The human homologue of drosophila tailless gene tll, TLX (NR2E1), is a member of the nuclear receptor (NR) family which act as ligand-dependent transcriptional regulators. In adults, expression of TLX is strongly limited to adult neural stem cells (NSCs) residing in the subventricular zone and dentate gyrus of the hippocampus as well as in retinal progenitor cells .