Complement C4-deficient mice have a high mortality rate during PTZ-induced epileptic seizures, which correlates with cognitive problems and the deficiency in the expression of Egr1 and other immediate early genes

Complement system plays an important role in the immune defense against pathogens; however, recent studies demonstrated an important role of complement subunits C1q, C4, and C3 in normal functions of the central nervous system (CNS) such as non-functional synapse elimination (synapse pruning), and during various neurologic pathologies. Humans have two forms of C4 protein encoded by C4A and C4B genes that share 99.5% homology, while mice have only one C4B gene that is functionally active in the complement cascade. Overexpression of the human C4A gene was shown to contribute to the development of schizophrenia by mediating extensive synapse pruning through the activation C1q-C4-C3 pathway, while C4B deficiency or low levels of C4B expression were shown to relate to the development of schizophrenia and autism spectrum disorders possibly via other mechanisms not related to synapse elimination. To investigate the potential role of C4B in neuronal functions not related to synapse pruning, we compared wildtype (WT) mice with C3- and C4B- deficient animals for their susceptibility to pentylenetetrazole (PTZ)- induced epileptic seizures. We found that C4B (but not C3)-deficient mice were highly susceptible to convulsant and subconvulsant doses of PTZ when compared to WT controls. Further gene expression analysis revealed that in contrast to WT or C3-deficient animals, C4B-deficient mice failed to upregulate expressions of multiple immediate early genes (IEGs) Egrs1-4, c-Fos, c-Jus, FosB, Npas4, and Nur77 during epileptic seizures. Moreover, C4B-deficient mice had low levels of baseline expression of Egr1 on mRNA and protein levels, which was correlated with the cognitive problems of these animals. C4-deficient animals also failed to upregulate several genes downstream of IEGs such as BDNF and pro-inflammatory cytokines IL-1β, IL-6, and TNF. Taken together, our study demonstrates a new role of C4B in the regulation of expression of IEGs and their downstream targets during CNS insults such as epileptic seizures.

Complement component C4 structural variation and quantitative traits contribute to sex-biased vulnerability in systemic sclerosis

Copy number (CN) polymorphisms of complement C4 play distinct roles in many conditions, including immune-mediated diseases. We investigated the association of C4 CN with systemic sclerosis (SSc) risk. Imputed total C4, C4A, C4B, and HERV-K CN were analyzed in 26,633 individuals and validated in an independent cohort. Our results showed that higher C4 CN confers protection to SSc, and deviations from CN parity of C4A and C4B augmented risk. The protection contributed per copy of C4A and C4B differed by sex. Stronger protection was afforded by C4A in men and by C4B in women. C4 CN correlated well with its gene expression and serum protein levels, and less C4 was detected for both in SSc patients. Conditioned analysis suggests that C4 genetics strongly contributes to the SSc association within the major histocompatibility complex locus and highlights classical alleles and amino acid variants of HLA-DRB1 and HLA-DPB1 as C4-independent signals.

Analysis of Differentially Expressed Genes in Coronary Artery Disease by Integrated Microarray Analysis

