Rapid spontaneous dihydrofolate reductase gene amplification shown by fluorescence-activated cell sorting

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Dihydrofolate reductase (DHFR) is a crucial enzyme in cellular metabolism.
• Gene copy number variation can impact cellular function and drug resistance.
• Understanding spontaneous gene amplification is key to cellular dynamics.

Purpose of the Study:

• To investigate spontaneous variations in the dihydrofolate reductase gene copy number in vitro.
• To determine the rate and conditions of gene amplification.

Main Methods:

• Cells were stained with fluoresceinated methotrexate, which binds to DHFR.
• Fluorescence-activated cell sorting (FACS) was used to isolate cells with high fluorescence.
• Cells were serially cultured and sorted over 10 rounds without metabolic stress.

Main Results:

• A 40-fold amplification of the DHFR gene content was observed after 10 rounds of sorting.
• The derived cell population exhibited a 50-fold increase in fluorescence intensity and methotrexate resistance.
• Cells with pre-amplified genes showed even faster rates of amplification and gene copy number changes.

Conclusions:

• Gene amplification of DHFR can occur spontaneously in cells.
• The rate of spontaneous gene amplification is dependent on the existing gene copy number.
• These findings have implications for understanding drug resistance and genetic instability.