[show abstract][hide abstract] ABSTRACT: Using the ImmunoChip custom genotyping array, we analyzed 14,498 subjects with multiple sclerosis and 24,091 healthy controls for 161,311 autosomal variants and identified 135 potentially associated regions (P < 1.0 × 10(-4)). In a replication phase, we combined these data with previous genome-wide association study (GWAS) data from an independent 14,802 subjects with multiple sclerosis and 26,703 healthy controls. In these 80,094 individuals of European ancestry, we identified 48 new susceptibility variants (P < 5.0 × 10(-8)), 3 of which we found after conditioning on previously identified variants. Thus, there are now 110 established multiple sclerosis risk variants at 103 discrete loci outside of the major histocompatibility complex. With high-resolution Bayesian fine mapping, we identified five regions where one variant accounted for more than 50% of the posterior probability of association. This study enhances the catalog of multiple sclerosis risk variants and illustrates the value of fine mapping in the resolution of GWAS signals.
[show abstract][hide abstract] ABSTRACT: Signals that promote myelination must be tightly modulated to adjust myelin thickness to the axonal diameter. In the peripheral nervous system, axonal neuregulin 1 type III promotes myelination by activating erbB2/B3 receptors and the PI3K/AKT/mTOR pathway in Schwann cells. Conversely, PTEN (phosphatase and tensin homolog on chromosome 10) dephosphorylates PtdIns(3,4,5)P3 and negatively regulates the AKT pathway and myelination. Recently, the DLG1/SAP97 scaffolding protein was described to interact with PTEN to enhance PIP3 dephosphorylation. Here we now report that nerves from mice with conditional inactivation of Dlg1 in Schwann cells display only a transient increase in myelin thickness during development, suggesting that DLG1 is a transient negative regulator of myelination. Instead, we identified DDIT4/RTP801/REDD1 as a sustained negative modulator of myelination. We show that DDIT4 is expressed in Schwann cells and its maximum expression level precedes the peak of AKT activation and of DLG1 activity in peripheral nerves. Moreover, loss of DDIT4 expression both in vitro and in vivo in Ddit4-null mice provokes sustained hypermyelination and enhanced mTORC1 activation, thus suggesting that this molecule is a novel negative regulator of PNS myelination.
Journal of Neuroscience 09/2013; 33(38):15295-15305. · 6.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: We conducted a genome-wide association study in a cohort of 176 Italian Alzheimer's disease (AD) patients with extreme phenotype of response to cholinesterase inhibitors. Patients were classified into responders in case of positive, stable, or ≤1 worsening of mini-mental state examination score and into nonresponders if >3 points worsening during a median follow-up of 0.85 years of treatment. Forty-eight single-nucleotide polymorphisms were selected for replication in 198 additional AD-treated patients. By using the dichotomous response trait and a quantitative trait approach (change of mini-mental state examination), a nominal replication and evidence of association when combining data were achieved for 2 single-nucleotide polymorphisms associated with response to treatment: rs6720975(A) (p(combined) = 2.9 × 10(-5), beta regression coefficient: 1.61) and rs17798800(A) (p(combined) = 6.8 × 10(-6), odds ratio = 0.38, 95% confidence interval = 0.25-0.58). Rs6720975 maps in the intronic region of PRKCE, a protein kinase involved in several cellular functions, whereas rs17798800 is intergenic and, according to expression quantitative trait locus (eQTL) analysis, it acts as a cis-regulator of NBEA, an A kinase-anchoring protein playing a substantial role in the maturation of the nervous system. Despite its limitations, this project paves the way for the application of personalized medicine in AD patients and for collaborative efforts in this field.
