A murine Otx1 cDNA was inserted at the translation start site of the Otx2 gene. An adjacent loxP-flanked neomycin resistance cassette was removed in zygotes from crosses of the chimeric males and C57BL/6 females by injection of a cre cDNA under the control of the beta-actin promoter to produce F1 mice in which the neo cassette was deleted. This allele expresses Otx1 under the control of the Otx2 promoter elements. (J:51989)