麩胺酸受器次單元NR2C在視交叉上核對於光線調控生理週期所扮演的角色

The role of NMDA receptor 2C subunit in suprachiasmatic nucleus for circadian photoentrainment

何介文(Chieh-Wen Ho)

指導教授 ： 陳示國

國立臺灣大學/生命科學院/生命科學系/碩士(2021年)

https://doi.org/10.6342/NTU202104326

摘要

視交叉上核(suprachiasmatic nucleus, SCN)是動物生理週期的調控核心，在光週期下會接收外來刺激，經內生感光視神經節細胞(intrinsically photosensitive retinal ganglion cell，ipRGC)藉glutamate送到SCN而產生生理週期。SCN細胞分為腹側的VIP和GRP，及背側的AVP細胞。過去認為ipRGC主要將訊息送至VIP，然而2016年發現，ipRGC也可以與AVP細胞產生synapse，且連結在AVP細胞本體上突觸數量較VIP和GRP細胞更多，和過去的假說並不一致。另外，先前研究顯示SCN的背側特別表現了NMDA receptor subunit的NR2C。因此，本研究為探討ipRGC在SCN背側訊息傳導對於生理時鐘調控的影響，利用CRISPR包裹於AAV藉由steriotaxis micro-injection打入wild type以及cre-dependent老鼠SCN中knock-out該處的NR2C，再觀察老鼠進行wheel-running時jet-lag、masking、phase shift，以及在skeleton photo period下生理時鐘的改變。我們發現，在SCN的NMDA受器被knock-out的老鼠在光masking效果變差，與phase shift增加。而在AVP細胞上專一性knock-out掉NMDA受器的老鼠的改變則不明顯，推測非AVP cell表現之NR2C與photoentrainment是有關係的。

關鍵字

生理時鐘 ； 光 ； 麩胺酸受器

並列摘要

The suprachiasmatic nucleus (SCN) is known as the master pacemaker which control the circadian rhythm in animal. Under normal light-dark cycle, the SCN receives the light input from the specific retinal ganglion cells called intrinsic photosensitive retinal ganglion cells (ipRGC). These ipRGCs can detect light intrinsically without classic photoreceptor cells such as rods and cones. The light signal is transmitted from the retina to the hypothalamus where the SCN is located via the retinohypothalamic tract (RHT). The neurotransmitter that RHT releases is mainly glutamate and PACAP. The SCN can be divided into ventral part that contains GRP and VIP cells, and the dorsal part where the AVP neuron is located. In SCN, it was generally believed that the RHT axons extend mainly into the ventral part, where the majority glutamate receptor is NMDA receptor. However, in 2016, it was found that the ipRGCs formed synapse directly with AVP neuron in dorsal part. Interestingly, previous research showed that NR2C, the subunit of NMDA receptor, is primiarly expressed at the dorsal SCN.
To test the circadian photoentrainment function of ipRGC input to the dorsal part of SCN, the adeno-associated virus containing CRISPR vector is applied to knock-out NMDA receptor 2C subunit in the whole SCN or specifically in the AVP neurons using conditional AVP-Cre mice. The wheel running behavior of these mice under normal light-dark cycle, advanced and delayed jet lag, skeleton photoperiod, and constant dark condition is performed to compare CRISPR injected mice and the control group. We found that NR2C KO mice showed a reduction in light masking, and an increased phase shift, while the AVP-specific NR2C KO mice exhibited a no effect on photoentrainment, indicating that NR2C expressed on non AVP cells involved in circadian photoentrainment.

並列關鍵字

Circadian rhythm ； NMDAR2C ； photoentrainment

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