Loss of Neuroligin3 specifically downregulates retinal GABAAα2 receptors without abolishing direction selectivity

PLoS One. 2017 Jul 14;12(7):e0181011. doi: 10.1371/journal.pone.0181011. eCollection 2017.

Abstract

The postsynaptic adhesion proteins Neuroligins (NLs) are essential for proper synapse function, and their alterations are associated with a variety of neurodevelopmental disorders. It is increasingly clear that each NL isoform occupies specific subsets of synapses and is able to regulate the function of discrete networks. Studies of NL2 and NL4 in the retina in particular have contributed towards uncovering their role in inhibitory synapse function. In this study we show that NL3 is also predominantly expressed at inhibitory postsynapses in the retinal inner plexiform layer (IPL), where it colocalizes with both GABAA- and glycinergic receptor clusters in a 3:2 ratio. In the NL3 deletion-mutant (knockout or KO) mouse, we uncovered a dramatic reduction of the number of GABAAα2-subunit containing GABAA receptor clusters at the IPL. Retinal activity was thereafter assessed in KO and wild-type (WT) littermates by multi-electrode-array recordings of the output cells of retina, the retinal ganglion cells (RGCs). RGCs in the NL3 KO showed reduced spontaneous activity and an altered response to white noise stimulation. Moreover, upon application of light flashes, the proportion of cells firing at light offset (OFF RGCs) was significantly lower in the NL3 KO compared to WT littermates, whereas the relative number of cells firing at light onset (ON RGCs) increased. Interestingly, although GABAAα2-bearing receptors have been related to direction-selective circuits of the retina, features of direction selective-retinal ganglion cells recorded remained unperturbed in the NL3 KO. Together our data underscore the importance of NL3 for the integrity of specific GABAAergic retinal circuits and identifies NL3 as an important regulator of retinal activity.

MeSH terms

  • Animals
  • Carrier Proteins / metabolism
  • Cell Adhesion Molecules, Neuronal / deficiency
  • Cell Adhesion Molecules, Neuronal / genetics*
  • Down-Regulation
  • Immunohistochemistry
  • Membrane Proteins / deficiency
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microscopy, Confocal
  • Nerve Tissue Proteins / deficiency
  • Nerve Tissue Proteins / genetics*
  • Patch-Clamp Techniques
  • Receptors, GABA-A / metabolism*
  • Retina / metabolism*
  • Retina / pathology
  • Retinal Ganglion Cells / metabolism
  • Synapses / metabolism

Substances

  • Carrier Proteins
  • Cell Adhesion Molecules, Neuronal
  • Gabra2 protein, mouse
  • Membrane Proteins
  • Nerve Tissue Proteins
  • Receptors, GABA-A
  • gephyrin
  • neuroligin 3

Grant support

This work was funded by the Cure Autism Now Foundation (F.V.) and the Swiss National Science Foundation (Marie-Heim Vögtlin grant PMPDP3_158377 to F.V.); the Hertie Foundation (M. H.); European Community Grants NEUREST MEST-CT-2004-504193 (to M.H.); the Deutsche Forschungsgemeinschaft Center for Molecular Physiology of the Brain (M. H., B. F. and F.V.); the Deutsche Forschungsgemeinschaft Collaborative Research Center 889, project C1 (T.G.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.