Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park Way, Cardiff, UK.
Eur J Hum Genet. 2012 Apr;20(4):411-9. doi: 10.1038/ejhg.2011.207. Epub 2011 Nov 23.
Neurofibromatosis type-1 (NF1), caused by heterozygous inactivation of the NF1 tumour suppressor gene, is associated with the development of benign and malignant peripheral nerve sheath tumours (MPNSTs). Although numerous germline NF1 mutations have been identified, relatively few somatic NF1 mutations have been described in neurofibromas. Here we have screened 109 cutaneous neurofibromas, excised from 46 unrelated NF1 patients, for somatic NF1 mutations. NF1 mutation screening (involving loss-of-heterozygosity (LOH) analysis, multiplex ligation-dependent probe amplification and DNA sequencing) identified 77 somatic NF1 point mutations, of which 53 were novel. LOH spanning the NF1 gene region was evident in 25 neurofibromas, but in contrast to previous data from MPNSTs, it was absent at the TP53, CDKN2A and RB1 gene loci. Analysis of DNA/RNA from neurofibroma-derived Schwann cell cultures revealed NF1 mutations in four tumours whose presence had been overlooked in the tumour DNA. Bioinformatics analysis suggested that four of seven novel somatic NF1 missense mutations (p.A330T, p.Q519P, p.A776T, p.S1463F) could be of functional/clinical significance. Functional analysis confirmed this prediction for p.S1463F, located within the GTPase-activating protein-related domain, as this mutation resulted in a 150-fold increase in activated GTP-bound Ras. Comparison of the relative frequencies of the different types of somatic NF1 mutation observed with those of their previously reported germline counterparts revealed significant (P=0.001) differences. Although non-identical somatic mutations involving either the same or adjacent nucleotides were identified in three pairs of tumours from the same patients (P<0.0002), no association was noted between the type of germline and somatic NF1 lesion within the same individual.
神经纤维瘤病 1 型（NF1）是由 NF1 肿瘤抑制基因的杂合失活引起的，与良性和恶性周围神经鞘瘤（MPNST）的发展有关。尽管已经鉴定出许多种系 NF1 突变，但在神经纤维瘤中描述的体细胞 NF1 突变相对较少。在这里，我们筛选了 46 名无关 NF1 患者切除的 109 个皮肤神经纤维瘤，以寻找体细胞 NF1 突变。NF1 突变筛查（涉及杂合性丢失（LOH）分析、多重连接依赖性探针扩增和 DNA 测序）确定了 77 个体细胞 NF1 点突变，其中 53 个是新的。在 25 个神经纤维瘤中明显存在跨越 NF1 基因区域的 LOH，但与来自 MPNST 的先前数据相反，在 TP53、CDKN2A 和 RB1 基因座中不存在 LOH。对源自神经纤维瘤衍生的施旺细胞培养物的 DNA/RNA 的分析表明，在四个肿瘤中存在 NF1 突变，这些突变在肿瘤 DNA 中被忽略。生物信息学分析表明，七个新的体细胞 NF1 错义突变（p.A330T、p.Q519P、p.A776T、p.S1463F）中的四个可能具有功能/临床意义。功能分析证实了位于 GTP 酶激活蛋白相关结构域内的 p.S1463F 突变具有这种预测，因为该突变导致激活的 GTP 结合 Ras 增加 150 倍。观察到的不同类型体细胞 NF1 突变与先前报道的种系突变的相对频率进行比较，发现存在显著差异（P=0.001）。尽管在来自同一患者的三对肿瘤中鉴定出涉及相同或相邻核苷酸的非相同体细胞突变（P<0.0002），但在同一个体中未观察到种系和体细胞 NF1 病变类型之间的关联。
