Esquiva Gema, Avivi Aaron, Hannibal Jens
Department of Clinical Biochemistry, Bispebjerg Hospital, University of CopenhagenCopenhagen, Denmark; Department of Physiology, Genetics and Microbiology, University of AlicanteAlicante, Spain.
Laboratory of Biology of Subterranean Mammals, Institute of Evolution, University of Haifa Haifa, Israel.
Front Neuroanat. 2016 Jun 9;10:61. doi: 10.3389/fnana.2016.00061. eCollection 2016.
The blind mole rat, Spalax ehrenbergi, can, despite severely degenerated eyes covered by fur, entrain to the daily light/dark cycle and adapt to seasonal changes due to an intact circadian timing system. The present study demonstrates that the Spalax retina contains a photoreceptor layer, an outer nuclear layer (ONL), an outer plexiform layer (OPL), an inner nuclear layer (INL), an inner plexiform layer (IPL), and a ganglion cell layer (GCL). By immunohistochemistry, the number of melanopsin (mRGCs) and non-melanopsin bearing retinal ganglion cells was analyzed in detail. Using the ganglion cell marker RNA-binding protein with multiple splicing (RBPMS) it was shown that the Spalax eye contains 890 ± 62 RGCs. Of these, 87% (752 ± 40) contain melanopsin (cell density 788 melanopsin RGCs/mm(2)). The remaining RGCs were shown to co-store Brn3a and calretinin. The melanopsin cells were located mainly in the GCL with projections forming two dendritic plexuses located in the inner part of the IPL and in the OPL. Few melanopsin dendrites were also found in the ONL. The Spalax retina is rich in rhodopsin and long/middle wave (L/M) cone opsin bearing photoreceptor cells. By using Ctbp2 as a marker for ribbon synapses, both rods and L/M cone ribbons containing pedicles in the OPL were found in close apposition with melanopsin dendrites in the outer plexus suggesting direct synaptic contact. A subset of cone bipolar cells and all photoreceptor cells contain recoverin while a subset of bipolar and amacrine cells contain calretinin. The calretinin expressing amacrine cells seemed to form synaptic contacts with rhodopsin containing photoreceptor cells in the OPL and contacts with melanopsin cell bodies and dendrites in the IPL. The study demonstrates the complex retinal circuitry used by the Spalax to detect light, and provides evidence for both melanopsin and non-melanopsin projecting pathways to the brain.
盲鼹鼠（Spalax ehrenbergi）尽管眼睛严重退化并被毛发覆盖，但由于其完整的昼夜节律计时系统，仍能与昼夜光暗周期同步，并适应季节变化。本研究表明，盲鼹鼠的视网膜包含一个光感受器层、一个外核层（ONL）、一个外网状层（OPL）、一个内核层（INL）、一个内网状层（IPL）和一个神经节细胞层（GCL）。通过免疫组织化学，详细分析了表达黑视蛋白的视网膜神经节细胞（mRGCs）和不表达黑视蛋白的视网膜神经节细胞的数量。使用具有多种剪接的神经节细胞标记物RNA结合蛋白（RBPMS）表明，盲鼹鼠的眼睛含有890±62个视网膜神经节细胞（RGCs）。其中，87%（752±40）含有黑视蛋白（细胞密度为788个黑视蛋白RGCs/mm²）。其余的视网膜神经节细胞被证明同时储存Brn3a和钙视网膜蛋白。表达黑视蛋白的细胞主要位于神经节细胞层，其突起形成两个树突丛，分别位于内网状层的内部和外网状层。在外核层也发现了少量表达黑视蛋白的树突。盲鼹鼠的视网膜富含视紫红质以及含有长/中波（L/M）视锥蛋白的光感受器细胞。通过使用Ctbp2作为带状突触的标记物，发现外网状层中含有视杆和L/M视锥的带状突触小体与外网状层中表达黑视蛋白的树突紧密相邻，提示存在直接的突触联系。一部分视锥双极细胞和所有的光感受器细胞都含有恢复蛋白，而一部分双极细胞和无长突细胞含有钙视网膜蛋白。表达钙视网膜蛋白的无长突细胞似乎与外网状层中含有视紫红质的光感受器细胞形成突触联系，并与内网状层中表达黑视蛋白的细胞体和树突形成突触联系。该研究展示了盲鼹鼠用于检测光线的复杂视网膜神经回路，并为黑视蛋白和非黑视蛋白向大脑投射的通路提供了证据。
