Fig. 4. Cardiac-specific expression of Rho GDI transgene. (A) Whole-mount in situ hybridization of nontransgenic (NTG) and transgenic F₁ embryos at E9.5 from the H2 founder (TG) with an antisense probe generated from the polyadenylation sequences of the transgene (human G-CSF cDNA). No signal was observed with a sense probe (data not shown). (B) Expression of the transgene was markedly increased in the adult mouse heart. Western blot analysis was performed with cardiac proteins extracted from nontransgenic and heterozygotes of the M2 founder line at E12.5 or 4 weeks after birth. The blot was probed with an anti-Rho GDI antibody recognizing both endogenous Rho GDI and the transgene. (C) The expression level of the transgene was proportional to the copy number. Western blot analysis was performed with cardiac proteins extracted from adult nontransgenic and transgenic heterozygotes of L1, L2, M1 and M2 founder lines using an anti-Rho GDI polyclonal antibody. An anti-Myc antibody recognizes only the transgene (data not shown).