Unraveling mitochondrial DNA methylation and dysfunction in the context of aging, using Nothobranchius furzeri.

Details

Supervisors

Page, Melissa

Faculty

Faculté des sciences

Degree label

Master [120] en biochimie et biologie moléculaire et cellulaire, à finalité approfondie

Abstract

Aging is characterized as a time-dependent functional decline where the accumulation of cellular and molecular damages increases the risk of age-associated diseases such as neurodegeneration. One biomarker of aging that has gained interest in the past decades is DNA methylation, a highly dynamic process regulated by a series of DNMT and TET enzymes, that can alter gene expression. Methylation patterns change throughout the lifespan as part of normal development. However, some precise genomic location undergoes an age-related hypermethylation that is highly concordant across individuals. Therefore, DNA methylation levels can be used to accurately predict age. However, the question of whether mitochondrial DNA undergoes age-dependent methylation remains controversial. Mitochondria, while essential for energy generation, are increasingly recognized as key contributors to the aging process through mechanisms that include oxidative stress and subsequent damage to DNA, proteins and lipids. The accumulation of such damages eventually leads to the progression of mitochondrial dysfunction. This study was part of a project that investigates whether mitochondrial DNA methylation occurs in the brain and liver of N. furzeri, and if there is an age-related change in DNA methylation pattern. The primary objective of this study was to assess if there are age-related changes in DNA methylation dynamics and mitochondrial dysfunction. For this, the relative expression levels of methylation associated genes including DNMTs, TETs, SAM carrier transporter and genes associated with mitochondrial biogenesis, were analysed across different ages (6, 12 and 30 weeks) and treatments (permethrin as a pro-aging agent and DMSO as the control). The secondary objective was to determine if changes in gene expression modify protein quantity and, if these proteins are located within mitochondria. Our results revealed that the expression of genes involved in DNA-methylation dynamics (DNMTS, TETs) and the mitochondrial SAM carrier (SCL25A26) decreases with age in the brain but remains stable in the liver. Because such genes are involved in brain development, adult neurogenesis and cognitive processes, the decreased expression could be a sign of brain functional decline. Genes involved in mitochondrial biogenesis (PGC1-α, TFAM and mtSsbp) underwent the same age-dependent decrease in gene expression, eventually pointing to a progression of mitochondrial dysfunction. Due to failure of commercial antibodies to detect the DNMT proteins in N. furzeri, we were unable to establish whether protein quantity declines with age and whether they are localized to mitochondria.