Hox9 genes and vertebrate limb specification

• Published in: Nature (London) Vol. 387; no. 6628; pp. 97 - 101
• Main Authors: Cohn, Martin J, Patel, Ketan, Krumlauf, Robb, Wilkinsont, David G, Clarke, Jonathan D. W, Tickle, Cheryll
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 01.05.1997; Nature Publishing Group
• Subjects: Animals; Biological and medical sciences; Biology; Cell Lineage; Chick Embryo; Embryology: invertebrates and vertebrates. Teratology; Embryonic Induction - drug effects; Embryonic Induction - genetics; Extremities - embryology; Fibroblast Growth Factor 2 - pharmacology; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Genes, Homeobox; Growth factors; Leg - embryology; Mesoderm - metabolism; Organogenesis. Fetal development; Organogenesis. Physiological fonctions; Vertebrates; Wings, Animal - embryology; Embryonic development; Fibroblast growth factor; Vertebrata; Embryo; Gene; Limb; Chicken; Ectopia; Aves; Gene expression
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/387097a0

Development of paired appendages at appropriate levels along the primary body axis is a hallmark of the body plan of jawed vertebrates. Hox genes are good candidates for encoding position in lateral plate mesoderm along the body axis and thus for determining where limbs are formed. Local application of fibroblast growth factors (FGFs) to the anterior prospective flank of a chick embryo induces development of an ectopic wing, and FGF applied to posterior flank induces an ectopic leg. If particular combinations of Hox gene expression determine where wings and legs develop, then formation of additional limbs from flank should involve changes in Hox gene expression that reflect the type of limb induced. Here we show that the same population of flank cells can be induced to form either a wing or a leg, and that induction of these ectopic limbs is accompanied by specific changes in expression of three Hox genes in lateral plate mesoderm. This then reproduces, in the flank, expression patterns found at normal limb levels. Hox gene expression is reprogrammed in lateral plate mesoderm, but is unaffected in paraxial mesoderm. Independent regulation of Hox gene expression in lateral plate mesoderm may have been a key step in the evolution of paired appendages.