Coronary artery disease (CAD) is a major cause of end-stage cardiac disease. Although profound efforts have been made to illuminate the pathogenesis, the molecular mechanisms of CAD remain to be analyzed. To identify the candidate genes in the advancement of CAD, microarray dataset GSE23766 was downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified, and pathway and gene ontology (GO) enrichment analyses were performed. The protein-protein interaction network was constructed and the module analysis was performed using the Biological General Repository for Interaction Datasets (BioGRID) and Cytoscape. Additionally, target genes-miRNA regulatory network and target genes-TF regulatory network were constructed and analyzed. There were 894 DEGs between male human CAD samples and female human CAD samples, including 456 up regulated genes and 438 down regulated genes. Pathway enrichment analyses revealed that DEGs (up and down regulated) were mostly enriched in the superpathway of steroid hormone biosynthesis, ABC transporters, oxidative ethanol degradation III and Complement and coagulation cascades. Similarly, geneontology enrichment analyses revealed that DEGs (up and down regulated) were mostly enriched in the forebrain neuron differentiation, filopodium membrane, platelet degranulation and blood microparticle. In the PPI network and modules (up and down regulated), MYC, NPM1, TRPC7, UBC, FN1, HEMK1, IFT74 and VHL were hub genes. In the target genes-miRNA regulatory network and target genes—TF regulatory network (up and down regulated), TAOK1, KHSRP, HSD17B11 and PAH were target genes. In conclusion, the pathway and GO ontology enriched by DEGs may reveal the molecular mechanism of CAD. Its hub and target genes, MYC, NPM1, TRPC7, UBC, FN1, HEMK1, IFT74, VHL, TAOK1, KHSRP, HSD17B11 and PAH were expected to be new targets for CAD. Our finding provided clues for exploring molecular mechanism and developing new prognostics, diagnostic and therapeutic strategies for CAD.

Association Study of the Complement Component C4 Gene in Tardive Dyskinesia

Tardive dyskinesia (TD) is a movement disorder that may develop in schizophrenia patients being treated long-term with antipsychotic medication. TD interferes with voluntary movements and leads to stigma, and can be associated with treatment non-adherence. The etiology of TD is unclear, but it appears to have a genetic component. There is emerging evidence of immune dysregulation in TD. In the current study, we set out to investigate the complex schizophrenia-associated complement component 4 (C4) gene for possible association with TD occurrence and TD severity as assessed by the Abnormal Involuntary Movement Scale (AIMS) in a sample of 129 schizophrenia patients of European ancestry. We have genotyped the copy numbers of long and short forms of C4A and C4B gene variants in 129 European ancestry patients with schizophrenia or schizoaffective disorder. We did not find predicted C4A or C4B expression to be nominally associated with TD risk or severity. However, we found the number of copies of C4BL to be nominally associated with TD severity (p = 0.020).

Role of complement system in pathological remodeling of the vascular wall

Cardiovascular diseases (CVD) remain the major cause of morbidity and mortality in Europe. The clinical complications associated to arterial wall rupture involve intimal cap rupture in complicated atherosclerotic plaques and medial rupture in abdominal aortic aneurysm (AAA). The mechanisms underlying pathological vascular remodeling include lipid accumulation, cell proliferation, redox imbalance, proteolysis, leukocyte infiltration, cell death, and eventually, thrombosis. The complement system could participate in vascular remodeling by several mechanisms, from an initial protective response that aims in the clearing of cell debris to a potential deleterious role participating in leukocyte chemotaxis and cell activation and bridging innate and adaptive immunity. We have reviewed the presence and distribution of complement components, as well as the triggers of complement activation in atherosclerotic plaques and AAA, to later assess the functional consequences of complement modulation in experimental models of pathological vascular remodeling and the potential role of complement components as potential circulating biomarkers of CVD. On the whole, complement system is a key mechanism involved in vascular remodelling, which could be useful in the diagnostic/prognostic setting, as well as a potential therapeutic target, of CVD.

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.

Complex and multi-allelic copy number variation in human disease

Hundreds of copy number variants are complex and multi-allelic, in that they have many structural alleles and have rearranged multiple times in the ancestors who contributed chromosomes to current humans. Not only are the relationships of these multi-allelic CNVs (mCNVs) to phenotypes generally unknown, but many mCNVs have not yet been described at the basic levels—alleles, allele frequencies, structural features—that support genetic investigation. To date, most reported disease associations to these variants have been ascertained through candidate gene studies. However, only a few associations have reached the level of acceptance defined by durable replications in many cohorts. This likely stems from longstanding challenges in making precise molecular measurements of the alleles individuals have at these loci. However, approaches for mCNV analysis are improving quickly, and some of the unique characteristics of mCNVs may assist future association studies. Their various structural alleles are likely to have different magnitudes of effect, creating a natural allelic series of growing phenotypic impact and giving investigators a set of natural predictions and testable hypotheses about the extent to which each allele of an mCNV predisposes to a phenotype. Also, mCNVs’ low-to-modest correlation to individual single-nucleotide polymorphisms (SNPs) may make it easier to distinguish between mCNVs and nearby SNPs as the drivers of an association signal, and perhaps, make it possible to preliminarily screen candidate loci, or the entire genome, for the many mCNV–disease relationships that remain to be discovered.

