Association studies of 19 candidate SNPs with sporadic Alzheimer's disease in the North Chinese Han population

CD33 polymorphisms and Parkinson's disease Parkinson's disease in northern Chinese Han population: A case-control study

OBJECTIVE

Parkinson's disease (PD) represents the multisystem illness involving immunological and neuroinflammatory dysfunction. The present work focused on evaluating link of CD33 single nucleotide polymorphisms (SNPs) with PD vulnerability of the northern Chinese Han people, considering CD33's role as a critical immunoregulatory receptor in neuroinflammatory responses.

METHODS

The present case-control study included 475 PD cases together with 475 normal controls. A further division of PD patients into two categories was made: 74 patients with early-onset PD (EOPD; onset age ≤ 50 years) and 401 patients with late-onset PD (LOPD; onset age > 50 years). DNA extraction was conducted, followed by genotyping for 2SNPs of CD33 polymorphisms with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Alleles (G vs. A, P = 0.028) and AA genotypes (P = 0.042) of rs12985029 were significantly different between the groups. Distinctions were observed between the two groups in the recessive, co-dominant, and additive models (nominal P = 0.030, nominal P = 0.045, and P = 0.032). AA genotype frequency among male PD was higher compared to corresponding male controls (P = 0.034), and in the male group allele A was a factor causing the disease (P = 0.026). The rs12985029 genotypes and allele frequency were different in EOPD compared with LOPD (P = 0.002, P = 0.002, respectively), and in LOPD group relative to healthy control group (P = 0.020 and P = 0.004, separately). Regarding the rs3826656 polymorphism, the frequency of GA genotype was higher in the control group than in the case group (nominal P = 0.036). Overdominance and co-dominant models were different between these groups (P = 0.026, nominal P = 0.030). Subgroup analysis revealed genotype frequency differences between rs3826656 LOPD group and control group (P = 0.018). Furthermore, relationship between rs3826656 and rs12985029 (D' = 0.162, r2 = 0.021) did not reach a complete level of linkage disequilibrium (LD) of northern Chinese Han people.

CONCLUSION

This study establishes an association between CD33 rs12985029 and rs3826656 polymorphisms and PD risk among the selected northern Chinese Han people. The GA genotype, rs3826656, may act as a protective factor against PD, while the A allele, rs12985029,could be genetic risk factor related to PD. Future research should include larger sample sizes and other human populations to further investigate how CD33 polymorphisms contribute to PD.

The Role of the JAK/STAT Signaling Pathway in the Pathogenesis of Alzheimer's Disease: New Potential Treatment Target

Alzheimer's disease is characterized by the accumulation of amyloid plaques and neurofibrillary tangles in the brain. However, emerging evidence suggests that neuroinflammation, mediated notably by activated neuroglial cells, neutrophils, and macrophages, also plays an important role in the pathogenesis of Alzheimer's disease. Therefore, understanding the interplay between the nervous and immune systems might be the key to the prevention or delay of Alzheimer's disease progression. One of the most important mechanisms determining gliogenic cell fate is the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway that is influenced by the overactivation of microglia and astrocytes. The JAK/STAT signaling pathway is one of the critical factors that promote neuroinflammation in neurodegenerative diseases such as Alzheimer's disease by initiating innate immunity, orchestrating adaptive immune mechanisms, and finally, constraining neuroinflammatory response. Since a chronic neuroinflammatory environment in the brain is a hallmark of Alzheimer's disease, understanding the process would allow establishing the underlying role of neuroinflammation, then estimating the prognosis of Alzheimer's disease development and finding a new potential treatment target. In this review, we highlight the recent advances in the potential role of JAK/STAT signaling in neurological diseases with a focus on discussing future research directions regarding novel therapeutic approaches and predictive biomarkers for Alzheimer's disease.

