Visual Circuit Development Requires Patterned Activity Mediated by Retinal Acetylcholine Receptors

Abstract

SUMMARY The elaboration of nascent synaptic connections into highly ordered neural circuits is an integral feature of the developing vertebrate nervous system. In sensory systems, patterned spontaneous activity before the onset of sensation is thought to influence this process, but this conclusion remains controversial largely due to the inherent difficulty recording neural activity in early development. Here, we describe novel genetic and pharmacological manipulations of spontaneous retinal activity, assayed in vivo, that demonstrate a causal link between retinal waves and visual circuit refinement. We also report a de-coupling of downstream activity in retinorecipient regions of the developing brain after retinal wave disruption. Significantly, we show that the spatiotemporal characteristics of retinal waves affect the development of specific visual circuits. These results conclusively establish retinal waves as necessary and instructive for circuit refinement in the developing nervous system and reveal how neural circuits adjust to altered patterns of activity prior to experience.

Retinal Wave Patterns Are Governed by Mutual Excitation among Starburst Amacrine Cells and Drive the Refinement and Maintenance of Visual Circuits

“…These mice possess loxP sites flanking ϳ2.2 kb of sequence of the targeted Chrnb2 gene that contains exon 5, the largest coding exon (970 bp) of the gene. Mice lacking ␤2 (Chrnb2) in cholinergic neurons (SAC-␤2-cKOs) were generated by crossing ␤2-floxed (␤2 fl/fl ) mice with ChAT-Cre mice using the breeding scheme previously described (Li et al, 2013;Burbridge et al, 2014;Xu et al, 2015). In brief, ChAT-Cre mice were crossed to ␤2-null mice to generate ChAT-Cre ϩ ; ␤2 ϩ/Ϫ , which were then crossed to ␤2 fl/fl mice to obtain SAC-␤2-cKO mice (ChAT-Cre ϩ ; ␤2 fl/Ϫ ), littermate WT (ChAT-Cre Ϫ ; ␤2 fl/ϩ ), and heterozygous (SACCre ϩ ; ␤2 fl/ϩ and ChAT-Cre Ϫ ; ␤2 fl/Ϫ ) controls.…”

“…AAV virus encoding GCaMP6 was injected into eyes at P0, and spontaneous retinal activity was recorded from axonal terminals of infected RGCs at P5-P6 from SC. The procedure of surgery and imaging has been described in detail previously (Ackman et al, 2012;Burbridge et al, 2014). In brief, mice aged P5-P6 were deeply anesthetized with isoflurane (2.5-3.5%) in oxygen and then placed on a heating pad set to 37°C using a homeothermic temperature monitor (NPI TC-20, ALA Scientific).…”

“…Stage II waves occur during the first postnatal week in mice, are mediated by acetylcholine receptors, and are critical for the development of precise connections within and between the retina and brain (Feller et al, 1996;Penn et al, 1998;Rossi et al, 2001;Grubb et al, 2003;McLaughlin et al, 2003;Chandrasekaran et al, 2005;Mrsic-Flogel et al, 2005;Torborg et al, 2005;Burbridge et al, 2014). The specific spatiotemporal features of Stage II waves also influence circuit development (Huberman et al, 2008;Xu et al, 2011Xu et al, , 2015Burbridge et al, 2014), emphasizing the importance of understanding the detailed mechanisms responsible for wave generation and propagation.…”

“…Stage II waves occur during the first postnatal week in mice, are mediated by acetylcholine receptors, and are critical for the development of precise connections within and between the retina and brain (Feller et al, 1996;Penn et al, 1998;Rossi et al, 2001;Grubb et al, 2003;McLaughlin et al, 2003;Chandrasekaran et al, 2005;Mrsic-Flogel et al, 2005;Torborg et al, 2005;Burbridge et al, 2014). The specific spatiotemporal features of Stage II waves also influence circuit development (Huberman et al, 2008;Xu et al, 2011Xu et al, , 2015Burbridge et al, 2014), emphasizing the importance of understanding the detailed mechanisms responsible for wave generation and propagation. Stage II waves are initiated by the spontaneous depolarization of starburst amacrine cells (SACs), and recurrent network models for wave propagation postulate that spontaneous activity emerges from an interplay between the intrinsic electrical properties of SACs and their mutual interconnectivity (Feller et al, 1997;Butts et al, 1999;Zheng et al, 2004Zheng et al, , 2006Godfrey and Eglen, 2009;Blankenship and Feller, 2010;Ford et al, 2012).…”

In vivo imaging of the zebrafish retinotectal map

“…In contrast, other species, including rats, mice, rabbits, turtles, and chicks, set up the retinotectal/retinocollicular connections before eye opening can provide patterned visual input [358]. These systems compensate for a lack of early visual experience by generating spontaneously occurring retinal activity waves, where activity moves through neighboring cells and assists in setting up circuits throughout the visual system [1,2,27,77,167,358]. When these waves are disrupted, the arbors are larger than usual and cannot be remodeled even by later visual experience [214].…”