Lineage specification and plasticity in CD19- early B cell precursors

Area of Science:

• Immunology
• Developmental Biology
• Hematopoiesis

Background:

• Early B cell development is crucial for adaptive immunity.
• Understanding progenitor cell plasticity is key to deciphering lineage commitment.
• Existing models often depict a more linear progression of B cell development.

Purpose of the Study:

• To characterize early B cell precursor populations in mouse bone marrow.
• To investigate the lineage potential and plasticity of these progenitor populations.
• To refine the understanding of early B cell development timing and commitment.

Main Methods:

• 12-color flow cytometry to identify CD19- B cell precursors.
• Cell transfer experiments to assess lineage potential.
• Single-cell in vitro assays to reveal lineage plasticity.
• Analysis of recombination activating gene 2 reporter activation.
• Assessment of heavy chain DJ rearrangements.
• Gene expression profiling of lineage-specific genes.

Main Results:

• Identified three CD19- B cell precursor populations: MLP, CLP, and Fr. A.
• Demonstrated lineage plasticity: CLP cells showed lymphoid/myeloid potential, Fr. A cells showed B/T lineage potential.
• Showed progressive B lineage specification initiation at MLP/CLP stages, with myeloid potential loss at Fr. A.
• B/T lymphoid plasticity persisted until the CD19+ pro-B stage.
• Detected recombination activating gene 2 reporter activation and heavy chain DJ rearrangements in progenitor cells.

Conclusions:

• MLP, CLP, and Fr. A represent progressively B lineage-specified stages.
• Early B cell development is asynchronous, with specification initiating before lineage restriction.
• Myeloid potential is retained longer than previously thought, until the pre-pro-B (Fr. A) stage.