Probe:	Hoxa4 probe2
Probe preparation:	Antisense labelled with S35 RNA

Structure	Level	Pattern	Image	Note
TS20: vertebral cartilage condensation	Present	Graded	3A	Labeling markedly declined over the first four thoracic vertebrae (pv8-11). Labelling intensity continued to decline progressively but remained above background until pv18. Anterior parts of thoracic vertebrae were labelled more intensely than posterior.

Structure	Level	Pattern	Image	Note
TS20: thyroid gland	Present		4A/B
TS20: pharynx	Absent		4A/B	Transcripts were not present generally in tissues that formed the floor of the pharynx. Transcripts were not detectable anterior to the thyroid duct.
TS20: trachea	Strong		4A/B
TS20: lung	Strong	Regionally restricted	4A/B	Labelling was restricted to mesodermal components and did not include the endodermally derived lung epithelium.

Structure	Level	Pattern	Image	Note
TS20: heart	Present	Regionally restricted		Transcripts were detected both within the walls of the aortic trunk and within a small patch of tissue restricted to the base of the heart.
TS20: outflow tract aortic component	Present	Regionally restricted		Transcripts were detected within the walls of the aortic trunk.
TS20: pharynx	Absent			Expression was not detected in ventral pharynx.
TS20: lung	Present
TS20: mesonephros	Present
TS20: metanephros	Present
TS20: thyroid gland	Present
TS20: trachea	Present
TS20: stomach	Present			Transcripts were restricted to the mesodermal components.
TS20: stomach epithelium	Absent

Structure	Level	Pattern	Image	Note
TS20: central nervous system	Present	Regionally restricted	6B	The anterior boundary lay about midway along the floor of the myelencephalon. The bounday is irregular in shape along the dorsoventral axis of the nervous tissue. These irregularities have been found to be consistent among different embryos.
TS20: medulla oblongata floor plate	Present	Regionally restricted	6B	The anterior boundary lay about midway along the floor of the myelencephalon. The bounday is irregular in shape along the dorsoventral axis of the nervous tissue. These irregularities have been found to be consistent among different embryos.

Structure	Level	Pattern	Image	Note
TS20: spinal cord	Present	Graded		A progressive anterior-to-posterior fall in abundance of transcripts was observed.