Mesnard Chris S, Hays Cassandra L, Townsend Lou E, Barta Cody L, Gurumurthy Channabasavaiah B, Thoreson Wallace B
Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA.
Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68106, USA.
bioRxiv. 2024 Mar 16:2023.06.27.546758. doi: 10.1101/2023.06.27.546758.
Synaptotagmin-9 (Syt9) is a Ca sensor mediating fast synaptic release expressed in various parts of the brain. The presence and role of Syt9 in retina is unknown. We found evidence for Syt9 expression throughout the retina and created mice to conditionally eliminate Syt9 in a cre-dependent manner. We crossed Syt9 mice with Rho-iCre, HRGP-Cre, and CMV-cre mice to generate mice in which Syt9 was eliminated from rods (rod), cones (cone), or whole animals (CMV). CMV mice showed an increase in scotopic electroretinogram (ERG) b-waves evoked by bright flashes with no change in a-waves. Cone-driven photopic ERG b-waves were not significantly different in CMV knockout mice and selective elimination of Syt9 from cones had no effect on ERGs. However, selective elimination from rods decreased scotopic and photopic b-waves as well as oscillatory potentials. These changes occurred only with bright flashes where cone responses contribute. Synaptic release was measured in individual rods by recording anion currents activated by glutamate binding to presynaptic glutamate transporters. Loss of Syt9 from rods had no effect on spontaneous or depolarization-evoked release. Our data show that Syt9 is acts at multiple sites in the retina and suggest that it may play a role in regulating transmission of cone signals by rods.
突触结合蛋白9（Syt9）是一种介导快速突触释放的钙传感器，在大脑的各个部位均有表达。Syt9在视网膜中的存在情况及作用尚不清楚。我们发现了Syt9在整个视网膜中表达的证据，并构建了以cre依赖方式有条件消除Syt9的小鼠。我们将Syt9小鼠与Rho-iCre、HRGP-Cre和CMV-cre小鼠杂交，以产生从视杆细胞（rod）、视锥细胞（cone）或整个动物（CMV）中消除Syt9的小鼠。CMV小鼠在明亮闪光诱发的暗视视网膜电图（ERG）b波增加，而a波无变化。CMV基因敲除小鼠中视锥细胞驱动的明视ERG b波无显著差异，从视锥细胞中选择性消除Syt9对视网膜电图无影响。然而，从视杆细胞中选择性消除Syt9会降低暗视和明视b波及振荡电位。这些变化仅在视锥细胞反应起作用的明亮闪光时出现。通过记录谷氨酸与突触前谷氨酸转运体结合激活的阴离子电流，在单个视杆细胞中测量突触释放。视杆细胞中Syt9的缺失对自发或去极化诱发的释放没有影响。我们的数据表明，Syt9在视网膜的多个部位起作用，并表明它可能在调节视杆细胞对视锥细胞信号的传递中发挥作用。
