The T-box genes Tbx4 and Tbx5 regulate limb outgrowth and identity.
During embryonic development, initially similar fields can develop into distinct structures, such as the vertebrate fore- and hindlimbs. Although considerable progress has been made in our understanding of the genetic control underlying the establishment of the different limb axes, the molecular cues that specify the differential development of the fore- and hindlimbs are unknown. Possible candidates for genes determining limb identity are Pitx1, a gene whose transcripts are detected in the early hind- but not forelimb bud, and two members of the T-box (Tbx) gene family, Tbx4 and Tbx5, which are specifically expressed in the hindlimb and forelimb buds, respectively. Here we show that Tbx4 and Tbx5 are essential regulators of limb outgrowth whose roles seem to be tightly linked to the activity of three signalling proteins that are required for limb outgrowth and patterning: fibroblast growth factor (FGF), bone morphogenetic protein (BMP) and Wnt. In addition, we provide evidence that Tbx4 and Tbx5 are involved in controlling limb identity. Our findings provide insight into how similar developmental fields can evolve into homologous but distinct structures.
Rodriguez-Esteban
C
C
Gene Expression Laboratory, The Salk Institute, La Jolla, California 92037-1099, USA.
Tsukui
T
T
Yonei
S
S
Magallon
J
J
Tamura
K
K
Izpisua Belmonte
J C
JC
D000818:Animals; D030161:Avian Proteins; D019485:Bone Morphogenetic Proteins / Q000502:physiology; D002642:Chick Embryo; D004625:Embryo, Nonmammalian / Q000502:physiology; D047108:Embryonic Development; D005346:Fibroblast Growth Factors / Q000502:physiology; D005552:Forelimb / Q000196:embryology; D018507:Gene Expression Regulation, Developmental; D006614:Hindlimb / Q000196:embryology; D018878:Limb Buds / Q000196:embryology; D009024:Morphogenesis / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D015398:Signal Transduction; D020825:T-Box Domain Proteins; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D051153:Wnt Proteins; D029961:Zebrafish Proteins
D030161:Avian Proteins; D019485:Bone Morphogenetic Proteins; D011518:Proto-Oncogene Proteins; D020825:T-Box Domain Proteins; C103172:T-box transcription factor 5; C491196:TBX4 protein, Gallus gallus; D014157:Transcription Factors; D051153:Wnt Proteins; D029961:Zebrafish Proteins; C491194:tbx4 protein, zebrafish; D005346:Fibroblast Growth Factors