Tbx genes and limb identity in chick embryo development.
Tbx-2, Tbx-3, Tbx-4 and Tbx-5 chick genes have been isolated and, like the mouse homologues, are expressed in the limb regions. Tbx-2 and Tbx-3 are expressed in anterior and posterior domains in wings and legs, as well as throughout the flank. Of particular interest, however, are Tbx-5, which is expressed in wing and flank but not leg, and Tbx-4, which is expressed very strongly in leg but not wing. Grafts of leg tissue to wing and wing tissue to leg give rise to toe-like or wing-like digits in wing and leg respectively. Expression of Tbx-4 is stable when leg tissue is grafted to wing, and Tbx-5 expression is stable when wing tissue is grafted to leg. Induction of either extra wings or legs from the flank by applying FGF-2 in different positions alters the expression of Tbx-4 and Tbx-5 in such a way that suggests that the amount of Tbx-4 that is expressed in the limb determines the type that will form. The ectopic limb always displays a limb-like Tbx-3 expression. Thus Tbx-4 and Tbx-5 are strong candidates for encoding 'wingness' and 'legness'.
Isaac
A
A
Department of Anatomy and Developmental Biology, University College London, London WC1E 6BT, UK. ucgaali@ucl.ac.uk
Rodriguez-Esteban
C
C
Ryan
A
A
Altabef
M
M
Tsukui
T
T
Patel
K
K
Tickle
C
C
Izpisúa-Belmonte
J C
JC
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D002642:Chick Embryo; D003001:Cloning, Molecular; D004627:Embryonic Induction; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D005809:Genes, Regulator / Q000235:genetics; D006614:Hindlimb / Q000196:embryology* / Q000637:transplantation; D018878:Limb Buds; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000235:genetics*; D014921:Wings, Animal / Q000196:embryology* / Q000637:transplantation
D030161:Avian Proteins; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; C491196:TBX4 protein, Gallus gallus; C103177:Tbx4 protein, mouse; D014157:Transcription Factors; D016222:Fibroblast Growth Factor 2