Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States.
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.
Elife. 2023 Feb 15;12:e81983. doi: 10.7554/eLife.81983.
Spontaneous activity is a hallmark of developing neural systems. In the retina, spontaneous activity comes in the form of retinal waves, comprised of three stages persisting from embryonic day 16 (E16) to eye opening at postnatal day 14 (P14). Though postnatal retinal waves have been well characterized, little is known about the spatiotemporal properties or the mechanisms mediating embryonic retinal waves, designated stage 1 waves. Using a custom-built macroscope to record spontaneous calcium transients from whole embryonic retinas, we show that stage 1 waves are initiated at several locations across the retina and propagate across a broad range of areas. Blocking gap junctions reduced the frequency and size of stage 1 waves, nearly abolishing them. Global blockade of nAChRs similarly nearly abolished stage 1 waves. Thus, stage 1 waves are mediated by a complex circuitry involving subtypes of nAChRs and gap junctions. Stage 1 waves in mice lacking the β2 subunit of the nAChRs (β2-nAChR-KO) persisted with altered propagation properties and were abolished by a gap junction blocker. To assay the impact of stage 1 waves on retinal development, we compared the spatial distribution of a subtype of retinal ganglion cells, intrinsically photosensitive retinal ganglion cells (ipRGCs), which undergo a significant amount of cell death, in WT and β2-nAChR-KO mice. We found that the developmental decrease in ipRGC density is preserved between WT and β2-nAChR-KO mice, indicating that processes regulating ipRGC numbers and distributions are not influenced by spontaneous activity.
自发性活动是发育中神经系统的一个标志。在视网膜中，自发性活动以视网膜波的形式出现，包括从胚胎第 16 天（E16）到出生后第 14 天（P14）睁眼的三个阶段。尽管已经很好地描述了出生后的视网膜波，但对于介导胚胎视网膜波（称为阶段 1 波）的时空特性或机制知之甚少。使用定制的宏镜从整个胚胎视网膜记录自发钙瞬变，我们表明阶段 1 波从视网膜的几个位置开始，并在广泛的区域传播。阻断缝隙连接会降低阶段 1 波的频率和大小，几乎使其消失。N 型乙酰胆碱受体（nAChRs）的全局阻断也几乎使阶段 1 波消失。因此，阶段 1 波由涉及 nAChR 和缝隙连接亚型的复杂电路介导。缺乏 nAChRs 的β2 亚基的小鼠（β2-nAChR-KO）中的阶段 1 波持续存在，但传播特性发生改变，并用缝隙连接阻滞剂可使其消失。为了研究阶段 1 波对视网膜发育的影响，我们比较了 WT 和β2-nAChR-KO 小鼠中一种视网膜神经节细胞（ipRGCs）的空间分布，该细胞经历了大量的细胞死亡。我们发现 WT 和β2-nAChR-KO 小鼠之间 ipRGC 密度的发育性下降得以保留，这表明调节 ipRGC 数量和分布的过程不受自发性活动的影响。
