Probe:	MLC3F-B
Probe preparation:	Antisense labelled with digoxigenin RNA

Structure	Level	Pattern	Image	Note
TS17: heart atrium	Present		2a
TS17: primitive ventricle	Present		2a
TS17: myotome	Weak		2a	Expressed in skeletal muscle in the myotomal compartment of the somite.

Structure	Level	Pattern	Image	Note
TS13: primitive ventricle	Present		2d
TS13: sinus venosus	Present		2d	The inflow region, composed of the sinus horns.
TS13: outflow tract	Absent		2d	Outflow region.
TS13: common atrial chamber	Present		2d	Primitive atrium.

Structure	Level	Pattern	Image	Note
TS15: heart atrium	Present	Non-Uniform	2g	Higher expression in the embryonic right atrium than in the left atrium.
TS15: primitive ventricle	Present	Non-Uniform	2g	More expression in the embryonic left ventricle than in the right.
TS15: outflow tract	Absent		2g

Structure	Level	Pattern	Image	Note
TS15: heart atrium	Present	Non-Uniform	2h	Higher expression in the embryonic right atrium than in the left atrium.
TS15: primitive ventricle	Present	Non-Uniform	2h	More expression in the embryonic left ventricle than in the right.
TS15: outflow tract	Absent		2h

Structure	Level	Pattern	Image	Note
TS15: heart atrium	Present		2i
TS15: primitive ventricle	Present		2i
TS15: outflow tract	Absent		2i	There was a clear boundary between the future right-ventricular region and the negative outflow tract.

Structure	Level	Pattern	Image	Note
TS17: heart atrium	Strong	Non-Uniform	3a	Robust expression in the right atrium. Reduced expression in the left.
TS17: primitive ventricle	Present	Non-Uniform	3a	Expression is stronger in the left than the right.
TS17: outflow tract	Absent		3a

Structure	Level	Pattern	Image	Note
TS17: heart atrium	Strong	Non-Uniform	3b	Robust expression in the right atrium. Reduced expression in the left.
TS17: primitive ventricle	Present	Non-Uniform	3b	Expression is stronger in the left than the right. Transcripts accumulate more in the ventricular trabeculations than the compact myocardium.
TS17: outflow tract	Absent		3b

Structure	Level	Pattern	Image	Note
TS19: left atrium	Strong		3c
TS19: right atrium	Strong		3c
TS19: heart left ventricle	Weak		3c	Very low level.
TS19: heart right ventricle	Absent		3c
TS19: outflow tract	Absent		3c

Structure	Level	Pattern	Image	Note
TS21: heart left ventricle	Absent		3e
TS21: heart right ventricle	Absent		3e
TS21: left atrium	Strong		3e
TS21: right atrium	Strong		3e

Structure	Level	Pattern	Image	Note
TS21: superior vena cava	Strong	Regionally restricted	3f	Expressed in myocardial cells of the superior caval veins.
TS21: left atrium	Strong		3f
TS21: right atrium	Strong		3f
TS21: heart left ventricle	Absent		3f
TS21: heart right ventricle	Absent		3f

Structure	Level	Pattern	Image	Note
TS11: heart	Present	Uniform		Symmetrically distributed in the cardiac crescent.

Structure	Level	Pattern	Image	Note
TS15: sinus venosus	Absent
TS15: atrioventricular canal	Present

Structure	Level	Pattern	Image	Note
TS17: cardinal vein	Present

Structure	Level	Pattern	Image	Note
TS20: left atrium	Present
TS20: right atrium	Present
TS20: heart atrium	Present			Both atria expressed to a similar level.
TS20: heart left ventricle	Trace			Barely detectable.