Neuillé Marion, Morgans Catherine W, Cao Yan, Orhan Elise, Michiels Christelle, Sahel José-Alain, Audo Isabelle, Duvoisin Robert M, Martemyanov Kirill A, Zeitz Christina
INSERM, U968, Paris, F-75012, France.
CNRS, UMR_7210, Paris, F-75012, France.
Eur J Neurosci. 2015 Aug;42(3):1966-75. doi: 10.1111/ejn.12959. Epub 2015 Jul 4.
Mutations in LRIT3 lead to complete congenital stationary night blindness (cCSNB). The exact role of LRIT3 in ON-bipolar cell signaling cascade remains to be elucidated. Recently, we have characterized a novel mouse model lacking Lrit3 [no b-wave 6, (Lrit3(nob6/nob6) )], which displays similar abnormalities to patients with cCSNB with LRIT3 mutations. Here we compare the localization of components of the ON-bipolar cell signaling cascade in wild-type and Lrit3(nob6/nob6) retinal sections by immunofluorescence confocal microscopy. An anti-LRIT3 antibody was generated. Immunofluorescent staining of LRIT3 in wild-type mice revealed a specific punctate labeling in the outer plexiform layer (OPL), which was absent in Lrit3(nob6/nob6) mice. LRIT3 did not co-localize with ribeye or calbindin but co-localized with mGluR6. TRPM1 staining was severely decreased at the dendritic tips of all depolarizing bipolar cells in Lrit3(nob6/nob6) mice. mGluR6, GPR179, RGS7, RGS11 and Gβ5 immunofluorescence was absent at the dendritic tips of cone ON-bipolar cells in Lrit3(nob6/nob6) mice, while it was present at the dendritic tips of rod bipolar cells. Furthermore, peanut agglutinin (PNA) labeling was severely reduced in the OPL in Lrit3(nob6/nob6) mice. This study confirmed the localization of LRIT3 at the dendritic tips of depolarizing bipolar cells in mouse retina and demonstrated the dependence of TRPM1 localization on the presence of LRIT3. As tested components of the ON-bipolar cell signaling cascade and PNA revealed disrupted localization, an additional function of LRIT3 in cone synapse formation is suggested. These results point to a possibly different regulation of the mGluR6 signaling cascade between rod and cone ON-bipolar cells.
LRIT3基因突变会导致完全性先天性静止性夜盲(cCSNB)。LRIT3在ON双极细胞信号级联反应中的确切作用仍有待阐明。最近,我们鉴定了一种缺乏Lrit3的新型小鼠模型[无b波6,(Lrit3(nob6/nob6))],该模型表现出与携带LRIT3基因突变的cCSNB患者相似的异常。在此,我们通过免疫荧光共聚焦显微镜比较野生型和Lrit3(nob6/nob6)视网膜切片中ON双极细胞信号级联反应成分的定位。制备了抗LRIT3抗体。野生型小鼠中LRIT3的免疫荧光染色在外丛状层(OPL)显示出特异性点状标记,而在Lrit3(nob6/nob6)小鼠中则不存在。LRIT3与ribeye或钙结合蛋白不共定位,但与mGluR6共定位。在Lrit3(nob6/nob6)小鼠中,所有去极化双极细胞树突尖端的TRPM1染色严重减少。在Lrit3(nob6/nob6)小鼠中,视锥ON双极细胞树突尖端不存在mGluR6、GPR179、RGS7、RGS11和Gβ5免疫荧光,而在视杆双极细胞树突尖端则存在。此外,Lrit3(nob6/nob6)小鼠的OPL中花生凝集素(PNA)标记严重减少。本研究证实了LRIT3在小鼠视网膜去极化双极细胞树突尖端的定位,并证明了TRPM1定位对LRIT3存在的依赖性。由于ON双极细胞信号级联反应的测试成分和PNA显示定位破坏,提示LRIT3在视锥突触形成中具有额外功能。这些结果表明视杆和视锥ON双极细胞之间mGluR6信号级联反应可能存在不同的调节。