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在小鼠视网膜的神经元细胞类型中,核心生物钟蛋白的异质性表达。

Heterogeneous expression of the core circadian clock proteins among neuronal cell types in mouse retina.

机构信息

Department of Ophthalmology and Visual Science, The University of Texas Health Science Center at Houston, Medical School, Houston, Texas, United States of America.

出版信息

PLoS One. 2012;7(11):e50602. doi: 10.1371/journal.pone.0050602. Epub 2012 Nov 26.

Abstract

Circadian rhythms in metabolism, physiology, and behavior originate from cell-autonomous circadian clocks located in many organs and structures throughout the body and that share a common molecular mechanism based on the clock genes and their protein products. In the mammalian neural retina, despite evidence supporting the presence of several circadian clocks regulating many facets of retinal physiology and function, the exact cellular location and genetic signature of the retinal clock cells remain largely unknown. Here we examined the expression of the core circadian clock proteins CLOCK, BMAL1, NPAS2, PERIOD 1(PER1), PERIOD 2 (PER2), and CRYPTOCHROME2 (CRY2) in identified neurons of the mouse retina during daily and circadian cycles. We found concurrent clock protein expression in most retinal neurons, including cone photoreceptors, dopaminergic amacrine cells, and melanopsin-expressing intrinsically photosensitive ganglion cells. Remarkably, diurnal and circadian rhythms of expression of all clock proteins were observed in the cones whereas only CRY2 expression was found to be rhythmic in the dopaminergic amacrine cells. Only a low level of expression of the clock proteins was detected in the rods at any time of the daily or circadian cycle. Our observations provide evidence that cones and not rods are cell-autonomous circadian clocks and reveal an important disparity in the expression of the core clock components among neuronal cell types. We propose that the overall temporal architecture of the mammalian retina does not result from the synchronous activity of pervasive identical clocks but rather reflects the cellular and regional heterogeneity in clock function within retinal tissue.

摘要

代谢、生理和行为的昼夜节律源于位于身体许多器官和结构中的细胞自主生物钟,这些生物钟基于时钟基因及其蛋白产物共享共同的分子机制。在哺乳动物的神经视网膜中,尽管有证据支持存在几个调节视网膜生理和功能许多方面的昼夜节律钟,但视网膜时钟细胞的确切细胞位置和遗传特征在很大程度上仍然未知。在这里,我们在小鼠视网膜的已鉴定神经元中检查了核心生物钟蛋白 CLOCK、BMAL1、NPAS2、PERIOD 1(PER1)、PERIOD 2(PER2)和 CRYPTOCHROME2(CRY2)在日常和昼夜节律周期中的表达。我们发现大多数视网膜神经元中存在时钟蛋白的共表达,包括视锥细胞、多巴胺能无长突细胞和表达内在光敏性节细胞的黑素细胞。值得注意的是,所有时钟蛋白的表达在视锥细胞中都呈现昼夜节律,而只有 CRY2 表达在多巴胺能无长突细胞中呈现节律性。在昼夜节律周期中的任何时间,在视杆细胞中仅检测到时钟蛋白的低水平表达。我们的观察结果提供了证据表明,视锥细胞而不是视杆细胞是自主昼夜节律钟,并揭示了核心时钟成分在神经元细胞类型中的表达存在重要差异。我们提出,哺乳动物视网膜的整体时间结构不是由普遍存在的相同时钟的同步活动产生的,而是反映了视网膜组织中时钟功能的细胞和区域异质性。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/c6dc/3506613/192ff9a0ceb6/pone.0050602.g001.jpg

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