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Neural cell adhesion molecule expression in Xenopus embryos.
Balak K
,
Jacobson M
,
Sunshine J
,
Rutishauser U
.
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The spatiotemporal pattern of expression of the neural cell adhesion molecule NCAM was mapped immunohistochemically in embryos of the frog Xenopus, from blastula to early swimming stages, using a polyclonal antibody that recognizes Xenopus NCAM. The neural plate stage was the earliest at which NCAM could be detected. The initial sites of NCAM immunoreactivity were neural ectoderm, somitic mesoderm, and chordamesoderm. During formation of the neural tube, NCAM immunoreactivity became restricted to the neuroectoderm and its derivatives. During closure of the neural tube and for 2-4 hr thereafter, NCAM was expressed in a distinctive radial pattern in coronal sections of the neural tube. NCAM was observed in neural crest cells before migration and after formation of cranial and spinal ganglia. During the period of initial neurite outgrowth, NCAM became concentrated in the developing central nerve fiber pathways. NCAM was seen on peripheral nerves from the time of their initial outgrowth and it was strongly expressed at neuromuscular junctions during the period of their formation. These results show that NCAM is expressed after neural induction and functions during morphogenesis of the neural plate and tube, some neural crest derivatives, development of nerve fiber tracts, and formation of neuromuscular connections.
FIG 1. Indirect immunofluorescent images on a video monitor showing NCAM in a coronal section of neural plate stage 1405 XWL’
embr: yo (a) and a sagittal section of a neural plate stage 16117 embryo (b). Strong immunofluorescence was seen on the neural ectoderm
adjacent mesoderm but was absent from endoderm and nonneural ectoderm. Magnification bar is 100 pm.
FIG. 2. Immunocytochemical detection of NCAM at the initial neural tube stage on a tissue section of a stage 20 Xenopus embryo. A coronal
section through the closed neural tube (NT) showing NCAM immunoreactivity over the whole neural tube with strong staining of the radial
profiles of the cells of the neuroepithelium. The notochord (N) and somites (S) are not immunoreactive. Magnification bar is 100 pm.
FIG. 3. Horizontal section through a somite of a Xenopus embryo at stage 32, during neural innervation of the somitic muscle fibers. Strong
NCAM immunoreactivity is observed at sites of neuromuscular contacts (arrows). Magnification bar is 100 pm.
FIG. 4. Coronal section of the rhomhencephalon of a stage 32 Xenopus embryo showing NCAM immunoreactivity on nerve cells (N) and
neuroepithelial germinal cells (G) and roots of cranial nerves VII/VIII (star) and more intensely on the longitudinal fiber tracts (arrows). The
pigment in the surface ectoderm is melanin. Magnification bar is 100 gm.
FIG. 5. Coronal section of spinal cord of Xenopus at stage 32 showing strong immunochemical staining on profiles of nerve cells (N) on the
longitudinal fiber tracts (L), commissural fibers (C) and spinal nerve roots (arrows). Pigment in the skin is melanin. Magnification bar is 100um
FIG. 6. Sagittal section through a Xenopus embryo at stage 26 showing NCAM immunochemical staining of the brain (N) and mandibular
branch of the trigeminal nerve (arrow). The pigment in the sucker (S) and skin is melanin. Magnification bar is 100 pm.
FIG. 7. Coronal section through the rhombencephalon of a stage 39 Xenows embryo showing NCAM immunoreactivity on profiles of cells in
the brain (N) and ganglia of cranial nerve V (arrows). Pigment in the skin is melanin. Magnification bar is 100 Frn.
