lllllu llAlly occur in the active progenitors the out the po

lllllu llAlly occur in the active progenitors, the out the possibility in oli differentiation occurs be- progenitors, godendrocyte lesions (23), this distribution is consistent that Olig is required to maintain olig2 fore it becomes localized to the with a role for oligi nuclear translocation in expression. Analysis of oligodendrocyte mat- With respect to the human disease, the the repair process in MS patients. uration in oligi animals after demyelina esions that define MS are now thought to 8 Fig, 4. Olig1 is critical for the maturation of g2 NG2 Nk x R 2, NG2 oligodendrocyte pro- 1000 enitors. (A) After emyelination with 800 cuprizone, cells posi- E tive for NG2, Nkx2.2, B 8600 and both of the Olig genes are present in S the corpus callosum. (B) olig1 and Olig2 Lesioned Unlesioned 200 are coexpressed in normal and lesioned white matter. White wT oliat-- wr olig1 wr origt arrows indicate colo Unlesioned 7 weeks 8 weeks calization of Olig1 and in the nucleus of cells in a remyelinating lesion (after 1 week of recovery) of the corpus callosum; gray arrows representative cells in which oug1 predominantly cytoplasmic and Olig2 is nuclear. MBP Nky 2.2l Olig2 (C) The loss of Olig1 has no obvious effect on the recruitment of NG2+/Nkx2.2+/Olig2+ pro- genitors after a cuprizone induced demyelinating injury, however, the induction of MBP is delayed Wild-type n the Olig1 mouse during week images shown in c are from mice after 1 recovery (7 weeks total) from cuprizone nduced demyelination. (D) Quantitation of the data shown in (C) for recruitment of NG2 MBP progenitors. Analysis was performed in at least three mice per time point, and cell counts for NG2+ progenitors were restricted to the midline corpus callosum at the level of the Olig1 17 DECEMBER 2004 VOL 306 IENCE www.sciencemag.org 2114

Solution

Answer: The initial event in remyelination after chemical treatment is an appearance of various markers like NG2, Olig1, Olig2, and Nkx2.2(a homeodomain transcription factor) on the progenitor cells.

Figure 4a) shows that remyelination is happening as shown by presence of Olig1, Olig2, NG2 and Nkx2.2 in the corpus callosum as seen by the immunostaining.

Figure 4b) indicates that the Olig1 and Olig 2 are both simulatneously expressed in the white matter of both normal and lesioned white matter cells. However in normal/unlesioned white matter Olig1 is cytoplasmic and Olig2 is nuclear as indicated by gray arrows. while in treated white matter with lesions, Olig 1 also migrated into the nucleus and have the same location (colocalized) as Olig2 i.e both are expressed in nucleus implying that Olig 1 is important for remylenation events to be successful.

Figure 4c) shows that though Olig1 is not required for the expression of other remylenating agents and presence of proginator markers (NG2, Olig2, and Nkx2.2) but the knock outs of Olig 1 (signifies as Olig-/-) have role in recruitment of Mylein Basic proteins (MBP) as this indicates that mylein is not being synthesised.

i.e cells lacking Olig1 (Olig1-/-) do not have high expression of MBP and thus have remyelenisation defects as seen by absence of green stainig in the fourth block in figure C as compared to wildtype cells.

Figure 4D) Histogram in figure 4D shows the expression level of NG2 per mmsquared in the same slides as figure 4c and it has been densitometrically analysed. Showing that even after 1 week of recovery (7 weeks in total) and 2 weeks after recovery (8 weeks in total) the expression of NG2 is not dependent on Olig 1 as even in Olig-/- mice brain sections after treatment with cuprizone, the levels of NG2 are higher than the wild type cells.

all this data indicates Olig1 is not required for recruitment of proginator + markers NG2, Olig2, and Nkx2.2

but is required for recruitment of Mylein Basic Protein (MBP) implying that myelin synthesis in remylenization is dependent on Olig1