Further characterization of factor VIII-deficient mice created by gene targeting: RNA and protein studies.

Previously we created two strains of factor VIII-deficient mice by insertion of a neo gene into (1) the 3' end of exon 16 and (2) exon 17 of the factor VIII gene. Affected mice of both strains have no plasma factor VIII activity, yet are healthy with no spontaneous bleeding. Factor VIII-deficient females bred with affected males survive pregnancy and delivery.

Alterations of yeast artificial chromosome transgenic sequences in stretched embryonic stem-cell chromatin visualized by fluorescence in situ hybridization.

Transgenic mice have been generated from embryonic stem (ES) cells carrying functional genes cloned within yeast artificial chromosomes (YACs). Information on the integrity and organization of the inserted sequences, including the number of copies and their orientation to each other, is still limited by current methods. We have applied fluorescence in situ hybridization to stretched chromatin preparations from YAC-transfected ES cells to analyze the organization and copy number of the integrated sequences.

Mice lacking ornithine-delta-aminotransferase have paradoxical neonatal hypoornithinaemia and retinal degeneration.

Deficiency of ornithine-delta-aminotransferase (OAT) in humans causes hyperornithinaemia and gyrate atrophy (GA), a blinding chorioretinal degeneration. Surprisingly, OAT-deficient mice produced by gene targeting exhibit neonatal hypoornithinaemia and lethality, rescuable by short-term arginine supplementation. Post-weaning, these mice develop hyperornithinaemia similar to human GA patients.