Antibody:	anti-Hoxa2 (orb184090)
Detection system:	Biotinylated secondary antibody/[Strept]avidin coupled to horseradish peroxidase

Structure	Level	Pattern	Image	Note
TS16: 2nd branchial arch ectoderm	Present	Diffuse	2B	Weaker expression.
TS16: 2nd branchial arch mesenchyme derived from neural crest	Strong	Regionally restricted	2B	Expressed in neural crest-derived cells around the facial nerve rudiment.
TS16: 2nd branchial arch	Present	Regionally restricted	2B	Heterogeneous staining in the lateral part.
TS16: 1st branchial arch	Absent		2B

Structure	Level	Pattern	Image	Note
TS16: 2nd branchial arch mesenchyme	Present	Regionally restricted	2C	Expressed in the more caudal part.
TS16: 3rd branchial arch	Present	Regionally restricted	2C	Heterogeneous staining in the lateral part.
TS16: 1st branchial arch	Absent		2C

Structure	Level	Pattern	Image	Note
TS20: Reichert's cartilage condensation	Strong		3A

Structure	Level	Pattern	Image	Note
TS21: Meckel's cartilage	Absent		3B

Structure	Level	Pattern	Image	Note
TS21: malleus pre-cartilage condensation	Present	Regionally restricted	3D	Expressed in the future handle and body.
TS21: Meckel's cartilage	Absent		3D

Structure	Level	Pattern	Image	Note
TS18: 1st branchial arch	Absent		4A

Structure	Level	Pattern	Image	Note
TS18: pre-cartilage condensation	Strong	Regionally restricted	4B	The Reichert's cartilage was characterized by a strong immunoreactivity compared to the Meckel's cartilage.
TS18: middle ear mesenchyme	Present	Regionally restricted	4B	The handle of malleus blastema was diffusely marked.

Structure	Level	Pattern	Image	Note
TS21: ossicle	Present	Diffuse	4D	Middle ear ossicles primordia exhibited a diffuse nuclear and peri-nuclear immunoreactivity. The processus brevis of the malleus, as well as the medial part of the handle was more positive, but the stapes appeared less immunoreactive than the otic capsule and other ossicular blastemata.
TS21: otic capsule	Strong		4D

Structure	Level	Pattern	Image	Note
TS18: middle ear mesenchyme	Present	Regionally restricted	5B , 5A	Expressed in the stapes.
TS18: pre-cartilage condensation	Present	Regionally restricted	5A	Expressed in the laterohyale of the Reichert's cartilage.
TS18: 2nd branchial arch mesenchyme	Present	Regionally restricted	5A	Expressed at the vicinity of the facial nerve.

Structure	Level	Pattern	Image	Note
TS21: ossicle	Present		5C	All ossicular blastemata were labelled, but the processus brevis of the malleus and lateral part of the handle seemed to be more positive.

Structure	Level	Pattern	Image	Note
TS21: ossicle	Present		5D	Expressed in the processus brevis of the malleus and handle of malleus primordium.

Structure	Level	Pattern	Image	Note
TS22: ossicle	Weak		6B	Decreased expression in ossicular blastemata, and appeared very weak in comparison with otic capsule and surrounding mesenchyme.
TS22: inner ear mesenchyme	Present		6B
TS22: otic capsule	Present		6B