Rice University, Undergraduate Program in Neuroscience, Houston, Texas, USA.
Summer Research Program, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
J Comp Neurol. 2021 Apr 1;529(5):1066-1080. doi: 10.1002/cne.25004. Epub 2020 Aug 31.
BMAL1 is a core component of the mammalian circadian clockwork. Removal of BMAL1 from the retina significantly affects visual information processing in both rod and cone pathways. To identify potential pathways and/or molecules through which BMAL1 alters signal transmission at the cone pedicle, we performed an RNA-seq differential expression analysis between cone-specific Bmal1 knockout cones (cone-Bmal1 ) and wild-type (WT) cones. We found 88 genes differentially expressed. Among these, Complexin3 (Cplx3), a SNARE regulator at ribbon synapses, was downregulated fivefold in the mutant cones. The purpose of this work was to determine whether BMAL1 and/or the cone clock controls CPLX3 protein expression at cone pedicles. We found that CPLX3 expression level was decreased twofold in cone-Bmal1 cones. Furthermore, CPLX3 expression was downregulated at night compared to the day in WT cones but remained constitutively low in mutant cones both day and night. The transcript and protein expression levels of Cplx4-the other complexin expressed in cones-were similar in WT and mutant cones; in WT cones, CPLX4 protein level did not change with the time of day. In silico analysis revealed four potential BMAL1:CLOCK binding sites upstream from exon one of Cplx3 and none upstream of exon one of Cplx4. Our results suggest that CPLX3 expression is regulated at the transcriptional level by the cone clock. The modulation of CPLX3 may be a mechanism by which the clock controls the cone synaptic transfer function to second-order cells and thereby impacts retinal signal processing during the day/night cycle.
BMAL1 是哺乳动物生物钟的核心组成部分。从视网膜中去除 BMAL1 会显著影响视杆和视锥两种途径中的视觉信息处理。为了确定 BMAL1 通过哪些潜在途径和/或分子改变视锥细胞足突处的信号转导，我们对特异性敲除 Bmal1 的视锥细胞（cone-Bmal1 ）和野生型（WT）视锥细胞之间进行了 RNA-seq 差异表达分析。我们发现了 88 个差异表达的基因。其中，突触囊泡融合相关蛋白 3（Complexin3，Cplx3）作为在 ribbon 突触处的 SNARE 调节因子，在突变体视锥细胞中下调了五倍。本研究旨在确定 BMAL1 和/或视锥生物钟是否控制视锥细胞足突处的 CPLX3 蛋白表达。我们发现 cone-Bmal1 视锥细胞中 CPLX3 的表达水平降低了两倍。此外，WT 视锥细胞中 CPLX3 的表达在夜间比白天下调，但在突变体视锥细胞中无论是白天还是夜间都保持着低水平。另一种在视锥细胞中表达的 complexin，Cplx4 的转录本和蛋白表达水平在 WT 和突变体视锥细胞中相似；在 WT 视锥细胞中，CPLX4 蛋白水平不会随一天中的时间而变化。计算机分析显示，在 Cplx3 的外显子 1 上游有四个潜在的 BMAL1:CLOCK 结合位点，而在 Cplx4 的外显子 1 上游没有。我们的结果表明，CPLX3 的表达受视锥生物钟的转录水平调控。CPLX3 的调节可能是生物钟控制视锥细胞突触传递功能的一种机制，从而影响昼夜节律期间视网膜信号处理。
