GABA Stems Proliferation

Abstract

Cell proliferation and differentiation, processes that are inversely correlated, are typically regulated during the G1 phase of the cell cycle. Self-renewing stem cells need to proliferate and remain multipotent; indeed, embryonic stem (ES) cells may lack the G1 pathways through which proliferation is regulated. Andäng et al . identified γ-aminobutyric acid type A receptor (GABA A R) subunits and GABA synthetic enzymes in mouse ES cells and peripheral neural crest stem (NCS) cells and combined electrophysiological analysis with use of a voltage-sensitive dye to confirm that the cells contained functional GABA A Rs. The GABA A R agonist muscimol inhibited proliferation of cultured stem cells, whereas the antagonist bicuculline promoted it, as did knockdown of the GABA A R β3 subunit (GABA A R β3) with RNA interference. Cell cycle distribution analysis indicated that receptor activation promoted the accumulation of ES cells in S phase. Moreover, muscimol stimulated the phosphorylation of histone H2AX (which is involved in the S/G2 DNA damage checkpoint response) by means of the checkpoint kinases ataxia telangiectasia mutated (ATM) and ataxia telangiectasia, Rad3-related (ATR), even though no overt DNA damage was evident. Furthermore, GABA-dependent inhibition of proliferation depended on H2AX. Muscimol decreased the incorporation of bromodeoxyuridine into blastocysts in vivo, and injection of siRNA directed against GABA A R β3 into zygotes led to the faster development of blastocyst-stage embryos. GABA also regulated proliferation of NCS cells. Thus the proliferation of ES and NCS cells appears to be regulated through autocrine- or paracrine-derived GABA through a pathway that uses components of the DNA damage checkpoint response. M. Andäng, J. Hjerling-Leffler, A. Moliner, T. K. Lundgren, G. Castelo-Branco, E. Nanou, E. Pozas, V. Bryja, S. Halliez, H. Nishimaru, J. Wilbertz, E. Arenas, M. Koltzenburg, P. Charnay, A. El Manira, C. F. Ibañez, P. Ernfors, Histone H2AX-dependent GABA A receptor regulation of stem cell proliferation. Nature 451 , 460-464 (2008). [PubMed]