New variants of alpha-1-antitrypsin: structural simulations and clinical expression.

BACKGROUND: Alpha-1 antitrypsin deficiency (AATD) is characterized by reduced serum levels of the AAT protein and predisposes to liver and lung disease. The characterization at structural level of novel pathogenic SERPINA1 mutants coding for circulating AAT could provide novel insights into the mechanisms of AAT misfolding. The present study aimed to provide a practical framework for the identification and analysis of new AAT mutations, combining structural simulations and clinical data. METHODS: We analysed a total of five mutations (four not previously described) in a total of six subjects presenting moderate to severe AATD: Gly95Alafs*18, Val210Glu, Asn247Ser, Pi*S + Asp341His and Pi*S + Leu383Phe + Lys394Ile. Clinical data, genotyping and phenotyping assays, structural mapping, and conformational characterization through molecular dynamic (MD) simulations were developed and combined. RESULTS: Newly discovered AAT missense variants were localized both on the interaction surface and the hydrophobic core of the protein. Distribution of mutations across the structure revealed Val210Glu at the solvent exposed s4C strand and close to the "Gate" region. Asn247Ser was located on the accessible surface, which is important for glycan attachment. On the other hand, Asp341His, Leu383Phe were mapped close to the "breach" and "shutter" regions. MD analysis revealed the reshaping of local interactions around the investigated substitutions that have varying effects on AAT conformational flexibility, hydrophobic packing, and electronic surface properties. The most severe structural changes were observed in the double- and triple-mutant (Pi*S + Asp341His and Pi*S + Leu383Phe + Lys394Ile) molecular models. The two carriers presented impaired lung function. CONCLUSIONS: The results characterize five variants, four of them previously unknown, of the SERPINA1 gene, which define new alleles contributing to the deficiency of AAT. Rare variants might be more frequent than expected, and therefore, in discordant cases, standardized screening of the S and Z alleles needs complementation with gene sequencing and structural approaches. The utility of computational modelling for providing supporting evidence of the pathogenicity of rare single nucleotide variations is discussed.

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA.

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Utility of the Enhanced Liver Fibrosis score as a blood biomarker of pulmonary fibrosis secondary to SARS-CoV-2 pneumonia.

INTRODUCTION: SARS-CoV-2 pneumonia can lead to several sequelae, among them, pulmonary fibrosis. The Enhanced Liver Fibrosis (ELF) score is a panel of serum markers of liver fibrosis. We aimed to describe the utility of the ELF score as a biomarker of pulmonary fibrosis secondary to COVID-19 pneumonia. METHODS: Chest computed tomography (CT) scan, lung function tests (LFT) and blood analysis were obtained at three months after discharge. Data were analysed according to ELF scores and posteriorly divided into ELF tertiles. RESULTS: One hundred twenty-nine patients were recruited; of these, 85.7% presented bilateral pneumonia at diagnosis of SARS-CoV2 infection. At 3 months after discharge, CT scan was available in 123 patients, 73 (59.3%) of whom presented parenchymal lung abnormalities (PLA) and LFT showed impairment in 28 (22.7%) patients. Globally, the most frequent PLA was ground glass opacities (50%), followed by bronchial thickening (26.8%), reticular pattern (19.5%), consolidation (10.5%) and air bronchogram sign (7.3%). Radiological findings were only significant in the higher tertile of ELF, with a reticular pattern as the predominant PLA (p = 0.002). Moreover, patients with both PLA and LFT impairment, presented a trend towards higher levels of ELF compared with patients with only PLA or LFT impairment, or no impairment (9.9 (0.7) vs 9.6 (0.8), 9.1 (1.1) and 9.3 (0.7); p = 0.054). CONCLUSION: Patients with both PLA and LFT alteration at 3 months after SARS-CoV-2 pneumonia had higher ELF scores. The ELF score may be useful to identify patients with risk of fibrotic changes after SARS-CoV-2 pneumonia.

Conservation and variability of hepatitis B core at different chronic hepatitis stages.

BACKGROUND: Since it is currently not possible to eradicate hepatitis B virus (HBV) infection with existing treatments, research continues to uncover new therapeutic strategies. HBV core protein, encoded by the HBV core gene (HBC), intervenes in both structural and functional processes, and is a key protein in the HBV life cycle. For this reason, both the protein and the gene could be valuable targets for new therapeutic and diagnostic strategies. Moreover, alterations in the protein sequence could serve as potential markers of disease progression. AIM: To detect, by next-generation sequencing, HBC hyper-conserved regions that could potentially be prognostic factors and targets for new therapies. METHODS: Thirty-eight of 45 patients with chronic HBV initially selected were included and grouped according to liver disease stage [chronic hepatitis B infection without liver damage (CHB, n = 16), liver cirrhosis (LC, n = 5), and hepatocellular carcinoma (HCC, n = 17)]. HBV DNA was extracted from patients' plasma. A region between nucleotide (nt) 1863 and 2483, which includes HBC, was amplified and analyzed by next-generation sequencing (Illumina MiSeq platform). Sequences were genotyped by distance-based discriminant analysis. General and intergroup nt and amino acid (aa) conservation was determined by sliding window analysis. The presence of nt insertion and deletions and/or aa substitutions in the different groups was determined by aligning the sequences with genotype-specific consensus sequences. RESULTS: Three nt (nt 1900-1929, 2249-2284, 2364-2398) and 2 aa (aa 117-120, 159-167) hyper-conserved regions were shared by all the clinical groups. All groups showed a similar pattern of conservation, except for five nt regions (nt 1946-1992, 2060-2095, 2145-2175, 2230-2250, 2270-2293) and one aa region (aa 140-160), where CHB and LC, respectively, were less conserved (P < 0.05). Some group-specific conserved regions were also observed at both nt (2306-2334 in CHB and 1935-1976 and 2402-2435 in LC) and aa (between aa 98-103 in CHB and 28-30 and 51-54 in LC) levels. No differences in insertion and deletions frequencies were observed. An aa substitution (P79Q) was observed in the HCC group with a median (interquartile range) frequency of 15.82 (0-78.88) vs 0 (0-0) in the other groups (P < 0.05 vs CHB group). CONCLUSION: The differentially conserved HBC and HBV core protein regions and the P79Q substitution could be involved in disease progression. The hyper-conserved regions detected could be targets for future therapeutic and diagnostic strategies.