PDF(Pubmed)
Abstract：
Heterozygous pathogenic variants in DNM1 cause developmental and epileptic encephalopathy (DEE) as a result of a dominant-negative mechanism impeding vesicular fission. Thus far, pathogenic variants in DNM1 have been studied with a canonical transcript that includes the alternatively spliced exon 10b. However, after performing RNA sequencing in 39 pediatric brain samples, we find the primary transcript expressed in the brain includes the downstream exon 10a instead. Using this information, we evaluated genotype-phenotype correlations of variants affecting exon 10a and identified a cohort of eleven previously unreported individuals. Eight individuals harbor a recurrent de novo splice site variant, c.1197-8G>A (GenBank: NM_001288739.1), which affects exon 10a and leads to DEE consistent with the classical DNM1 phenotype. We find this splice site variant leads to disease through an unexpected dominant-negative mechanism. Functional testing reveals an in-frame upstream splice acceptor causing insertion of two amino acids predicted to impair oligomerization-dependent activity. This is supported by neuropathological samples showing accumulation of enlarged synaptic vesicles adherent to the plasma membrane consistent with impaired vesicular fission. Two additional individuals with missense variants affecting exon 10a, p.Arg399Trp and p.Gly401Asp, had a similar DEE phenotype. In contrast, one individual with a missense variant affecting exon 10b, p.Pro405Leu, which is less expressed in the brain, had a correspondingly less severe presentation. Thus, we implicate variants affecting exon 10a as causing the severe DEE typically associated with DNM1-related disorders. We highlight the importance of considering relevant isoforms for disease-causing variants as well as the possibility of splice site variants acting through a dominant-negative mechanism.
摘要：
DNM1中的杂合致病变异导致发育性和癫痫性脑病（DEE），这是由于显性负机制阻碍了囊泡裂变。到目前为止,DNM1中的致病变体已经用包括可变剪接外显子10b的规范转录本进行了研究。然而,在对39例小儿脑样本进行RNA测序后，我们发现在大脑中表达的初级转录物包括下游外显子10a。利用这些信息，我们评估了影响外显子10a的变异的基因型-表型相关性,并确定了一个由11名以前未报告的个体组成的队列.八个个体有一个反复的从头剪接位点变异体，c.1197-8G>A（GenBank：NM_001288739.1），影响外显子10a并导致与经典DNM1表型一致的DEE。我们发现这种剪接位点变异通过意想不到的显性阴性机制导致疾病。功能测试揭示了框内上游剪接受体，导致两个氨基酸的插入，预测会损害寡聚化依赖性活性。这得到了神经病理样品的支持，该样品显示了粘附在质膜上的扩大的突触小泡的积累，这与受损的小泡裂变一致。另外两个人的错义变异影响外显子10a，p.Arg399Trp和p.Gly401Asp,具有相似的DEE表型。相比之下,一个人的错义变异影响外显子10b，p.Pro405Leu,在大脑中表达较少，有一个相应的不那么严重的陈述。因此，我们认为影响外显子10a的变异会导致通常与DNM1相关疾病相关的严重DEE.我们强调了考虑致病变异的相关同工型的重要性，以及剪接位点变异通过显性阴性机制起作用的可能性。
