Mouse horizontal cells do not express connexin26 or connexin36 - PubMed (original) (raw)

Mouse horizontal cells do not express connexin26 or connexin36

M R Deans et al. Cell Commun Adhes. 2001.

Abstract

Gap junctions between neurons function as electrical synapses, and are present in all layers of mammalian and teleost retina. These synapses are largest and most prominent between horizontal cells where they function to increase the receptive field of a single neuron beyond the width of its dendrites. Receptive field size and the extent of gap junctional coupling between horizontal cells is regulated by ambient light levels and may mediate light/dark adaptation. Furthermore, teleost horizontal cell gap junction hemichannels may facilitate a mechanism of feedback inhibition between horizontal cells and cone photoreceptors. As a prelude to using mouse genetic models to study horizontal cell gap junctions and hemichannels, we sought to determine the connexin complement of mouse horizontal cells. Cx36, Cx37, Cx43, Cx45 and Cx57 mRNA could be detected in mouse retina by RT-PCR. Microscopy was used to further examine the distribution of Cx26 and Cx36. Cx26 immunofluorescence and a beta-gal reporter under regulatory control of the Cx36 promoter did not colocalize with a horizontal cell marker, indicating that these genes are not expressed by horizontal cells. The identity of the connexin(s) forming electrical synapses between mouse horizontal cells and the connexin that may form hemichannels in the horizontal cell telodendria remains unknown.

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Figures

Figure 1

Figure 1

Mouse retina RNA was screened by RT-PCR for the presence of each of the 16 cloned connexin genes. mRNA was detected for 5 connexins; Cx36, Cx37, Cx43, Cx45 and Cx57. To control against amplification of genomic DNA, cRNA was generated in two reactions, one containing (+) and the other lacking (−) the reverse transcriptase enzyme. Results were identical between oligo-dT and random hexamer primed cRNA.

Figure 2

Figure 2

Cx26 immunopositive puncta (green) could not be detected on calbindin positive processes(red) in the OPL(A), but could be easily located in control sections from mouse liver (B) counterstained with the nuclear label DAPI (blue). In retina from mice in which one copy of Cx36 was replaced with β-gal, immunofluorescence for this reporter (green) does not colocalize with calbindin (red) positive horizontal cells (C). ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer. Arrows indicate horizontal cell bodies.

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