The human, F-actin-based cytoskeleton as a mutagen sensor.

Area of Science:

• Cell biology
• Genetics
• Cancer research

Background:

• Actin cytoskeleton disruption was noted in hereditary colon cancer fibroblasts 40 years ago.
• Recent genomic data reveal a significant stochastic component in mammalian mutagenesis.
• Large coding regions, including cytoskeletal protein-related coding regions (CPCRs), are common mutation targets in cancer.

Purpose of the Study:

• To investigate if mutagen sensitivity of the actin cytoskeleton can be experimentally assessed.
• To explore the link between cytoskeleton integrity and mutagenesis.

Main Methods:

• Tissue culture cells were treated with a mutagen (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone).
• Overall cytoskeleton integrity was quantified using rhodamine-phalloidin stains for F-actin.

Main Results:

• Cytoskeletal degradation increased with mutagen exposure, correlating with CPCR mutagenesis.
• A strong correlation (R² = 0.8694, p < 0.00001) was observed between overall mutation rates and CPCR mutation rates in TCGA smoker samples.
• Mutagen exposure led to a decreased cell perimeter to area ratio, suggesting potential impacts on intracellular drug diffusion.

Conclusions:

• Cytoskeletal integrity assessment may offer a method to evaluate mutation burdens in non-clonal cell populations.
• This approach could be valuable for intact tissues where DNA sequencing for heterogeneous mutations is challenging.