In the June 24th online edition of Stem Cells, A. V. Sánchez-Sánchez et al. from the Universidad de Valencia (Spain) published their study results on genes responsible for specification and migration of primordial germ cells (PGCs) during gonadal development in vertebrates. The investigators found that the pluripotency gene, medaka Nanog (Ol-Nanog), is expressed in developing PGCs and regulates the expression of CXCR-4b by binding to its promoter region. PGC migration is guided by CXCR-4b receptor expression and binding to its ligand SDF-1a. The experimental data revealed that depletion of the Ol-Nanog protein results in aberrant migration of PGCs as well as downregulating the expression of CXCR-4b. Similarily, overexpression of CXCR-4b and depletion of Ol-Nanog protein can rescue defective migration, whereas, overexpression of SDF-1a cannot restore proper PGC migration. The authors concluded that their results "indiciate that Ol-Nanog mediates PGC migration by regulating CXCR-4b expression."