Dynamic single-cell imaging of direct reprogramming reveals an early specifying event

Area of Science:

• Cell Biology
• Stem Cell Research
• Developmental Biology

Background:

• Traditional studies of induced pluripotency average cell populations, masking individual cell behaviors.
• Most cells in reprogramming experiments do not achieve pluripotency, complicating efficiency calculations.

Purpose of the Study:

• To investigate the single-cell dynamics of induced pluripotency using high-resolution imaging.
• To develop a normalized reprogramming efficiency metric based on responsive cells.
• To identify key cellular events during the early stages of reprogramming.

Main Methods:

• Utilized high-resolution, time-lapse imaging to track individual mouse embryonic fibroblasts (MEFs) over two weeks.
• Monitored the transition from MEFs to pluripotency factor-positive colonies.
• Calculated a normalized reprogramming efficiency considering only initial responding MEFs.

Main Results:

• Successfully reprogramming cells exhibit a rapid change in proliferation rate and a decrease in cellular area.
• These critical events occur as early as the first cell division.
• The observed kinetics are consistent across all cells forming induced pluripotent stem (iPS) cell colonies.

Conclusions:

• The reprogramming process, particularly early events, may involve defined, non-stochastic steps.
• These findings aid in the theoretical modeling of cellular reprogramming.
• Single-cell analysis provides a more accurate understanding of reprogramming efficiency and dynamics.