Untangling huge literature to disinter genetic underpinnings of Alzheimer's Disease: A systematic review and meta-analysis

Drug discovery for Alzheimer's Disease (AD) is channeled towards unravelling key disease specific drug targets/genes to predict promising therapeutic candidates. Though enormous literature on AD genetics is available, there exists dearth in data pertinent to drug targets and crucial pathological pathways intertwined in disease progression. Further, the research findings revealing genetic associations failed to demonstrate consistency across different studies. This scenario prompted us to initiate a systematic review and meta-analysis with an aim of unearthing significant genetic hallmarks of AD. Initially, a Boolean search strategy was developed to retrieve case-control studies from PubMed, Cochrane, ProQuest, Europe PMC, grey literature and HuGE navigator. Subsequently, certain inclusion and exclusion criteria were framed to shortlist the relevant studies. These studies were later critically appraised using New Castle Ottawa Scale and Q-Genie followed by data extraction. Later, meta-analysis was performed only for those Single Nucleotide Polymorphisms (SNPs) which were evaluated in at least two different ethnicities from two different reports. Among, 204,351 studies retrieved, 820 met our eligibility criteria and 117 were processed for systematic review after critical appraisal. Ultimately, meta-analysis was performed for 23 SNPs associated with 15 genes which revealed significant associations of rs3865444 (CD33), rs7561528 (BIN1) and rs1801133 (MTHFR) with AD risk.

Innate immune activation in Alzheimer's disease

Alzheimer's disease (AD) is known as the most predominant cause of dementia among the aged people. Previously, two hallmarks of AD pathology including extracellular amyloid-β (Aβ) deposition and neurofibrillary tangles (NFTs) inside neurons have been identified. With a better understanding of this disease, neuroinflammation has been a focus, and as its initial event, innate immune activation plays an indispensable role. In brain, as an endogenous stimulator, extracellular Aβ deposition activates innate immunity through binding to the pattern recognition receptors (PRR), thus leading to the production and release of substantial inflammatory mediators (NO and ROS) and cytokines (IL-1β, IL-10, IL-33 and TNF-α) contributing to the development of AD. Epidemiologic evidence has suggested an affirmative influence of non-steroidal anti-inflammatory drugs (NSAIDs) on delaying the progression of AD. Therefore, blocking the inflammatory process may be an effective way to delay or even cure AD. In this review, we mainly elucidate the mechanism underlying these immune responses in AD pathogenesis and attempt to seek the therapeutic methods targeting neuroinflammation.

Meta-analysis of the association between CD33 and Alzheimer's disease

Background

The cluster of differentiation 33 (CD33) gene is compelling among the susceptibility genes of Alzheimer's disease (AD) in Genome-wide association study (GWAS). Researches of the relationship between AD and polymorphism in CD33 have showed conflicting results. In order to more precisely evaluate whether CD33 variants are associated with AD, we performed the meta-analysis presented in this manuscript.

Methods

We searched from three databases including PubMed, Cochrane library and EMbase for related case-control researches based on criteria of determination. A total of 18 case-control studies, containing 50,030 cases and 77,405 controls were involved in CD33 rs3865444 polymorphism. And a total of 4 case-control studies, containing 826 cases and 984 controls were involved in CD33 rs3826656 polymorphism.

Results

This study demonstrated that different variants in CD33 were associated with AD (rs3865444: OR =0.94; 95% CI, 0.90-0.98, P<0.01; rs3826656: OR =0.94; 95% CI, 0.62-1.41, P<0.01). We made subgroup analysis which was stratified by race. There were protective associations in Caucasians but not in Asians among CD33 rs3865444 polymorphism (Caucasians: OR =0.92; 95% CI, 0.90-0.94, P=0.05; Asians: OR =0.87; 95% CI, 0.65-1.17, P<0.01).

Conclusions

The CD33 rs3865444 polymorphism could be a protective factor in AD. Meanwhile, there was no association between the CD33 rs3826656 polymorphism and AD. Further confirmation is needed in larger and better-designed researches.

Association of GWAS Top Genes With Late-Onset Alzheimer's Disease in Colombian Population

OBJECTIVE

The association of variants in CLU, CR1, PICALM, BIN1, ABCA7, and CD33 genes with late-onset Alzheimer's disease (LOAD) was evaluated and confirmed through genome-wide association study. However, it is unknown whether these associations can be replicated in admixed populations.

METHODS

The association of 14 single-nucleotide polymorphisms in those genes was evaluated in 280 LOAD cases and 357 controls from the Colombian population.

RESULTS

In a multivariate analysis using age, gender, APOE∊4 status, and admixture covariates, significant associations were obtained ( P < .05) for variants in BIN1 (rs744373, odds ratio [OR]: 1.42), CLU (rs11136000, OR: 0.66), PICALM (rs541458, OR: 0.69), ABCA7 (rs3764650, OR: 1.7), and CD33 (rs3865444, OR: 1.12). Likewise, a significant interaction effect was observed between CLU and CR1 variants with APOE.

