PDGF-AA mediates B104CM-induced oligodendrocyte precursor cell differentiation of embryonic neural stem cells through Erk, PI3K, and p38 signaling.

The conditioned medium from B104 neuroblastoma cells (B104CM) induces neural stem cells (NSCs) to differentiate into OPCs in vitro, which indicates that certain factor(s) contained within the B104CM must give instructional signals that direct OPC differentiation of NSCs. However, the OPC-inductive factor(s) present within the B104CM has not been well identified yet. Platelet-derived growth factor AA (PDGF-AA) was not only known to be a potent mitogen for OPC proliferation but also to act as a regulator of oligodendrocyte differentiation from multipotent embryonic NSCs. This raises the possibility that B104CM induces OPC differentiation of NSCs through secretion of PDGF-AA. In the present study, we detected the expression of PDGF-AA mRNA in B104 cells and the high level of PDGF-AA protein in B104CM. Most importantly, B104CM-induced OPC differentiation of NSCs could be completely blocked by AG1295, a specific inhibitor of PDGFR signal pathway, suggesting that the PDGF-AA in B104CM is the key factor that induces NSCs to differentiate into OPCs. Moreover, such B104CM-induced OPC differentiation appears to be mediated by the extracellular signal-regulated kinases 1 and 2 (Erk1/2), phosphatidylinositol-3 kinase (PI3K), and p38 signal pathway because B104CM elicited the activation of Erk1/2, PI3K, and p38, which could be markedly blocked by U0126, LY294002, and SB203580, several specific inhibitors of these signal pathway, respectively. These inhibitors also abolished OPC differentiation of NSCs completely. Together our study suggests that PDGF-AA contained in B104CM is the key regulating molecule that instructs OPC differentiation from embryonic NSCs through the activation of Erk, PI3K, and p38 signal pathway in vitro.

BMP signaling mediates astrocyte differentiation of oligodendrocyte progenitor cells.

Oligodendrocyte precursor cells (OPCs) can differentiate into oligodendrocytes or astrocytes, depending on cellular microenvironments. OPCs, cultured in medium supplemented with 10% (v/v) fetal bovine serum (FBS), give rise to type II astrocytes that express glial fibrillary acidic protein and a cell surface ganglioside that is recognized by A2B5 monoclonal antibody. However, the factors in FBS that direct the astrocyte differentiation are not determined. Moreover, bone morphogenetic proteins (BMPs) have been reported to be involved in astrocyte differentiation of neural progenitor cells. We therefore examined whether BMPs are responsible for the serum-mediated astrocyte differentiation from OPCs. OPCs were isolated from the spinal cords of Wistar rat embryos (at day 14) using the A2B5 antibody. We measured the concentrations of BMP-2 and BMP-4 in FBS and rat and human sera and the expression of mRNAs for three types of BMP receptors (BMPRIa, Ib and II) in OPCs by RT-PCR. The serum samples of the three species contained BMP-2 and BMP-4, as judged by ELISA with each monoclonal antibody, and the BMP receptor mRNAs are expressed in OPCs. When OPCs were cultured in the medium containing 10% FBS, cells (more than 95%) differentiated into type II astrocytes. However, when OPCs were pretreated with noggin, a soluble antagonist of BMP action, the degree of astrocyte differentiation was markedly decreased from 95.39 to 38.36%. Taken together, these results suggest that BMP signaling may be responsible for the serum-mediated astrocyte differentiation of OPCs. Our findings provide new insights into the molecular basis of differentiation of OPCs.

[Folate gene polymorphism and the risk of Down syndrome pregnancies in young Chinese women].

To explore the relationship between genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR), methionine synthase reductase (MTRR), reduced folate carrier1 (RFC-1), methionine synthase (MTR) involved in folate metabolism and the risk of offsprings of young Chinese women with Down syndrome (DS) through a case-control study, the polymorphisms of MTHFR 677C>T, MTRR 66A>G, RFC-1 80G>A, and MTR 2756A>G in 60 mothers of children with DS and 68 control mothers were investigated by PCR-RFLP. Significant differences in alle-lic frequencies were present between the cases and controls for MTHFR (Plt;0.05), but not in allelic frequencies for MTRR, RFC-1, and MTR. Homozygous MTHFR 677C>T polymorphism was more prevalent among the mothers of children with DS than among the control mothers, with an odds ratio of 3.51 (OR=3.51, 95% CI=1.30~9.46, Plt;0.05). No significant association was observed in the combined heterozygotes. In addition, the homozygous MTRR 66A>G polymorphism was independently associated with a 3.16-fold increase in estimated risk (OR=3.16, 95% CI=1.20~8.35, Plt;0.05). The increased risk of DS for homozygous RFC-1 80G>A was not associated with MTR 2756A>G. Positive interactions were found for the following genotype-pairs: MTHFR(CT+TT)/MTRR GG, MTHFR (CT+TT)/RFC-1 AA, MTHFR CC/MTR(AG+GG), MTHFR (CT+TT)/MTR AA, MTRR GG/MTR AA, and RFC-1 AA/MTRAA. In conclusion, MTHFR 677C>T and MTRR 66A>G polymorphisms are two independent risk factors for DS pregnancies in young women, but RFC-1 80G>A and MTR 2756A>G polymorphism are not independent risk factor. A role for combined genotypes in the risk of DS pregnancies cannot be excluded.