Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States.
Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
Invest Ophthalmol Vis Sci. 2014 Apr 24;55(7):4063-72. doi: 10.1167/iovs.14-13997.
Juvenile-onset autosomal dominant Stargardt-like macular dystrophy (STGD3) is caused by mutations in ELOVL4 (elongation of very long fatty acids-4), an elongase necessary for the biosynthesis of very long chain fatty acids (VLC-FAs ≥ C26). Photoreceptors are enriched with VLC polyunsaturated fatty acids (VLC-PUFAs), which are necessary for long-term survival of rod photoreceptors. The purpose of these studies was to determine the effect of deletion of VLC-PUFAs on rod synaptic function in retinas of mice conditionally depleted (KO) of Elovl4.
Retina function was assessed in wild-type (WT) and KO by electroretinography. Outer plexiform structure was evaluated by immunofluorescence and transmission electron microscopy. Single-cell recordings measured rod ion channel operation and rod bipolar glutamate signaling. Sucrose gradient centrifugation was used to isolate synaptosomes from bovine retina. Proteins and lipids were analyzed by Western blotting and tandem mass spectroscopy, respectively.
Inner retinal responses (b-wave, oscillatory potentials, and scotopic threshold responses) of the ERG were decreased in the KO mice compared to controls. However the rod ion channel operation and bipolar glutamate responses were comparable between groups. Biochemical analysis revealed that conventional and ribbon synapses have VLC-PUFAs. Ultrastructural analysis showed that the outer plexiform layer was disorganized and the diameter of vesicles in rod terminals was smaller in the KO mice.
Very long chain PUFAs affect rod function by contributing to synaptic vesicle size, which may alter the dynamics of synaptic transmission, ultimately resulting in a loss of neuronal connectivity and death of rod photoreceptors.
青少年起病的常染色体显性遗传斯塔加特样黄斑营养不良（STGD3）是由 ELOVL4（长链脂肪酸延长酶 4）突变引起的，该酶是生物合成超长链脂肪酸（VLC-FAs≥C26）所必需的。感光器富含超长链多不饱和脂肪酸（VLC-PUFAs），这对于杆状感光器的长期存活是必需的。这些研究的目的是确定 VLC-PUFAs 缺失对 Elovl4 条件性缺失（KO）的小鼠视网膜中杆状突触功能的影响。
通过视网膜电图评估野生型（WT）和 KO 型的视网膜功能。通过免疫荧光和透射电子显微镜评估外丛状层结构。单细胞记录测量杆状离子通道的操作和杆状双极谷氨酸信号。蔗糖梯度离心从牛视网膜中分离突触体。通过 Western blot 和串联质谱分别分析蛋白质和脂质。
与对照组相比，KO 小鼠的内视网膜反应（b 波、振荡电位和暗适应阈值反应）降低。然而，两组之间的杆状离子通道操作和双极谷氨酸反应相似。生化分析表明，常规和带状突触具有 VLC-PUFAs。超微结构分析显示，KO 小鼠的外丛状层结构紊乱，杆状末端囊泡的直径较小。
超长链 PUFAs 通过影响突触小泡的大小来影响杆状功能，这可能改变突触传递的动力学，最终导致神经元连接的丧失和杆状感光器的死亡。