The complement system and toll-like receptors as integrated players in the pathophysiology of atherosclerosis

Despite recent medical advances, atherosclerosis is a global burden accounting for numerous deaths and hospital admissions. Immune-mediated inflammation is a major component of the atherosclerotic process, but earlier research focus on adaptive immunity has gradually switched towards the role of innate immunity. The complement system and toll-like receptors (TLRs), and the crosstalk between them, may be of particular interest both with respect to pathogenesis and as therapeutic targets in atherosclerosis. Animal studies indicate that inhibition of C3a and C5a reduces atherosclerosis. In humans modified LDL-cholesterol activate complement and TLRs leading to downstream inflammation, and histopathological studies indicate that the innate immune system is present in atherosclerotic lesions. Moreover, clinical studies have demonstrated that both complement and TLRs are upregulated in atherosclerotic diseases, although interventional trials have this far been disappointing. However, based on recent research showing an intimate interplay between complement and TLRs we propose a model in which combined inhibition of both complement and TLRs may represent a potent anti-inflammatory therapeutic approach to reduce atherosclerosis.

A vital role for complement in heart disease

Heart diseases are common and significant contributors to worldwide mortality and morbidity. During recent years complement mediated inflammation has been shown to be an important player in a variety of heart diseases. Despite some negative results from clinical trials using complement inhibitors, emerging evidence points to an association between the complement system and heart diseases. Thus, complement seems to be important in coronary heart disease as well as in heart failure, where several studies underscore the prognostic importance of complement activation. Furthermore, patients with atrial fibrillation often share risk factors both with coronary heart disease and heart failure, and there is some evidence implicating complement activation in atrial fibrillation. Moreover, Chagas heart disease, a protozoal infection, is an important cause of heart failure in Latin America, and the complement system is crucial for the protozoa-host interaction. Thus, complement activation appears to be involved in the pathophysiology of a diverse range of cardiac conditions. Determination of the exact role of complement in the various heart diseases will hopefully help to identify patients that might benefit from therapeutic complement intervention.

Glycogen synthase kinase 3 beta gene structural variants as possible risk factors of bipolar depression

The glycogen synthase kinase 3B (GSK3B) is an important target protein of several antidepressants, such as lithium, a mood stabilizer. Recent studies associated structural variations of the GSK3B gene to bipolar disorder (BP), although replications were not conclusive. Here we present data on copy number variations (CNVs) of the GSK3B gene probing the 9th exon region in 846 individuals (414 controls, 172 patients with major depressive disorder (MDD) and 260 with BP). A significant accumulation (odds ratio: 5.5, P = 0.00051) of the amplified exon 9 region was found in patients (22 out of 432) compared to controls (4 of 414). Analyzing patient subgroups, GSK3B structural variants were found to be risk factors of BP particularly (P = 0.00001) with an odds ratio of 8.1 while no such effect was shown in the MDD group. The highest odds (19.7 ratio) for bipolar disorder was observed in females with the amplified exon 9 region. A more detailed analysis of the identified GSK3B CNV by a set of probes covering the GSK3B gene and the adjacent NR1I2 and C3orf15 genes showed that the amplified sequences contained 3' (downstream) segments of the GSK3B and NR1I2 genes but none of them involved the C3orf15 gene. Therefore, the copy number variation of the GSK3B gene could be described as a complex set of structural variants involving partial duplications and deletions, simultaneously. In summary, here we confirmed significant association of the GSK3B CNV and bipolar disorder pointing out that the copy number and extension of the CNV varies among individuals.

