Branco Claudia C, Gomes Cidália T, De Fez Laura, Bulhões Sara, Brilhante Maria José, Pereirinha Tânia, Cabral Rita, Rego Ana Catarina, Fraga Cristina, Miguel António G, Brasil Gracinda, Macedo Paula, Mota-Vieira Luisa
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal; Instituto Gulbenkian de Ciência, Oeiras, Portugal; BioISI - Biosystems & Integrative Sciences Institute, Faculty of Sciences, University of Lisboa, Lisboa, Portugal.
Molecular Genetics and Pathology Unit, Hospital of Divino Espirito Santo of Ponta Delgada, EPE, São Miguel Island, Azores, Portugal.
PLoS One. 2015 Oct 26;10(10):e0140228. doi: 10.1371/journal.pone.0140228. eCollection 2015.
Iron overload is associated with acquired and genetic conditions, the most common being hereditary hemochromatosis (HH) type-I, caused by HFE mutations. Here, we conducted a hospital-based case-control study of 41 patients from the São Miguel Island (Azores, Portugal), six belonging to a family with HH type-I pseudodominant inheritance, and 35 unrelated individuals fulfilling the biochemical criteria of iron overload compatible with HH type-I. For this purpose, we analyzed the most common HFE mutations- c.845G>A [p.Cys282Tyr], c.187C>G [p.His63Asp], and c.193A>T [p.Ser65Cys]. Results revealed that the family's HH pseudodominant pattern is due to consanguineous marriage of HFE-c.845G>A carriers, and to marriage with a genetically unrelated spouse that is a -c.187G carrier. Regarding unrelated patients, six were homozygous for c.845A, and three were c.845A/c.187G compound heterozygous. We then performed sequencing of HFE exons 2, 4, 5 and their intron-flanking regions. No other mutations were observed, but we identified the -c.340+4C [IVS2+4C] splice variant in 26 (74.3%) patients. Functionally, the c.340+4C may generate alternative splicing by HFE exon 2 skipping and consequently, a protein missing the α1-domain essential for HFE/ transferrin receptor-1 interactions. Finally, we investigated HFE mutations configuration with iron overload by determining haplotypes and genotypic profiles. Results evidenced that carriers of HFE-c.187G allele also carry -c.340+4C, suggesting in-cis configuration. This data is corroborated by the association analysis where carriers of the complex allele HFE-c.[187C>G;340+4T>C] have an increased iron overload risk (RR = 2.08, 95% CI = 1.40-2.94, p<0.001). Therefore, homozygous for this complex allele are at risk of having iron overload because they will produce two altered proteins--the p.63Asp [c.187G], and the protein lacking 88 amino acids encoded by exon 2. In summary, we provide evidence that the complex allele HFE-c.[187C>G;340+4T>C] has a role, as genetic predisposition factor, on iron overload in the São Miguel population. Independent replication studies in other populations are needed to confirm this association.
铁过载与获得性和遗传性疾病相关，最常见的是由HFE突变引起的I型遗传性血色素沉着症（HH）。在此，我们对来自圣米格尔岛（葡萄牙亚速尔群岛）的41名患者进行了一项基于医院的病例对照研究，其中6名属于具有I型HH假显性遗传的家族，35名无亲缘关系的个体符合与I型HH相符的铁过载生化标准。为此，我们分析了最常见的HFE突变——c.845G>A [p.Cys282Tyr]、c.187C>G [p.His63Asp] 和c.193A>T [p.Ser65Cys]。结果显示，该家族的HH假显性模式是由于HFE - c.845G>A携带者的近亲结婚，以及与一名携带 - c.187G的无亲缘关系配偶结婚所致。对于无亲缘关系的患者，6名是c.845A纯合子，3名是c.845A/c.187G复合杂合子。然后，我们对HFE外显子2、4、5及其内含子侧翼区域进行了测序。未观察到其他突变，但我们在26名（74.3%）患者中鉴定出了 - c.340 + 4C [IVS2 + 4C] 剪接变体。在功能上，c.340 + 4C可能通过HFE外显子2跳跃产生可变剪接，从而产生一种缺失对HFE/转铁蛋白受体-1相互作用至关重要的α1结构域的蛋白质。最后，我们通过确定单倍型和基因型谱来研究HFE突变构型与铁过载的关系。结果表明，HFE - c.187G等位基因的携带者也携带 - c.340 + 4C，提示顺式构型。关联分析证实了这一数据，其中复合等位基因HFE - c.[187C>G;340 + 4T>C]的携带者铁过载风险增加（RR = 2.08，95% CI = 1.40 - 2.94，p<0.001）。因此，该复合等位基因的纯合子有铁过载风险，因为他们将产生两种改变的蛋白质——p.63Asp [c.187G]，以及由外显子2编码的缺失88个氨基酸的蛋白质。总之，我们提供的证据表明，复合等位基因HFE - c.[187C>G;340 + 4T>C]作为遗传易感性因素，在圣米格尔人群的铁过载中起作用。需要在其他人群中进行独立的重复研究来证实这种关联。
