Early postnatal GFAP-expressing cells are thought to be immature astrocytes. However, it is not clear if they possess multilineage capacity and if they can generate different lineages (astrocytes, neurons and oligodendrocytes) in the brain of adult mice. In order to identify the fate of astroglial cells in the postnatal brain, hGFAP-Cre-ERT2 transgenic mice were crossed with the R26R Cre reporter mouse strains which exhibit constitutive expression of beta-galactosidase (beta-gal). Mice carrying the hGFAP-Cre-ERT2/R26R transgene were treated with Tamoxifen to induce Cre recombination in astroglial cells at postnatal (P) day 6 and Cre recombinase-expressing cells were identified by X-gal staining. Immunohistochemical staining was used to identify the type(s) of these reporter-tagged cells. Sixty days after recombination, X-gal-positive cells in different cerebral regions of the adult mice expressed the astroglial markers Blbp and GFAP, the neuronal marker NeuN, the oligodendrocyte precursor cell marker NG2 and the mature oligodendrocyte marker CC1. X-gal-positive cells in the cerebellum coexpressed the astroglial marker Blbp, but not the granule cell marker NeuN, Purkinje cell marker Calbindin or oligodendrocyte precursor cell marker NG2. Our genetic fate mapping data demonstrated that early postnatal GFAP-positive cells possessed multilineage potential and eventually differentiated into neurons, astrocytes, and oligodendrocyte precursor cells in the cerebrum and into astrocytes (including Bergmann glia) in the cerebellum of adult mice. (c) 2013 Elsevier B.V. All rights reserved.