To solve this conundrum, we generated synthetic peptides of 36 amino acids corresponding to a wild-type (WT) SEPN1 EF-hand and three mutants with single amino acid substitution: D80A, bearing a mutation of the most important calcium coordinating residue in canonical EF-hands, and two mutants, M85V and Y86C, described in the ClinVar database as genomic variations possibly associated with SEPN1-related myopathy (https://www.ncbi.nlm.nih.gov/clinvar/variation/195363/ and https://www.ncbi.nlm.nih.gov/clinvar/variation/461631/) (Fig. 2A). Here, SELENON is linked to myopathy.