Probe:	Sek-1 cDNA1
Probe preparation:	Antisense labelled with digoxigenin RNA
Visualized with:	Alkaline phosphatase

Structure	Level	Pattern	Image	Note
TS11: future brain	Present	Regionally restricted		A large domain of homogeneous expression was detected in the hindbrain, covering the region between the pre- and post-otic sulci.

Structure	Level	Pattern	Image	Note
TS12: future hindbrain	Present	Regionally restricted	1A	Expression was up-regulated in the anterior part.

Structure	Level	Pattern	Image	Note
TS12: future hindbrain	Present	Regionally restricted	1B	Expression was up-regulated in the anterior part. The expression domain coincided with the narrow band of cells initially activating Egr2 (Krox-20 - Xgal staining).

Structure	Level	Pattern	Image	Note
TS12: future hindbrain	Present	Regionally restricted	1C	Initally, expression at a low level in a broad domain occurred normally in the mutant.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1D	Expression was restricted along the antero-posterior axis to prospective rhombomere3 and to a more posterior domain consisting of only a few cells in the lateral neural plate corresponding to prospective rhombomere 5.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1E	Expression was restricted along the antero-posterior axis to prospective rhombomere3 and rhombomere 5. Lower expression was noted in prospective rhombomere 2, 4 and 6.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Absent		1F	Up-regulation of expression in prospective rhombomeres 3 and 5 did not happen in the mutant.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1G	The stripes of expression in prospective rhombomeres 3 and 5 broadened and formed sharp boundaries.
TS12: head mesenchyme	Present	Regionally restricted	1G	Expression was detected in the lateral mesoderm adjacent to rhombomeres 3-6.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1H	The stripes of expression in prospective rhombomeres 3 and 5 broadened and formed sharp boundaries. The domains coincided with Egr2 (Krox-20 lacZ staining). Expression was downregulated in rhombomere 4, but persisted at low level in 2 and dorsally in 6.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1I	At the 6-8 somite stage, no expression was observed in rhombomere 3 and 5. However, low levels of expression were detected in rhombomeres 2, 4 and 6 as in wild type.
TS12: head mesenchyme	Present	Regionally restricted	1I	Expression was detected in the lateral head mesoderm as in wild type.

Structure	Level	Pattern	Image	Note
TS12: rhombomere	Present	Regionally restricted	1J	At the 6-8 somite stage, no expression was observed in rhombomere 3 and 5. However, low levels of expression were detected in rhombomeres 2, 4 and 6 as in wild type.
TS12: head mesenchyme	Present	Regionally restricted	1J	Expression was detected in the lateral head mesoderm as in wild type.

Structure	Level	Pattern	Image	Note
TS13: rhombomere 5	Absent		1K

Structure	Level	Pattern	Image	Note
TS14: rhombomere 3	Present		1L
TS14: rhombomere 5	Present		1L
TS14: rhombomere 2	Weak		1L

Structure	Level	Pattern	Image	Note
TS14: rhombomere 3	Absent		1M
TS14: rhombomere 5	Absent		1M
TS14: rhombomere 2	Weak		1M	Low levels of expression persisted in rhombomere 2 cells.

Structure	Level	Pattern	Image	Note
TS14: migrating neural crest	Present	Regionally restricted	2B	Expression was detected in neural crest cells emerging from the rhombomere 5/6 boundary region and migrating ventrally into the third branchial arch as a thin stream clearly separated from the otic vesicle.
TS14: head mesenchyme	Present	Regionally restricted	2B	Expression was detected in mesenchymal cells lateral to the hindbrain.

Structure	Level	Pattern	Image	Note
TS14: migrating neural crest	Present	Regionally restricted	2C	Expression was detected in neural crest cells emerging from the rhombomere 5/6 boundary region and migrating ventrally into the third branchial arch as a thin stream clearly separated from the otic vesicle.
TS14: prosencephalon	Present	Regionally restricted	2C	Expression was detected in the diencephalic and telencephalic areas.
TS14: future diencephalon	Present		2C
TS14: head mesenchyme	Present	Regionally restricted	2C	Expression was detected in mesenchymal cells lateral to the hindbrain.
TS14: otic pit	Present		2C	Expression was detected in the otic vesicle.

Structure	Level	Pattern	Image	Note
TS14: migrating neural crest	Absent		2E	No expression was detected in populations of neural crest migrating from rhombomere 5.
TS14: head mesenchyme	Present	Regionally restricted	2E	Normal expression was detected in mesenchymal cells lateral to the hindbrain.

Structure	Level	Pattern	Image	Note
TS14: migrating neural crest	Absent		2F	No expression was detected in populations of neural crest migrating from rhombomere 5.
TS14: prosencephalon	Present	Regionally restricted	2F	Normal expression was detected in the diencephalic and telencephalic areas.
TS14: future diencephalon	Present		2F	Expression was detected as in wild type.
TS14: head mesenchyme	Present	Regionally restricted	2F	Normal expression was detected in mesenchymal cells lateral to the hindbrain.
TS14: otic pit	Present		2F	Normal expression was detected in the otic vesicle.

Structure	Level	Pattern	Image	Note
TS14: somite	Present	Regionally restricted		Expression was detected in condensing somites.
TS14: mesenchyme derived from lateral plate	Present	Regionally restricted		Expression was detected in non-segmented lateral mesoderm in the posterior part of the embryo.

Structure	Level	Pattern	Image	Note
TS14: somite	Present	Regionally restricted		Normal expression was detected in condensing somites.
TS14: mesenchyme derived from lateral plate	Present	Regionally restricted		Normal expression was detected in non-segmented lateral mesoderm in the posterior part of the embryo.