Abstract

The hereditary transthyretin amyloidosis (ATTRv amyloidosis) is an autosomal dominant genetic disease characterized by amyloid formation in different tissues due to pathogenic variants in the TTR gene. Great heterogeneity in the penetrance and manifestation of ATTRv amyloidosis is observed. In Bulgaria, the most common TTR pathogenic variant is Glu89Gln. Other TTR pathogenic variants are also found – Val30Met, Ser77Phe, Gly47Glu and Ser52Pro. There is a proven founder effect for the Glu89Gln variant, thus the aim of the present study is to investigate the founder effect for the other TTR pathogenic variants in Bulgaria. Haplotype analysis was performed by using microsatellite markers close to the TTR gene. DNA samples from ATTRv amyloidosis patients and their healthy relatives were analyzed. Theoretical haplotype reconstruction was done with Arlequin v.3.01 software. The age of the most recent common ancestor (hypothetical founder) for the studied variants was calculated with the DMLE 2.2 software. In addition, DBS screening among 100 Roma newborns was done for the Gly47Glu TTR variant via direct Sanger sequencing. The reconstructed haplotypes of the patients were compared to their healthy relatives and to a control group of 40 healthy individuals. The results showed a possible founder effect for each of the studied variants. The Val30Met haplotype was compared to published haplotype data for this variant and no similarity was found. The result from the DBS screening showed no pathogenic TTR variants in exon 2 of the gene, so we considered the presence of the Gly47Glu variant in our population a sporadic event. With this study, we succeeded to gain a more complete picture of the population genetics of ATTRv amyloidosis in Bulgaria and made another step towards a more detailed understanding of the disease epidemiology.

摘要

遗传性转甲状腺素蛋白淀粉样变性（ATTRv淀粉样变性）是一种常染色体显性遗传疾病，其特征在于由于TTR基因的致病变异在不同组织中形成淀粉样蛋白。观察到 ATTRv 淀粉样变性的外显率和表现存在很大的异质性。在保加利亚，最常见的TTR致病变异是Glu89Gln。还发现了其他TTR致病变异——Val30Met、Ser77Phe、Gly47Glu和Ser52Pro。Glu89Gln变体的创始人效应已得到证实，因此本研究的目的是研究其他TTR的创始人效应保加利亚的致病变异。通过使用接近TTR基因的微卫星标记进行单倍型分析。分析了来自 ATTRv 淀粉样变性患者及其健康亲属的 DNA 样本。使用 Arlequin v.3.01 软件进行理论单倍型重建。使用 DMLE 2.2 软件计算所研究变体的最近共同祖先（假设创始人）的年龄。此外，通过直接 Sanger 测序对 100 名罗姆新生儿进行了 DBS 筛查，以检测 Gly47Glu TTR变体。将患者的重建单倍型与他们的健康亲属和 40 名健康个体的对照组进行比较。结果显示了每个研究变体的可能的创始人效应。Val30Met _将单倍型与该变体的已发表单倍型数据进行比较，未发现相似性。DBS 筛选的结果显示该基因的外显子 2 中没有致病性TTR变体，因此我们认为我们人群中Gly47Glu变体的存在是零星的事件。通过这项研究，我们成功地更全面地了解了保加利亚 ATTRv 淀粉样变性的群体遗传学，并朝着更详细地了解疾病流行病学又迈出了一步。