Rb. Yang et al., Disruption of a retinal guanylyl cyclase gene leads to cone-specific dystrophy and paradoxical rod behavior, J NEUROSC, 19(14), 1999, pp. 5889-5897
One of two orphan photoreceptor guanylyl cyclases that are highly conserved
from fish to mammals, GC-E (or retGC1) was eliminated by gene disruption.
Expression of the second retinal cyclase (GC-F) as well as the numbers and
morphology of rods remained unchanged in GC-E null mice. However, rods isol
ated from such mice, despite having a normal dark current, recovered from a
light flash markedly faster. Unexpectedly, the a- and b-waves of electrore
tinograms (ERG) from dark-adapted null mice were suppressed markedly. Cones
, initially present in normal numbers in the retina, disappeared by 5 weeks
, based on ERG and histology. Thus, the GC-E-deficient mouse defines a mode
l for cone dystrophy, but it also demonstrates that morphologically normal
rods display paradoxical behavior in their responses to light.