CD133 is a glycoprotein also known in humans and rodents as Prominin 1 (PROM1).It is the founding member of pentaspan transmembrane glycoproteins (5-transmembrane, 5-TM), which specifically localizes to cellular protrusions. CD133 is expressed in hematopoietic stem cells, endothelial progenitor cells, glioblastomas, neuronal and glial stem cells and some other cell types.
In contrast, AC133-1 was prominent in fetal brain and adult skeletal muscle and absent in fetal liver and kidney and in adult pancreas, kidney, bone marrow, hematopoietic stem cells, and placenta. RT-PCR and flow cytometric analysis revealed expression of AC133-2 in basal epidermal stem cells, and the expression was downregulated in cultured basal cells.