Patterning of an ascidian embryo along the anterior-posterior axis through spatial regulation of competence and induction ability by maternally localized PEM.
In ascidian embryos, anterior-posterior (A-P) patterning of the vegetal cells is regulated by posteriorizing activities of a localized egg region known as posterior-vegetal cortex/cytoplasm (PVC). PEM is an essential component of the PVC and is involved in the posterior-specific cell cleavage pattern. Here we report a novel function of PEM independently of its function in cleavage regulation; it controls cell fate by excluding competence to respond to the FGF signal for notochord induction from posterior-vegetal cells. PEM was found to regulate the nuclear accumulation of beta-catenin, an upstream activator of the competence factor. PEM also influences A-P patterning in the animal hemisphere. It was found to regulate FGF signal expression and restrict the occurrence of brain induction only in the anterior region. Our results suggest a model in which PEM patterns the embryo along the A-P axis through regulation of the spatial distribution of competence and induction ability.
Kumano
Gaku
G
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. kumano@bio.sci.osaka-u.ac.jp
Nishida
Hiroki
H
D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002455:Cell Division; D004527:Egg Proteins / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000502:physiology*; D005260:Female; D005346:Fibroblast Growth Factors / Q000235:genetics; D054261:Neurulation / Q000235:genetics / Q000502:physiology; D009672:Notochord / Q000254:growth & development; D014158:Transcription, Genetic; D014561:Urochordata / Q000196:embryology* / Q000235:genetics*
D004527:Egg Proteins; D005346:Fibroblast Growth Factors