Spectrum Of Mitochondrial Genomic Variation In Parathyroid Neoplasms By Ultra-Deep Targeted Dna Sequencing

Background Parathyroid neoplasms are characterized with hypersecretion of parathyroid hormone and potentially exhibit disruption of metabolic pathways. Mitochondria are essential for energy homeostasis and mitochondrial DNA (mtDNA) abnormalities are related to multiple types of malignancies. However, the status of mtDNA mutation and copy number variations in parathyroid carcinoma (PC) is not well known. Methods Ultra-deep targeted sequencing of mitochondrial genome was performed using tissues of 12 PCs and 12 parathyroid adenomas (PAs). Germline variants and somatic mutations in the mitochondrial genome were scanned and analysed in comparison with clinical features. The relative copy number of mtDNA in PCs and PAs was determined via quantitative real-time polymerase chain reaction. Results A total of 528 germline variants and 16 somatic mutations were identified in 24 samples of parathyroid neoplasms. All 62 non-synonymous germline variants in coding sequence (CDS) were predicted to be of low pathogenicity in PA and PC samples. Five somatic mutations with high pathogenicity in CDSs were identified in 4 (33.3%, 4/12) PC samples and 1 PA sample (8.3%, 1/12). A somatic mutation in a CDS was correlated with high mtDNA copy number in parathyroid neoplasm (p = 0.004), CDC73 gene mutation (p = 0.017) and PC recurrence (p = 0.024). More C-19 genotypes in the D310 region were found in PA than in the PC samples (3.5% vs 1.9%, p = 0.045). Conclusions More somatic CDS mutations with high pathogenicity were identified in PC than in PA. A high mtDNA copy number was found in parathyroid neoplasms with somatic CDS mutations and in PCs with CDC73 mutations and recurrence. Legal entity responsible for the study The authors. Funding This work was supported by the Chinese Academy of Medical Sciences (CAMS) Initiative for Innovative Medicine (CAMS-I2M) (2017-I2M-1-001), Peking Union Medical College Innovative Team Development Program, the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (2018PT32014) and the 2016 Peking Union Medical College Hospital Science Foundation for Junior Faculty (pumch-2016.2.7). Disclosure All authors have declared no conflicts of interest.