Fig. 1

Expression of V2 transcription factors in wild-type embryos. (A–R and X) Lateral views of the spinal cord and underlying notochord in wild-type embryos at 16 somites (17 h), 18 somites (18 h) and 24 h. Anterior is left, dorsal is up. Scale bar = 50 μm (A–R). (A–F) chx10 and vsx1 are expressed in the V2 domain (rows 3–5 depending on stage). (G–R) lhx3, scl, gata3 and gata2 are expressed both in the V2 domain and more ventral spinal cells. At 16 somites, vsx1 (D) and lhx3 (P) are already expressed in the V2 domain, but gata2 (G), gata3 (J), scl (M) and chx10 (A) are not. By 18 somites gata2 (H) and scl (N) are also expressed in the V2 domain. (S–W) number of cells in rows 1–5 expressing particular genes at 16 s (blue bars), 18 s (red bars) and 24 h (yellow bars). None of these genes were expressed in cells dorsal to row 5. All cell counts are from a 5 somite length of spinal cord adjacent to somites 6–10. Values shown are the mean from 5 different embryos. Error bars indicate standard deviations. Panel X shows a magnified view of the white dotted box in panel L demonstrating how cell rows were counted. For each positive cell, the number of cells between it and the notochord were counted to determine which row it was in. Cell row numbers were counted ventral to dorsal (e.g. cells directly above the notochord are in row 1). Example row numbers are illustrated for the column of cells on the left of the picture. Panel Y shows a schematic representation of when genes are expressed in the V2 domain (red: gene not expressed at that time point in the V2 domain, green: gene expressed at that time point in the V2 domain).