthesis in mild cognitive impairment and Alzheimer disease.

BACKGROUND: Immunoreactivity for several chemokines and for their related receptors has been demonstrated in resident cells of the central nervous system, and the up-regulation of some of them is associated with pathological changes found in Alzheimer disease (AD). OBJECTIVE: To determine interferon-gamma-inducible protein 10 (IP-10), monocyte chemotactic protein 1 (MCP-1), and interleukin 8 (IL-8) levels in cerebrospinal fluid (CSF) from subjects with amnestic mild cognitive impairment (MCI) and patients with AD as compared with age-matched controls. PATIENTS: Thirty-eight subjects with amnestic MCI, 36 patients with AD, and 41 age-matched subjects with noninflammatory affections of the nervous system. DESIGN: Evaluation of CSF chemokine production at time of diagnosis of MCI and AD; correlation with clinical and personal data. Longitudinal evaluation of subjects with MCI until conversion to AD. RESULTS: Cerebrospinal fluid IP-10 concentration was significantly increased in patients with MCI and mild AD but not in patients with severe AD (Mini-Mental State Examination score <15), whereas MCP-1 and IL-8 levels were increased in patients with MCI and all patients with AD. A significant positive correlation between Mini-Mental State Examination score and CSF IP-10 or MCP-1 concentration was observed in patients with AD. No correlation between IP-10 levels and age was found, whereas MCP-1 and IL-8 levels correlated positively with age. Out of 38 subjects with MCI, 19 developed AD within a 1- to 3-year follow-up. CONCLUSIONS: The presence of inflammatory molecules is likely to be a very early event in AD pathogenesis, even preceding the clinical onset of the disease, as demonstrated by subjects with MCI who developed AD over time. Interferon-gamma-inducible protein 10 is specifically increased in MCI and seems to decrease with the progression of AD, whereas MCP-1 and IL-8 are up-regulated also in late stages of the disease, suggesting a role in phases in which neurodegeneration is prevalent.

Candidate gene analysis of IP-10 gene in patients with Alzheimer's disease.

Interferon-gamma-inducible Protein-10 (IP-10) is supposed to play a role in Alzheimer's disease (AD) development, as demonstrated by increased levels in cerebrospinal fluid from patients with AD. A mutation scanning of IP-10 exonic region was carried out in 10 patients with AD and 10 age-matched controls, demonstrating the presence of two previously reported single nucleotide polymorphisms (SNPs) in exon 4 (G-->C and T-->C) as well as a novel SNP in exon 2 (C-->T). Exon 4 G-->C and T-->C allelic variants were next evaluated in a population of 279 AD patients and 251 controls, in order to determine whether their presence could influence the susceptibility towards the development of the disease. These two SNPs were in complete linkage disequilibrium. No differences in haplotype frequencies were found in AD patients as compared with controls, even stratifying according to the presence of Apolipoprotein E varepsilon4 allele, gender or age at onset. A new protocol was developed to easily determine the C-->T SNP in exon 2. A preliminary analysis revealed a very low frequency of this allelic variant (1%). Therefore, the complete association study was not carried out because the size of our population was not sufficient to draw reliable conclusions. According to these results, IP-10 does not seem to be a risk factor for AD. However, a novel rare polymorphism has been identified, which could exert a role in AD susceptibility. Thus, further studies on larger populations are needed before confidently excluding IP-10 as a susceptibility gene for AD.

SELPLG and SELP single-nucleotide polymorphisms in multiple sclerosis.

P-Selectin (SELP) and P-selectin glycoprotein ligand-1 (SELPLG) constitute a receptor/ligand complex involved in the recruitment of activated lymphocytes, a critical event in the pathogenesis of multiple sclerosis (MS). In order to determine whether genetic variation in these pivotal molecules influences susceptibility to MS, we genotyped 214 Italian patients compared with 220 Italian controls for three single-nucleotide polymorphisms (SNPs): SELPLG Met62Ile, SELP C-2123G and SELP Thr715Pro. No significant differences in both SELP SNPs were found between patients and controls, whereas a decreased frequency of the Met62Ile SNP was found in patients versus controls in the Italian population (P = 0.025). To confirm these preliminary findings, the Met62Ile SNP was analysed in 938 UK trio families. This SNP did not show evidence for association with susceptibility to MS in the larger UK cohort. Therefore, none of the SNPs investigated is associated with MS, although this analysis does not conclusively exclude SELPLG and SELP as genetic risk factors for MS as much variation remains untested.

