Immunohistochemical observation of growth-associated protein 43 (GAP-43) in the developing circumvallate papilla of the rat.
The distribution and development of growth-associated protein 43 (GAP-43)-like immunoreactivity (-LI) in the rat circumvallate papilla (CVP) were compared to those of protein gene product 9.5 (PGP 9.5)-LI. In the adult, thick GAP-43-like immunoreactive (-IR) structures gathered densely in the subgemmal region. Some of these further penetrated the apical epithelium and trench wall epithelium. At least two types of GAP-43-IR structures were recognized; taste bud-related and non-gustatory GAP-43-IR neural elements. Immunoelectron microscopy revealed that GAP-43-LI was localized predominantly in the Schwann cells, and a few axons displayed GAP-43-LI in the lamina propria. In the trench epithelium, GAP-43-LI was detected in the cytoplasmic side of the axonal membrane. Some intragemmal GAP-43-IR axons made synaptic-like contacts with taste bud cells. At least four developmental stages were defined on the basis of the changes in distribution of GAP-43-LI. In stage I [embryonic day (E) 16-17] GAP-43-IR structures accumulated at the lamina propria just beneath the newly-formed circumvallate papilla. In stage II (E18-19) GAP-43-IR nerve fibers began to penetrate the apical epithelium. In stage III [E20-postnatal day (P) 0] GAP-43-IR nerve fibers first appeared in the trench wall epithelium. Penetration of GAP-IR nerve fibers occurred in the inner trench wall epithelium first, and then in the outer trench wall epithelium. In stage IV (P1-) the distribution of GAP-43-LI was similar to that observed in the adult; but the density of GAP-43-LI was much higher than in adults. PGP 9.5-LI showed a similar distribution pattern to that of GAP-43-LI, except for round-shaped cells in the apical epithelium at the late embryonic stages, and in taste bud cells and intralingual ganglionic cells which lacked GAP-43-LI. The similarities in distribution patterns of GAP-43-LI and PGP 9.5-LI during the development and mature circumvallate papilla suggest that GAP-43 may be a key neuronal molecule for induction and maintenance of the taste buds.
Department of Oral Anatomy and Developmental Biology, Osaka University Faculty of Dentistry, 1-8, Yamadaoka, Suita, Osaka 565-0871, Japan. wakisaka@dent.osaka-u.ac.jp
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S
Wakisaka
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Daikoku
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Miyawaki
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SH
Youn
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Maeda
K
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Kurisu
D000818:Animals; D005260:Female; D019922:GAP-43 Protein / Q000378:metabolism*; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013650:Taste Buds / Q000196:embryology* / Q000378:metabolism*; D013869:Thiolester Hydrolases / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
D019922:GAP-43 Protein; D009419:Nerve Tissue Proteins; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase