Fig. 8. Pan-myocardial expression of XMLC2-lacZ in transgenic mice. (A,B) E7.5-8.0 (early and late respectively) showing nuclear localised staining in the cardiac crescent; (C,D) E8.0-8.5 (early and late respectively) showing staining throughout the linear heart tube; (E) E9.5; (F) E10.5; (G) isolated heart tube from E9.5. The atrial (A), ventricular (V) and outflow tract (OFT) regions are indicated; (H) oblique frontal view of isolated heart from E10.5. The right atrium (RA) and right ventricle (RV) are marked. Note the abrupt boundary in staining in the outflow tract (arrowheads); (I) neonatal heart with attached thymus. (J) Transverse wax section (6 µm) through the newly formed linear heart tube (E8.0); (K) Cryostat section (10 µm) through the E10.5 heart. In each case, expression is confined to nuclei of the myocardium (mc) and is entirely absent from the endocardium (ec). (L) Cryostat section through the E16.5 heart (8 µm). High levels of expression are detected throughout the myocardium of all four heart chambers but absent from the walls of the great vessels, such as the aorta (arrowheads). (M) Nuclear staining is detected in the myocardium of the right atrial appendage (RAp) and right ventricle (RV). (N) A noticeably higher density of stained nuclei is evident in the myocardium of the left ventricle (LV) but absent from the coronary arteries (inset; ca). (O) Staining is also absent from tissue of the aortic valve (av) and the wall of the aorta (arrowheads).