IKAROS and AIOLOS directly regulate AP-1 transcriptional complexes and are essential for NK cell development

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Ikaros transcription factors (e.g., IKZF1) are vital for adaptive immunity.
• The role of Ikaros in innate lymphopoiesis, specifically natural killer (NK) cell development, remains largely uncharacterized.

Purpose of the Study:

• To investigate the function of Ikzf1/Ikaros in innate lymphopoiesis, particularly NK cell development.
• To elucidate the molecular mechanisms by which Ikaros regulates NK cell homeostasis and function.

Main Methods:

• Conditional genetic inactivation of Ikzf1 in mice.
• Analysis of NK cell populations, gene expression (including Cish, Bcl2l11, BIM, AP-1 complex members), and apoptosis.
• Chromatin immunoprecipitation (ChIP) to assess direct binding of Ikaros family members to target genes.

Main Results:

• Conditional deletion of Ikzf1 impairs NK cell lymphopoiesis, leading to NK cell lymphopenia.
• IKZF1 directly represses Cish, a negative regulator of interleukin-15 receptor signaling, impacting cytokine responsiveness.
• Ikzf1 deficiency increases Bcl2l11/BIM levels and intrinsic apoptosis, contributing to lymphopenia.
• Ikzf1-null NK cells exhibit altered transcription, with reduced AP-1 complex activity and increased Ikzf2/Helios and Ikzf3/Aiolos expression.
• Co-deletion of Ikzf1 and Ikzf3 further reduces AP-1 activity and results in a complete loss of peripheral NK cells.

Conclusions:

• Ikaros family members (IKZF1, IKZF3) are essential regulators of NK cell lymphopoiesis and homeostasis.
• Ikaros controls NK cell function by modulating apoptosis, cytokine signaling (via Cish repression), and AP-1 transcriptional activity.