Data_Sheet_1_Novel Pathogenic Variants in a Cassette Exon of CCM2 in Patients With Cerebral Cavernous Malformations.PDF

Autosomal dominant cerebral cavernous malformation (CCM) represents a genetic disorder with a high mutation detection rate given that stringent inclusion criteria are used and copy number variation analyses are part of the diagnostic workflow. Pathogenic variants in either CCM1 (KRIT1), CCM2 or CCM3 (PDCD10) can be identified in 87–98% of CCM families with at least two affected individuals. However, the interpretation of novel sequence variants in the 5′-region of CCM2 remains challenging as there are various alternatively spliced transcripts and different transcription start sites. Comprehensive genetic and clinical data of CCM2 patients with variants in cassette exons that are either skipped or included into alternative CCM2 transcripts in the splicing process can significantly facilitate clinical variant interpretation. We here report novel pathogenic CCM2 variants in exon 3 and the adjacent donor splice site, describe the natural history of CCM disease in mutation carriers and provide further evidence for the classification of the amino acids encoded by the nucleotides of this cassette exon as a critical region within CCM2. Finally, we illustrate the advantage of a combined single nucleotide and copy number variation detection approach in NGS-based CCM1/CCM2/CCM3 gene panel analyses which can significantly reduce diagnostic turnaround time.

常染色体显性遗传性脑海绵状血管畸形（autosomal dominant cerebral cavernous malformation, CCM）是一类遗传性疾病，当采用严格的纳入标准并将拷贝数变异（copy number variation, CNV）分析纳入诊断流程时，其突变检出率可维持较高水平。在至少包含2名受累个体的CCM家族中，87%~98%可检出CCM1（KRIT1）、CCM2或CCM3（PDCD10）基因的致病变异。然而，CCM2基因5'端区域存在多种可变剪接转录本及不同的转录起始位点，导致该区域中新发现的序列变异解读仍颇具挑战性。若能获取携带盒式外显子（cassette exon）变异的CCM2患者的完整遗传与临床数据——此类变异在剪接过程中可发生外显子跳跃或被整合至可变CCM2转录本中——将可显著助力临床变异的解读工作。本研究报道了CCM2基因第3外显子及其邻近供体剪接位点的新型致病变异，描述了突变携带者的CCM疾病自然史，并为将该盒式外显子核苷酸序列所编码的氨基酸归类为CCM2基因内的关键区域提供了进一步证据。最后，本研究阐明了在基于下一代测序（next-generation sequencing, NGS）的CCM1/CCM2/CCM3基因面板检测中，联合单核苷酸与拷贝数变异检测策略的优势，该策略可显著缩短诊断周转时间。