TGF-beta signals and a pattern in Xenopus laevis endodermal development.
We have analyzed two gene products expressed in the early endoderm of Xenopus laevis: Xlhbox-8, a pancreas-specific transcription factor and intestinal fatty acid binding protein (IFABP), a marker of small intestinal epithelium. Expression of the pancreas marker relies on cell signaling mediated by both the TGF-beta and FGF classes of secreted peptide growth factors, whereas, expression of the more posterior small intestinal marker does not. Endodermal explants devoid of mesoderm express both markers in a regionalized manner. Cortical rotation is required for the expression of the more anterior marker, Xlhbox-8, but not for the small intestinal marker, IFABP. These findings suggest that endodermal patterning is dependent, in part, on the same events and signals known to play important roles in mesodermal development. Furthermore, inhibition of TGF-beta signaling in the endoderm leads to ectopic expression of both mesodermal and ectodermal markers, suggesting the TGF-beta signaling may play a general role in the segregation of the three embryonic germ layers.
Henry
G L
GL
Howard Hughes Medical Institute, Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Brivanlou
I H
IH
Kessler
D S
DS
Hemmati-Brivanlou
A
A
Melton
D A
DA
D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics; D004475:Ectoderm / Q000378:metabolism; D004627:Embryonic Induction; D004707:Endoderm / Q000166:cytology* / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D008297:Male; D008969:Molecular Sequence Data; D009024:Morphogenesis; D018996:Myelin P2 Protein / Q000378:metabolism*; D009363:Neoplasm Proteins; D012333:RNA, Messenger / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000502:physiology*; D051879:Twist-Related Protein 1; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology*
D002352:Carrier Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D050556:Fatty Acid-Binding Proteins; D018398:Homeodomain Proteins; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; C089627:PDX1 protein, Xenopus; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D051879:Twist-Related Protein 1; D029867:Xenopus Proteins; C493314:intestinal fatty acid binding protein, Xenopus; C581761:twist basic helix-loop-helix transcription factor 1, Xenopus