Investigation of complement component C4 copy number variation in human longevity

Genetic factors have been estimated to account for about 25% of the variation in an adult's life span. The complement component C4 with the isotypes C4A and C4B is an effector protein of the immune system, and differences in the overall C4 copy number or gene size (long C4L; short C4S) may influence the strength of the immune response and disease susceptibilities. Previously, an association between C4B copy number and life span was reported for Hungarians and Icelanders, where the C4B*Q0 genotype, which is defined by C4B gene deficiency, showed a decrease in frequency with age. Additionally, one of the studies indicated that a low C4B copy number might be a genetic trait that is manifested only in the presence of the environmental risk factor "smoking". These observations prompted us to investigate the role of the C4 alleles in our large German longevity sample (∼ 700 cases; 94-110 years and ∼ 900 younger controls). No significant differences in the number of C4A, C4B and C4S were detected. Besides, the C4B*Q0 carrier state did not decrease with age, irrespective of smoking as an interacting variable. However, for C4L*Q0 a significantly different carrier frequency was observed in the cases compared with controls (cases: 5.08%; controls: 9.12%; p = 0.003). In a replication sample of 714 German cases (91-108 years) and 890 controls this result was not replicated (p = 0.14) although a similar trend of decreased C4L*Q0 carrier frequency in cases was visible (cases: 7.84%; controls: 10.00%).

ACTH-induced cortisol release is related to the copy number of the C4B gene encoding the fourth component of complement in patients with non-functional adrenal incidentaloma

OBJECTIVE

According to our previous findings, carriers of the C4B*Q0 genotype, which means zero or one copy of the C4B gene, which is located in the RCCX copy number variation region on chromosome 6, have a significantly shorter life-expectancy and higher risk of cardiovascular disease than non-carriers. We have postulated that the C4B*Q0 genotype is linked to variant(s) of the neighboring CYP21A2 gene encoding a steroid 21-hydroxylase with altered function.

DESIGN

Single-center, observational, retrospective study.

PATIENTS

Seventy-six patients with non-functional, benign adrenal incidentaloma.

MEASUREMENTS

Serum cortisol, aldosterone, 17-hydroxyprogesterone, corticosterone and ACTH levels basally and after ACTH-stimulation, metyrapone or dexamethasone tests were determined. C4B gene copy number was quantified.

RESULTS

The ratio of ACTH-stimulated and baseline cortisol concentrations was significantly higher (P = 0·001) in the group of patients carrying the C4B*Q0 genotype compared to the rest of the patients. This difference remained significant (P = 0·004) after adjustment for sex and age, as well as for tumor size. A significant (P = 0·018), adjusted difference between carriers and non-carriers was found also for ACTH-induced/basal aldosterone ratio. In C4B*Q0 carriers, metyrapone hardly reduced the serum cortisol level, while in non-carriers it induced a highly significant (P = 0·002) decrease.

CONCLUSIONS

The C4B*Q0 genotype may be associated with hyperreactivity of the HPA axis (manifested as an increased responsiveness to ACTH-stimulation), probably through enhanced function of steroid 21-hydroxylase. Since hyperreactivity of the HPA axis is known to be associated with an increased risk of cardiovascular disease, our present findings may explain the increased cardiovascular morbidity and mortality of C4B*Q0 carriers.

Copy number variation at leptin receptor gene locus associated with metabolic traits and the risk of type 2 diabetes mellitus

Background

Recent efforts have been made to link complex human traits and disease susceptibility to DNA copy numbers. The leptin receptor (LEPR) has been implicated in obesity and diabetes. Mutations and genetic variations of LEPR gene have been discovered in rodents and humans. However, the association of DNA copy number variations at the LEPR gene locus with human complex diseases has not been reported. In an attempt to study DNA copy number variations associated with metabolic traits and type 2 diabetes mellitus (T2DM), we targeted the LEPR gene locus in DNA copy number analyses.