Neurobiology of aging 01/2013; · 5.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: One of the current challenge in Alzheimer's disease (AD) is the identification of reliable biomarkers that might improve diagnostic accuracy, possibly correlating with the disease progression and patient's response to therapy. As the clinically validated AD biomarkers evaluate cerebrospinal fluid (CSF) parameters, the need for less invasive diagnostic markers is well evident. To this respect, blood circulating cytokines or growth factors have provided some encouraging results, even though no clinically validated to date. In 2007 Ray et al suggested a panel of 18 circulating molecules that might increase AD diagnostic accuracy. In an attempt of replicating their data, we designed a multiplex fluorimetric assay comprising 16 independent analytes and covering 15 out of the 18 described proteins. We collected serum samples from three diagnostic groups: probable AD (n=33), matched healthy controls (CNT, n=23) and non AD demented (NAD, n=14). After correction for age, we found an increased level of EGF-1 in AD in comparison to CNT and NAD, while an increase of TRAIL-R4 was found in NAD. However, evaluation of specificity/sensitivity by ROC curve analysis gave weak evidence of diagnostic accuracy (area under the curve = 0.63 and 0.66 for EGF and TRAIL-R4, respectively). Finally, we tried to find a diagnostic classifier by a multivariate algorithm. We found indication of diagnostic evidence for AD only, while NAD samples did not show a diagnostic pattern.
American journal of neurodegenerative disease. 01/2013; 2(1):40-5.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: In this study, we investigated the role of the dipeptidyl-peptidase-6 (DPP6) gene in the etiopathogenesis of progressive forms of multiple sclerosis (PrMS). This gene emerged as a candidate gene in a genome-wide association study (GWAS) performed in an Italian sample of PrMS and controls in which two SNPs located in the gene (rs6956703 and rs11767658) showed evidence of association (nominal p-value<10(-4)) (Martinelli-Boneschi et al.) . Moreover, the gene is highly expressed in the central nervous system, and it has been found to be associated with sporadic cases of amyotrophic lateral sclerosis which shares some feature with PrMS. METHODS: We genotyped 19 SNPs selected using a direct and tagging approach in 244 Italian PrMS and 225 controls, and we measured the expression levels of the gene in 13 PrMS cases and 25 controls. RESULTS: Five out of 19 SNPs were found to be associated with the disease (adjusted p<0.05), and they have been tested in an independent sample of 179 primary progressive MS and 198 controls from Northern Europe. None of the SNPs was replicated, but combined analysis confirmed the presence of association for rs2046748 (p=2.5×10(-3),OR=1.82, 95%CI=1.24-2.69). CONCLUSIONS: These results, inflated by the limited sample size determined by the rarity of this condition, suggest a possible role of this gene in the susceptibility to PrMS, at least in Southern Europeans. Moreover, DPP6 was over-expressed in PrMS patients compared to controls.
[show abstract][hide abstract] ABSTRACT: The epigenetic silencing of exogenous transcriptional units integrated into the genome represents a critical problem both
for long-term gene therapy efficacy and for the eradication of latent viral infections. We report here that limitation of
essential amino acids, such as methionine and cysteine, causes selective up-regulation of exogenous transgene expression in
mammalian cells. Prolonged amino acid deprivation led to significant and reversible increase in the expression levels of stably
integrated transgenes transcribed by means of viral or human promoters in HeLa cells. This phenomenon was mediated by epigenetic
chromatin modifications, because histone deacetylase (HDAC) inhibitors reproduced starvation-induced transgene up-regulation,
and transcriptome analysis, ChIP, and pharmacological and RNAi approaches revealed that a specific class II HDAC, namely HDAC4,
plays a critical role in maintaining the silencing of exogenous transgenes. This mechanism was also operational in cells chronically
infected with HIV-1, the etiological agent of AIDS, in a latency state. Indeed, both amino acid starvation and pharmacological
inhibition of HDAC4 promoted reactivation of HIV-1 transcription and reverse transcriptase activity production in HDAC4+ ACH-2 T-lymphocytic cells but not in HDAC4− U1 promonocytic cells. Thus, amino acid deprivation leads to transcriptional derepression of silenced transgenes, including
integrated plasmids and retroviruses, by a process involving inactivation or down-regulation of HDAC4. These findings suggest
that selective targeting of HDAC4 might represent a unique strategy for modulating the expression of therapeutic viral vectors,
as well as that of integrated HIV-1 proviruses in latent reservoirs without significant cytotoxicity.
Proceedings of the National Academy of Sciences 08/2012; 109(34):E2284-E2293. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: The role played by genetic factors in influencing the clinical course of multiple sclerosis (MS) is not yet well established.
