Complementary and countervailing actions of Jak2 and Ikk2 in hematopoiesis in mice

Area of Science:

• Hematology
• Molecular Biology
• Oncology

Background:

• Janus kinase 2 (JAK2) kinase hyperactivation, often via the JAK2 V617F mutation, is central to myeloproliferative neoplasms (MPNs).
• Nuclear Factor kappa B (NFκB) pathway hyperactivation is observed in myeloid neoplasms, yet direct mutations are rare.

Purpose of the Study:

• To investigate the combined impact of JAK2 V617F and NFκB pathway hyperactivation (using Ikk2-CA mice) on hematopoiesis and MPN phenotypes.
• To identify molecular mechanisms underlying the antagonistic regulation between JAK2 and Ikk2 in hematopoietic stem and progenitor cells.

Main Methods:

• Utilized Ikk2-CA mice to model NFκB pathway hyperactivation.
• Generated double mutant mice combining Ikk2-CA and Jak2 V617F mutations.
• Performed single-cell RNA sequencing on hematopoietic stem and progenitor cells from mutant mice.

Main Results:

• Pan-hematopoietic Ikk2-CA alone caused hematopoietic stem cell depletion and B cell reduction.
• The Jak2 V617F mutation rescued the polycythemia vera phenotype in Ikk2-CA mice, and vice versa.
• Single-cell RNA sequencing revealed genes antagonistically regulated by Jak2 and Ikk2, with expression normalized in double mutants.

Conclusions:

• JAK2 signaling promotes hematopoietic stem cell self-renewal, while Ikk2 signaling drives myeloid differentiation.
• Dual hyperactivation of JAK2 and NFκB pathways may create unique therapeutic vulnerabilities in myeloid neoplasms.
• Understanding the interplay between JAK2 and NFκB is crucial for developing targeted therapies for MPNs.