A novel polymorphism in SEL1L confers susceptibility to Alzheimer's disease.

Alzheimer's disease (AD) is considered to be a conformational disease arising from the accumulation of misfolded and unfolded proteins in the endoplasmic reticulum (ER). SEL1L is a component of the ER stress degradation system, which serves to remove unfolded proteins by retrograde degradation using the ubiquitin-proteosome system. In order to identify genetic variations possibly involved in the disease, we analysed the entire SEL1L gene sequence in Italian sporadic AD patients. Here we report on the identification of a new polymorphism within the SEL1L intron 3 (IVS3-88 A>G), which contains potential binding sites for transcription factors involved in ER-induced stress. Our statistical analysis shows a possible role of the novel polymorphism as independent susceptibility factor of Alzheimer's dementia.

Influence of the Glu298Asp polymorphism of NOS3 on age at onset and homocysteine levels in AD patients.

The distribution of the Glu298Asp polymorphism in NOS3 gene was determined in 405 Italian patients with "probable" Alzheimer's disease (AD) compared with 253 age-matched controls. Total plasma homocysteine (tHcy) levels were evaluated in 97 patients and 23 controls, and were correlated with the Glu298Asp genotype. A significantly increased frequency of the Glu/Glu genotype in late onset AD (LOAD) patients was found. tHcy levels were significantly increased in patients compared with controls and, notably, higher in LOAD than in early onset AD (EOAD). Stratifying by the Glu298Asp genotype, a trend toward an increase of tHcy was present in Glu/Glu homozygous. This wild type genotype seems to be associated with LOAD. tHcy levels are significantly increased in AD compared with controls and, moreover, higher in LOAD than in EOAD, possibly in correlation with the microvascular disease occurring with aging. Besides, a contribution of the Glu/Glu genotype in increasing tHcy levels has been observed.

E-selectin A561C and G98T polymorphisms influence susceptibility and course of multiple sclerosis.

Three hundred seven patients with MS and 300 controls were genotyped for G98T and A561C SNPs in the E-selectin gene, and genetic data were correlated with the course of the disease. The frequency of the T/T genotype of the G98T SNP was significantly increased in RR-MS patients compared with controls, while was absent in PP-MS. The frequency of the A561C SNP was significantly decreased in SP-MS compared with benign RR-MS. The T/T genotype of the G98T SNP is likely to confer an increased risk to develop MS. The A561C polymorphism seems to act as protective factor towards the progression to SP-MS.

The T-786C NOS3 polymorphism in Alzheimer's disease: association and influence on gene expression.

A common single nucleotide polymorphism (SNP), consisting in a T-->C transition (T-786C) in endothelial nitric oxide synthase (NOS3), has been reported to be associated with vascular pathologies, but no information are available on a possible association with AD. T-786C genotype was determined by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) assay in an Italian population of 432 AD patients compared with 360 healthy controls, matched for ethnic background, age and gender. Peripheral blood mononuclear cells (PBMC) from 22 subjects (11 AD and 11 controls) carrying different genotypes were isolated. Total RNA was extracted and analyzed by real-time PCR. No significant differences either in allelic or genotypic frequencies of the T-786C polymorphism between AD and normal population were observed, even stratifying AD patients by age at onset, gender, or ApoE status. However, expression of NOS3 in PBMC seems to be influenced by the presence of the C mutated allele, as demonstrated by a tendency towards a decrease in mRNA levels in C carriers, assessed by real-time PCR assay. This effect was observed both in patients and controls, independently from the cognitive impairment, and is likely to be dose-dependent, being mostly evident in CC homozygous. In conclusion, the T-786C SNP does not seem to be a risk factor for sporadic AD, but its presence correlates with a trend toward lower NOS3 expression rate, possibly exerting a beneficial effect in AD by contributing to lower oxidative damage.

