A Critical Role for PDGFRα Signaling in Medial Nasal Process Development

Abstract

The primitive face is composed of neural crest cell (NCC) derived prominences. The medial nasal processes (MNP) give rise to the upper lip and vomeronasal organ, and are essential for normal craniofacial development, but the mechanism of MNP development remains largely unknown. PDGFRα signaling is known to be critical for NCC development and craniofacial morphogenesis. In this study, we show that PDGFRα is required for MNP development by maintaining the migration of progenitor neural crest cells (NCCs) and the proliferation of MNP cells. Further investigations reveal that PI3K/Akt and Rac1 signaling mediate PDGFRα function during MNP development. We thus establish PDGFRα as a novel regulator of MNP development and elucidate the roles of its downstream signaling pathways at cellular and molecular levels.

Author Summary

Craniofacial anomalies, including cleft lip and palate, are frequent birth defects. Although these are often associated with defects in neural crest development, the more severe phenotypic manifestations of midline defects is facial clefting, which is poorly understood. In this work, we show that the facial clefting phenotype of PDGFRα mutants is not associated with a defect in neural crest cell specification but rather a subsequent defect in the medial nasal process (MNP), a facial primordium derived from the frontonasal prominence. We further show that this defect is associated with alterations in both cell proliferation and cell migration, and that PI3K and Rac1 signaling are essential to maintain a normal level of cell proliferation. Last, we provide evidence that Rac1 regulates cell migration at the level of cell motility as well as chemotaxis under the regulation of PDGFRα. We thus establish PDGFRα as a novel regulator of MNP development and elucidate the roles of its downstream signaling pathways at cellular and molecular levels.