A parallel study in a Japanese population (n = 129) confirmed the significance of rare variants, identifying five genes (including SLC41A3, whose deletion disrupts the expression of myogenin (MYOG)—a key regulator of myogenic differentiation), and discovered a protective effect of the HLA-DPB1*02:01 allele, underscoring the role of immune regulation in sarcopenia. This evidence concerns the gene MYOG and sarcopenia.