Reliable and rapid characterization of functional FCN2 gene variants reveals diverse geographical patterns

Ficolin-3 and MASP-2 gene variants in Siberian arctic populations: Summarized evidence of selective pressure for the high frequency of lectin complement pathway deficiency

Herewith, we provide novel original data about the prevalence of FCN3 rs532781899 and MASP2 rs72550870 variants among the newborns of aboriginal Siberian Arctic populations (Nenets and Dolgan-Nganasans) and Russians of East Siberia. This novel data has been analysed along with the genetic data about other proteins of the lectin pathway of the complement system (mannose-binding lectin and ficolin-2) obtained earlier. A total of 926 specimens of dried blood spots of the newborns were genotyped. The newborns represented four populations: Nenets, Dolgan-Nganasans, Mixed aboriginal population, and Russians (Caucasians) to study the prevalence of single nucleotide polymorphisms of FCN3 rs532781899 and MASP2 rs72550870. The prevalence of the deletion allele of the rs532781899 variant in the FCN3 gene associated with the decreased production of ficolin-3 was found to be increased in Russians compared to the Nenets aboriginal populations (P = .002). The prevalence of the rs72550870*G allele in the MASP2 gene associated with low serum protease activity was found to be increased in Russians compared with Nenets and Dolgan-Nganasans (P < .001 and P = .03, respectively). The results of the current study and our previous findings corroborate with a hypothesis that human evolution has been directed toward the accumulation of genotypes associated with low activity of the lectin complement activation pathway.

Selected SNPs of FCN2 Associated with Chronic Tonsillitis in the Polish Adult Population

Chronic tonsillitis is a problem related to bacterial and viral infections. Ficolins play a key role in the defence against various pathogens. In the present study, we investigated the associations between the selected single nucleotide polymorphisms (SNPs) of the FCN2 gene and chronic tonsillitis in the Polish population. The study included 101 patients with chronic tonsillitis and 101 healthy individuals. The selected SNPs of FCN2 (rs3124953, rs17514136 and rs3124954) were genotyped using TaqMan SNP Genotyping Assays (Applied Biosystem, Foster City, CA, USA). The analysis of rs17514136 and rs3124953 showed no significant differences in genotype frequencies between the chronic tonsillitis patients and controls (p > 0.01). The CT genotype of rs3124954 was significantly more frequent, while the CC genotype was less frequent in chronic tonsillitis patients (p = 0.003 and p = 0.001, respectively). The frequency of the A/G/T haplotype (rs17514136/rs3124953/rs3124954) was significantly more common in chronic tonsillitis patients (p = 0.0011). Moreover, the FCN2 CT genotype of rs3124954 was associated with a higher risk of chronic tonsillitis, while the CC genotype of rs3124954 decreased this risk. Our findings demonstrate that FCN2 rs3124954 may be associated with chronic tonsillitis in the Polish adult population.

Pattern Recognition Molecules of Lectin Complement Pathway in Ischemic Stroke

Purpose

The current study aimed to investigate in an Armenian population the levels of pattern recognition molecules (PRMs) of lectin complement pathway (LCP), MBL (mannan-binding lectin) and M-ficolin in plasma in ischemic stroke (IS), and the possible association of 11 single nucleotide polymorphisms (SNPs) in MBL2, FCN1 and FCN2 genes.

Patients and Methods

A total of 122 patients with IS and 150 control subjects were included in this study. Immunofluorometric assays (TRIFMAs) and real-time polymerase chain reactions with TaqMan probes were conducted.

Results

According to the results, the levels of M-ficolin in IS patients are significantly higher than in control subjects, and the MBL2 rs11003125 and rs12780112 SNPs, as well as MBL2 rs12780112*T and FCN1 rs10120023*T minor alleles (MAs) are negatively associated with the risk of IS. Further, MBL2 rs11003125 and rs1800450 SNPs and the carriage of their MAs, as well as FCN1 rs2989727 SNP and the carriage of FCN1 rs10120023*T MA significantly alter plasma MBL and M-ficolin levels in IS patients, respectively. Five common haplotypes in MBL2 gene and three common haplotypes in FCN1 and FCN2 genes were revealed, among which CGTC was negatively associated with IS and decreasing MBL plasma levels in IS.

