Figure 4.

Retrograde labeling identifies distinct Sox14 projection populations. A, B,Injections of green RetroBeads into the ipsilateral oculomotor nucleus (A) and red RetroBeads into the contralateral inferior olive (B) of the Sox14^Gfp/+ mouse. C, The cerebellar nucleus and surrounding regions. Scale bar, 100 μm. Endogenous Sox14:GFP was stained with a far-red secondary antibody and is shown in blue. Red RetroBeads were found in Sox14:GFP⁺ cells of the cerebellar nucleus, whereas green RetroBeads were only observed in the vestibular nuclei. The nucleus Y region of the vestibular nuclei contains Sox14:GFP⁺ cells that colabel with either green RetroBeads or red RetroBeads, but never both colors in one cell (C′). D, Unilateral injection of green RetroBeads into the inferior olive of a Sox14^Gfp/+ mouse at P19. E, F, Green RetroBeads were observed in the cerebellar nuclei only in cells that express Sox14:GFP (in magenta). The differential distribution of RetroBeads found in the contralateral and ipsilateral cerebellar nuclei (F) shows that projections to the inferior olive come from similar regions of both hemispheres but fewer cells contribute to the ipsilateral olive. G, Summary of Sox14⁺ nucleo-olivary topography shown in AAV and RetroBead injections. The nucleo-olivary neurons of the lateral cerebellar nucleus (green) project to the principle olive and the dorsomedial cell group. The nucleo-olivary neurons of the interposed cerebellar nuclei (blue) project to the medial olivary nucleus and the dorsal olivary nucleus. The Sox14⁺ neurons of the vestibular nuclei (red) project to the cap of Kooy of the medial nucleus and the ventrolateral protrusion. No Sox14⁺ neurons were observed from the medial cerebellar nucleus. All the projections were seen bilaterally in the inferior olive, but the contralateral contribution was consistently more intense (solid color) compared with the ipsilateral contribution (stripe pattern). Scale bars: C′, 20 μm; A, 50 μm; B, D, F, 200 μm. Lat, Lateral nucleus; LatPC, parvicellular lateral nucleus; IntDL, dorsolateral interposed nucleus; IntA, anterior interposed nucleus; Nuc Y, nucleus Y; IOC, inferior olive subnucleus C of medial nucleus; IOD, inferior olive dorsal nucleus; IOK, inferior olive cap of Kooy of the medial nucleus; IOPr, inferior olive principal nucleus; IODM, inferior olive dorsomedial cell group; IOM, inferior olive medial nucleus; IOB, inferior olive subnucleus B of medial nucleus; IOVL, inferior olive ventrolateral protrusion; Med, medial nucleus; VN, vestibular nucleus.