Thus Fgf8 may be required to maintain proper levels of Foxc1 in the PA1 mesenchyme and conversely Foxc1 may be required to maintain proper levels of Fgf8 in the PA1 oral ectoderm forming a feedback loop critical for jaw development and in the pathogenesis of syngnathia and TMJ agenesis. The gene discussed is FGF8; the disease is cleft palate-lateral synechia syndrome.