Conclusion

In conclusion, we suggest that LCP PRMs are associated with the risk of developing IS, and may also participate in pathological events leading to post-ischemic brain damage. This study emphasizes the important contribution of alterations of LCP PRMs on genomic and proteomic levels to the pathomechanisms of ischemic stroke, at least in an Armenian population.

Novel FCN2 Variants and Haplotypes are Associated with Rheumatic Heart Disease

Ficolins are pattern recognition molecules that are involved in innate immune defense. Ficonin-2 (FCN2) has a specific affinity for lipoteichoic acid present in the cell wall of Streptococcus pyogenes, an etiological agent for rheumatic heart disease (RHD). We have estimated FCN2 serum levels and analyzed the functional variants of FCN2 in 400 RHD patients, 617 healthy controls, and 581 individuals belonged to various ethnic populations, who are inhabited in various geographical regions of India. Our study revealed that the FCN2 -986A and +6359T alleles were the risk factors for RHD susceptibility (p = 0.0007 for -986G>A; p = 0.0004 for +6359C>T). The haplotype AGGT (p = 0.0024) was observed to be a risk factor for RHD susceptibility, and the haplotype GGAC (p = 0.002) was found to confer protection against RHD. The level of serum FCN2 was significantly higher in controls (p < 0.0001) and in controls with GGAC haplotypes (p < 0.0001). The frequency of the risk alleles -986A and +6359T was found to be more prevalent in Northern and North-Western (Indo-European) India. The protective GGAC haplotype was found more prevalent in Eastern (Tibeto-Burman) and South-Western (Dravidian) India. Alleles -986A and +6359T were in positive correlation with the prevalence of RHD (regression coefficient = 1.84 and 1.94, respectively), whereas GGAC haplotype was in negative correlation with prevalence of RHD (regression coefficient = -1.71). In conclusion, we found that low level of serum ficolin-2 is significantly associated with RHD. Further, FCN2 -986A and +6359T alleles and AGGT haplotype are associated with increased susceptibility to RHD, while GGAC haplotype is associated with moderate protection against RHD.

Association of ficolin-2 (FCN2) functional polymorphisms and protein levels with rheumatic fever and rheumatic heart disease: relationship with cardiac function

Introduction

A role for ficolin (FCN) 2 gene polymorphisms in the pathogenesis of recurrent severe streptococcal infections and rheumatic carditis has been suggested. The aim of the study was to evaluate a possible relationship between single nucleotide polymorphisms located at positions -602 and -4 of the FCN2 gene and FCN2 serum levels and risk of development of rheumatic fever (RF) and rheumatic heart disease (RHD).

Material and methods

Seventy-seven Caucasian Egyptian patients with RF were recruited with a control group of 43 healthy subjects. DNA was extracted for analysis of the FCN2 gene at positions -602 and -4 and serum protein level was measured by ELISA.

Results

FCN2 AA genotype at the -4 position was more frequently observed in RF and RHD patients, as compared to healthy subjects (p = 0.005 and p = 0.013, respectively); furthermore, the A allele was identified as a possible risk factor for the development of RF (p = 0.023, OR = 1.852, 95% CI: 1.085–3.159). The haplotype –602/–4 G/A, which was associated with low median levels of L-ficolin, was observed more frequently in the RF group when compared to the healthy subjects (74/162, 48.1% vs. 29/420, 33.7%, OR = 1.834, 95% CI: 1.034–3.252, p = 0.038). Low serum ficolin-2 level was associated with ESV and EDV increases. FCN 2 level was significantly lower with AA genotypes than GG+AG genotypes of the -4 position (56.68 ±17.90 vs. 66.05 ±18.79, p = 0.008).

Conclusions

Polymorphisms linked to low levels of L-ficolin may render an individual at risk of recurrent and/or severe streptococcal infection. The -4 AA genotype and -602/-4 G/A haplotype are possible risk factors for the development of carditis.

