Gsh2 homeobox transcription factors play a crucial role in the development of GABAergic neurons. Caenorhabditis elegans's mab-5 gene is homologous to Gsh2; its expression is controlled by dpy-19. This study produced the polyclonal anti-mammalian DPY-19 (MDPY-19) antibody and showed the distribution of anti-MDPY-19 immunopositive cells. In addition, the mammalian dpy-19 (Mdpy-19) 5'-flanking region was analyzed by in vivo transient transfection assays. Mdpy-19 is expressed in ependymal cells in the adult rat brain, embryonic neuroepithelial cells, and cultured neural stem cells. In the adult rat ventricular zone, immunoreactivity with MDPY-19 of the dorsal area is stronger than that of the ventral area. Embryonic neuroepithelial cells and radial glial cells show strong anti-MDPY-19 immunoreactivity. We created the Mdpy-19 green fluorescent protein (GFP) reporter gene. Our results show that Mdpy-19 is expressed in neural stem cells and progenitor cells, especially radial glial cells. Only ependymal cells among differentiated cells express Mdpy-19 gene. However, the possibility exists that the Mdpy-19 gene is able to transcript in GABAergic neurons. It is suggested that a factor existing in mature neurons withdraws the expression of Mdpy-19.