We have investigated the pattern and regulation of Hoxa3 expression in the hindbrain and associated neural crest cells in the chick embryo, using whole mount in situ hybridization in conjunction with DiI labeling of neural crest cells and microsurgical manipulations. Hoxa3 is expressed in the neural plate and later in the neural tube with a rostral border of expression corresponding to the boundary between rhombomeres (r) 4 and 5. Initial expression is diffuse and becomes sharp after boundary formation. Hoxa3 exhibits uniform expression within r5 after formation of rhombomeric borders. Cell marking experiments reveal that neural crest cells migrating caudally, but not rostrally, from r5 and caudally from r6 express Hoxa3 in normal embryo. Results from transposition experiments demonstrate that expression of Hoxa3 in r5 neural crest cells is not strictly cell-autonomous. When r5 is transposed with r4 by rostrocaudal rotation of the rhomobomeres, Hoxa3 is expressed in cells migrating lateral to transposed r5 and for a short time, in condensing ganglia, but not by neural crest within the second branchial arch. Since DiI-labeled cells from transposed r5 are present in the second arch, Hoxa3-expressing neural crest cells from r5 appear to down-regulate their Hoxa3 expression in their new environment. In contrast, when r6 is transposed to the position of r4 after boundary formation, Hoxa3 is maintained in both migrating neural crest cells and those positioned within the second branchial arch and associated ganglia. These results suggest that Hoxa3 expression is cell-autonomous in r6 and its associated neural crest. Our results suggest that neural crest cells expressing the same Hox gene are not eqivalent; they respond differently to environmental signals and exhibit distinct degrees of cell autonomy depending upon their rhombomere of origin.

Akam
M.
(
1989
)
Hox and HOM: homologous gene clusters in insects and vertebrates.
Cell
5
,
347
349
Birgbauer
E.
,
Fraser
S. E.
(
1994
)
Violation of cell lineage compartments in the chick hindbrain.
Development
120
,
1347
1356
Birgbauer
E.
,
Sechrist
J.
,
Bronner-Fraser
M.
,
Fraser
S.
(
1995
)
Rhombomeric origin and rostrocaudal reassortment of neural crest cells revealed by intravital microscopy.
Development
121
,
935
945
Carpenter
E. M.
,
Goddard
J. M.
,
Chisaka
O.
,
Manley
N. R.
,
Capecchi
M. R.
(
1993
).
Loss of Hox-a1 (Hox-1.6) function results in the reorganization of the murine hindbrain.
Development
118
,
1063
1075
Dolle
P.
,
Lufkin
T.
,
Krumlauf
R.
,
Mark
M.
,
Duboule
D.
,
Chambon
P.
(
1993
)
Local alterations of Krox-20 and Hox gene expression in the hindbrain of Hox-a1 (Hox-1. 6) homozygote null mutant embryos.
Proc. Natl. Acad. Sci. USA
90
,
7666
7670
Fraser
S. E.
,
Keynes
R. J.
,
Lumsden
A.
(
1990
)
Segmentation in the chick embryo hindbrain is defined by cell lineage restrictions.
Nature
344
,
431
435
Gendron-Maguire
M.
,
Mallo
M.
,
Zhang
M.
,
Gridley
T.
(
1993
)
Hoxa-2 mutant mice exhibit homeotic transformation of skeletal elements derived from cranial neural crest.
Cell
75
,
1317
1331
Graham
A.
,
Francis-West
P.
,
Brickell
P.
,
Lumsden
A.
(
1994
)
The signalling molecule BMP4 mediates apoptosis in the rhombencephalic neural crest.
Nature
372
,
684
686
Graham
A.
,
Heyman
I.
,
Lumsden
A.
(
1993
)
Even numbered rhombomeres control the apoptotic elimination of neural crest cells from odd numbered rhombomeres in the chick hindbrain.
Development
119
,
233
245
Hamburger
V.
,
Hamilton
L.
(
1951
)
A series of normal stages in the development of the chick embryo.
J. Morphol
88
,
49
92
Hunt
P.
,
Guilisano
M.
,
Cook
M.
,
Sham
M.
,
Faiella
A.
,
Wilkinson
D. G.
,
Boncinelli
E.
,
Krumlauf
R.
(
1991
)
A distinct Hox code for the branchial region of the vertebrate head.
Nature
353
,
861
864
Hunt
P.
,
Wilkinson
D.
,
Krumlauf
R.
(
1991
)
Patterning the vertebrate head: murine Hox-2 genes mark distinct subpopulations of premigratory and cranial neural crest.
Development
112
,
43
50
Ingham
P.
,
Martinez Arias
A.
(
1992
)
Boundaries and fields in early embryos.
Cell
68
,
221
235
Izpisua-Belmonte
J. C.
,
De Robertis
E. M.
,
Story
K. G.
,
Stern
C. D.
(
1993
)
The homeobox gene goosecoid and the origin of organizer cells in the early chick blastoderm.
Cell
74
,
645
659
Keynes
R.
,
Lumsden
A.
(
1990
)
Segmentation and the origin of regional diversity in the vertebrate central nervous system.
Neuron
2
,
1
9
Krumlauf
R.
(
1993
)
Hox genes and pattern formation in the branchial region of the vertebrate head.
Trends Genet
9
,
106
112
Krumlauf
R.
(
1994
)
Hox genes in vertebrate development.
Cell
78
,
191
201
Kuratani
S. C.
,
Eichele
G.
(
1993
)
Rhombomere transplantation repatterns the segmental organization of cranial nerves and reveals cell-autonomous expression of a homeodomain protein.
Development
117
,
105
117
Lumsden
A.
,
Keynes
R. J.
(
1989
)
Segmental patterns of neuronal development in the chick hindbrain.
Nature
337
,
424
428
Lumsden
A.
,
Sprawson
N.
,
Graham
A.
(
1991
)
Segmental origin and migration of neural crest cells in the hindbrain region of the chick embryo.
Development
113
,
1281
1291
Mark
M.
,
Lufkin
T.
,
Vonesch
J.-L.
,
Ruberte
E.
,
Olivo
J.-C.
,
Dolle
P.
,
Gorry
P.
,
Lumsden
A.
,
Chambon
P.
(
1993
)
Two rhombomeres are altered in Hoxa-1 mutant mice.
Development
119
,
319
338
McGinnis
W.
,
Krumlauf
R.
(
1992
)
Homeobox genes and axial patterning.
Cell
68
,
283
302
Nieto
M. A.
,
Sechrist
J.
,
Wilkinson
D. G.
,
Bronner-Fraser
M.
(
1995
)
Relationship between spatially restricted Krox-20 gene expression in branchial neural crest and segmentation in the chick embryo hindbrain.
EMBO J
14
,
1697
1710
Noden
D. M.
(
1983
)
The role of neural crest in patterning avian cranial skeletal, connective and muscle tissues.
Dev. Biol
96
,
144
165
Prince
V.
,
Lumsden
A.
(
1994
)
Hoxa-2 expression in normal and transposed rhombomeres: independent regulation in the neural tube and neural crest.
Development
120
,
911
923
Rijli
F. M.
,
Mark
M.
,
Lakkaraju
S.
,
Dierich
A.
,
Dolle
P.
,
Chambon
P.
(
1993
)
A homeotic transformation is generated in the rostral branchial region of the head by disruption of Hoxa-2, which acts as a selector gene.
Cell
5
,
1333
1349
Sechrist
J.
,
Serbedzija
G.
,
Scherson
T.
,
Fraser
S. E.
,
Bronner-Fraser
M.
(
1993
)
Segmental migration of the hindbrain neural crest does not arise from its segmental generation.
Development
118
,
691
703
Sham
M. H.
,
Vesque
C.
,
Nonchev
S.
,
Marshall
H.
,
Frain
M.
,
Das Gupta
R.
,
Whiting
J.
,
Wilkinson
D.
,
Charnay
P.
,
Krumlauf
R.
(
1993
)
The zinc finger gene Krox 20 regulates HoxB2 (Hox2. 8) during hindbrain segmentation.
Cell
72
,
183
196
Vaage
S.
(
1969
)
The segmentation of the primitive neural tube in chick embryos (Gallus domesticus).
Adv. Anat. Embryol. Cell Biol
41
,
1
88
Wilkinson
D.
,
Bhatt
S.
,
Cook
M.
,
Boncinelli
E.
,
Krumlauf
R.
(
1989
)
Segmental expression of Hox-2 homeobox-containing genes in the developing mouse hindbrain.
Nature
341
,
405
409
Wilkinson
D. G.
,
Bhatt
S.
,
Chavrier
P.
,
Bravo
R.
,
Charnay
P.
(
1989
)
Segment-specific expression of a zinc-finger gene in the developing nervous system of the mouse.
Nature
337
,
461
464
Wilkinson
D. G.
,
Nieto
A. M.
(
1993
)
Analysis of gene expression by in situ hybridisation to tissue sections and in whole mounts.
Methods Enzymol
225
,
361
373
Zhang
M.
,
Kim
H.-J.
,
Marshall
H.
,
Gendron-Maguire
M.
,
Lucas
D.
,
Baron
A.
,
Gudas
L.
,
Gridley
T.
,
Krumlauf
R.
,
Grippo
J.
(
1994
)
Ectopic Hoxa-1 induces rhombomere transformation in the mouse hindbrain.
Development
120
,
2431
2442
This content is only available via PDF.