Investigation of complement component C4 copy number variation in human longevity

Parkinson's disease and multiple system atrophy patient iPSC-derived oligodendrocytes exhibit alpha-synuclein-induced changes in maturation and immune reactive properties

Our results demonstrate the existence of early cellular pathways and network alterations in oligodendrocytes in the alpha-synucleinopathies Parkinson’s disease and multiple system atrophy. They further reveal the involvement of an immune component triggered by alpha-synuclein protein, as well as a connection between (epi)genetic changes and immune reactivity in multiple system atrophy. The knowledge generated in this study could be used to devise novel therapeutic approaches to treat synucleinopathies.

Limited evidence has shed light on how aSYN proteins affect the oligodendrocyte phenotype and pathogenesis in synucleinopathies that include Parkinson’s disease (PD) and multiple system atrophy (MSA). Here, we investigated early transcriptomic changes within PD and MSA O4⁺ oligodendrocyte lineage cells (OLCs) generated from patient-induced pluripotent stem cells (iPSCs). We found impaired maturation of PD and MSA O4⁺ OLCs compared to controls. This phenotype was associated with changes in the human leukocyte antigen (HLA) genes, the immunoproteasome subunit PSMB9, and the complement component C4b for aSYN p.A53T and MSA O4⁺ OLCs, but not in SNCA^trip O4⁺ OLCs despite high levels of aSYN assembly formation. Moreover, SNCA overexpression resulted in the development of O4⁺ OLCs, whereas exogenous treatment with aSYN species led to significant toxicity. Notably, transcriptome profiling of genes encoding proteins forming Lewy bodies and glial cytoplasmic inclusions revealed clustering of PD aSYN p.A53T O4⁺ OLCs with MSA O4⁺ OLCs. Our work identifies early phenotypic and pathogenic changes within human PD and MSA O4⁺ OLCs.

Complement C4 Gene Copy Number Variation Genotyping by High Resolution Melting PCR

BACKGROUND

Complement C4 gene copy number variation plays an important role as a determinant of genetic susceptibility to common diseases, such as systemic lupus erythematosus, schizophrenia, rheumatoid arthritis, and infectious diseases. This study aimed to develop an assay for the quantification of copy number variations in the C4 locus.

METHODS

the assay was based on a gene ratio analysis copy enumeration (GRACE) PCR combined with high resolution melting (HRM) PCR. The test was optimized using samples of a known genotype and validated with 72 DNA samples from healthy blood donors.

RESULTS

to validate the assay, standard curves were generated by plotting the C4/RP1 ratio values against copy number variation (CNV) for each gene, using genomic DNA with known C4 CNV. The range of copy numbers in control individuals was comparable to distributions observed in previous studies of European descent.

CONCLUSIONS

the method herein described significantly simplifies C4 CNV diagnosis to validate the assay.

Complement Components, C3 and C4, and the Metabolic Syndrome

INTRODUCTION

Increased systemic inflammation plays a significant role in the development of adult cardiometabolic diseases such as insulin resistance, dyslipidemia, atherosclerosis, and hypertension. The complement system is a part of the innate immune system and plays a key role in the regulation of inflammation. Of particular importance is the activation of complement components C3 and C4. C3 is produced primarily by the liver but is also produced in adipocytes, macrophages and endothelial cells, all of which are present in adipose tissues. Dietary fat and chylomicrons stimulate C3 production. Adipocytes in addition to producing C3 also have receptors for activated C3 and other complement components and thus also respond to as well as produce a target for complement. C3adesArg, also known as acylation stimulation factor, increases adipocyte triglyceride synthesis and release. These physiological effects play a significant role in the development of metabolic syndrome. Epidemiologically, obese adults and non-obese adults with cardiometabolic disease who are not obese have been shown to have increased complement levels. C4 levels also correlate with body mass index. Genetically, specific C3 polymorphisms have been shown to predict future cardiovascular events and. D decreased C4 long gene copy number is associated with increased longevity.

CONCLUSION

Future research is clearly needed to clarify the role of complement in the development of cardiovascular disease and mechanisms for its action. The complement system may provide a new area for intervention in the prevention of cardiometabolic diseases.

Influence of aging on the activity of mice Sca-1+CD31- cardiac stem cells

Therapeutic application of cardiac resident stem/progenitor cells (CSC/CPCs) is limited due to decline of their regenerative potential with donor age. A variety of studies have shown that the cardiac aging was the problem of the stem cells, but little is known about the impact of age on the subgroups CSC/CPCs, the relationship between subgroups CSC/CPCs ageing and age-related dysfunction. Here, we studied Sca-1+CD31− subgroups of CSCs from younger(2~3months) and older(22~24months) age mice, biological differentiation was realized using specific mediums for 14 days to induce cardiomyocyte, smooth muscle cells or endothelial cells and immunostain analysis of differentiated cell resulting were done. Proliferation and cell cycle were measured by flow cytometry assay, then used microarray to dissect variability from younger and older mice. Although the number of CSCs was higher in older mice, the advanced age significantly reduced the differentiation ability into cardiac cell lineages and the proliferation ability. Transcriptional changes in Sca-1+CD31− subgroups of CSCs during aging are related to Vitamin B6 metabolism, circadian rhythm, Tyrosine metabolism, Complement and coagulation cascades. Taking together these results indicate that Cardiac resident stem/progenitor cells have significant differences in their proliferative, pluripotency and gene profiles and those differences are age depending.

Low copy numbers of complement C4 and homozygous deficiency of C4A may predispose to severe disease and earlier disease onset in patients with systemic lupus erythematosus

Objectives Low copy numbers and deletion of complement C4 genes are potent risk factors for systemic lupus erythematosus (SLE). However, it is not known whether this genetic association affects the clinical outcome. We investigated C4 copy number variation and its relationship to clinical and serological features in a Northern European lupus cohort. Methods We genotyped the C4 gene locus using polymerase chain reaction (PCR)-based TaqMan assays in 169 patients with SLE classified according to the 1997 revised American College of Rheumatology (ACR) criteria and in 520 matched controls. In the patient group the mean C4 serum protein concentrations nephelometrically measured during a 12-month period prior to genetic analysis were compared to C4 gene copy numbers. Severity of disease was classified according to the intensity of the immunosuppressive regimens applied and compared to C4 gene copy numbers, too. In addition, we performed a TaqMan based analysis of three lupus-associated single-nucleotide polymorphisms (SNPs) located inside the major histocompatibility complex (MHC) to investigate the independence of complement C4 in association with SLE. Results Homozygous deficiency of the C4A isotype was identified as the strongest risk factor for SLE (odds ratio (OR) = 5.329; p = 7.7 × 10^-3) in the case-control comparison. Moreover, two copies of total C4 were associated with SLE (OR = 3.699; p = 6.8 × 10^-3). C4 serum levels were strongly related to C4 gene copy numbers in patients, the mean concentration ranging from 0.110 g/l (two copies) to 0.256 g/l (five to six copies; p = 4.9 × 10^-6). Two copies of total C4 and homozygous deletion of C4A were associated with a disease course requiring cyclophosphamide therapy (OR = 4.044; p = 0.040 and OR = 5.798; p = 0.034, respectively). Homozygous deletion of C4A was associated with earlier onset of SLE (median 24 vs. 34 years; p = 0.019) but not significant after correction for multiple testing. SNP analysis revealed a significant association of HLA-DRB1*0301 with SLE (OR = 2.231; p = 1.33 × 10^-5). Conclusions Our findings confirm the important role of complement C4 genes in the development of SLE. Beyond the impact on the susceptibility for lupus, C4 copy numbers may be related to earlier onset and a more severe course of the disease. The association of homozygous deletion of C4A and SLE is accompanied by the presence of HLA-DRB1*0301 without a proven pathophysiological mechanism.

Association between C4, C4A, and C4B copy number variations and susceptibility to autoimmune diseases: a meta-analysis

Although several studies have investigated the association between C4, C4A, and C4B gene copy number variations (CNVs) and susceptibility to autoimmune diseases, the results remain inconsistency for those diseases. Thus, in this study, a comprehensive meta-analysis was conducted to assess the role of C4, C4A, and C4B CNVs in autoimmune diseases in different ethnic groups. A total of 16 case-control studies described in 12 articles (8663 cases and 11099 controls) were included in this study. The pooled analyses showed that a low C4 gene copy number (GCN) (<4) was treated as a significant risk factor (odds ratio [OR] = 1.46, 95% confidence interval [CI] = 1.19–1.78) for autoimmune diseases compared with a higher GCN (>4). The pooled statistical results revealed that low C4 (<4) and low C4A (<2) GCNs could be risk factors for systemic lupus erythematosus (SLE) in Caucasian populations. Additionally, the correlation between C4B CNVs and all type of autoimmune diseases could not be confirmed by the current meta-analysis (OR = 1.07, 95% CI = 0.93–1.24). These data suggest that deficiency or absence of C4 and C4A CNVs may cause susceptibility to SLE.

Genome-Wide Copy Number Variation Scan Identifies Complement Component C4 as Novel Susceptibility Gene for Crohn's Disease

BACKGROUND

The genetic component of Crohn's disease (CD) is well known, with 140 susceptibility loci identified so far. In addition to single nucleotide polymorphisms typically studied in genome-wide scans, copy number variation is responsible for a large proportion of human genetic variation.

METHODS

We performed a genome-wide search for copy number variants associated with CD using array comparative genomic hybridization. One of the found regions was validated independently through real-time PCR. Serum levels of the found gene were measured in patients and control subjects.

RESULTS

We found copy number differences for the C4S and C4L gene variants of complement component C4 in the central major histocompatibility complex region on chromosome 6p21. Specifically, we saw that CD patients tend to have lower C4L and higher C4S copies than control subjects (P = 5.00 × 10 and P = 9.11 × 10), which was independent of known associated classical HLA I and II alleles (P = 7.68 × 10 and P = 6.29 × 10). Although C4 serum levels were not different between patients and control subjects, the relationship between C4 copy number and serum level was different for patients and control subjects with higher copy numbers leading to higher serum concentrations in control subjects, compared with CD patients (P < 0.001).

CONCLUSIONS

C4 is part of the classical activation pathway of the complement system, which is important for (auto)immunity. Low C4L or high C4S copy number, and corresponding effects on C4 serum level, could lead to an exaggerated response against infections, possibly leading to (auto)immune disease.

Genetic factors associated with longevity: a review of recent findings

Given the rising rate of survival into advanced old age in the United States, achieving longevity and healthy aging is becoming increasingly important. Besides maintaining healthy lifestyle behaviors, positive aging outcomes may also be heritable, with estimates ranging from 20% to 35%. In this qualitative review, we summarize recent findings on genetic factors linked to longevity across different populations and study designs. Recent studies not only confirm the association of APOE with longevity in different populations, but also implicate several other pathways that may influence longevity including nitric oxide production, inflammation, immunity, and DNA damage response and repair. Recent evidence also suggests that mitochondrial DNA may play an important role in attaining longevity. Despite these implicated pathways, longevity may be a polygenic trait influenced by a complex interplay of multiple genes. Future genetic studies on aging would benefit from larger samples of long-lived individuals, birth-cohort matched controls, inclusion of different aging phenotypes (e.g., aging free of morbidities), and analysis of gender differences.