Fig. 2. Transient downregulation of numerous cardiac-specific genes after cardiac injury in newts. RT-PCR of RNA isolated from sham-operated animals (sham), and 7, 14 and 21 days after injury (7d pi, 14d pi, 21d pi). Two separate hearts were analyzed for each time point. Note that hearts shown in lanes 4, 6, and 8 received a more extensive damage than those shown in lanes 5, 7 and 9. The expression of MyHC, cTnT, cTnI, cTnC and cardiac actin was downregulated 1 week after heart injury but returned to levels of sham-operated hearts within three weeks. 40S ribosomal protein S21 was expressed at constant levels during regeneration and served as an internal control. Lane 1, molecular mass marker; lanes 2 and 3, sham operated hearts; lanes 4 and 5, 7 days post injury (pi); lanes 6 and 7, 14 days pi; lanes 8 and 9, 21 days pi.