Interactions between rhombomeres modulate Krox-20 and follistatin expression in the chick embryo hindbrain.
The rhombomeres of the embryonic hindbrain display compartment properties, including cell lineage restriction, genetic definition and modular anatomical phenotype. Consistent with the idea that rhombomeres are autonomous developmental units, previous studies have shown that certain aspects of rhombomere phenotype are determined early, at the time of rhombomere formation. By contrast, the apoptotic depletion of neural crest from rhombomeres 3 and 5 is due to an interaction with their neighbouring rhombomeres, involving the signalling molecule Bmp4. In this paper, we have examined whether inter-rhombomere interactions control further aspects of rhombomere phenotype. We find that the expression of Krox-20 and the repression of follistatin in r3 is dependent upon neighbour interaction, whereas these genes are expressed autonomously in r5. We further demonstrate that modulation of Krox-20 and follistatin expression is not dependent on Bmp4, indicating the existence of multiple pathways of interaction between adjacent rhombomeres. We also show that, although some phenotypic aspects of r3 are controlled by neighbour interactions, the axial identity of the segment is intrinsically determined.
Graham
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MRC Brain Development Programme, Division of Anatomy and Cell Biology, UMDS, Guys Hospital, London, UK.
Lumsden
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016380:Brain Tissue Transplantation / Q000502:physiology; D002642:Chick Embryo; D003001:Cloning, Molecular; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D051767:Early Growth Response Protein 2; D016332:Fetal Tissue Transplantation / Q000502:physiology; D038681:Follistatin; D005786:Gene Expression Regulation; D006023:Glycoproteins / Q000096:biosynthesis* / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D009420:Nervous System / Q000196:embryology; D009924:Organ Culture Techniques; D010641:Phenotype; D012249:Rhombencephalon / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis*; D014981:Xenopus; D016335:Zinc Fingers
D017931:DNA Primers; D004268:DNA-Binding Proteins; C497329:EGR2 protein, Xenopus; D051767:Early Growth Response Protein 2; C497327:Egr2 protein, mouse; D038681:Follistatin; D006023:Glycoproteins; D014157:Transcription Factors