Retinal TrkB receptors regulate neural development in the inner, but not outer, retina.
BDNF signaling through its TrkB receptor plays a pivotal role in activity-dependent refinement of synaptic connectivity of retinal ganglion cells. Additionally, studies using TrkB knockout mice have suggested that BDNF/TrkB signaling is essential for the development of photoreceptors and for synaptic communication between photoreceptors and second order retinal neurons. Thus the action of BDNF on refinement of synaptic connectivity of retinal ganglion cells could be a direct effect in the inner retina, or it could be secondary to its proposed role in rod maturation and in the formation of rod to bipolar cell synaptic transmission. To address this matter we have conditionally eliminated TrkB within the retina. We find that rod function and synaptic transmission to bipolar cells is not compromised in these conditional knockout mice. Consistent with previous work, we find that inner retina neural development is regulated by retinal BDNF/TrkB signaling. Specifically we show here also that the complexity of neuronal processes of dopaminergic cells is reduced in conditional TrkB knockout mice. We conclude that retinal BDNF/TrkB signaling has its primary role in the development of inner retinal neuronal circuits, and that this action is not a secondary effect due to the loss of visual signaling in the outer retina.
Neuroscience Program, School of Medicine, University of California San Francisco, San Francisco, California 94143, USA.
Ruslan N
RN
Grishanin
Haidong
H
Yang
Xiaorong
X
Liu
Kate
K
Donohue-Rolfe
George C
GC
Nune
Keling
K
Zang
Baoji
B
Xu
Jacque L
JL
Duncan
Matthew M
MM
Lavail
David R
DR
Copenhagen
Louis F
LF
Reichardt
D000818:Animals; D019208:Brain-Derived Neurotrophic Factor / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009415:Nerve Net / Q000254:growth & development / Q000378:metabolism; D020813:Receptor, trkB / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D012160:Retina / Q000254:growth & development* / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D019208:Brain-Derived Neurotrophic Factor; D020813:Receptor, trkB