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B-50/GAP-43 expression by the olfactory receptor cells and the neurons migrating from the olfactory placode in
V Pellier1, L Astic, A B Oestreicher
1Laboratoire de Physiologie Neurosensorielle, UCB/Lyon I, Villeurbanne, France.
Insights
Growth-associated phosphoprotein B-50/GAP-43 expression marks early neuronal development in the rat olfactory system. Its presence coincides with neurite outgrowth and neuronal migration during embryogenesis.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- B-50/GAP-43 is a key growth-associated phosphoprotein in developing neuronal systems.
- Understanding its role in the olfactory system is crucial for deciphering neural development.
- Early expression patterns can reveal critical events in olfactory system formation.
Purpose of the Study:
- To investigate B-50/GAP-43 expression in the developing rat olfactory system.
- To focus on the early embryogenesis and neonatal development of the olfactory placode.
- To correlate B-50/GAP-43 presence with neurite outgrowth and neuronal migration.
Main Methods:
- Immunocytochemistry was employed to detect B-50/GAP-43 protein.
- Analysis spanned embryonic day 12 (E12) through neonatal development.
- Double-labeling experiments used neuron-specific enolase (NSE) to confirm cell identity.
Main Results:
- B-50/GAP-43 immunoreactivity was detected as early as E12 in olfactory receptor cells with nascent neurites.
- Expression rapidly increased from E13, with nearly all neurons positive by E18.
- B-50/GAP-43 was also found in migrating cells at E13, confirmed as neuronal by NSE staining.
Conclusions:
- B-50/GAP-43 expression is an early indicator of olfactory neuron differentiation and outgrowth.
- The protein marks migrating neuronal cells involved in the early olfactory system's structural organization.
- The disappearance of these migrating neurons may relate to their role in peripheral olfactory system development.
Abstract:
B-50/GAP-43 is a growth-associated phosphoprotein that is commonly expressed in all developing neuronal systems. Using an immunocytochemistry approach, we have investigated the expression of this protein in the rat olfactory system during embryogenesis and neonatal development with a particular emphasis on the early developmental stages of the olfactory placode. Data show that already at embryonic day 12 (E12), a strong B-50/GAP-43 immunoreactivity was detected in few olfactory receptor cells well-recognizable by their positive short neuritic processes. The B-50/GAP-43 expression in the placodal epithelium thus appeared to coincide with the onset of neurite outgrowth. From E13 onwards, there was a rapid increase in the number of B-50/GAP-43-positive olfactory neurons and from E18, the protein was strongly expressed by nearly all neurons. In addition, results clearly demonstrate that as early as E13, B-50/GAP-43 was strongly expressed by many migrating cells which were seen leaving the pit epithelium in association with the first olfactory axons that penetrated the nasal mesenchyme. Many immunoreactive cells were also observed in the presumptive olfactory nerve layer. Experiments of double-labeling showed that B-50/GAP-43-immunostained migrating cells were also stained with anti-neuron-specific enolase (NSE). This confirms the neuronal nature of these early labeled migrating cells. The progressive disappearance of migrating neurons noted during the late stages of embryonic development is discussed in relation with their possible function in the early stages of development of the peripheral olfactory system.