The morphogenetic cell movements responsible for growth and morphogenesis in vertebrate embryos are poorly understood. Myotome precursor cells undergo myotomal translocation; a key morphogenetic cell movement whereby myotomal precursor cells leave the dermomyotome epithelium and enter the subjacent myotome layer where myogenic differentiation ensues. The precursors to the embryonic epaxial myotome are concentrated in the dorsomedial lip (DML) of the somite dermomyotome (W. F. Denetclaw, B. Christ and C. P. Ordahl (1997) Development 124, 1601–1610), a finding recently substantiated through surgical transplantation studies (C. P. Ordahl, E. Berdougo, S. J. Venters and W. F. Denetclaw, Jr (2001) Development 128, 1731–1744). Confocal microscopy was used here to analyze the location and pattern of myotome cells whose precursors had earlier been labeled by fluorescent dye injection into the middle region of the DML, a site that maximizes the potential to discriminate among experimental outcomes. Double-dye injection experiments conducted at this site demonstrate that cells fated to form myotome do not involute around the recurved epithelium of the DML but rather are displaced laterally where they transiently intermingle with cells fated to enter the central epithelial sheet region of the dermomyotome. Time- and position-dependent labeling experiments demonstrated that myotome precursor cells translocate directly from the middle region of the DML without prior intra-epithelial ‘translational’ movements of precursor cells to either the cranial or caudal lips of the dermomyotome epithelium, nor were any such translational movements evident in these experiments. The morphogenetic cell movements demonstrated here to be involved in the directional growth and segmental patterning of the myotome and dermomyotome bear interesting similarities with those of other morphogenetic systems.

Reference

Adams
D.
,
Keller
R.
,
Koehl
M.
(
1990
)
The mechanics of notochord elongation, straightening and stiffening in the embryo of Xenopus laevis.
Development
110
,
115
130
Aoyama
H.
,
Asamoto
K.
(
1988
)
Determination of somite cells: independence of cell differentiation and morphogenesis.
Development
104
,
15
28
Borycki
A. G.
,
Emerson
C. P.
Jr
(
2000
)
Multiple tissue interactions and signal transduction pathways control somite myogenesis.
Curr. Top. Dev. Biol
48
,
165
224
Cinnamon
Y.
,
Kahane
N.
,
Kalcheim
C.
(
1999
)
Characterization of the early development of specific hypaxial muscles from the ventrolateral myotome.
Development
126
,
4305
4315
Denetclaw
W. F.
,
Ordahl
C. P.
(
2000
)
The growth of thedermomyotome and formation of early myotome lineages in thoracolumbar somites of chicken embryos.
Development
127
,
893
905
Denetclaw
W. F.
,
Christ
B.
,
Ordahl
C. P.
(
1997
)
Location and growth of epaxial myotome precursor cells.
Development
124
,
1601
1610
Dockter
J.
,
Ordahl
C. P.
(
2000
)
Dorsoventral axis determination in the somite: a re-examination.
Development
127
,
2201
2206
Eloy-Trinquet
S.
,
Mathis
L.
,
Nicolas
J. F.
(
2000
)
Retrospective tracing of the developmental lineage of the mouse myotome.
Curr. Top. Dev. Biol
47
,
33
80
Hazelton
R. D.
(
1970
)
A radioautographic analysis of the migration and fate of cells derived from the occipital somites in the chick embryo with specific reference to the development of the hypoglossal musculature.
J. Embryol. Exp. Morph
24
,
455
465
Huang
R.
,
Christ
B.
(
2000
)
Origin of the epaxial and hypaxial myotome in avian embryos.
Anat. Embryol. (Berl)
202
,
369
374
Kaehn
K.
,
Jacob
H.
,
Christ
B.
,
Hinrichsen
K.
,
Poelmann
R.
(
1988
)
The onset of myotome formation in the chick.
Anat. Embryol
177
,
191
201
Kahane
N.
,
Cinnamon
Y.
,
Kalcheim
C.
(
1998
)
The cellular mechanism by which the dermomyotome contributes to the second wave of myotome development.
Development
125
,
4259
4271
Kahane
N.
,
Cinnamon
Y.
,
Kalcheim
C.
(
1998
)
The origin and fate of pioneer myotomal cells in the avian embryo.
Mech. Dev
74
,
59
73
Kalcheim
C.
,
Cinnamon
Y.
,
Kahane
N.
(
1999
)
Myotome formation: a multistage process.
Cell Tissue Res
296
,
161
173
Moore
S.
,
Keller
R.
,
Koehl
M.
(
1995
)
The dorsal involuting marginal zone stiffens anisotropically during its convergent extension in the gastrula of Xenopus laevis.
Development
121
,
3131
3140
Nicolas
J. F.
,
Mathis
L.
,
Bonnerot
C.
,
Saurin
W.
(
1996
)
Evidence in the mouse for self-renewing stem cells in the formation of a segmented longitudinal structure, the myotome.
Development
122
,
2933
2946
Ordahl
C. P.
,
Berdougo
E.
,
Venters
S. J.
,
Denetclaw
W. F.
Jr
(
2001
)
The dermomyotome dorsomedial lip drives growth and morphogenesis of both the primary myotome and dermomyatome epithelium.
Development
128
,
1731
1744
Tajbakhsh
S.
,
Bober
E.
,
Babinet
C.
,
Pournin
S.
,
Arnold
H.-H.
,
Buckingham
M.
(
1996
)
Gene targeting the myf-5 locus with nlacZ reveals expression of this myogenic factor in mature skeletal muscle fibres as well as early embryonic muscle.
Dev. Dynam
206
,
291
300
Venters
S. J.
,
Thorsteinsdottir
S.
,
Duxson
M. J.
(
1999
)
Early development of the myotome in the mouse.
Dev. Dyn
216
,
219
232
Williams
L.
(
1910
)
The somites of the chick.
Am. J. Anat
11
,
55
100
Wolpert
L.
,
Lewis
J.
,
Summerbell
D.
(
1975
)
Morphogenesis of the vertebrate limb.
Ciba Found. Symp
0
,
95
130
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