engleski

Neuroplastin: from neurodevelopment to neurodegeneration

Neuroplastin (np), heavily glycosylated transmembrane glycoprotein, is a member of the immunoglobulin (Ig) superfamily of cell adhesion molecules. Neuroplastin appears in two isoforms, np55 and np65. Np65 mediates homophilic trans-interactions which modulate synaptic activity, interacts with GABAA receptor subunits in hippocampal inhibitory synapses and is involved in the maintenance of hippocampal CA1 synaptic plasticity. On the other hand, np55 mediates only heterophilic interactions and is known to bind fibroblast growth factor receptor 1. Despite of the growing body of knowledge on neuroplastin, the distribution in human brain has not been described in neurodevelopmental or neurodegenerative processes. The aim of our study was to investigate the expression of neuroplastin in human fetal hippocampal tissue and in hippocampal tissue affected by Alzheimer’s neurodegeneration compared to control hippocampal tissue. Materials used in this study were formalin-fixed paraffin-embedded fetal human hippocampal sections, in gestational age of 22-40 gestational weeks and human middle childhood and young adulthood hippocampal sections, as well as hippocampal tissue affected by Alzheimer’s degeneration. Neuroplastin expression was analyzed using immunohistochemistry. Neuroplastin immunoreactivity in human hippocampal tissue was not observed earlier than 22nd gestational week. Gradually higher neuroplastin immunoreactivity was observed with increasing gestational age. Also, development of characteristic pattern in different layers of dentate gyrus was observed. Immunohistochemical analysis of tissue affected by Alzheimer’s degeneration showed increased immunoreactivity of neuroplastin in tissues affected by neurodegeneration, markedly in the internal and external molecular layer of the dentate gyrus. Furthermore, immunoreactive fibers of the CA1 radial layer demonstrated a disturbed organization. Increasing neuroplastin expression in hippocampus during brain development coincides with formation of hippocampal synapses and suggests that neuroplastin is one of the molecules involved in regulation of synaptic plasticity. Additionally, increased expression of neuroplastin in the hippocampus in Alzheimer’s disease indicates an additional compensatory mechanism in response to neurodegeneration that was not previously described. This study is the first report encompassing data on neuroplastin expression in human fetal hippocampal tissue and hippocampal tissue affected by Alzheimer’s neurodegeneration suggesting the important role of neuroplastin in neurodevelopmental as well as neurodegenerative processes.

neuroplastin; neurodevelopment; neurodegeneration

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