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Intracellular Nogo-A facilitates initiation of neurite formation in mouse midbrain neurons in vitro
Z Kurowska1, P Brundin2, M E Schwab3
1Neural Plasticity and Repair Unit, Wallenberg Neuroscience Center, Lund University, BMC A10, 22184 Lund, Sweden; Neurodegeneration and Inflammation Genetics Unit, Wallenberg Neuroscience Center, Lund University, BMC A10, 22184 Lund, Sweden.
Abstract:
Nogo-A is a transmembrane protein originally discovered in myelin, produced by postnatal CNS oligodendrocytes. Nogo-A induces growth cone collapse and inhibition of axonal growth in the injured adult CNS. In the intact CNS, Nogo-A functions as a negative regulator of growth and plasticity. Nogo-A is also expressed by certain neurons. Neuronal Nogo-A depresses long-term potentiation in the hippocampus and modulates neurite adhesion and fasciculation during development in mice. Here we show that Nogo-A is present in neurons derived from human midbrain (Lund human mesencephalic (LUHMES) cell line), as well as in embryonic and postnatal mouse midbrain (dopaminergic) neurons. In LUHMES cells, Nogo-A was upregulated threefold upon differentiation and neurite extension. Nogo-A was localized intracellularly in differentiated LUHMES cells. Cultured midbrain (dopaminergic) neurons from Nogo-A knock-out mice exhibited decreased numbers of neurites and branches when compared with neurons from wild-type (WT) mice. However, this phenotype was not observed when the cultures from WT mice were treated with an antibody neutralizing plasma membrane Nogo-A. In vivo, neither the regeneration of nigrostriatal tyrosine hydroxylase fibers, nor the survival of nigral dopaminergic neurons after partial 6-hydroxydopamine lesions was affected by Nogo-A deletion. These results indicate that during maturation of cultured midbrain (dopaminergic) neurons, intracellular Nogo-A supports neurite growth initiation and branch formation.
Insights
Intracellular Nogo-A supports neurite growth and branching in developing midbrain neurons. Deleting Nogo-A reduced neurites, but this effect was not seen in vivo, suggesting a role specific to neuronal maturation.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Nogo-A is a myelin-associated protein inhibiting axonal growth in the adult central nervous system (CNS).
- Neuronal Nogo-A also influences neural plasticity and development, modulating neurite adhesion and fasciculation.
- Its role in neuronal development, particularly in dopaminergic neurons, remains less understood.
Purpose of the Study:
- To investigate the presence and function of Nogo-A in human and mouse midbrain dopaminergic neurons.
- To determine the role of intracellular versus cell surface Nogo-A in neuronal development and regeneration.
Main Methods:
- Expression analysis of Nogo-A in LUHMES cells and primary mouse midbrain neurons.
- Assessment of neurite outgrowth and branching in Nogo-A knockout (KO) and wild-type (WT) neurons.
- In vivo studies using partial 6-hydroxydopamine lesions in Nogo-A KO and WT mice.
Main Results:
- Nogo-A is present in human LUHMES and mouse midbrain dopaminergic neurons, with increased expression during differentiation.
- Nogo-A localizes intracellularly in differentiated LUHMES cells.
- Nogo-A KO neurons showed reduced neurite numbers and branching in vitro, a phenotype not rescued by neutralizing cell surface Nogo-A.
- Nogo-A deletion did not affect in vivo nigrostriatal fiber regeneration or dopaminergic neuron survival after injury.
Conclusions:
- Intracellular Nogo-A plays a crucial role in supporting neurite growth initiation and branching during the maturation of cultured midbrain dopaminergic neurons.
- The function of Nogo-A in neuronal development appears to be context-dependent, with a significant role observed in vitro but not in vivo regeneration models.
