De. Jones et al., EXPRESSION OF BETA-GALACTOSIDASE UNDER THE CONTROL OF THE HUMAN C-MYCPROMOTER IN TRANSGENIC MICE IS INHIBITED BY MITHRAMYCIN, Oncogene, 10(12), 1995, pp. 2323-2330
In order to assess the functional contribution of the human c-myc prom
oter region in the expression of the c-myc gene, transgenic mouse line
s 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 da
y 11 of embryogenesis by histochemical staining of whole embryos using
-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal) as substra
te, localizing specifically to early spinal cord tissue. beta-galactos
idase activity can be demonstrated by histochemical staining in brain
tissue of day 14 embryos, localizing mainly to the prefrontal cortex r
egion, while relative amounts of beta-galactosidase in spinal cord tis
sue are reduced. Determination of specific activity of beta-galactosid
ase using resorufin-beta galactopyranoside as substrate in homogenates
of whole embryos heterozygous for the human c-myc/lac Z transgene dem
onstrates significantly elevated beta-galactosidase activity over cont
rol embryos in day 11 and day 14 embryos. Surprisingly, cell homogenat
es of brain tissue from adult G(1) generation mice heterozygous for th
e human c-myc/lac Z transgene demonstrate greater than 10-foId higher
specific activity of beta-galactosidase over normal control brain tiss
ue. Specific inhibition of the c-myc/lac Z transgene was also demonstr
ated in developing embryos using mithramycin given at a dose of 150 mu
g kg(-1) d(-1) intraperitoneal to pregnant females on days 7-13 of ge
station. Both histochemical staining of beta-galactosidase and specifi
c activity assays of day 14 embryos demonstrated significantly lower l
evels of beta-galactosidase than untreated controls. These results are
unique since we are able to detect expression of beta-galactosidase i
n developing embryonic central nervous system tissue along with adult
brain tissue of animals carrying the human c-myc Z transgene and we ar
e able to specifically inhibit expression of the transgene using mithr
amycin administered in utero.