Model Description: A Dre-Wpre-polyA expression cassette was knocked into the Wnt1 gene start codon site. Wnt1 gene is involved in stem cell poliferation in multiple systems, including the hematopoietic system and the embryonic nervous system. This strain may be useful for studying central nervous system development. When crossed with a strain carrying a gene flanked by rox sites, the flanked gene will be removed in cells expressing dre.