| Neural stem cells (NSCs) posses the capability of self-cleavage, self-duplication, self-renewing, and the potentiality of differentiating into various neural cells. NSCs exist in developing and adult mammal nervous system. Lateral ventricle (LV) nearby and hippocampus are the main areas where NSCs were localized. So these two areas are the key targets of NSCs research. It has been confirmed that the anterior subventricular zone (SVZa) NSCs posses particular migratory and differentiating properties. First, the SVZa NSCs continuously migrate from SVZa to olfactory bulb (OB) in mammal whole life, form the rostral migratory stream (RMS) and become the resource of OB interneuron renewing. After arriving the center of OB, the NSCs migrate into granular cell layer (GCL) and external plexiform layer (EPL), where they.differentiate into granular cell or external plexiform cell. There are about 30% gamma aminobutyric acid (GABA) neurons and 70% dopaminergic (DA) neurons in EPL. Compared to NSCs of other areas, The SVZa NSCs posses special characteristics as follows: (1) SVZa NSCs have the characteristic of developing into neurons. (2) SVZa NSCs can keep proliferating situation and neuronal progenitor characteristic, and no further differentiation, in the whole migratory stream. (3) SVZa NSCs differentiate into GABA and DA neurons while they migrating to destination.Wnt is the combination of wingless (drosophila megalogaster) and Int (insert, it is once more being activated after mouse mammary carcinoma related virus gene inserted), Wnt families are secretory glycoprotein signal factors. There are more than ten members in the Wnt group. It can combine with the frizzled (Fz) receptor and transfer the signal to cytoplasm and then increase the concentration of free β-catenin in the cytoplasm. β-catenin will enter nucleus in coordination with transcriptional control factors and regulate the transcription of downstream genes. Wnt-1 as a member of Wnt families had been widely investigated. It has importment effect on the development of nervous system, as well as the maturation and apoptosis of neural cells. It is observed that there were always expression of Wnt-1 during the course of cell differentiation, and the expression of Wnt-1 would terminate just as cell differentiation stopped. These researches implied that Wnt-1 was extremely correlated with differentiation and maturation of neural cells. Other researchers confirmed that Wnt-1 is easy to induce embryonic stem (ES) cell differentiating to neural cells, defend apoptosis of neuron, and induce P19 cell differentiating into neuron. Nevertheless,the effect of Wnt-1 on the SVZa NSCs while they migrate from SVZa into OB through RMS has not been properly studied. The name of Pax-6 is come from the paired domain of 128 amino acids. As a transcriptional control factor, Pax-6 plays important role in tissue and organ specialization, and takes part in the development of nervous system. Pax-6 regulates the migration of brain neural cells. It had been confirmed that Pax-6 was essential for the migration of midbrain crest cells, and the deficiency of Pax-6 would delay the migration and settlement of medulla oblongata neurons. Also Pax-6 regulates the development of dopaminergic neuron. Researchers observed that Pax-6 controled the development of TH positive dopaminergic neurons of ventralateral thalamus, and lower Pax-6 expression would suppress the differentiation of dopaminergic neurons within the suprachiasmatic nucleus. Besides of mesencephalon, OB is another main area where DA neuron gathered. When Pax-6 knocked out, the quantity of NSCs migrated from SVZa into OB would be reduced and OB become smaller, the number of DA neuron of EPL are also reduced. These results imply that Pax-6 is closely related with the migration of SVZa NSCs and the development of OB, espically with the development of TH positive neurons. However, the role of Pax-6 on the SVZa NSCs in its special migratory course has not been studied, and few studies have been involved in the effect of Pax-6 on the... |
PDF Full Text Request