Ficolin-2 Gene rs7851696 Polymorphism is Associated with Delayed Graft Function and Acute Rejection in Kidney Allograft Recipients

Ficolin-2 is an activator of the complement system that acts via the lectin pathway. Complement activation plays a substantial role in the renal injury inherent to kidney transplantation. In this study, we examined the associations between ficolin-2 gene polymorphisms in exon 8 and kidney allograft function. This study comprised 270 Caucasian deceased-donor renal transplant recipients. The following parameters were recorded in each case: delayed graft function (DGF), acute rejection (AR), and chronic allograft dysfunction. Among patients with DGF, we observed a significantly increased frequency of rs7851696 GT and TT genotypes as well as T allele (TT + GT vs GG OR 1.98, 95% CI 1.12-3.48, p = 0.02; T vs G OR 2.08, 95% CI 1.27-3.41, p = 0.005). There was also an increased frequency of rs4521835 GG and TG genotypes as well as G alleles; however, these differences were on the borderline of statistical significance (GG + TG vs TT, OR 1.75, 95% CI 0.98-3.12, p = 0.07; G vs T OR 1.45, 95% CI 1.00-2.09, p = 0.050). In addition, we observed an increased frequency of acute allograft rejection in carriers of ficolin-2 rs7851696 T alleles on the borderline of statistical significance (TT + GT vs GG OR 1.75, 95% CI 0.97-3.16, p = 0.08), but the frequency of T allele was significantly higher in patients with AR (T vs G OR 1.71, 95% CI 1.02-2.87, p = 0.048). The results of our study suggest that ficolin-2 rs7851696 gene polymorphism influences kidney allograft functions, with T allele increasing the risk of DGF and AR.

MBL2 and FCN2 gene polymorphisms in a cohort of Italian children with rheumatic fever: A case-control study

BACKGROUND

Mannose-binding lectins and human ficolins are pattern-recognition proteins involved in innate immunity. A role for MBL2 and FCN2 gene polymorphisms in the pathogenesis of recurrent severe streptococcal infections and rheumatic carditis has been suggested.

OBJECTIVES

The aim of this study is to evaluate the presence of MBL2 and FCN2 gene polymorphisms (SNPs) in children with a history of rheumatic fever (RF) and to investigate their possible role in RF clinical presentation and disease course.

METHODS

A total of 50 Caucasian patients with RF were recruited with a control group of 52 healthy children. DNA was extracted for analysis of MBL2 gene (exon 1, codons: 52, 54, and 57) and FCN2 gene (promoter region at position -986, -602, and -4).

RESULTS

The FCN2 AG genotype at the -986 position was more frequently observed in patients, as compared to healthy subjects (p = 0.006); furthermore, the A allele was identified as a possible risk factor for the development of RF (OR = 7.14, CI: 2.439-20.89). Conversely, the GG genotype at the same position was observed more frequently in the control group and can be considered a protective factor for the development of the disease (p = 0.001, OR = 8.37, 95% CI: 2.763-25.33). In addition, the FCN2 GG and AG genotypes in the -4 position were also found to be protective factors for the development of RF and for carditis respectively (OR = 3.32, CI: 1.066-10.364; OR = 0.15, 95% CI: 0.037-0.566). Finally, the AA genotype in the -602 position was associated with a late onset of RF (p = 0.006). The analysis of the MBL2 gene only resulted in a higher frequency of the AA genotype on position 57 in controls as compared to patients (p = 0.025).

CONCLUSIONS

This is the first study evaluating the FCN2 gene polymorphisms in patients with RF and rheumatic carditis finding a protective effect of -986 GG and -4 GG genotypes in the development of RF and the -4 AG genotype for the development of carditis. Our data do not support a possible role for MBL2 polymorphisms in the pathogenesis and in the clinical manifestations of RF.

FCN2 c.772G>T polymorphism is associated with chronic adenoiditis and/or tonsillitis, but not -4 A>G and -602 G>A

OBJECTIVE

Ficolins are complement activating peptides that play a role in the initial host defense against infectious pathogens. In the present study, we investigated the relationship between single nucleotide polymorphisms (SNPs) in the ficolin 2 gene (FCN2) and chronic adenotonsillitis in pediatric cases.

STUDY DESIGN

Case-control study.

METHODS

A total of 101 pediatric patients diagnosed with chronic adenotonsillitis and 100 healthy children were enrolled in the study. Genotypes of FCN2 promoter SNPs - 602 G>A and -4 A>G, and the exonic SNP c.772G>T were determined by light SNP assay after realtime PCR analysis using genomic DNA samples obtained from peripheral blood samples of all participants.

