Tracking tissue movements in anteromedial Xenopus neural plate using a grid scoring system and distribution maps

Graft movements in the anteromedial neural plate and anterior neural ridge of Xenopus frog embryos were examined because the presumptive preoptic area of the hypothalamus is located in this region (embryonic staging according to Nieuwkoop and Faber, 1956). Reciprocal orthotopic grafts were performed between pairs of stage 13 embryos. The grafts were videotaped and recorded at subsequent stages using a standard square grid system. Graft movements, both from stage 13 to stage 15, and from stage 14 to stage 15, were assessed and summarized in distribution tables and maps and in transition matrices for use in predicting where a graft at stage 13 or stage 14 would likely be located at stage 15. Statistically significant graft movements were found in the posteroanterior but not mediolateral direction, both from stage 13 to stage 15, and from stage 14 to stage 15. Prospective locations were identified in the stage 13 and stage 14 neural plate for grafts targeted at the future preoptic area.