Expression and regulation of chicken fibroblast growth factor homologous factor (FHF)-4 during craniofacial morphogenesis

Fibroblast growth factor homologous factors (FHFs) have been implicated in limb and nervous system development. In this paper we describe the expressi on of the cFHF-4 gene during chicken craniofacial development. cFHF-4 is ex pressed in the mesenchyme of the frontonasal process, and in the mesenchyme and ectoderm of the mandibular processes. The expression of cFHF-4 and oth er genes implicated in facial patterning have been analyzed in talpid(2) em bryos or in the presence of exogenous retinoic acid. Talpid(2) mutants show abnormal patterns of gene expression, including up-regulation of cFHF-4 in the developing face, which correlate with defects in cartilage formation. By contrast, expression of cFHF-4 in the developing face is strongly downre gulated by teratogenic doses of all-trans retinoic acid in a dose-dependent manner. Low levels of retinoic acid that produce distal upper beak truncat ions do not affect cShh, c-Patched-1, or c-Bmp-2 expression in the face, bu t downregulate cFHF-4 in the frontonasal process. (C) 2001 Wiley-Liss, Inc.