CONCLUSION

This study replicated the associations previously reported in populations of European ancestry and shows that APOE variants have a regulatory role on the effect that variants in other loci have on LOAD, reflecting the importance of gene-gene interactions in the etiology of neurodegenerative diseases.

Association of CD33 and MS4A cluster variants with Alzheimer's disease in East Asian populations

CD33 and MS4A cluster variants have been identified to modulate the risk of Alzheimer's disease (AD) in several recent genome-wide association studies (GWAS) in Caucasians. In the present study, we first conducted a case-control study to investigate the CD33 single nucleotide polymorphisms (SNPs) rs3865444 and rs3826656 and the MS4A cluster SNPs rs610932 and rs670139 in a cohort from eastern China that comprised 126 late-onset Alzheimer's disease (LOAD) patients and 129 healthy controls. The results revealed that the frequency of rs3826656 major (G) allele carriers was higher among the LOAD patients than among the controls [P=0.005; odds ratio (OR), 1.760; 95% confidence interval (CI), 1.185-2.615]. In apolipoprotein E (APOE) ε4 allele carriers, the G allele of the SNP rs3865444 was found to be associated with an increased risk of LOAD (P=0.002; OR, 3.391; 95% CI, 1.512-7.605). Next, we re-evaluated the association between these variants and LOAD by conducting a meta-analysis using data from studies of East Asian populations, including the present case-control study, and confirmed that rs3826656 increased the risk of LOAD. In addition, we identified a significant association between rs610932 and LOAD (P=0.035; OR, 0.79; 95% CI, 0.63-0.98). Note that heterogeneity should be considered during the interpretation of these results; significant heterogeneity was identified among studies on rs3865444, even in a subgroup analysis based on stratification of studies by the country of origin. In summary, our results suggest that CD33 and MS4A cluster variants are associated with LOAD susceptibility in East Asian populations.

CD33 modulates TREM2: convergence of Alzheimer loci

Here, we report results from a protein quantitative trait analysis in monocytes from 226 individuals to evaluate cross-talk between Alzheimer loci. We find that the NME8 locus influences PTK2B and that the CD33 risk allele leads to greater TREM2 expression. Further, we observe (1) a decreased TREM1/TREM2 ratio with a TREM1 risk allele, (2) decreased TREM2 expression with CD33 suppression, and (3) elevated cortical TREM2 mRNA expression with amyloid pathology.

Association of CD33 polymorphism rs3865444 with Alzheimer's disease pathology and CD33 expression in human cerebral cortex

Recent findings identified the minor A allele present in the single-nucleotide polymorphism rs3865444 in the CD33 gene as being associated with the reduced risk of developing Alzheimer's disease (AD). CD33 (Siglec-3) is an immune function protein with anti-inflammatory signaling, cell adhesion, and endocytosis functions with sialic acid-modified proteins or lipids as ligands. Its involvement in AD pathologic mechanisms is still unclear; so, the goal of this study was to investigate if the rs3865444 polymorphism affects the development of AD pathology and the expression of CD33 messenger RNA (mRNA) and protein. For this study, we used DNA from 96 nondemented (ND) and 97 AD neuropathologically diagnosed cases to identify the different rs3865444 alleles and correlate with different measures of AD pathology. Using semiquantitative histologic measures of plaque and tangle pathology, we saw no significant differences between the different genotypes within these disease groups. However, increased expression of CD33 mRNA was associated with increasing AD pathology in temporal cortex brain samples. We also showed that cases with A/A alleles had reduced levels of CD33 protein in temporal cortex but increased levels of the microglia protein IBA-1. Using immunohistochemistry on temporal cortex sections, CD33 was selectively localized to microglia, with greater expression in activated microglia. The factors causing increased CD33 expression by microglia in brain are still unclear, although both genetic and disease factors are involved. Treatment of human microglia isolated from autopsy brains with amyloid-beta peptide and a range of other inflammatory activating agents resulted in reduced CD33 mRNA and protein levels.

