Separating early sensory neuron and blood vessel patterning.

The anatomical association between sensory nerves and blood vessels is well recognised in the adult, and interactions between the two are important during development. Here we have examined the relationship between developing blood vessels and sensory neuronal cell bodies, which is less well understood. We show in the chick that the nascent dorsal root ganglia (DRG) lie dorsal to the longitudinal anastomosis, adjacent to the developing neural tube at the level of the sulcus limitans. Furthermore, the blood vessel is present prior to the neurons suggesting that it may play a role in positioning the DRG. We use the zebrafish cloche mutation to analyse DRG formation in the absence of blood vessels and show that the DRG are positioned normally. Thus, despite their close anatomical relationship, the patterning of the blood vessel and DRG alongside the neural tube is separable rather than interdependent.