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Fig. 4. The mouse ventral midbrain has a medial arc expressing molecular markers of
the OMC and the pRN. (A) Emx2 labeling identifies arcs in mouse E12.5
midbrain wholemounts, oriented as in Fig.
1. (B,C) Isl1 (B) and Brn3a (C) labeling of the
OMC and the pRN in the mouse medial arc. (D) Combined Isl1 and
Emx2 labeling confirms that the organization of the mouse medial arc
is similar to that of the chick. IS, isthmus; OMC, oculomotor complex; rFP,
rostral, or midbrain, floor plate; RN, red nucleus.