Muscle-specific mutations accumulate with aging in critical human mtDNA control sites for replication

Area of Science:

• Genetics
• Molecular Biology
• Aging Research

Background:

• Aging is associated with accumulating point mutations in mitochondrial DNA (mtDNA), particularly in the control region of human fibroblasts.
• The presence and significance of these mutations in postmitotic tissues, such as skeletal muscle, remained largely unexplored.

Purpose of the Study:

• To investigate the occurrence of aging-dependent mtDNA point mutations in human skeletal muscle.
• To identify potential tissue-specific mtDNA mutation patterns related to aging and neuromuscular health.

Main Methods:

• Analysis of biopsied and autopsied human skeletal muscle and fibroblast samples from individuals across a wide age range.
• Sequencing to detect specific point mutations (A189G, T408A, T414G) in mitochondrial DNA.
• Comparison of mutation frequencies between different tissues (muscle, skin, fibroblasts) and age groups.

Main Results:

• Skeletal muscle showed an absence or minimal presence of fibroblast-specific mtDNA mutations.
• Most older individuals (53-92 years) exhibited accumulation of two novel mtDNA mutations (A189G, T408A) in muscle, which were rare in younger individuals (<34 years).
• These muscle-specific mutations were largely absent in fibroblasts, while fibroblast-specific mutations (T414G) were found in skin but not muscle, indicating striking tissue specificity.

Conclusions:

• Aging skeletal muscle accumulates distinct point mutations in mtDNA, particularly at replication control sites.
• The tissue-specific nature of these mtDNA mutations suggests a specialized mutagenic process in muscle tissue.
• These findings highlight the functional relevance of muscle-specific mtDNA mutations in the aging process and potentially in neuromuscular diseases.