The Polymorphic AluYb8 Insertion in the MUTYH Gene is Associated with Reduced Type 1 Protein Expression and Reduced Mitochondrial DNA Content

The human mutY homolog ( MUTYH ) participates in base excision repair (BER), which is critical for repairing oxidized DNA bases and maintaining DNA replication fidelity. The polymorphic AluYb8 insertion in the 15 th intron of the MUTYH gene ( AluYb8MUTYH ) has been shown to associate with an aggregated 8-hydroxy-2′-deoxyguanosine (8-OH-dG) lesion in genomic DNA and to serve as a risk factor for age-related diseases. In this work, we demonstrate that this variant is associated with a significant reduction of the type 1 MUTYH protein that localizes to mitochondria. Notably, this variant affects mitochondrial DNA (mtDNA) maintenance and functional mitochondrial mass in individuals homozygous for the AluYb8MUTYH variant. These findings provide evidence for an association between the AluYb8MUTYH variant and decreased mitochondrial homeostasis and, consequently, contribute to elucidating the roles of the AluYb8MUTYH variant in impairing the mitochondrial base excision repair (mtBER) system and increasing the risk of acquiring an age-related disease.