Generation of liver-specific, tetracycline-regulated Hepc1 transgenic mice. (A) Southern blot analysis identified 4 TRE.Hepc1 founders (no. 2180, 2181, 2183, 2185) among 14 mice. (B) Because expression of the TRE.Hepc1 transgene requires binding of the tTA to the TRE, the TRE.Hepc1 transgene was only expressed in the presence of tTA. (C) Mice homozygous for the hepatocyte-specific tTA transgene (shown in black on the left) were mated to mice hemizygous for the TRE.Hepc1 transgene (shown in white on the right; Tg denoted by a black oval). Neither of the parental strains expressed Hepc1 from the transgene. All progeny (shown in gray) from this cross carried the tTA transgene. Only mice that additionally carried the TRE.Hepc1 transgene (Tg⁺) could express transgenic Hepc1. (D) Northern blot analysis confirmed expression of TRE.Hepc1 transgene mRNA (Hepc Tg, lanes 5-8) and down-regulation of endogenous Hepc when compared with controls (lanes 1-4).