Prominin-1 (CD133) is commonly used to isolate stem and progenitor cells from 
the developing and adult nervous system and to identify cancer stem cells in 
brain tumors. However, despite extensive characterization of Prominin-1(+) 
precursor cells from the adult subventricular zone, no information about the 
expression of Prominin-1 by precursor cells in the subgranular zone (SGZ) of the 
adult hippocampus has been available. We show here that Prominin-1 is expressed 
by a significant number of cells in the SGZ of adult mice in vivo and ex vivo, 
including postmitotic astrocytes. A small subset of Prominin-1(+) cells 
coexpressed the nonspecific precursor cell marker Nestin as well as GFAP and 
Sox2. Upon fluorescence-activated cell sorting, only Prominin-1/Nestin 
double-positive cells fulfilled the defining stem cell criteria of 
proliferation, self-renewal, and multipotentiality as assessed by a neurosphere 
assay. In addition, isolated primary Prominin-1(+) cells preferentially migrated 
to the neurogenic niche in the SGZ upon transplantation in vivo. Finally, 
despite its expression by various stem and progenitor cells, Prominin-1 turned 
out to be dispensable for precursor cell proliferation in vitro and in vivo. 
Nevertheless, a net decrease in hippocampal neurogenesis, by ∼30% was found in 
Prominin-1 knock-out mice, suggesting other roles in controlling adult 
hippocampal neurogenesis. Remarkably, an upregulation of Prominin-2 was detected 
in Prominin-1-deficient mice highlighting a potential compensatory mechanism, 
which might explain the lack of severe symptoms in individuals carrying 
mutations in the Prom1 gene.