We aimed to identify genetic variants associated with progressive MS (PrMS).
We conducted a genome-wide association study (GWAS) in 197 patients with PrMS and 234 controls of Italian origin. We tested the top 20 single nucleotide polymorphisms (SNPs) with suggestive evidence of association (p-value<10(-4)) in two independent sets of primary progressive MS cases and controls.
We identified a risk-associated SNP in the HLA region in linkage disequilibrium (LD) with DRB1*1501 and DQB*0602 loci, with genome-wide significance (rs3129934(T), p (combined)=6.7×10(-16), OR=2.34, 95% CI=1.90-2.87), and a novel locus on chromosome 7q35 with suggestive evidence of association (rs996343(G), p (combined)=2.4×10(-5), OR=0.70, 95% CI=0.59-0.83) which maps within a human endogenous retroviral (HERV) element. The new locus did not have a 'cis' effect on RNA expression in lymphoblastic cell lines, but pathway analyses of 'trans' effects point to an expression regulation of genes involved in neurodegeneration, including glutamate metabolism (p<0.01) and axonal guidance signalling (p<0.02).
We have confirmed the established association with the HLA region and, despite the low statistical power of the study, we found suggestive evidence for association with a novel locus on chromosome 7, with a putative regulatory role.
[show abstract][hide abstract] ABSTRACT: Identification of novel targets and biomarkers, such as microRNAs, is extremely helpful to understand the pathogenetic mechanisms in a disease like multiple sclerosis (MS). We tested the expression profile of 1145 microRNAs in peripheral blood mononuclear cells (PBMCs) of 19 MS patients and 14 controls, and we further explored their function by performing a whole-genome mRNA profiling in same subjects and using bioinformatic prediction tool. A total of 104 miRNAs have been identified as deregulated in MS patients; 2/10 which ranked highest (let-7g and miR-150) have been validated in a replication sample, leading to the identification of putative target genes.
[show abstract][hide abstract] ABSTRACT: MGAT5 was demonstrated to be associated to multiple sclerosis (MS) severity. We evaluated its role in progressive MS. We studied 11 SNPs mapping to MGAT5 in an Italian cohort of primary progressive or progressive-relapsing patients. The rs1257169(G) allele is associated with lower disease severity (p-value = 0.02). Adding the age of onset as covariate, another SNP, rs539588, is nominally significant. None of the SNPs survived after multiple testing correction. These results, even if suggestive of MGAT5 involvement also in progressive MS severity, require a bigger sample size to confirm and better explore the role of this locus in this rare disease course.
Journal of neuroimmunology 01/2011; 230(1-2):143-7. · 2.84 Impact Factor
[show abstract][hide abstract] ABSTRACT: KIF1B gene represents the first non-inflammatory gene with a putative role on axonal loss and neurodegeneration found to be associated with multiple sclerosis (MS). The objective of this study is to test the association of the rs10492972 C allelic variant of KIF1B gene in a large Italian cohort of patients with primary progressive and progressive relapsing MS (PPMS and PRMS), which represents a subtype of MS mainly driven by neurodegenerative phenomena.
rs10492972 has been genotyped in an outbred sample of 222 primary PPMS and PRMS and 221 healthy controls of unique northern Italian origin using the TaqMan assay.
A non-significant age- and sex-adjusted odds ratio of 0.96 [95% confidence interval (CI) 0.71-1.31] has been found in C carriers, and a non-significant risk of 0.99 [95% CI 0.77-1.63] in C carriers according to a dominant model. Stratification by sex, age at onset younger than 35 years and symptoms at the onset of the disease did not reveal any significant findings. No influence on disability progression, measured with the multiple sclerosis severity score, was found in C carriers.
These results suggest that there is no effect in carrying the rs10492972 C variant on the risk of disease as well as on the rate of disability progression in a cohort of Italian patients with PPMS and patients with PRMS. These data need to be confirmed in an independent sample of patients with progressive MS.
European Journal of Neurology 05/2010; 17(5):740-5. · 4.16 Impact Factor