GP73 is upregulated by hepatitis C virus (HCV) infection and enhances HCV secretion

Hepatitis C virus (HCV) is a major cause of chronic liver disease. However, little is known about the details of its assembly and secretion. Golgi-related proteins have been recently proven to have a key function in HCV secretion. Golgi protein 73 (GP73), a resident Golgi membrane protein, is a potential serum biomarker for the diagnosis of liver diseases and hepatocellular carcinoma. Previous studies have demonstrated the upregulation of GP73 in the liver samples and sera of HCV-infected patients. However, the function and regulatory mechanism of GP73 in HCV infection at the cellular level remain unknown. In this study, we examined the expression level of GP73 in HCV infected cells and its effect on HCV life cycle in cell culture systems. Both the protein expression and mRNA levels of GP73 significantly increased in HCV subgenomic replicon-harboring cells and HCV-infected cells, which imply that GP73 was upregulated by HCV infection. HCV production was significantly enhanced when GP73 was overexpressed, but dramatically inhibited when GP73 was silenced. However, the overexpression and knockdown of GP73 showed no evident effect on the entry, protein translation, RNA replication, and assembly of HCV, which indicates that GP73 enhanced the secretion process. Moreover, the coiled-coil domain of GP73 was required to increase HCV secretion. GP73 increased and interacted with apolipoprotein E, an identified host factor that assists in HCV secretion. These results demonstrate the critical function of GP73 in HCV secretion and provide new insights into the therapeutic design of antiviral strategies.

CXCL10 decreases GP73 expression in hepatoma cells at the early stage of hepatitis C virus (HCV) infection

Golgi protein 73 (GP73), which is up-regulated in hepatocellular carcinoma (HCC), has recently been identified as a novel serum marker for HCC diagnosis. Several reports also noted the increased levels of GP73 expression in chronic liver disease in patients with acute hepatitis of various etiologies, chronic Hepatitis C virus (HCV) infection and alcoholic liver disease. The molecular mechanisms of GP73 expression in HCV related liver disease still need to be determined. In this study, we aimed to evaluate the effect of HCV infection on GP73 expression. GP73 was highly expressed in Huh7, Hep3B, 293T and HUVEC cells, and was low-expressed in HepG2 cells. HCV infection led to down-regulation of GP73 in Huh7 and HepG2/CD81 cells at the early stage of infection. CXCL10 decreased GP73 expression in Huh7 and HepG2 cells. Up-regulation of GP73 was noted in hepatocytes with cytopathic effect at advanced stage of HCV infection, and further research is needed to determine the unknown factors affecting GP73 expression. In conclusion, our study provided additional evidence for the roles of GP73 in liver disease.

CD33 in Alzheimer's disease

The amyloid-beta peptide (Aβ) cascade hypothesis posits that Aβ accumulation is the fundamental initiator of Alzheimer's disease (AD), and mounting evidence suggests that impaired Aβ clearance rather than its overproduction is the major pathogenic event for AD. Recent genetic studies have identified cluster of differentiation 33 (CD33) as a strong genetic locus linked to AD. As a type I transmembrane protein, CD33 belongs to the sialic acid-binding immunoglobulin-like lectins, mediating the cell-cell interaction and inhibiting normal functions of immune cells. In the brain, CD33 is mainly expressed on microglial cells. The level of CD33 was found to be increased in the AD brain, which positively correlated with amyloid plaque burden and disease severity. More importantly, CD33 led to the impairment of microglia-mediated clearance of Aβ, which resulted in the formation of amyloid plaques in the brain. In this article, we review the recent epidemiological findings of CD33 that related with AD and discuss the levels and pathogenic roles of CD33 in this disease. Based on the contributing effects of CD33 in AD pathogenesis, targeting CD33 may provide new opportunities for AD therapeutic strategies.

Golgi phosphoprotein 2 in physiology and in diseases

Golgi phosphoprotein 2 (GOLPH2, also termed GP73 and GOLM1) is a type II transmembrane protein residing in the cis and medial-Golgi cisternae. GOLPH2 is predominantly expressed in the epithelial cells of many human tissues. Under poorly defined circumstances, GOLPH2 can be cleaved and released to the extracellular space. Despite of its relatively “young age” since the first description in 2000, the physiological and pathological roles of GOLPH2 have been the subject that has attracted considerable amount of attention in recent years. Here, we review the history of GOLPH2’s discovery and the multitude of studies by many groups around the world aimed at understanding its molecular, cellular, physiological, and pathogenic activities in various settings.