AJP - Cell Physiology, Vol 258, Issue 3 C489-C494, Copyright © 1990 by American Physiological Society
Vector-free gravity disrupts synapse formation in cell culture
R. Gruener and G. Hoeger
Department of Physiology, University of Arizona College of Medicine, Tucson 85724.
Terrestrial organisms evolved under and are subjected to the constancy of
gravity. The organisms having adapted to this environmental factor, it is
possible that embryonic development may be modified by exposure to altered
gravity. To test the effects of gravity on embryonic development, we
monitored the formation of nerve-associated acetylcholine receptor patches
(NARPs) as an index of synaptogenesis. Embryonic spinal neuron and myotomal
myocyte cocultures were placed in a horizontally rotating clinostat. From
the cell's perspective, this results in the cancellation of the
gravitational vector because of continuous averaging, thus mimicking the
reduced gravitational force encountered in space. NARPs from cultures in
which nerve-muscle contact was established before the onset of rotation
were unaffected. In contrast, cultures in which nerve contact took place
during rotation showed a marked inhibition of NARPs. Moreover, in the
myocytes which did exhibit NARPs, the area of the patch was significantly
reduced compared with control sister cultures. Several paradigms were used
to ascertain that these findings did not result simply from loss of contact
between neurites and myocytes, accelerated diffusion of a putative
aggregating factor secreted by neurites, or from turbulence in the medium.
Our data suggest that the process of synapse formation is sensitive to the
gravitational vector. Embryonic development of the nervous system, in
space, may therefore be markedly different from that normally occurring on
earth.
