microRNAs regulate cell-to-cell variability of endogenous target gene expression in developing mouse thymocytes

Area of Science:

• Molecular Biology
• Developmental Biology
• Genetics

Background:

• Gene regulation is crucial for multicellular organism development and homeostasis.
• MicroRNAs (miRNAs) are post-transcriptional regulators that enhance gene expression robustness.
• Co-regulation of miRNAs and target mRNAs is predicted to reduce cell-to-cell expression variability.

Purpose of the Study:

• To investigate whether microRNAs directly regulate endogenous gene expression variability in mammalian cells.
• To elucidate the mechanisms by which microRNAs control protein expression variability during mouse thymocyte development.

Main Methods:

• Quantitative flow cytometry was employed to measure protein expression variability.
• Analysis focused on the activation-induced expression of the microRNA target CD69 in mouse thymocytes.

Main Results:

• MicroRNAs were shown to impact cell-to-cell variability of protein expression in developing mouse thymocytes.
• Two distinct mechanisms involving microRNAs were identified: an incoherent feed-forward loop (miR-17/miR-20a with Cd69 mRNA) and upstream modulation (miR-181a).
• These mechanisms contribute to reducing variability in CD69 expression upon activation.

Conclusions:

• MicroRNAs play a direct role in reducing endogenous gene expression variability in mammalian cells.
• MicroRNA-mediated gene expression uniformity may be critical for normal development and disease processes.
• Specific microRNA regulatory circuits fine-tune cellular responses and gene expression levels.