FIGURE 4.

Onecut factors regulate the distribution of V2b interneurons. (A–C) At e12.5 in control embryos, V2b cells are distributed in a major central (brachial level) or lateral (thoracic and lumbar levels) cluster with minor subsets located more medially (arrows) or ventrally (arrowheads). (D–L) In OC mutant embryos at e12.5, the major population remains more compact, more centrally located and slightly more ventral. In addition, the ventral V2b subset is significantly depleted (asterisks; n = 3, p ≤ 0.001 at brachial and thoracic levels; p = 0.31 at brachial level). (M–X) Consistently, at e14.5, V2b interneurons in the central cluster are more compact in the absence of OC factors at thoracic level, and a small contingent of V2b migrating toward the medio-dorsal spinal cord in control embryos (arrowheads) is missing in OC mutant littermates (n = 3, p ≤ 0.001 at thoracic level; p = 0.31 and 0.80 at thoracic and lumbar levels, respectively).