GABA produced by multiple bone marrow cell types regulates hematopoietic stem and progenitor cells

Area of Science:

• Hematology
• Cell Biology
• Biochemistry

Background:

• Hematopoietic stem and progenitor cells (HSPCs) maintain blood homeostasis through proliferation and differentiation.
• The bone marrow microenvironment contains unknown signals regulating HSPC balance.

Purpose of the Study:

• To investigate the role of gamma aminobutyric acid (GABA) as a regulator of HSPCs in the bone marrow.
• To identify the cellular sources of GABA within the bone marrow microenvironment.

Main Methods:

• Conditional deletion of glutamate decarboxylase enzymes (Gad1/2) in B lineages and endothelial cells (ECs).
• Measurement of bone marrow GABA levels.
• Analysis of HSPC numbers and gene expression profiles.

Main Results:

• Deletion of Gad1/2 in B cells or ECs moderately reduced bone marrow GABA levels and HSPC numbers.
• Simultaneous blockade of GABA production from both cell types significantly decreased GABA levels and HSPC numbers.
• Lower bone marrow GABA levels reduced proliferation-associated gene expression and increased B lineage gene expression in HSPCs.

Conclusions:

• GABA, produced by B cells and endothelial cells, acts as a crucial regulator of HSPC activity.
• Bone marrow GABA levels coordinate to balance HSPC proliferation and differentiation, particularly favoring B cell development.