MicroRNA-155 Controls iNKT Cell Development and Lineage Differentiation by Coordinating Multiple Regulating Pathways.

Area of Science:

• Immunology
• Molecular Biology
• Epigenetics

Background:

• Invariant natural killer T (iNKT) cell development relies on precise transcription factor regulation, which is not fully understood.
• MicroRNA-155 (miR-155) is a known regulator of cellular processes, impacting cell development and homeostasis.

Purpose of the Study:

• To investigate the role of miR-155 in the regulation and coordination of iNKT cell development.
• To determine if the downregulation of miR-155 is essential for proper iNKT cell maturation.

Main Methods:

• Generated a CD4Cre.miR-155 knock-in (KI) mouse model for conditional overexpression of miR-155 in T cells.
• Analyzed iNKT cell development, differentiation (iNKT1, iNKT2, iNKT17), and secondary CD8 T cell development in KI mice.
• Investigated miR-155's molecular targets, including Jarid2, Tab2, and Rictor, and their impact on signaling pathways.

Main Results:

• Conditional miR-155 overexpression in T cells led to impaired iNKT cell development, with diminished iNKT1 and iNKT17 cells and augmented iNKT2 cells.
• Defective iNKT cells in KI mice resulted in altered secondary innate-like CD8 T cell development.
• miR-155 was found to modulate Jarid2, Tab2, and Rictor, affecting histone modification, NF-κB signaling, and mTORC2 pathways, respectively.

Conclusions:

• miR-155 acts as a key epigenetic regulator controlling iNKT cell development and lineage specification.
• The precise regulation of miR-155 levels is critical for balanced iNKT cell differentiation and secondary CD8 T cell development.
• miR-155 coordinates multiple signaling pathways and transcriptional programs essential for iNKT cell maturation.