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consequences, since the electroporated chick embryos displayed slower (53 vs.
100beats perminute) and arrhythmic heart beats compared to controls (13). The
use of morpholino-‐oligonucleotides against thmRNA allowed the knock-‐down of
its expression in the chick embryo, leading to a decrease in AMHC1 and Tbx5
expression together with an atrophic sinoatrial region and oversized ventricular
region(13). Thus, THactionnot only induces cardiacdifferentiation invivobut the
catecholaminepathwayregulatesheartpatterning, conferringatriogenic identity.
Figure 7. Induction of cardiac genes and cardiomyocytes differentiation by L-‐DOPA and
Dopamine.
A) Drawing corresponds to a stage 5 embryo scheme with a microbead implanted.
Beads were soaked with either PBS (vehicle), or a solution of 10 µmol/L L-‐DOPA or dopamine.
Stage 10-‐12 chick embryos were subjected to whole-‐mount in situ hybridization for the genes
indicated (Nkx2.5, Tbx5, AMHC1) or immunohistochemistry for MF20. Ectopic tissue adjacent to
the bead coatedwith L-‐DOPA or dopamine (arrow) expressed all markers. PBS did not induce any
signal (not shown). B) Ultrastructure of the ectopic tissue induced. Thewhite arrowheads indicate
theZbands and thepurple andyellowlines delineate I andAbands of the cardiomyocytes adjacent
to thebead. (Modified from[13]).
