title: Expression of beta-galactosidase under the control of the human c-myc promoter in transgenic mice is inhibited by mithramycin.
abstract: In order to assess the functional contribution of the human c-myc promoter region in the expression of the c-myc gene, transgenic mouse lines containing a bacterial lac Z gene encoding beta-galactosidase under the control of the human c-myc protooncogene promoter were generated. Transgenic mouse embryos heterozygous for the human c-myc Z transgene demonstrate high amounts of beta-galactosidase activity as early as day 11 of embryogenesis by histochemical staining of whole embryos using 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) as substrate, localizing specifically to early spinal cord tissue. beta-galactosidase activity can be demonstrated by histochemical staining in brain tissue of day 14 embryos, localizing mainly to the prefrontal cortex region, while relative amounts of beta-galactosidase in spinal cord tissue are reduced. Determination of specific activity of beta-galactosidase using resorufin-beta-galactopyranoside as substrate in homogenates of whole embryos heterozygous for the human c-myc/lac Z transgene demonstrates significantly elevated beta-galactosidase activity over control embryos in day 11 and day 14 embryos. Surprisingly, cell homogenates of brain tissue from adult G1 generation mice heterozygous for the human c-myc/lac Z transgene demonstrate greater than 10-fold higher specific activity of beta-galactosidase over normal control brain tissue. Specific inhibition of the c-myc/lac Z transgene was also demonstrated in developing embryos using mithramycin given at a dose of 150 micrograms kg-1 d-1 intraperitoneal to pregnant females on days 7-13 of gestation. Both histochemical staining of beta-galactosidase and specific activity assays of day 14 embryos demonstrated significantly lower levels of beta-galactosidase than untreated controls. These results are unique since we are able to detect expression of beta-galactosidase in developing embryonic central nervous system tissue along with adult brain tissue of animals carrying the human c-myc Z transgene and we are able to specifically inhibit expression of the transgene using mithramycin administered in utero.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Jones
authors.forename: D M
authors.initials: DM
authors.lastname: Cui
authors.forename: D M
authors.initials: DM
authors.lastname: Miller
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology; D004622:Embryo, Mammalian / Q000201:enzymology; D005260:Female; D005697:Galactosides / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D016259:Genes, myc / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008926:Plicamycin / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism
chemical_list: D005697:Galactosides; D016271:Proto-Oncogene Proteins c-myc; C007816:beta-galactoside; D008926:Plicamycin