BCOR regulates myeloid cell proliferation and differentiation.

Area of Science:

• Hematology
• Molecular Biology
• Epigenetics

Background:

• BCOR (BCL9-related) is a component of a variant Polycomb repressive complex 1 (PRC1).
• Somatic BCOR loss-of-function mutations are recurrent in myelodysplastic syndrome and acute myeloid leukemia (AML).
• The role of BCOR in normal hematopoiesis remains largely uncharacterized.

Purpose of the Study:

• To investigate the function of BCOR in myeloid cell development and hematopoiesis.
• To elucidate the molecular mechanisms by which BCOR regulates gene expression and cell fate.

Main Methods:

• Utilized murine models with conditional Bcor loss-of-function or overexpression alleles in myeloid cells.
• Analyzed bone marrow cell proliferation and differentiation rates.
• Assessed expression levels of Hox genes and PRC1 components (e.g., RING1B).
• Quantified H2AK119ub levels, a key epigenetic mark regulated by PRC1.
• Performed global RNA expression profiling in murine cells and human AML samples.

Main Results:

• Bcor mutant myeloid cells exhibited significantly increased proliferation and differentiation.
• BCOR loss-of-function was associated with upregulated Hox gene expression.
• Mutation of Bcor led to reduced RING1B protein levels and decreased H2AK119ub.
• Global gene expression analysis indicated enhanced cell proliferation and myeloid differentiation upon BCOR loss.
• Findings were corroborated in AML patient samples with BCOR loss-of-function mutations.

Conclusions:

• BCOR plays a critical role in suppressing myeloid cell proliferation and differentiation during normal hematopoiesis.
• BCOR functions by regulating the epigenetic landscape, including Hox gene expression via the PRC1 complex and H2AK119ub.
• Disruption of BCOR function contributes to aberrant hematopoiesis and provides mechanistic insight into its role in myeloid malignancies like AML.