MT-TW: The molecular pathomechanisms of m.5541C > T can be summarized as follows: This mutation firstly loses the appropriate base pair interaction, from Watson-Crick to T-G mismatching, in the anticodon-stem of MT-TW gene and induces defects in mitochondrial tRNATrp-associated translation machinery most likely due to inadequate anticodon recognition of mitochondrial tryptophan by its altered conformation [1]. The panel covered known genetic causes of channelopathies and cardiomyopathies and included a sequence analysis and copy number variation analysis of various genes [3]. Of 22 mt-tRNAs, MT-TE, MT-TA, MT-TN, MT-TC, MT-TY, MT-TS1, MT-TQ, and MT-TP occur at the L-strand, the rest, MT-TF, MT-TV, MT-TL1, MT-TL2, MT-TI, MT-TM, MT-TS2, MT-TW, MT-TD, MT-TK, MT-TG, MT-TR, MT-TH, and MT-TT, are present in the H-strand [2]. In this study, a disease-causative mutation, m.5541C > T heteroplasmy in MT-TW gene, was found in a patient exhibiting MELAS with multiple organ involvement [1]. However, it should be noted that when considering multiple tests, such as P-value analysis, the specific gene (MT-TW) did not show significant results [4]. References: [1] Sasarman F et al. (2015) The 3' addition of CCA to mitochondrial tRNASer(AGY) is specifically impaired in patients with mutations in the tRNA nucleotidyl transferase TRNT1. Hum Mol Genet 24(9):2841-2847. [PMC4546323] [2] Mercer TR et al. (2012) The human mitochondrial transcriptome Cell 146(4):645-658. [PMC9657367] [3] Ackerman MJ et al. (2020) Genetic Causes of Channelopathies and Cardiomyopathies in Patients With Sudden Unexplained Death. Mayo Clin Proc 95(4):822-834. [PMC7290503] [4] Li MX et al. (2014) Evaluating the internal consistency of the 1000 Genomes Project data. Brief Bioinform 15(6):963-975. [PMC4350597]