Ontogeny of mouse vestibulo-ocular reflex following genetic or environmental alteration of gravity sensing.
The vestibular organs consist of complementary sensors: the semicircular canals detect rotations while the otoliths detect linear accelerations, including the constant pull of gravity. Several fundamental questions remain on how the vestibular system would develop and/or adapt to prolonged changes in gravity such as during long-term space journey. How do vestibular reflexes develop if the appropriate assembly of otoliths and semi-circular canals is perturbed? The aim of present work was to evaluate the role of gravity sensing during ontogeny of the vestibular system. In otoconia-deficient mice (ied), gravity cannot be sensed and therefore maculo-ocular reflexes (MOR) were absent. While canals-related reflexes were present, the ied deficit also led to the abnormal spatial tuning of the horizontal angular canal-related VOR. To identify putative otolith-related critical periods, normal C57Bl/6J mice were subjected to 2G hypergravity by chronic centrifugation during different periods of development or adulthood (Adult-HG) and compared to non-centrifuged (control) C57Bl/6J mice. Mice exposed to hypergravity during development had completely normal vestibulo-ocular reflexes 6 months after end of centrifugation. Adult-HG mice all displayed major abnormalities in maculo-ocular reflexe one month after return to normal gravity. During the next 5 months, adaptation to normal gravity occurred in half of the individuals. In summary, genetic suppression of gravity sensing indicated that otolith-related signals might be necessary to ensure proper functioning of canal-related vestibular reflexes. On the other hand, exposure to hypergravity during development was not sufficient to modify durably motor behaviour. Hence, 2G centrifugation during development revealed no otolith-specific critical period.
CNRS UMR 8194, Université Paris Descartes, Sorbonne Paris Cité, Paris, France. mathieu.beraneck@parisdescartes.fr
Mathieu
M
Beraneck
Mickael
M
Bojados
Anne
A
Le Séac'h
Marc
M
Jamon
Pierre-Paul
PP
Vidal
D000375:Aging / Q000502:physiology*; D000818:Animals; D004777:Environment; D018466:Gravity Sensing / Q000235:genetics*; D018471:Hypergravity; D051379:Mice; D008810:Mice, Inbred C57BL; D010037:Otolithic Membrane / Q000378:metabolism; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*