S. Minobe et al., NERVE-CELL DIFFERENTIATION IN NERVE-FREE TISSUE OF EPITHELIAL HYDRA FROM PRECURSOR CELLS INTRODUCED BY GRAFTING .1. TENTACLES AND HYPOSTOME, Developmental biology, 172(1), 1995, pp. 170-181
The differentiation of hydra nerve cells in the nerve-free tissue of e
pithelial hydra was examined in Hydra magnipapillata. Nerve cell precu
rsors, the interstitial cells, were introduced into the upper half of
epithelial hydra by grafting it onto the lower half of normal hydra. I
n the tentacles of grafted epithelial hydra, a small number of RF(+) g
anglion cells first appeared in the proximal area at 1.5 days after gr
afting, followed by the appearance of NV1(+) sensory cells in the same
area about a day later. In the following days, both neuron types appe
ared more numerously in more distal positions. The front boundary for
each type moved gradually from the base to the tip of the tentacles in
about 7 days. In the hypostome, a small number of RF(+) ganglion cell
s first appeared in the apex at 1.5 days. More nerve cells appeared in
the following days, eventually forming a cluster of RF(+) sensory cel
ls at the apex surrounded by numerous RF(+) ganglion cells in the adja
cent tissue. These results show that nerve cells do not differentiate
randomly in the epithelial hydra host. Instead, differentiation occurs
in a strongly region-specific manner in the same way as in normal hyd
ra, suggesting that epithelial cells in each region provide different
cues or signals to produce region-specific nerve cell distribution in
normal hydra tissue. (C) 1995 Academic Press, Inc.