Fig. 5

Pregnancy of cloned embryos derived from tetracycline dependent gene expression. a Illustration of the tetracycline dependent gene expression system in cattle; the somatic cell nuclear transfer protocol was presented in our previous publication [15]. In brief, piggyBac (PB) DNA containing red fluorescence protein (RFP) under tetracycline-controlled transcription activation promoter (tet-on) was transfected into bovine somatic cells with the PB-transposase and -reverse tetracycline-controlled transactivator (rtTA). An RFP expressing cell was microinjected into enucleated bovine oocytes, fused, and activated chemically. The blastocysts were transferred into a recipient cow. b Representative confirmation pictures of pregnancy using ultrasonography (upper) and collected fetuses (lower); c RFP expression following doxycycline treatments; to know if RFP expression was induced by tetracycline, a small piece of tissue was exposed with Doxycycline [Dox (+)] or without Doxycycline [Dox (−)]; d Identification of the transgene integration site via next generation sequencing analysis. Four transgene integration sites were identified