Characterization of a monoclonal antibody, Namu mAb, which reacts to the subventricular zone in mouse brain.

The lateral ventricle in adult mammalian brain is widely acknowledged as one of the areas that undifferentiated neural cells such as neural stem cells and neural progenitor cells inhabit. However, immunological aspects of neural stem cells in the lateral ventricle are still under debate. Here, we report the generation and characterization of a novel monoclonal antibody (mAb), called Namu mAb, which stains the subventricular zone in the lateral ventricle of adult mouse brain. Namu mAb reacted to the cells in the subventricular zone and never reacted to differentiated neural cells such as neurons and glial cells such as astrocytes and oligodendrocytes. Its reaction pattern for the subventricular zone and the neurospheres was similar to that of Nestin and glial fibrillary acidic protein mAbs. Namu mAb recognition molecule, Namu antigen, was a 50 kDa protein present in the cytoplasmic fraction of mouse brain, and its expression was clearly observed in neurospheres cultured in the presence of epidermal growth factor, but it was never or only weakly induced in the presence of basic fibroblast growth factor or leukemia inhibitory factor. Collectively, it is concluded that Namu mAb specifically reacts to undifferentiated neural cells in mouse brain.

Protein processing and releases of neuregulin-1 are regulated in an activity-dependent manner.

Identification of the key molecules that bridge presynaptic neuronal events and long-term modification of the postsynaptic process is an important challenge which will have to be met in order to further our understanding of the mechanisms for learning and memory. This study is focused on neuregulin-1 (NRG-1), a neurotrophic factor, that is known to regulate the development of various tissues and/or the life/death of cells through activation of the ErbB family receptor tyrosine kinases. It was discovered that the soluble form of NRG-1 (sNRG-1) is produced from the transmembrane form of NRG through proteolytic cleavage during electrical stimulation of either cultured cerebellar granule cells (GCs) or pontine nucleus neurons (PNs) that are presynaptic to GCs. sNRG-1 was assayed by measuring the phosphorylation of both the ErbB receptors and cyclic AMP-responsive element-binding protein (CREB), and by means of antibodies to sNRG-1. The cleavage and release of NRG-1 depended on the frequency of electrical stimulation; the peak effect was at 50 Hz in both GCs and PNs. Activation of protein kinase C (PKC) mimicked this effect. The culture apparatus provided along with the mass-electrical stimulation that was employed proved to be a powerful tool for combining neuronal electrical events and chemical events. We conclude from the results that, in mossy fibre (PN axon)-GC synapses, electrical activity controls the proteolytic processing of NRG-1 in a frequency-dependent fashion and involves PKC. Furthermore, cleaved sNRG-1 plays an important functional role in regulating transmission across these synapses.