Fig. 7. Schematic diagram summarizing the role of BMPs in the development of noradrenergic sympathetic and parasympathetic ciliary neurons. BMPs are sufficient and essential for the development of both noradrenergic sympathetic (Varley et al., 1995; Reissmann et al., 1996; Shah et al., 1996; Schneider et al., 1999) and parasympathetic ciliary neurons (the present study). The differential expression of the BMP-downstream transcription factor dHand suggests that sympathetic and ciliary neuron precursors display differences that determine BMP downstream signaling and in turn neuron identity (illustrated by the different shading of sympathetic and parasympathetic precursor cells). dHand is implicated in the maintenance of noradrenergic differentiation (TH, DBH) in sympathetic neurons.

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