Apoptotic foci and apoptosis-related gene expression in the E11 AGM. TUNEL staining was performed on transverse sections from the truncal region of an E11 embryo to localize apoptotic cells in the AGM region. (A-B) A representative section is shown at 10 × magnification (A) and at 40 × magnification (B). TUNEL⁺ (black/gray) foci and diffuse scattered individual cells are observed. DA indicates lumen of dorsal aorta; UGR, urogenital ridge; M, mesentery. TUNEL staining was performed 3 times on 2 wild-type and 2 Bcl-2 transgenic embryos. No obvious difference in the TUNEL staining pattern was observed when sections from Bcl-2 transgenic embryos were compared to sections from nontransgenic embryos. (C) Expression of the antiapoptotic genes Bcl-2 and Bcl-x and the proapoptotic Bim gene in the E11 AGM, aorta, UGRs, and liver region of a nontransgenic embryo. RT-PCR analysis was performed on cDNAs made from the indicated midgestation tissues. Signal intensity from the actin PCR fragment was used as a normalization control. Note that, as expected, the Bim primers amplify 2 different transcript isoforms (splice variants). (D) RT-PCR analysis of a Bcl-2 transgenic embryo reveals altered levels of Bcl-2, Bcl-x, and Bim gene expression in the E11 aorta and UGR. RT-PCR analysis was performed 3 times and confirmed on 3 independent sets of cDNAs.