Gabbr1, encoding the GABAB receptor subunit 1, is a key component of GABAB receptors. These receptors are obligatory heterodimers responsible for prolonged neuronal inhibition in the central nervous system [1]. Additionally, the hematopoietic and nervous systems are linked, and hematopoietic stem/progenitor cells (HSPCs) express Gabbr1, suggesting it may directly regulate HSPCs via neurotransmitters like GABA [2].

In a constitutive Gabbr1-knockout mouse model, HSPC numbers were significantly reduced in the bone marrow compared to wild-type littermates. Gabbr1-null hematopoietic stem cells had diminished capacity to reconstitute irradiated recipients in a competitive transplantation model. Gabbr1-null HSPCs were less proliferative under steady-state conditions and upon stress, and almost all were in a slow or non-cycling state. In vitro differentiation of Gabbr1-null HSPCs produced fewer overall cell numbers with significant defects in B-cell lineage differentiation and expansion [2]. Also, four individuals with monoallelic Gabbr1 de novo non-synonymous variants exhibited motor and/or language delay, and in one case, epilepsy. Functional characterization of these variants in transfected HEK293 cells showed that GABA fails to efficiently activate the variant receptors, likely increasing the excitation/inhibition balance in the central nervous system [1].

In conclusion, Gabbr1 plays essential roles in both the regulation of HSPC proliferation and function and in neuronal inhibition in the central nervous system. The Gabbr1-knockout mouse model has provided insights into its role in hematopoietic processes, while human genetic studies have revealed its potential association with neurodevelopmental delay and epilepsy. Understanding Gabbr1 is crucial for uncovering the mechanisms underlying these biological processes and associated diseases.