Polarization Activity of Fgf8 in Mouse Brain Figure 5. The position of FGF8- related secondary organizers determines the polarity of ERK1/2 activation. A-D’) show the type 1 experimental manipulation in ONTCs where a dissection of the IsO region was made, left for 24 hours in vitro and thereafter it was incubated with PLoS ONE | www.plosone.org 7 July 2012 | Volume 7 | Issue 7 | e39977