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Fig. 8 Knockdown of ttl restores ventricular conduction in mapre2 knockout (KO) hearts. Voltage mapping of hearts isolated from homozygous mapre2 KO larvae injected with control (ctl) vs ttl morpholinos (MOs). ttl knockdown resulted in a significant increase of ventricular conduction velocity (CV; Mann-Whitney U test, P=0.0177; A) and maximum upstroke velocity of the action potential (Vmax; dV/dt; unpaired t test, P<0.0001; B), as well as a significant decrease in ventricular action potential duration (APD; unpaired t test, P=0.0401; C). All hearts (represented by dots) were isolated from 5-dpf zebrafish larvae. The dotted squares in A reflect the main ventricular area from which the parameters were measured. APD was measured at 80% repolarization while the hearts were paced at 100 bpm.