Early maskers of neuronal differentiation in DRG: Islet-1 expression precedes that of Hu

The Hu and Islet-1 proteins are early markers of neuronal differentiation i n the avian embryo. We here examine which of these markers is expressed fir st in avian dorsal root ganglia (DRG). Recently we showed that neural tube and DRG cells express Islet-1 after leaving the cell cycle, while sympathet ic ganglion cells express Islet-1 while still dividing. Others have shown t hat Hu is found in cells that take up BrDU in the DRG, suggesting that it i s expressed even earlier in the differentiation process than Islet-1. In th is study we double-label sections for Hu and Islet-1 at several stages of e mbryonic development, using a simple antigen retrieval method in paraffin s ections. At early stages many more cells are Islet-1(+) than Hu(-). In addi tion, although many cells express both markers, some Islet-1(+)/Hu(-) cells are observed but the converse is never found. At later stages, almost all DRG neurons express both markers, although a few Islet-1(+)/Hu(-) cells are still observed. Staining for Hu and Islet-1 at a later stage than previous ly reported shows that neither marker is expressed in DRG satellite cells. Our results suggest that Islet-1 is a useful marker for DRG neurons at earl iest embryonic stages, and is likely to be expressed in DRG neurons before the Hu antigen. (C) 2000 Elsevier Science B.V. All rights reserved.