Dericquebourg Amy, Fretigny Mathilde, Chatron Nicolas, Tardy Brigitte, Zawadzki Christophe, Chambost Hervé, Vinciguerra Christine, Jourdy Yohann
Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France; Université Claude Bernard Lyon 1, UR4609 Hémostase et thrombose, Lyon, France.
Hospices Civils de Lyon, Groupe Hospitalier Est, Service d'hématologie biologique, Bron, France.
J Thromb Haemost. 2023 Apr;21(4):828-837. doi: 10.1016/j.jtha.2022.12.005. Epub 2022 Dec 22.
The disease-causative variant remains unidentified in approximately 0.5% to 2% of hemophilia B patients using conventional genetic investigations, and F9 deep intronic variations could be responsible for these phenotypes.
This study aimed to characterize deep intronic variants in hemophilia B patients for whom genetic investigations failed.
We performed whole F9 sequencing in 17 genetically unsolved hemophilia B patients. The pathogenic impact of the candidate variants identified was studied using both in silico analysis (MaxEntScan and spliceAI) and minigene assay.
In total, 9 candidate variants were identified in 15 patients; 7 were deep intronic substitutions and 2 corresponded to insertions of mobile elements. The most frequent variants found were c.278-1806A>C and the association of c.278-1244A>G and c.392-864T>G, identified in 4 and 6 unrelated individuals, respectively. In silico analysis predicted splicing impact for 4 substitutions (c.278-1806A>C, c.392-864T>G, c.724-2385G>T, c.723+4297T>A). Minigene assay showed a deleterious splicing impact for these 4 substitutions and also for the c.278-1786_278-1785insLINE. In the end, 5 variants were classified as likely pathogenic using the American College of Medical Genetics and Genomics guidelines, and 4 as of unknown significance. Thus, the hemophilia B-causing variant was identified in 13/17 (76%) families.
We elucidated the causing defect in three-quarters of the families included in this study, and we reported new F9 deep intronic variants that can cause hemophilia B.
在约0.5%至2%的乙型血友病患者中，使用传统基因检测方法仍无法鉴定出致病变异，F9基因内含子深处的变异可能是这些表型的原因。
本研究旨在对基因检测失败的乙型血友病患者的内含子深处变异进行特征分析。
我们对17例基因检测未解决的乙型血友病患者进行了F9基因全测序。使用计算机分析（MaxEntScan和spliceAI）和小基因检测研究了鉴定出的候选变异的致病影响。
总共在15例患者中鉴定出9个候选变异；7个是内含子深处的替换，2个对应于移动元件的插入。最常见的变异是c.278-1806A>C以及c.278-1244A>G和c.392-864T>G的组合，分别在4例和6例无亲缘关系的个体中鉴定出。计算机分析预测4个替换（c.278-1806A>C、c.392-864T>G、c.724-2385G>T、c.723+4297T>A）会影响剪接。小基因检测显示这4个替换以及c.278-1786_278-1785insLINE具有有害的剪接影响。最后，根据美国医学遗传学与基因组学学会的指南，5个变异被分类为可能致病，4个意义不明。因此，在13/17（76%）的家庭中鉴定出了导致乙型血友病的变异。
我们阐明了本研究中四分之三家庭的致病缺陷，并报告了可导致乙型血友病的新的F9基因内含子深处变异。
