Mainstream tobacco smoke causes paternal germ-line DNA mutation

Area of Science:

• Genetics
• Toxicology
• Reproductive Biology

Background:

• Cigarette smoke contains mutagens and carcinogens.
• No prior evidence linked smoking to heritable genetic mutations.

Purpose of the Study:

• To investigate if mainstream tobacco smoke (MTS) exposure causes heritable genetic mutations in male mice.
• To determine the effect of MTS on germ-line mutation frequency in spermatogonial stem cells.

Main Methods:

• Mature male mice were exposed to MTS for 6 or 12 weeks.
• Mutations were analyzed at the Ms6-hm tandem repeat locus in spermatogonial stem cells.
• Mutation frequency was compared between exposed mice and sham controls.

Main Results:

• MTS exposure significantly increased germ-line mutation frequency (P = 0.0214).
• Mutation frequency was 1.4x higher after 6 weeks and 1.7x higher after 12 weeks of MTS exposure.
• Mutation spectra were similar in exposed and control groups, suggesting indirect mutation mechanisms.

Conclusions:

• MTS exposure induces mutations in male mouse spermatogonial stem cells.
• Mutations accumulate with extended exposure duration.
• Smoking may have heritable genetic consequences for offspring, extending beyond the smoker.