Transmission from the dominant input shapes the stereotypic ratio of photoreceptor inputs onto horizontal cells.
Many neurons receive synapses in stereotypic proportions from converging but functionally distinct afferents. However, developmental mechanisms regulating synaptic convergence are not well understood. Here we describe a heterotypic mechanism by which one afferent controls synaptogenesis of another afferent, but not vice versa. Like other CNS circuits, zebrafish retinal H3 horizontal cells (HC) undergo an initial period of remodelling, establishing synapses with ultraviolet and blue cones while eliminating red and green cone contacts. As development progresses, the HCs selectively synapse with ultraviolet cones to generate a 5:1 ultraviolet-to-blue cone synapse ratio. Blue cone synaptogenesis increases in mutants lacking ultraviolet cones, and when transmitter release or visual stimulation of ultraviolet cones is perturbed. Connectivity is unaltered when blue cone transmission is suppressed. Moreover, there is no cell-autonomous regulation of cone synaptogenesis by neurotransmission. Thus, biased connectivity in this circuit is established by an unusual activity-dependent, unidirectional control of synaptogenesis exerted by the dominant input.
1] Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA [2].
Takeshi
T
Yoshimatsu
1] Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA [2] Institute of Neuronal Cell Biology, Technische Universität München, Biedersteiner Street 29, D-80802 München, Germany [3].
Philip R
PR
Williams
Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA.
Florence D
FD
D'Orazi
Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA.
Sachihiro C
SC
Suzuki
Department of Biological Science and Program in Neuroscience, The Florida State University, 600W College Avenue, Tallahassee, Florida 32306, USA.
James M
JM
Fadool
Departments of Biological Sciences and Medical Genetics, University of Alberta, CW 405, Edmonton, Alberta, Canada T6G 2E9.
W Ted
WT
Allison
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 N University Avenue, Ann Arbor, Michigan 48109, USA.
Pamela A
PA
Raymond
Department of Biological Structure, University of Washington, 1959 NE Pacific Street, Seattle, Washington 98195, USA.
Rachel O
RO
Wong
D000818:Animals; D009473:Neuronal Plasticity; D012160:Retina / Q000502:physiology; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D051248:Retinal Horizontal Cells / Q000502:physiology*; D013569:Synapses / Q000502:physiology*; D015027:Zebrafish