Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.
Division of Pediatric Otolaryngology, Department of Head and Neck Surgery, University of Washington, Seattle, Washington, USA.
JCI Insight. 2019 Nov 1;4(21):129884. doi: 10.1172/jci.insight.129884.
Lymphatic malformations (LMs) are congenital, nonneoplastic vascular malformations associated with postzygotic activating PIK3CA mutations. The mutation spectrum within LMs is narrow, with the majority having 1 of 3 hotspot mutations. Despite this relative genetic homogeneity, clinical presentations differ dramatically. We used molecular inversion probes and droplet digital polymerase chain reaction to perform deep, targeted sequencing of PIK3CA in 271 affected and unaffected tissue samples from 81 individuals with isolated LMs and retrospectively collected clinical data. Pathogenic PIK3CA mutations were identified in affected LM tissue in 64 individuals (79%) with isolated LMs, with variant allele fractions (VAFs) ranging from 0.1% to 13%. Initial analyses revealed no correlation between VAF and phenotype variables. Recognizing that different mutations activate PI3K to varying degrees, we developed a metric, the genotype-adjusted VAF (GVAF), to account for differences in mutation strength, and found significantly higher GVAFs in LMs with more severe clinical characteristics including orofacial location or microcystic structure. In addition to providing insight into LM pathogenesis, we believe GVAF may have broad applicability for genotype-phenotype analyses in mosaic disorders.
淋巴管畸形（LMs）是一种与合子后激活的 PIK3CA 突变相关的先天性、非肿瘤性血管畸形。LMs 中的突变谱较窄，大多数具有 3 个热点突变之一。尽管存在这种相对的遗传同质性，但临床表现却有很大差异。我们使用分子反转探针和液滴数字聚合酶链反应对 81 名孤立性 LMs 患者的 271 个受累和未受累组织样本进行了 PIK3CA 的深度靶向测序，并回顾性收集了临床数据。在 64 名（79%）孤立性 LMs 患者的受累 LM 组织中发现了致病性 PIK3CA 突变，变异等位基因分数（VAF）范围为 0.1%至 13%。初步分析显示 VAF 与表型变量之间无相关性。鉴于不同的突变以不同的程度激活 PI3K，我们开发了一种衡量标准，即基因型调整的 VAF（GVAF），以考虑突变强度的差异，并发现具有更严重临床特征（包括口面位置或微囊结构）的 LMs 的 GVAF 显著更高。除了为 LM 发病机制提供深入了解外，我们还认为 GVAF 可能在镶嵌性疾病的基因型-表型分析中具有广泛的适用性。
