IngentaConnect The Dynamic Expression Pattern of frzb-1 Suggests Multiple Roles ...

Abstract:

The Wnt family of secreted proteins has been shown to have multiple roles in embryonic development. Wnt signals are thought to be propagated by binding to the cysteine-rich extracellular domain (CRD) of Frizzled, a seven-transmembrane-domain cell surface receptor. Secreted Frizzled-related proteins (generally denoted Frzb or Sfrp) possess a domain with a high degree of sequence identity and structural similarity with the CRD of Frizzled. Current data indicate that the cysteine-rich domain of secreted Frzb proteins can bind Wnt proteins, suggesting the possibility that Frzbs compete with membrane-bound Frizzled for Wnt binding and consequently act as competitive inhibitors of Wnt signaling. In order to gain a better understanding of the potential roles of Frzb-1 in chick development, we utilized the polymerase chain reaction to isolate a partial cDNA of the chick orthologue of frzb-1, cfrzb-1, and compared its expression pattern to that of Wnt-1, Wnt-3a, Wnt-5a, Wnt-7a, and Wnt-8c. Whole-mount in situ hybridizations have revealed three major phases of expression for cfrzb-1 in the developing chick. The earliest expression of cfrzb-1 is in cells fated to become neural ectoderm in streak-stage embryos. Expression of cfrzb-1 in the neural ectoderm continues up through stage 8. After stage 8, cfrzb-1 expression is gradually attenuated in the closing neural tube of the trunk and is concomitantly up-regulated in neural crest cells. Finally, cfrzb-1 appears in the condensing mesenchyme of the bones in both the limb and the trunk in stage 25+ embryos. Comparative analysis of the cfrzb-1 and the Wnt gene expression patterns suggests possible interactions between cFrzb-1 and all of the Wnt family members examined. Copyright 2000 Academic Press.

Keywords: chick; chondrogenesis; development; embryo; Frizzled; Frzb; gastrulation; Hensen'; s node; HNK-1, limb; neural crest; neurulation; Sarp; Sfrp; whole-mount in situ hybridization; Wnt

Language: English

Document Type: Research article

Affiliations: 1: Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, California, 94132 2: Department of Biology, Lake Forest College, 555 North Sheridan Road, Lake Forest, Illinois, 60045

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The Dynamic Expression Pattern of frzb-1 Suggests Multiple Roles in Chick Development