Results

We identified DNA copy number variations at the LEPR gene locus among a Korean population using genome-wide SNP chip data, and then quantified copy numbers of the E2 DNA sequence in the first two exons overlapped between LEPR and LEPROT genes by the quantitative multiplex PCR of short fluorescent fragment (QMPSF) method. Among the non-diabetic subjects (n = 1,067), lower E2 DNA copy numbers were associated with higher fasting glucose levels in men (p = 1.24 × 10^-7) and women (p = 9.45 × 10^-5), as well as higher total cholesterol levels in men (p = 9.96 × 10^-7). In addition, the significant association between lower E2 DNA copy numbers and lower level of postprandial 2hr insulin was evident only in non-diabetic women, whereas some obesity-related phenotypes and total cholesterol level exhibited significant associations only in non-diabetic men. Logistic regression analysis indicated that lower E2 DNA copy numbers were associated with T2DM (odds ratio, 1.92; 95% CI, 1.26~2.96; p < 0.003) in our nested case-control study. Interestingly, the E2 DNA copy number exhibited a negative correlation with LEPR gene expression, but a positive correlation with LEPROT gene expression.

Conclusions

This work suggests that a structural variation at the LEPR gene locus is functionally associated with complex metabolic traits and the risk of T2DM.

Structural Variation in the Human Genome and its Role in Disease

During the last quarter of the twentieth century, our knowledge about human genetic variation was limited mainly to the heterochromatin polymorphisms, large enough to be visible in the light microscope, and the single nucleotide polymorphisms (SNPs) identified by traditional PCR-based DNA sequencing. In the past five years, the rapid development and expanded use of microarray technologies, including oligonucleotide array comparative genomic hybridization and SNP genotyping arrays, as well as next-generation sequencing with “paired-end” methods, has enabled a whole-genome analysis with essentially unlimited resolution. The discovery of submicroscopic copy-number variations (CNVs) present in our genomes has changed dramatically our perspective on DNA structural variation and disease. It is now thought that CNVs encompass more total nucleotides and arise more frequently than SNPs. CNVs, to a larger extent than SNPs, have been shown to be responsible for human evolution, genetic diversity between individuals, and a rapidly increasing number of traits or susceptibility to traits; such conditions have been referred to as genomic disorders. In addition to well-known sporadic chromosomal microdeletion syndromes and Mendelian diseases, many common complex traits including autism and schizophrenia can result from CNVs. Both recombination- and replication-based mechanisms for CNV formation have been described.

Linkage analysis of the C4A/C4B copy number variation and polymorphisms of the adjacent steroid 21-hydroxylase gene in a healthy population

Genes encoding the steroid 21-hydroxylase (CYP21A2) and the complement component C4 proteins (C4A and C4B) are located in the MHC region in a strongly linked structure named RCCX module. Previous studies found that carriers of C4B gene deficiency (C4B*Q0) have higher risk for cardiovascular diseases. A potential explanation is that lacking the C4B gene may result in altered function of the neighboring CYP21A2 gene. Therefore we sequenced the CYP21A2 gene in 96 healthy individuals to identify polymorphisms and to characterize their linkage pattern. Fifty-three variations were detected including a new one which alters the TATA-box of the gene. Only three known mutations (V281L, Q318X and R479L) associated with congenital adrenal hyperplasia, were found in 7, 2 and 1 subjects, respectively. Linkage analysis revealed that some variations exhibit strong correlation with the C4 copy number polymorphism and constituents of the MHC III region. Rare alleles of three polymorphisms were identified as components of the 8.1 ancestral haplotype. Haplotyping and family study confirmed that the variant alleles of two intronic SNPs were constituents of haplotype blocks lacking the C4B gene. These results suggest that variations of CYP21A2 gene can be involved in disease associations of the 8.1 haplotype and the C4B*Q0 genotype.