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Human microtubule-associated protein-2c localizes to dendrites and axons in fetal spinal motor neurons
1Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Abstract:
Microtubule-associated protein-2 (MAP-2) functions to maintain neuronal morphology by promoting the assembly of microtubules. MAP-2c is an alternately spliced form of MAP-2, containing the first 151 amino acids of high-molecular-weight (HMW) MAP-2 joined to the last 321 amino acids, eliminating 1,352 amino acids specific to HMW MAP-2. A polyclonal antibody generated to the splice site of human MAP-2c was used to determine its cellular localization. The MAP-2c antiserum was depleted of any HMW MAP-2 reactivity by absorption with HMW MAP-2 fusion protein. Western blot analysis of human fetal spinal cord homogenates demonstrated that the antibody is specific for human MAP-2c. MAP-2c immunoreactivity was found in the perinuclear cytoplasm and processes of anterior motor neurons and large processes of the posterior column in sections from 22-24-week human fetal spinal cord. Double-label confocal microscopy was performed using the MAP-2c polyclonal antibody and either a HMW MAP-2 or a neurofilament protein (highly phosphorylated 160- and 200-kDa protein) monoclonal antibody to identify these processes as dendrites or axons, respectively. HMW MAP-2 and MAP-2c colocalized in cell bodies and dendrites of anterior motor neurons, demonstrating for the first time the presence of native MAP-2c within dendrites. In addition, immunoelectron microscopy showed MAP-2c associated with microtubules in dendrites of motor neurons. MAP-2c and the neurofilament proteins were found in axons of the dorsal and ventral roots. The presence of MAP-2c within axons and dendrites suggests that MAP-2c contributes to neuronal plasticity during human fetal development.
Insights
Microtubule-associated protein-2c (MAP-2c) is found in both dendrites and axons of developing human motor neurons. This suggests MAP-2c plays a role in neuronal plasticity during fetal development.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Microtubule-associated protein-2 (MAP-2) is crucial for maintaining neuronal structure by promoting microtubule assembly.
- MAP-2c is a specific splice variant of MAP-2, differing significantly in its amino acid sequence from high-molecular-weight (HMW) MAP-2.
Purpose of the Study:
- To determine the cellular localization of the MAP-2c splice variant in the developing human spinal cord.
- To investigate the potential role of MAP-2c in neuronal plasticity during human fetal development.
Main Methods:
- Generation and validation of a specific polyclonal antibody for human MAP-2c.
- Western blot analysis of human fetal spinal cord homogenates.
- Immunohistochemistry and double-label confocal microscopy on fetal spinal cord sections.
- Immunoelectron microscopy to examine subcellular localization.
Main Results:
- The anti-MAP-2c antibody demonstrated specificity for MAP-2c in human fetal spinal cord.
- MAP-2c immunoreactivity was detected in the cytoplasm and processes of anterior motor neurons and posterior column neurons.
- MAP-2c colocalized with HMW MAP-2 in cell bodies and dendrites of motor neurons.
- MAP-2c was found associated with microtubules in motor neuron dendrites and also present in axons of dorsal and ventral roots.
Conclusions:
- This study provides the first evidence for the presence of native MAP-2c in neuronal dendrites.
- MAP-2c is also localized to axons, suggesting a broader role than previously understood.
- The distribution of MAP-2c in both axons and dendrites indicates its potential contribution to neuronal plasticity during human fetal development.