Lin Bin, Jakobs Tatjana C, Masland Richard H
Howard Hughes Medical Institute, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
J Neurosci. 2005 Jul 13;25(28):6696-701. doi: 10.1523/JNEUROSCI.1894-05.2005.
Rod signals are transmitted to ON retinal ganglion cells by means of gap junctions between AII amacrine cells and ON bipolars. The AII amacrine cells are known to express connexin36 (Cx36), but previous studies of Cx36 in ON cone bipolars have been ambiguous. Here, we studied bipolar cells in a transgenic mouse line that expresses high levels of green fluorescent protein (GFP) in one type of ON cone bipolar cell. We found strong Cx36 immunostaining in the axon terminals of the GFP-labeled type 357 bipolar cells in both vertical sections and whole mounts of the retina. This finding was confirmed by single-cell immunostaining and single-cell reverse transcription-PCR (RT-PCR). As reported previously (Maxeiner et al., 2005), Cx45 was found in some ON bipolar cells, but RT-PCR showed Cx36 and not Cx45 to be expressed by the type 357 bipolar cells. Some of the remaining GFP-negative bipolar cells expressed Cx45 but not Cx36. It appears that different types of ON cone bipolar cells express different connexins at their gap junctions with AII amacrine cells.
视杆信号通过AII无长突细胞与ON双极细胞之间的缝隙连接传递到ON视网膜神经节细胞。已知AII无长突细胞表达连接蛋白36（Cx36），但之前关于ON视锥双极细胞中Cx36的研究结果并不明确。在这里，我们研究了一种转基因小鼠品系中的双极细胞，该品系在一种ON视锥双极细胞中高水平表达绿色荧光蛋白（GFP）。我们在视网膜的垂直切片和整装片中发现，GFP标记的357型双极细胞的轴突终末有强烈的Cx36免疫染色。这一发现通过单细胞免疫染色和单细胞逆转录-聚合酶链反应（RT-PCR）得到了证实。如之前报道（马克西纳等人，2005年），在一些ON双极细胞中发现了Cx45，但RT-PCR显示357型双极细胞表达的是Cx36而非Cx45。其余一些GFP阴性双极细胞表达Cx45但不表达Cx36。看来不同类型的ON视锥双极细胞在与AII无长突细胞的缝隙连接处表达不同的连接蛋白。
