Sonic hedgehog mediates the polarizing activity of the ZPA.
The zone of polarizing activity (ZPA) is a region at the posterior margin of the limb bud that induces mirror-image duplications when grafted to the anterior of a second limb. We have isolated a vertebrate gene, Sonic hedgehog, related to the Drosophila segment polarity gene hedgehog, which is expressed specifically in the ZPA and in other regions of the embryo, that is capable of polarizing limbs in grafting experiments. Retinoic acid, which can convert anterior limb bud tissue into tissue with polarizing activity, concomitantly induces Sonic hedgehog expression in the anterior limb bud. Implanting cells that express Sonic hedgehog into anterior limb buds is sufficient to cause ZPA-like limb duplications. Like the ZPA, Sonic hedgehog expression leads to the activation of Hox genes. Sonic hedgehog thus appears to function as the signal for antero-posterior patterning in the limb.
Riddle
R D
RD
Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Johnson
R L
RL
Laufer
E
E
Tabin
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D017931:DNA Primers / Q000737:chemistry; D029721:Drosophila Proteins; D004627:Embryonic Induction; D005121:Extremities / Q000196:embryology*; D015870:Gene Expression / Q000187:drug effects; D053823:Hedgehog Proteins; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009024:Morphogenesis; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014212:Tretinoin / Q000494:pharmacology
D017931:DNA Primers; D029721:Drosophila Proteins; D053823:Hedgehog Proteins; D011506:Proteins; D012333:RNA, Messenger; C077245:hh protein, Drosophila; D014212:Tretinoin