Celsr3 Is Required for Normal Development of GABA Circuits in the Inner Retina

Abstract

The identity of the specific molecules required for the process of retinal circuitry formation is largely unknown. Here we report a newly identified zebrafish mutant in which the absence of the atypical cadherin, Celsr3, leads to a specific defect in the development of GABAergic signaling in the inner retina. This mutant lacks an optokinetic response (OKR), the ability to visually track rotating illuminated stripes, and develops a super-normal b-wave in the electroretinogram (ERG). We find that celsr3 mRNA is abundant in the amacrine and ganglion cells of the retina, however its loss does not affect synaptic lamination within the inner plexiform layer (IPL) or amacrine cell number. We localize the ERG defect pharmacologically to a late-stage disruption in GABAergic modulation of ON-bipolar cell pathway and find that the DNQX-sensitive fast b1 component of the ERG is specifically affected in this mutant. Consistently, we find an increase in GABA receptors on mutant ON-bipolar terminals, providing a direct link between the observed physiological changes and alterations in GABA signaling components. Finally, using blastula transplantation, we show that the lack of an OKR is due, at least partially, to Celsr3-mediated defects within the brain. These findings support the previously postulated inner retina origin for the b1 component and reveal a new role for Celsr3 in the normal development of ON visual pathway circuitry in the inner retina.

Evidence for opposing roles of Celsr3 and Vangl2 in glutamatergic synapse formation

“…Previous studies deleted the Celsr3 gene either from early embryonic development or early embryonic brain development (8)(9)(10). When Celsr3 was deleted from the embryonic forebrain using Emx1-Cre, a number of defects were found in neuronal cell numbers, migration, and axon guidance.…”

“…Recent studies suggest that mutations of some components of the PCP signaling pathway, Celsr3/Fmi and Vangl2, affect GABAergic circuit development in zebrafish retina, GABAergic motoneuron synapse development in Caenorhabditis elegans, and hippocampal/cortical glutamatergic and GABAergic synapse formation (5)(6)(7)(8)(9)(10)(11). PCP components are critical regulators of neuronal migration and axon guidance, which take place before synapse formation and their mutations may secondarily affect synapse formation (8)(9)(10)(12)(13)(14)(15)(16)(17)(18)(19). Therefore, evaluating the specific functions of PCP components in synapse formation requires conditionally knocking out these components in defined synapses after the development of axons and dendrites.…”

Regulation of the Protocadherin Celsr3 Gene and Its Role in Globus Pallidus Development and Connectivity

“…The mammalian Celsr genes are the so-called core PCP genes that have conserved as well as newly diversified functions. In particular, the vertebrate Celsr3 gene has been shown to regulate axonal projections, dendrite development, neuronal migration, ciliogenesis, and retina circuit development (8)(9)(10)(11)(12)(13)(14)(15)(16). However, very little is known about Celsr gene regulation.…”

Effects of picrotoxin on light adapted frog electroretinogram are not due entirely to its action in proximal retina

“…The authors concluded that picrotoxininduced reduction in the b-wave results from inactivation of the GABA C receptors of ON bipolar cells. However, many other data including those obtained in our laboratory indicate that the blockade of ionotropic GABA receptors by picrotoxin leads to an increase of the b-wave amplitude (frog: Arnarsson & Eysteinsson, 1997;Belcheva & Kupenova, 1980;Belcheva & Vitanova, 1974;Bonaventure, Wioland, & Jardon, 1986;DeVries & Friedman, 1978;Katz et al, 1991;Kupenova, Popova, & Vitanova, 2008;Popova, 1989Popova, , 2000Popova et al, 1986;turtle: Belcheva & Vitanova, 1978;Kupenova et al, 1991Kupenova et al, , 1997Vitanova et al, 1997;fish: Chappell & Rosenstein, 1996;Lewis et al, 2011). The effect is evident in conditions of both dark and light adaptation, indicating that it does not depend on the type of the photoreceptor input.…”

“…The effects of picrotoxin on the d-wave resembled that on the b-wave. Although Bonaventure, Wioland, and Jardon (1986) did not find any effect of picrotoxin on the d-wave, other authors reported that picrotoxin enhances the amplitude and delays the time course of the d-wave (Arnarsson & Eysteinsson, 1997;Belcheva & Kupenova, 1980;Belcheva & Vitanova, 1974Kupenova et al, 1991Kupenova et al, , 1997Lewis et al, 2011;Popova, 1989Popova, , 2000Popova et al, 1986;Vitanova et al, 1997;Xu & Karwoski, 1995). Picrotoxin revealed a prominent OFF component in all rod retina of skate (Chappell & Rosenstein, 1996) and in dark adapted toad retina (Katz et al, 1991).…”