Journal of Neuroscience, Vol 7, 2630-2638, Copyright © 1987 by Society for Neuroscience
Segment-specific morphogenesis of leech Retzius neurons requires particular peripheral targets
CM Loer, J Jellies and WB Kristan Jr
In most segments of the leech, a pair of Retzius (Rz) cells innervate the
body wall musculature and skin; however, in the segments specialized for
reproduction (midbody segments 5 and 6), these neurons innervate the
reproductive tissue instead. Whereas all Rz cells have the same morphology
early in embryogenesis, those in the reproductive segments [Rz(5,6)] become
considerably different from their segmental homologs. Unlike standard Rz
cells, Rz(5,6) do not have axons in the interganglionic connectives or in
the body wall (Glover and Mason, 1986). Rz(5,6) also have significantly
smaller somata and fewer branches in the ganglionic neuropil than do
standard Rz cells (Jellies et al., 1987). Since these differences between
Rz cells do not become apparent until after Rz(5,6) processes appear to
contact the reproductive tissue primordia, interactions between Rz(5,6)
processes and the reproductive tissue may determine the segmental
specializations of these neurons. We have tested this possibility by
ablating the reproductive tissue primordia early in embryogenesis and
subsequently examining Rz(5,6) morphology. In the absence of reproductive
tissue, Rz(5,6) became more like standard Rz cells: they retained axons in
the interganglionic connectives, they projected into the body wall, and the
density of their arborization within the neuropil increased. These results
indicate that the development of some segmental specializations of Rz(5,6)
involves an interaction with their unique target tissue.
Previous Article | Next Article
