Paraxis is expressed in myoblasts during their migration and proliferationin the chick limb bud

The Paraxis gene encodes a basic helix-loop-helix (bHLH) transcription fact or expressed in paraxial mesoderm and whose mutant displays an inability to form epithelial somites. We analyzed the later expression pattern of Parax is transcripts in the chick limb. Paraxis transcripts are located in the Pa x3-expressing myoblasts migrating from the somites and persist in prolifera ting myoblasts in the limb bud. Moreover, the QH1 antibody, which recognize s quail endothelial cells, reacts with a subset of the Paraxsis/Pax3 expres sing cells in the quail limb. Paraxis is then down-regulated during muscle differentiation. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved .