Pediatric Research Center, Children's Hospital, Helsinki University Hospital, University of Helsinki, Helsinki, Finland.
Applied Tumor Genomics Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Front Immunol. 2023 Sep 13;14:1249958. doi: 10.3389/fimmu.2023.1249958. eCollection 2023.
Complement system has a postulated role in endothelial problems after hematopoietic stem cell transplantation (HSCT). In this retrospective, singlecenter study we studied genetic complement system variants in patients with documented endotheliopathy. In our previous study among pediatric patients with an allogeneic HSCT (2001-2013) at the Helsinki University Children´s Hospital, Finland, we identified a total of 19/122 (15.6%) patients with vascular complications, fulfilling the criteria of capillary leak syndrome (CLS), venoocclusive disease/sinusoidal obstruction syndrome (VOD/SOS) or thrombotic microangiopathy (TMA).
We performed whole exome sequencing (WES) on 109 patients having an adequate pre-transplantation DNA for the analysis to define possible variations and mutations potentially predisposing to functional abnormalities of the complement system. In our data analysis, we focused on 41 genes coding for complement components.
50 patients (45.9%) had one or several, nonsynonymous, rare germline variants in complement genes. 21/66 (31.8%) of the variants were in the terminal pathway. Patients with endotheliopathy had variants in different complement genes: in the terminal pathway (C6 and C9), lectin pathway (MASP1) and receptor ITGAM (CD11b, part of CR3). Four had the same rare missense variant (rs183125896; Thr279Ala) in the C9 gene. Two of these patients were diagnosed with endotheliopathy and one with capillary leak syndrome-like problems. The C9 variant Thr279Ala has no previously known disease associations and is classified by the ACMG guidelines as a variant of uncertain significance (VUS). We conducted a gene burden test with gnomAD Finnish (fin) as the reference population. Complement gene variants seen in our patient population were investigated and Total Frequency Testing (TFT) was used for execution of burden tests. The gene variants seen in our patients with endotheliopathy were all significantly (FDR < 0.05) enriched compared to gnomAD. Overall, 14/25 genes coding for components of the complement system had an increased burden of missense variants among the patients when compared to the gnomAD Finnish population (N=10 816).
Injury to the vascular endothelium is relatively common after HSCT with different phenotypic appearances suggesting yet unidentified underlying mechanisms. Variants in complement components may be related to endotheliopathy and poor prognosis in these patients.
补体系统在造血干细胞移植（HSCT）后内皮问题中具有推测作用。在这项回顾性、单中心研究中，我们研究了已确诊内皮病患者的遗传补体系统变异。在我们之前的研究中，在芬兰赫尔辛基大学儿童医院接受同种异体 HSCT（2001-2013 年）的儿科患者中，我们总共发现了 19/122（15.6%）名血管并发症患者，符合毛细血管渗漏综合征（CLS）、静脉闭塞病/窦阻塞综合征（VOD/SOS）或血栓性微血管病（TMA）的标准。
我们对 109 名有足够的移植前 DNA 进行全外显子组测序（WES）分析，以确定可能导致补体系统功能异常的潜在变异和突变。在我们的数据分析中，我们重点关注了编码补体成分的 41 个基因。
50 名患者（45.9%）在补体基因中有一个或多个非同义、罕见的种系变异。21/66（31.8%）的变异发生在末端途径。内皮病患者的补体基因有不同的变异：末端途径（C6 和 C9）、凝集素途径（MASP1）和受体 ITGAM（CD11b，CR3 的一部分）。有 4 人在 C9 基因中具有相同的罕见错义变异（rs183125896；Thr279Ala）。其中 2 人被诊断为内皮病，1 人被诊断为毛细血管渗漏综合征样问题。C9 变体 Thr279Ala 与先前已知的疾病无关，根据 ACMG 指南，被归类为意义不明的变异（VUS）。我们用 gnomAD 芬兰（fin）作为参考人群进行了基因负担测试。研究了在我们的患者人群中发现的补体基因变异，并使用总频率测试（TFT）执行负担测试。与 gnomAD 相比，我们的内皮病患者的基因变异均显著富集（FDR<0.05）。总体而言，与 gnomAD 芬兰人群（N=10816）相比，编码补体系统成分的 25 个基因中有 14 个基因的错义变异负担增加。
HSCT 后血管内皮损伤较为常见，表型不同，提示潜在机制尚不清楚。补体成分的变异可能与这些患者的内皮病和不良预后有关。
