Probe:	Hoxa-2 cDNA2
Probe preparation:	Antisense labelled with radioactivity RNA

Structure	Level	Pattern	Image	Note
TS20: head mesenchyme	Present	Regionally restricted	1A , 1B/C	Widely expressed throughout the second branchial arch mesenchyme. But expressions in the condensations forming the second arch skeletal elements were mostly negative.
TS20: middle ear mesenchyme	Present	Regionally restricted	1A , 1B/C	No expression in the developing stapes, identified as a condensation surrounding the stapedial artery.
TS20: otic capsule	Present	Regionally restricted	1A , 1B/C	Expressed around the stapes in the oval window.

Structure	Level	Pattern	Image	Note
TS20: head mesenchyme	Present	Regionally restricted	1G	Widely expressed throughout the second branchial arch mesenchyme. But expressions in the condensations forming the second arch skeletal elements were mostly negative.
TS20: otic capsule	Present	Regionally restricted	1G	Expressed around the stapes in the oval window.
TS20: middle ear mesenchyme	Absent		1G	No expression in the developing stapes, identified as a condensation surrounding the stapedial artery.

Structure	Level	Pattern	Image	Note
TS21: head mesenchyme	Present	Regionally restricted	1I/J	Widely expressed throughout the second branchial arch mesenchyme. But expressions in the condensations forming the second arch skeletal elements were mostly negative.
TS21: stapes pre-cartilage condensation	Absent		1I/J
TS21: middle ear mesenchyme	Present	Regionally restricted	1I/J	Expressed around the stapes and through the prospective wall of the otic capsule in the region of the oval window.
TS21: otic capsule	Present	Regionally restricted	1I/J	Expressed around the stapes and through the prospective wall of the otic capsule in the region of the oval window.

Structure	Level	Pattern	Image	Note
TS20: temporal bone petrous part	Absent		1L/M	No expression in the developing styloid process.

Structure	Level	Pattern	Image	Note
TS21: chondrocranium	Absent		7A/B	Expression is absent from the mesenchyme forming the dermal bones of the skull.

Structure	Level	Pattern	Image	Note
TS17: 2nd branchial arch mesenchyme	Present	Regionally restricted		Widely expressed throughout the second branchial arch mesenchyme. But expressions in the condensations forming the second arch skeletal elements were mostly negative.

Structure	Level	Pattern	Image	Note
TS22: head mesenchyme	Present	Regionally restricted		Widely expressed throughout the second branchial arch mesenchyme. But expressions in the condensations forming the second arch skeletal elements were mostly negative.