Primary biliary cirrhosis (PBC) is an uncommon autoimmune disease with a homogeneous clinical phenotype that reflects incomplete disease concordance in monozygotic (MZ) twins. We have taken advantage of a unique collection consisting of genomic DNA and mRNA from peripheral blood cells of female MZ twins (n = 3 sets) and sisters of similar age (n = 8 pairs) discordant for disease. We performed a genome-wide study to investigate differences in (i) DNA methylation (using a custom tiled four-plex array containing tiled 50-mers 19,084 randomly chosen methylation sites), (ii) copy number variation (CNV) (with a chip including markers derived from the 1000 Genomes Project, all three HapMap phases, and recently published studies), and/or (iii) gene expression (by whole-genome expression arrays). Based on the results obtained from these three approaches we utilized quantitative PCR to compare the expression of candidate genes. Importantly, our data support consistent differences in discordant twins and siblings for the (i) methylation profiles of 60 gene regions, (ii) CNV of 10 genes, and (iii) the expression of 2 interferon-dependent genes. Quantitative PCR analysis showed that 17 of these genes are differentially expressed in discordant sibling pairs. In conclusion, we report that MZ twins and sisters discordant for PBC manifest particular epigenetic differences and highlight the value of the epigenetic study of twins.

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SummaryScleroderma (SSc) is a rare connective tissue disease characterized by fibrosis, microvasculopathy and autoimmune features. The role of genetics is limited in SSc, as suggested by similar concordance rates in monozygotic and dizygotic twin pairs, while environmental factors may act through epigenetic changes, as demonstrated for specific genes. Further, sex chromosome changes have been reported in SSc and may explain the female preponderance. In the present study we compared the methylation profile of all X chromosome genes in peripheral blood mononuclear cells from monozygotic twins discordant (n = 7) and concordant (n = 1) for SSc. Methylated DNA immunoprecipitations from each discordant twin pair were hybridized to a custom-designed array included 998 sites encompassing promoters of all X chromosome genes and randomly chosen autosomal genes. Biostatistical tools identified sites with an elevated probability to be consistently hypermethylated (n = 18) or hypomethylated (n = 25) in affected twins. Identified genes include transcription factors (ARX, HSFX1, ZBED1, ZNF41) and surface antigens (IL1RAPL2, PGRMC1), and pathway analysis suggests their involvement in cell proliferation (PGK1, SMS, UTP14A, SSR4), apoptosis (MTM1), inflammation (ARAF) and oxidative stress (ENOX2). In conclusion, we propose that X chromosome genes with different methylation profiles in monozygotic twin pairs may constitute candidates for SSc susceptibility.

PurposeNailfold videocapillaroscopy (NVC) identifies the microvascular hallmarks of systemic sclerosis (SSc) and vascular endothelial growth factor (VEGF) and may play a pivotal role in the associated vasculopathy. The aim of the present study was to compare NVC alterations with clinical subsets, internal organ involvement, and serum VEGF levels in a cohort of selected SSc cases.MethodsWe studied 44 patients with SSc who were evaluated within 3 months from enrollment by NVC, skin score, severity index, pulmonary function tests, carbon monoxide diffusing capacity (DLCO), echocardiography, pulmonary high-resolution computed tomography (HRCT), gastroesophageal (GE) endoscopy or manometry or X-ray, and serum autoantibodies. Serum VEGF-A levels were determined by ELISA in 72 SSc patients and 31 healthy controls.ResultsGiant capillaries were inversely correlated with age (p = 0.034, r = −0.34) and to the extent of reticular pattern at HRCT (p = 0.04, r = −0.5). Avascular areas were directly correlated with capillaroscopy skin ulcer risk index (CSURI) (p = 0.006, r = +0.4) and severity index (p = 0.004, r = +0.5). The mean capillary density was directly correlated to the ulcer number (p = 0.02, r = +0.4) and to DLCO/alveolar volume (p = 0.02, r = +0.4) and inversely correlated with severity index (p = 0.01, r = −0.4) and skin score (p = 0.02, r = −0.4). Serum VEGF levels were higher in the SSc population vs controls (p = 0.03) and inversely correlated with DLCO (p = 0.01, r =−0.4) and directly with ground-glass and reticular pattern at HRCT (p = 0.04, r = +0.4 for both).ConclusionsOur data suggest the importance of NVC not only for the diagnosis, but also for the global evaluation of SSc patients. Of note, serum VEGF levels may act as a biomarker of interstitial lung involvement.

Abstract. Primary biliary cirrhosis (PBC)is a chronic autoimmune cholestatic liver disease that manifests a latitudinal gradient in prevalence and incidence. The mechanisms leading to the initiation and perpetuation of PBC remain largely enigmatic, although it is established that a combination of genetic predisposition and environmental stimulation is required. PBC is also characterized by a high concordance rate in monozygotic twins and is considered a model autoimmune disease because of several features common to other conditions and the relatively homogeneous serological and biochemical features. From a diagnostic standpoint, PBC is characterized by the highest specificity of serum autoantibodies directed at mitochondrial proteins. Several risk factors have been suggested to be associated with PBC, including exposure to infectious agents and chemical xenobiotics that will be critically discussed in the present review article.