The LIM domain-containing homeo box gene Xlim-1 is expressed specifically in the organizer region of Xenopus gastrula embryos.
A novel cysteine-rich motif, named LIM, has been identified in the homeo box genes lin-11, Isl-1, and mec-3; the mec-3 and lin-11 genes determine cell lineages in Caenorhabditis elegans. We isolated LIM class homeo box genes from Xenopus laevis that are closely related to lin-11 and mec-3 in the LIM and homeo domains. This paper deals with one of these genes, Xlim-1. Xlim-1 mRNA is found at low abundance in the unfertilized egg, has a major expression phase at the gastrula stage, decreases, and rises again during the tadpole stage. In adult tissues the brain shows the highest abundance, by far, of Xlim-1 mRNA. The maternal and late expression phases of the Xlim-1 gene suggest that it has multiple functions at different stages of the Xenopus life cycle. In the gastrula embryo, Xlim-1 mRNA is localized in the dorsal lip and the dorsal mesoderm, that is, in the region of Spemann's organizer. Explant experiments showed that Xlim-1 mRNA is induced by the mesoderm-inducer activin A and by retinoic acid, which is not a mesoderm inducer but affects patterning during Xenopus embryogenesis; application of activin A and retinoic acid together results in synergistic induction. The structure, inducibility, and localized expression in the organizer of the Xlim-1 gene suggest that it has a role in establishing body pattern during gastrulation.
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20852.
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Taira
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Jamrich
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Good
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Dawid
D028341:Activins; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005775:Gastrula; D015870:Gene Expression; D005801:Genes, Homeobox; D007265:Inhibins / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology; D014981:Xenopus / Q000196:embryology / Q000235:genetics*
D012333:RNA, Messenger; D028341:Activins; D014212:Tretinoin; D007265:Inhibins