Morphogenesis of the medial region of the developing mandible is regulatedby multiple signaling pathways

Experimental evidence indicates that the mandibular primordia are specified as at least two independent functional regions: two large lateral (proxima l) regions where morphogenesis is dependent on FGF-8 signaling, and a small medial region where morphogenesis is independent of FGF-8 and dependent on other signals. The patterns of expression of multiple signaling molecules and regulatory genes in the epithelium and mesenchyme of the medial region suggest that the regulatory hierarchies controlling morphogenesis of the me dial region of the developing mandible are complex and involve multiple pat hways. Recent genetic studies indicate that the 'ET-1-dHAND-Msx1 pathway' c onstitutes one of the genetic pathways involved in outgrowth and morphogene sis of the medial region. Functional studies in chick mandible suggest that FGFs (other then FGF-8) and BMPs are also part of signaling pathways that regulate morphogenesis of the medial region. These studies suggest that in the medial region of the developing mandible, FGF-mediated signaling is inv olved in growth-promoting interaction, whereas BMP-mediated signaling is in volved in chondrogenesis. Copyright (C) 2001 S. Karger AG, Basel.