Study On The Effect Of SHP2 On The Differentiation Of Oligodendrocytes

The progressive loss of CNS myelin in patients with multiple sclerosis (MS) has been proposed to result from the combined effects of damage to oligodendrocytes and failure of remyelination. Remyelination is constituted of series of steps, such as neural stem cells fate decision, OPCs migration, proliferation and differentiation. In the end, a maturing oligodendrocyte is able to enwrap about 40 axons, and then compacted to form myelination sheath. OLs differentiation is one of key phases of remyelination, and it is during this phase that remyelination generally fails. Recent studies suggest that once myelin damaged, it is hard to remylination. Myelin is necessary for conduction of action electricity. In addition, it also provides tropic support for neuron axons. However, the relative regulators of OLs differentiation are incompletely understood.OLs differentiation has a close relation with lots of growth factors, as well as their downstream signaling molecular. For example, CNTF,NT3 and ErBb2 and so on. Growth factors influence the differentiation of OLs mainly completed by conduction of downstream signaling. In these processes of signaling conduction, phosphorylation of signaling molecular becomes key event. It is reported that the phosphorylation of PI3K/Akt, Fyn/Rho, and MAPK and other signaling molecular play an important role in oligodendrocytes differentiation and myelination. The level of tryosine phosphorylation of intracellar signaling moleculars results from the balance between tyrosine kinases and phosphatases. So far, it becomes hot point in the study of relation between tyrosine kinases and remyeliantion. However, there is little about the relation of tyrosine phosphatases and remyelination.SOV, as a comprehensive inhibitor of tryosine phosphatases, up-regulates tyrosine kinase-linked growth factor receptor signaling via the inhibition of tyrosine residue dephosphorylation. But the role of SOV on oligodendrocyte precursor cells remains unknown. SHP2 is a cytoplasmic non-receptor protein tyrosine phosphatase, which is enriched and widely expressed in nervous tissue. Recent studies suggested that the fate decision of neural stem cells into oligodendrocyte decreased dramatically in SHP2 knockout mice. Additionally, it is an observation that level of SHP2 expression increased after injury of focal cerebral ischemia. However, whether SHP2 is involved in the regulation of OLs differentiation and outgrowth of processes remains unknown.Here we show that non-receptor protein tyrosine phosphatase SHP2 (PTPN11) is an important positive regulator of phosphatase activation and signaling that is required for the differentiation of oligodendrocyte progenitor cells. In our study, we take advantage of oral administration of SOV on pregnant rats, and then observe the degree of myelination at P7 newborn rat. We found that the experiment group showed distinct hypomyelination with less expression of MBP compared to control group. To further identify the data in vivo, by using of purified OPCs in vitro, through different dose of SOV we draw a conclusion that 25μM or more SOV was able to hamper the differentiation of OLs and outgrowth of processes of oligodendrocyte development. Next, by using dose-dependent tyrosine phosphatases inhibitor, we observed when PTP inhibitor IV reached 2μM or more, it could inhibit OLs differentiation from precursor cells to myelinating oligodendrocytes. Moreover, we went further to confirm that SHP2 is expressed both in oligodendrocytes precursor cells and myelinating oligodendrocytes with in vitro and in vivo experiments. Besides, we used knockdown and over-expression system respectively to examine the role of SHP2 in OLs differentiation:the primary OPCs isolated from wild-type neonatal rat where SHP2 expression was silenced by small interfering RNA and over-expression with SHP2 plasmid. In the Lentivirus transfection system, the knockdown of SHP2 inhibited OLs differentiation and the morphological changes that accompany this process. In contrast, through over-expressing SHP2 with GFP plasmid by using of Lipofectamine 2000, our finding was that SHP2 could promote OLs differentiation. To study the mechanism, we finally found that stimulus of triiodothyronine (T3) played an important role in the process that SHP2 was involved in OLs differentiation and processes outgrowth.Taken together, our findings indicated that SHP2 is a novel and critical regulator for promoting OLs differentiation in the mammalian CNS.