RESULTS

Of the 101 chronic tonsillitis patients, 38 were girls and 63 were boys; the mean age was 5.2 ± 2.3 years. The c.772G>T SNP frequency was significantly higher in chronic adenotonsillitis cases compared to the control group (p = 0.00); however, no significant difference was determined at positions -602 G>A or -4 A>G (p > 0.05).

CONCLUSIONS

The FCN2 c.772G>T genotype appears to be associated with predisposition to chronic adenotonsillitis in the pediatric age group. This nucleotide change is likely to influence the level of gene expression and contribute to the development of disease.

Frequency and distribution of FCN2 and FCN3 functional variants among MBL2 genotypes

The six types of pattern recognition molecules (PRMs) that initiate complement via the lectin pathway (LP) comprise collectins and ficolins. The importance of having various PRMs to initiate the LP is currently unclear. Mannan-binding lectin (MBL) is a collectin member of the LP PRMs. MBL deficiency is common with mild clinical consequence. Thus, the lack of MBL may be compensated for by the other PRMs. We hypothesized that variants FCN2 + 6424 and FCN3 + 1637delC that cause gene-dose-dependent reduction in ficolin-2 and ficolin-3 levels, respectively, may be rare in MBL-deficient individuals due to the importance of compensation within the LP. The aim of this study was to investigate the distribution and frequency of these variants among MBL2 genotypes in healthy subjects. The allele frequency of FCN2 + 6424 and FCN3 + 1637delC was 0.099 and 0.015, respectively, in the cohort (n = 498). The frequency of FCN2 + 6424 tended to be lower among MBL-deficient subjects (n = 53) than among MBL-sufficient subjects (n = 445) (0.047 versus 0.106, P = 0.057). In addition, individuals who were homozygous for FCN2 + 6424 were sufficient MBL producers. The frequency of FCN3 + 1637delC did not differ between the groups. The frequency of FCN2 + 6424 was similar in FCN3 + 1637delC carriers (n = 15) versus wild type (n = 498). Furthermore, subjects that were heterozygote carriers of both FCN2 + 6424 and FCN3 + 1637delC were sufficient MBL producers. In conclusion, FCN2 + 6424 carriers with MBL deficiency tend to be rare among healthy individuals. MBL-deficient individuals with additional LP PRM defects may be at risk to morbidity.

Association of the FCN2 Gene Single Nucleotide Polymorphisms with Susceptibility to Pulmonary Tuberculosis

Ficolin-2 (FCN2) is an innate immune pattern recognition molecule that can activate the complement pathway, opsonophagocytosis, and elimination of the pathogens. The present study aimed to investigate the association of the FCN2 gene single nucleotide polymorphisms (SNPs) with susceptibility to pulmonary tuberculosis (TB). A total of seven SNPs in exon 8 (+6359 C>T and +6424 G>T) and in the promoter region (-986 G>A, -602 G>A, -557 A>G, -64 A>C and -4 A>G) of the FCN2 gene were genotyped using the PCR amplification and DNA sequencing methods in the healthy controls group (n = 254) and the pulmonary TB group (n = 282). The correlation between SNPs and pulmonary TB was analyzed using the logistic regression method. The results showed that there were no significant differences in the distribution of allelic frequencies of seven SNPs between the pulmonary TB group and the healthy controls group. However, the frequency of the variant homozygous genotype (P = 0.037, -557 A>G; P = 0.038, -64 A>C; P = 0.024, +6424 G>T) in the TB group was significantly lower than the control group. After adjustment for age and gender, these variant homozygous genotypes were found to be recessive models in association with pulmonary TB. In addition, -64 A>C (P = 0.047) and +6424 G>T (P = 0.03) were found to be codominant models in association with pulmonary TB. There was strong linkage disequilibrium (r2 > 0.80, P < 0.0001) between 7 SNPs except the -602 G>A site. Therefore, -557 A>G, -64 A>C and +6424 G>T SNPs of the FCN2 gene were correlated with pulmonary TB, and may be protective factors for TB. This study provides a novel idea for the prevention and control of TB transmission from a genetics perspective.

