Hansen Kristi A, Torborg Christine L, Elstrott Justin, Feller Marla B
Neurobiology Section, Division of Biological Sciences, University of California at San Diego, La Jolla, 92093-0357, USA.
J Comp Neurol. 2005 Dec 12;493(2):309-20. doi: 10.1002/cne.20759.
With the advent of transgenic mice, much has been learned about the expression and function of gap junctions. Previously, we reported that retinal ganglion cells in mice lacking the neuronal gap junction protein connexin 36 (Cx36) have nearly normal firing patterns at postnatal day 4 (P4) but many more asynchronous action potentials than wild-type mice at P10 (Torborg et al. [2005] Nat. Neurosci. 8:72-78). With the goal of understanding the origin of this increased activity in Cx36-/- mice, we used a transgenic mouse (Deans et al. [2001] Neuron 31:477-485) to characterize the developmental expression of a Cx36 reporter in the retina. We found that Cx36 was first detected weakly at P2 and gradually increased in expression until it reached an adult pattern at P14. Although the onset of expression varied by cell type, we identified Cx36 in the glycinergic AII amacrine cell, glutamatergic cone bipolar cell, and retinal ganglion cells (RGCs). In addition, we used calcium imaging and multielectrode array recording to characterize further the firing patterns in Cx36-/- mice. Both correlated and asynchronous action potentials in P10 Cx36-/- RGCs were significantly inhibited by bath application of an ionotropic glutamate receptor antagonist, indicating that the increase in activity was synaptically mediated. Hence, both the expression patterns and the physiology suggest an increasing role for Cx36-containing gap junctions in suppressing RGC firing between waves during postnatal retinal development.
随着转基因小鼠的出现,人们对缝隙连接的表达和功能有了更多了解。此前,我们报道过,缺乏神经元缝隙连接蛋白连接蛋白36(Cx36)的小鼠视网膜神经节细胞在出生后第4天(P4)具有近乎正常的放电模式,但在P10时比野生型小鼠有更多的异步动作电位(Torborg等人,[2005]《自然神经科学》8:72 - 78)。为了理解Cx36基因敲除小鼠中这种活动增加的起源,我们使用了一种转基因小鼠(Deans等人,[2001]《神经元》31:477 - 485)来表征视网膜中Cx36报告基因的发育表达。我们发现Cx36在P2时首次被微弱检测到,其表达逐渐增加,直到P14达到成年模式。尽管表达的起始时间因细胞类型而异,但我们在甘氨酸能AII无长突细胞、谷氨酸能视锥双极细胞和视网膜神经节细胞(RGCs)中鉴定出了Cx36。此外,我们使用钙成像和多电极阵列记录来进一步表征Cx36基因敲除小鼠的放电模式。通过浴用离子型谷氨酸受体拮抗剂,P10的Cx36基因敲除RGCs中的相关和异步动作电位均受到显著抑制,这表明活动的增加是由突触介导的。因此,表达模式和生理学都表明,在出生后视网膜发育过程中,含Cx36的缝隙连接在抑制RGCs波间放电方面的作用越来越大。