Fig. 4. p1 and p2 progenitors expand into the ventral spinal cord and intermingle in Gli2^-/-;Gli3^xt/xt mutants. (A,B) In wild-type embryos, Mash1 is co-expressed with Nkx6.1 in p2 progenitors. In Gli2^-/-;Gli3^xt/xt mutants, Mash1+/Nkx6.1+ p2 progenitors are scattered throughout the Nkx6.1 domain. (C,D) In wild-type embryos, p1, p0 and pd6 progenitors express Dbx2 and are distinct from Mash1+ p2 progenitors ventrally and dorsally. In Gli2^-/-;Gli3^xt/xt mutants, Dbx2+ and Mash1+ progenitors are intermingled in the ventral spinal cord, but co-expression of these two factors was not seen. (E,F) In wild-type embryos, Jag1 is expressed between Mash1 domains, but is excluded from the p0 domain. In Gli2^-/-;Gli3^xt/xt mutants, only the ventral Jag1 expression domain in p1 progenitors has expanded ventrally, while the more dorsal domain, as well as the intervening Jag1-negative domain, were similar to wild type. Co-expression of Jag1 and Mash1 was not detected.