New insights into the role of ficolins in the lectin pathway of innate immunity

In the innate immune system, a variety of recognition molecules provide the first-line host defense to prevent infection and maintain endogenous homeostasis. Ficolin is a soluble recognition molecule, which senses pathogen-associated molecular patterns on microbes and aberrant sugar structures on self-cells. It consists of a collagen-like stalk and a globular fibrinogen-like domain, the latter binding to carbohydrates such as N-acetylglucosamine. Ficolins have been widely identified in animals from higher invertebrates to mammals. In mammals, ficolins form complexes with mannose-binding lectin-associated serine proteases (MASPs), and ficolin-MASP complexes trigger complement activation via the lectin pathway. Once activated, complement mediates many immune responses including opsonization, phagocytosis, and cytokine production. Although the precise function of each ficolin is still under investigation, accumulating information suggests that ficolins have a crucial role in host defense by recognizing a variety of microorganisms and interacting with effector proteins.

Mannose binding lectin and susceptibility to rheumatoid arthritis in Brazilian patients and their relatives

Introduction

Rheumatoid arthritis (RA) is a commonly occurring systemic inflammatory auto immune disease and is believed to be associated with genetic factors. The innate immune complement protein Mannose binding lectin (MBL) and their MBL2 genetic variants are associated with different infectious and autoimmune diseases.

Methods

In a Brazilian cohort, we aim to associate the functional role of circulating MBL serum levels and MBL2 variants in clinically classified patients (n = 196) with rheumatoid arthritis including their relatives (n = 200) and ethnicity matched healthy controls (n = 200). MBL serum levels were measured by ELISA and functional MBL2 variants were genotyped by direct sequencing.

Results

The exon1+54 MBL2*B variant was significantly associated with an increased risk and the reconstructed haplotype MBL2*LYPB was associated with RA susceptibility. Circulating serum MBL levels were observed significantly lower in RA patients compared to their relatives and controls. No significant contribution of MBL levels were observed with respect to functional class, age at disease onset, disease duration and/or other clinical parameters such as nodules, secondary Sjögren syndrome, anti-CCP and rheumatoid factor. Differential distribution of serum MBL levels with functional MBL2 variants was observed in respective RA patients and their relatives.

Conclusions

Our results suggest MBL levels as a possible marker for RA susceptibility in a Brazilian population.

Risk of infection and sepsis in severely injured patients related to single nucleotide polymorphisms in the lectin pathway

BACKGROUND

Infectious complications remain a serious threat to patients with multiple trauma. Susceptibility and response to infection is, in part, heritable. The lectin pathway plays a major role in innate immunity. The aim of this study was to assess whether single nucleotide polymorphisms (SNPs) in three key genes within the lectin pathway affect susceptibility to infectious complications in severely injured patients.

METHODS

A prospective cohort of severely injured patients admitted to a level I trauma centre between January 2008 and April 2011 were genotyped for SNPs in MBL2 (mannose-binding lectin 2), MASP2 (MBL-associated serine protease 2) and FCN2 (ficolin 2). Association of genotype with prevalence of positive culture findings and infection was tested by χ(2) and logistic regression analysis.

RESULTS

A total of 219 patients were included, of whom 112 (51·1 per cent) developed a positive culture from sputum, wounds, blood or urine. A systemic inflammatory response syndrome (SIRS) developed in 139 patients (63·5 per cent), sepsis in 79 (36·1 per cent) and septic shock in 37 (16·9 per cent). Patients with a MBL2 exon 1 variant allele were more prone to positive wound cultures (odds ratio (OR) 2·51, 95 per cent confidence interval 1·12 to 5·62; P = 0·025). A MASP2 Y371D DD genotype predisposed to SIRS (OR 4·78, 1·06 to 21·59; P = 0·042) and septic shock (OR 2·53, 1·12 to 4·33; P = 0·003). A FCN2 A258S AS genotype predisposed to positive wound cultures (OR 3·37, 1·45 to 7·85; P = 0·005) and septic shock (OR 2·18, 1·30 to 4·78; P = 0·011).

CONCLUSION

Severely injured patients with SNPs in MBL2, MASP2 Y371D and FCN2 A258S of the lectin pathway of complement activation are significantly more susceptible to positive culture findings, and to infectious complications, SIRS and septic shock than patients with a wildtype genotype.

