Spaceflight alters expression of microRNA during T-cell activation

Area of Science:

• Space Biology
• Immunology
• Molecular Biology

Background:

• Altered immune function in astronauts poses a significant challenge for long-term space exploration.
• Previous studies noted immune changes during spaceflight, but the underlying molecular mechanisms remain unclear.

Purpose of the Study:

• To investigate the hypothesis that spaceflight induces changes in microRNA (miRNA) expression.
• To determine the role of gravity in regulating T-cell activation at the molecular level.

Main Methods:

• Human leukocytes were stimulated with mitogens aboard the International Space Station.
• MicroRNA expression was analyzed using quantitative real-time PCR.
• Global gene expression was assessed using microarray analysis.

Main Results:

• MicroRNA-21 (miR-21) was significantly upregulated during early T-cell activation under normal gravity.
• Gene expression was suppressed under microgravity, with 85 genes showing significant downregulation.
• Identified EGR3, FASLG, BTG2, SPRY2, and TAGAP as co-upregulated targets of miR-21.

Conclusions:

• Spaceflight regulates miRNA expression, representing the first report of such a phenomenon.
• Gravity influences T-cell activation through transcriptional promotion and noncoding RNA-mediated translational repression.
• T-cell activation may be self-limited by miR-21-mediated inhibition of target gene translation.