Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio, USA.
Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA.
FASEB J. 2019 Apr;33(4):5782-5792. doi: 10.1096/fj.201802493R. Epub 2019 Jan 15.
Cone photoreceptors are essential for vision under moderate to high illuminance and allow color discrimination. Their fast dark adaptation rate and resistance to saturation are believed to depend in part on an intraretinal visual cycle that supplies 11- cis-retinaldehyde to cone opsins. Candidate enzymes of this pathway have been reported, but their physiologic contribution to cone photoresponses remains unknown. Here, we evaluate the role of a candidate retinol isomerase of this pathway, sphingolipid δ4 desaturase 1 (Des1). Single-cell RNA sequencing analysis revealed Des1 expression not only in Müller glia but also throughout the retina and in the retinal pigment epithelium. We assessed cone functional dependence on Müller cell-expressed Des1 through a conditional knockout approach. Floxed Des1 mice, on a guanine nucleotide-binding protein subunit α transducin 1 knockout ( Gnat1) background to allow isolated recording of cone-driven photoresponses, were bred with platelet-derived growth factor receptor α (Pdgfrα)-Cre mice to delete Des1 in Müller cells. Conditional knockout of Des1 expression, as shown by tissue-selective Des1 gene recombination and reduced Des1 catalytic activity, caused no gross changes in the retinal structure and had no effect on cone sensitivity or dark adaptation but did slightly accelerate the rate of cone phototransduction termination. These results indicate that Des1 expression in Müller cells is not required for cone visual pigment regeneration in the mouse.-Kiser, P. D., Kolesnikov, A.V., Kiser, J. Z., Dong, Z., Chaurasia, B., Wang, L., Summers, S. A., Hoang, T., Blackshaw, S., Peachey, N. S., Kefalov, V. J., Palczewski, K. Conditional deletion of Des1 in the mouse retina does not impair the visual cycle in cones.
视锥细胞在中高强度光照下对视觉至关重要，并且能够进行颜色分辨。其快速的暗适应速度和抗饱和能力被认为部分依赖于视网膜内的视觉循环，该循环为视锥蛋白提供 11-顺式视黄醛。该途径的候选酶已被报道，但它们对视锥光反应的生理贡献仍不清楚。在这里，我们评估了该途径中的候选视黄醇异构酶——神经酰胺 δ4 去饱和酶 1（Des1）的作用。单细胞 RNA 测序分析显示，Des1 不仅在 Müller 胶质细胞中表达，而且在整个视网膜和视网膜色素上皮中均有表达。我们通过条件性基因敲除方法评估了视锥细胞对 Müller 细胞表达的 Des1 的功能依赖性。在 G 蛋白亚基α转导素 1（Gnat1）基因敲除背景下，用 floxed Des1 小鼠进行研究，以允许单独记录视锥驱动的光反应，然后与血小板衍生生长因子受体α（Pdgfrα）-Cre 小鼠杂交，以在 Müller 细胞中敲除 Des1。组织选择性 Des1 基因重组和降低的 Des1 催化活性表明，Des1 表达的条件性敲除并没有引起视网膜结构的明显变化，对视锥细胞的敏感性或暗适应没有影响，但稍微加速了视锥光转导终止的速度。这些结果表明，Müller 细胞中 Des1 的表达对于小鼠视锥视觉色素的再生不是必需的。
