Ficolin-1 and ficolin-3 polymorphisms and susceptibility to rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease, which compromises the synovial membrane resulting in chronic inflammation. Ficolins are key proteins of the lectin pathway of complement able to recognize pathogen-associated molecular patterns, apoptotic cells, and cellular debris mediating the clearance by phagocytes. High ficolin-1 and ficolin-3 levels have been observed in RA patients, however, the influence of polymorphisms in the FCN1 gene in RA is not completely established, while no study evaluated FCN3 gene polymorphisms in RA to date. We investigated the influence of FCN1 and FCN3 gene polymorphisms in the susceptibility and clinical presentation of RA. A total of 148 patients with RA and up to 160 controls from Southern Brazil were genotyped by sequence-specific PCR (PCR-SSP) for five FCN1 promoter polymorphisms (rs2989727, rs10120023, rs17039495, rs10117466, and rs10858293) and three FCN3 gene variants (rs532781899, rs28362807, and rs4494157). The FCN1 g.-542GG (rs10120023) genotype and g.-542G allele, were associated with increased susceptibility to RA (p = .025, OR = 1.69 [1.07–2.69]; p = .041, OR = 1.47 [1.02–2.12], respectively) and related to decreased FCN1 gene expression in whole blood (p A] polymorphism in the promoter region might contribute to RA susceptibility, probably by impacting FCN1 gene expression

Association of Mannose-Binding Lectin Gene Polymorphism but Not of Mannose-Binding Serine Protease 2 with Chronic Severe Aortic Regurgitation of Rheumatic Etiology▿

N-Acetylglucosamine (GlcNAc) is the major immunoepitope of group A streptococcal cell wall carbohydrates. Antistreptococcal antibodies cross-reactive with anti-GlcNAc and laminin are present in sera of patients with rheumatic fever. The cross-reactivity of these antibodies with human heart valvular endothelium and the underlying basement membrane has been suggested to be a possible cause of immune-mediated valve lesion. Mannose-binding lectin (MBL) encoded by the MBL2 gene, a soluble pathogen recognition receptor, has high affinity for GlcNAc. We postulated that mutations in exon 1 of the MBL2 gene associated with a deficient serum level of MBL may contribute to chronic severe aortic regurgitation (AR) of rheumatic etiology. We studied 90 patients with severe chronic AR of rheumatic etiology and 281 healthy controls (HC) for the variants of the MBL2 gene at codons 52, 54, and 57 by using a PCR-restriction fragment length polymorphism-based method. We observed a significant difference in the prevalence of defective MBL2 alleles between patients with chronic severe AR and HC. Sixteen percent of patients with chronic severe AR were homozygotes or compound heterozygotes for defective MBL alleles in contrast to 5% for HC (P = 0.0022; odds ratio, 3.5 [95% confidence interval, 1.6 to 7.7]). No association was detected with the variant of the MASP2 gene. Our study suggests that MBL deficiency may contribute to the development of chronic severe AR of rheumatic etiology

Association of a new <i>FCN3</i> haplotype with high ficolin-3 levels in leprosy

<div><p>Leprosy is a chronic inflammatory disease caused by <i>Mycobacterium leprae</i> that mainly affects the skin and peripheral nervous system, leading to a high disability rate and social stigma. Previous studies have shown a contribution of genes encoding products of the lectin pathway of complement in the modulation of the susceptibility to leprosy; however, the ficolin-3/<i>FCN3</i> gene impact on leprosy is currently unknown. The aim of the present study was to investigate if <i>FCN3</i> polymorphisms (rs532781899: <i>g</i>.<i>1637delC</i>, rs28362807: <i>g</i>.<i>3524_3532insTATTTGGCC</i> and rs4494157: <i>g</i>.<i>4473C>A</i>) and ficolin-3 serum levels play a role in the susceptibility to leprosy. We genotyped up to 190 leprosy patients (being 114 (60%) lepromatous), and up to 245 controls with sequence-specific PCR. We also measured protein levels using ELISA in 61 leprosy and 73 controls. <i>FCN3</i> polymorphisms were not associated with disease, but ficolin-3 levels were higher in patients with <i>FCN3 *2B1</i> (C<i>ins</i>A) haplotype (p = 0.032). Median concentration of ficolin-3 was higher in leprosy <i>per se</i> (26034 ng/mL, p = 0.005) and lepromatous patients (28295 ng/mL, p = 0.016) than controls (18231 ng/mL). In addition, high ficolin-3 levels (>33362 ng/mL) were more common in leprosy <i>per se</i> (34.4%) and in lepromatous patients (35.5%) than controls (19.2%; p = 0.045 and p = 0.047, respectively). Our results lead us to suggest that polymorphisms in the <i>FCN3</i> gene cooperate to increase ficolin-3 concentration and that it might contribute to leprosy susceptibility by favoring <i>M</i>. <i>leprae</i> infection.</p></div

Linkage disequilibrium between <i>FCN3</i> single nucleotide polymorphisms.

<p>LD was calculated based on the data for controls and leprosy patients. Black squares represent high LD and white low LD as measured by the correlation coefficient (r²) between sites, which values are shown inside of the squares. SNP identifiers are indicated on the abscissas.</p

Schematic representation of the regulatory intronic region of the <i>FCN3</i> gene.

<p>Introns 5 and 7 contain many potential methylation sites (CpG islands that may act as enhancers to transcription initiation), H3K27ac and H3K4me1 histone modifications (known to flank active enhancers) and sites to transcription factors known to regulate cell activation. CTCF—CCCTC-binding factor and SPI1—Spleen focus forming virus (SFFV) Proviral Integration 1, are the most evident regulatory proteins that may bind to intron 5 and 7, respectively, data from ENCODE [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005409#pntd.0005409.ref037" target="_blank">37</a>]. SNPs investigated in the present work are indicated by the red arrows. The insertion allele in intron 5 (<i>g</i>.<i>3524_3532insTATTTGGCC</i>) and the <i>A</i> at position +4473 in intron 7 (<i>g</i>.<i>4473A</i>), may increase enhancer activity in response to inflammation signals, increasing gene transcription. Exons (blue boxes) and introns are drawn to scale.</p

Phylogenetic tree of <i>FCN3</i> haplotypes.

<p>The maximum parsimony tree was rooted on the haplotype shared with <i>Pan troglodytes</i> (ENSPTRT00000000796), named as *<i>1</i>, and the derived haplotype as *<i>2</i>, following the schema numerals/letters/ numerals, if they diverge further [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005409#pntd.0005409.ref030" target="_blank">30</a>]. Recombinants are named according to the most common inferred parental haplotypes, separated by a dot [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005409#pntd.0005409.ref031" target="_blank">31</a>]. SNPs in haplotypes were ordered according to their chromosomal position. *Allelic frequency in the African population, from the 1000 Genomes project [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005409#pntd.0005409.ref014" target="_blank">14</a>].</p