Figure 2.

Recombination induced by cTnT-Cre. (a,b) The cTnT Cre;R26R^+/- embryos at E7.5 (a) and E10.5 (b) were stained with X-gal. (c) The heart dissected from the embryo in panel b. (d,e) Sagittal sections of a cTnT-Cre; R26R^+/- embryo at E10.5 stained with X-gal. Panel d represents the view in bright field and panel e corresponds to the dark-field view. X-gal staining products appear pink, and are more easily detected in the dark field. Sections were counterstained with eosin. (f) Embryonic hearts were collected from Bmp4^{loxp-lacZ/tm1} (-Cre) or Bmp4^{cre;loxp-lacZ/tm1} (+Cre) embryos from stages E9.5 to E11.5. RT-PCR analysis was performed to examine the expression of Bmp4, and β-Actin was used as a positive control. No PCR products were obtained if reverses transcriptase was omitted (data not shown). (H) Heart; (hf) head fold; (la) left atrium; (ot) outflow tract; (pc) precardiac crescent; (a) atrium; (ra) right atrium; (v) ventricle; (lv) left ventricle. Bars, 0.4 mm.