髓母细胞瘤是最常见的恶性儿童脑肿瘤，其中第四组髓母细胞瘤（G4 MBs）占40％。然而，这个亚组的分子机制仍然知之甚少。我们在多个基因中检测到低发生率的点突变，而通常需要应用长读技术来检测反复受影响基因中的复杂结构变异。在这里，我们应用链接读取测序，将长读取测序的长范围基因组信息与短读取测序的高碱基对准确性以及极低的样本输入需求结合在一起。我们展示了在这些肿瘤中检测到复杂结构变异和点突变的能力，并且首次检测到了与链接读取相关的染色体外DNA（ecDNA）。我们进一步提供了G4 MBs中体细胞突变的高异质性的证据，并添加了与其相关的新的复杂事件。我们检测到了几个增强子劫持事件，一个含有MYCN基因的ecDNA，以及罕见的结构重排，比如G4髓母细胞瘤中的染色体断裂（chromothripsis），涉及8个不同的染色体的染色体交错（chromoplexy），TERT基因的重排和PRDM6的重复。版权所有© 2023 Zwaig, Johnston, Lee, Farooq, Gallo, Jabado, Taylor和Ragoussis.

Medulloblastoma is the most common type of malignant pediatric brain tumor with group 4 medulloblastomas (G4 MBs) accounting for 40% of cases. However, the molecular mechanisms that underlie this subgroup are still poorly understood. Point mutations are detected in a large number of genes at low incidence per gene while the detection of complex structural variants in recurrently affected genes typically requires the application of long-read technologies.Here, we applied linked-read sequencing, which combines the long-range genome information of long-read sequencing with the high base pair accuracy of short read sequencing and very low sample input requirements.We demonstrate the detection of complex structural variants and point mutations in these tumors, and, for the first time, the detection of extrachromosomal DNA (ecDNA) with linked-reads. We provide further evidence for the high heterogeneity of somatic mutations in G4 MBs and add new complex events associated with it.We detected several enhancer-hijacking events, an ecDNA containing the MYCN gene, and rare structural rearrangements, such a chromothripsis in a G4 medulloblastoma, chromoplexy involving 8 different chromosomes, a TERT gene rearrangement, and a PRDM6 duplication.Copyright © 2023 Zwaig, Johnston, Lee, Farooq, Gallo, Jabado, Taylor and Ragoussis.