Journal of Neuroscience, Vol 11, 277-286, Copyright © 1991 by Society for Neuroscience
Developmental expression of REGA-1, a regionally expressed glial antigen in the central nervous system of grasshopper embryos
EM Carpenter and MJ Bastiani
Department of Biology, University of Utah, Salt Lake City 84112.
Glial cells are a large component of the developing nervous system,
appearing before the onset of axon outgrowth in a variety of developing
systems. Their time of appearance and their location in conjunction with
developing axon pathways may allow them to define the position of axon
pathways. Specific glial cells may be utilized as guideposts by growing
axons, allowing them to recognize the appropriate pathway, or conversely,
glial cells may inhibit axons from growing along an inappropriate pathway.
The 7F7 monoclonal antibody labels a subset of glial cells in grasshopper
embryos that may play a role in defining the location of selected axonal
pathways. This antibody recognizes the REGA- 1 molecule, a cell-surface
antigen with a molecular weight of 60 kDa, which is regionally expressed on
developing glial cells. REGA-1 is expressed around the edges of clusters of
glial cells and on lamellae extending from glial cells to line the edges of
some axonal pathways. REGA-1 expression is first seen in the neuroblast
sheet, surrounding neuroblast 4-1. Slightly later in development, 2 glial
cells extend processes that express REGA-1 and demarcate the caudal edge of
the anterior commissure. As the animal matures, cell processes expressing
REGA-1 line the edges of the longitudinal connective, then expand to
surround the central neuropil of the segmental ganglia. REGA-1 expression
is also seen in conjunction with axons leaving the segmental ganglia via
the segmental nerves and the intersegmental connectives. REGA-1 expression
is limited to a subset of glial cells; some known glial cells such as the
segment boundary cell do not express REGA-1. Glial cell processes
expressing REGA-1 are seen only in association with axons, which suggests
that these processes may act as borders or guard rails confining axons to
the appropriate regions of the developing CNS. Axons navigating a path
through the CNS may be prohibited from growing into inappropriate regions
based on their inability to cross the boundaries established by glial cells
expressing REGA-1.