P-selectin glycoprotein ligand-1 variable number of tandem repeats (VNTR) polymorphism in patients with multiple sclerosis.

P-selectin glycoprotein ligand-1 (PSGL-1) is an important adhesion molecule involved in lymphocyte recruitment into the brain, which represents a crucial step in the pathogenesis of multiple sclerosis (MS). Three hundred twenty-one MS patients and 342 controls were genotyped for the presence of a polymorphism in the PSGL-1 gene, consisting of a variable number of tandem repeats (VNTR) originating three possible alleles: A, B and C, in order to test whether they influence the susceptibility and the course of the disease. No significant differences among allelic frequencies of A, B and C alleles in MS as compared with controls were observed. Stratifying patients according to the course of the disease, a significantly increased frequency of the shortest C allele in PP-MS was found (7.1%), either in comparison with controls (P=0.011) or with all other MS patients, who had acute inflammatory attacks at onset and an initial RR form (P=0.036). Besides, none of SP-MS patients was a carrier of the C allele and B carriers converted later from RR to SP course as compared with A/A subjects (after 15.8 rather than 8.8 years, P=0.01). In conclusion, the C allele of the VNTR polymorphism in PSGL-1 is likely to be associated with PP-MS. As this allele has been demonstrated to have a very low efficiency in mediating lymphocyte binding to brain endothelium during attacks, its high frequency in PP-MS could be related to the absence of exacerbations in such patients.

CCR2-64I polymorphism and CCR5Delta32 deletion in patients with Alzheimer's disease.

Monocyte chemoattractant protein-1 (MCP-1) and RANTES, as well as their related receptors, have been shown to be involved in Alzheimer's disease (AD) pathogenesis. Genes for their related receptors, CCR2 and CCR5, respectively, are characterized by the presence of two polymorphisms: a conservative change of a valine with an isoleucine at codon 64 of CCR2 (CCR2-64I) and a 32-bp deletion in the coding region of CCR5 (CCR5Delta32), which leads to the expression of a nonfunctional receptor. The distribution of the CCR2-64I and CCR5Delta32 polymorphisms was determined in 290 AD patients and in 222 controls. A decreased frequency and an absence of homozygous for the polymorphism CCR2-64I were found, thus suggesting a protective effect of the mutated allele on the occurrence of AD. However, these findings must be cautiously interpreted as the overall significance was found without adjustment for multiple comparisons and is coming from the complete absence of the genotype 64I/64I in AD patients. Conversely, no different distribution of the CCR5Delta32 deletion in the two populations was shown. Stratifying by the presence of ApoE varepsilon4 allele, gender or age at onset, no differences in either allele frequencies were observed.

BAG1 is a protective factor for sporadic frontotemporal lobar degeneration but not for Alzheimer's disease.

BCL2-associated athanogene 1 (BAG1) is an anti-apoptotic factor that interacts with tau and regulates its proteasomal degradation. A significant increase of the BAG-1M isoform was found in Alzheimer's disease (AD) brains, and the protein co-localized with tau and amyloid. We carried out an association study of BAG1 in a population of 291 patients clinically diagnosed with frontotemporal lobar degeneration (FTLD), none of whom was a carrier of mutations in progranulin or microtubule associated protein tau genes and 374 with AD as compared with 314 age- and gender-matched controls. In addition, another candidate named Chromatin-modifying protein 5 (CHMP5) and located in the same linkage disequilibrium block, has been included in this study. The distribution of the two single nucleotide polymorphism (SNPs), rs844239 in CHMP5 and rs706118 in BAG1, covering 100% gene variability, were determined. A statistically significant decreased allelic frequency of the BAG-1 rs706118 SNP was observed in patients with FTLD as compared with controls (16.7 versus 23.9%; p = 0.007, OR: 0.35, CI: 0.25-0.50), whereas allelic frequency of the SNP in patients with AD was similar to controls (24.3%, p > 0.05). Conversely, no significant association was found as regards CHMP5 rs844239. Stratifying according to gender, no differences were observed. BAG-1 rs706118 SNP likely acts as protective factor for sporadic FTLD, but not for AD, suggesting its specific role in a pathogenic event in FTLD. Nevertheless, a replication study would be needed to confirm these preliminary results.