A trivial role of STAT4 variant in chronic hepatitis B induced hepatocellular carcinoma

Two polymorphisms in the STAT4 and HLA-DQ loci were more recently reported to associate with chronic hepatitis B (CHB) induced hepatocellular carcinoma (HCC). We utilised an independent Vietnamese cohort of clinically classified HBV patients of chronic hepatitis B carriers (n=206), liver cirrhosis (n=222) and hepatocellular carcinoma (n=239) and assessed the influence of the reported variants. The STAT4 variant (rs7574865) was marginally associated with HCC susceptibility in CHB carriers in allelic and recessive genetic models (OR=0.84, 95%CI=0.7-0.99, P=0.048 and OR=0.7, 95%CI=0.5-0.99, P=0.047). No significant association between the studied variant with several clinical parameters such as liver enzymes (ALT, AST), total and direct bilirubin, AFP, HBV genotype and viral loads were observed. Our study highlights the reported variant to be a trivial factor and possibly other confounding factors may regulate STAT4 expression during HCC development.

Swierzko A, Cedzynski M. Cost-effective procedures for genotyping of human FCN2 gene single nucleotide polymorphisms

L-ficolin (ficolin-2) is a complement-activating pattern-recognition lectin taking part in the innate immune response. Both its serum concentration and sugar binding capacity are influenced by single nucleotide polymorphisms (SNP) of the corresponding FCN2 gene. Cost-effective and simple procedures, based on polymerase chain reaction (PCR) or PCR-restriction fragment length polymorphism for an investigation of four FCN2 SNPs are proposed: -64 A > C (rs7865453), -4 A > G (rs17514136; both located in the promoter region), +6359 C > T (rs17549193), +6424 G > T (rs7851696; both in exon 8). Variant alleles of -64 and +6424 (in strong linkage disequlibrium) are known to be associated with low L-ficolin level or activity. In contrast, variant alleles at positions -4 and +6359 (also in strong linkage disequlibrium) correspond to higher values. Since several L-ficolin clinical associations have been reported, FCN2 genotyping seems to be a valuable tool for disease association studies.

Association of L-ficolin levels and FCN2 genotypes with chronic Chagas disease

BACKGROUND

L-ficolin (encoded by FCN2) binds to acetylated sugar moieties of many pathogens, including Trypanosoma cruzi, promoting their phagocytosis and lysis by the complement system.

METHODS

We investigated L-ficolin levels in 160 T. cruzi infected patients with chronic Chagas disease and 71 healthy individuals, and FCN2 polymorphisms (-986 G>A, -602 G>A, and -4 A>G in the promoter and A258S in exon 8) in 243 patients, being 88 indeterminate (asymptomatic), 96 with cardiac, 23 with digestive and 33 with cardiodigestive manifestations (two were unspecified) and 305 controls (135 for A258S).

RESULTS

Patients presented lower L-ficolin plasma levels than controls (p<0.0001). Among the different groups of cardiac commitment, individuals with moderate forms had higher L-ficolin levels than the severe forms (P = 0.039). Lower L-ficolin levels were found associated with the 258S variant in the patients (P = 0.034). We found less -4A/G heterozygotes in the cardiac patients, than in the controls (OR = 0.56 [95% CI = 0.33-0.94], P = 0.034). Heterozygote -4A/G genotypes with the 258S variant and 258SS homozygotes were nevertheless more frequent among cardiodigestive patients than in controls (OR = 14.1 [95% CI = 3.5-56.8], P = 0.0001) and in indeterminate patients (OR = 3.2 [95% CI = 1.1-9.4], P = 0.037). We also found an association of the allelic frequency of the 258S variant with cardiodigestive Chagas disease compared to controls (OR = 2.24 [95% CI = 1.1-4.5], P = 0.037). Thus, decreased patient levels of L-ficolin reflect not only protein consumption due to the disease process, but also the higher frequency of the 258S variant in patients with cardiodigestive symptoms.

CONCLUSION

The very first study on Brazilian cohort associates both L-ficolin plasma levels and FCN2 variants to Chagas disease and subsequent disease progression. The prognostic value of L-ficolin levels and the FCN2*A258S polymorphism should be further evaluated in other settings.