Neuroligin3 splice isoforms shape inhibitory synaptic function in the mouse hippocampus

Motokazu Uchigashima,Ming Leung,Takuya Watanabe,Amy Cheung,Timmy Le,Sabine Pallat,Alexandre Luis Marques Dinis,Masahiko Watanabe,Yuka Imamura Kawasawa,Kensuke Futai

doi:10.1074/jbc.ac120.012571

Abstract

Synapse formation is a dynamic process essential for the development and maturation of the neuronal circuitry in the brain. At the synaptic cleft, trans-synaptic protein-protein interactions are major biological determinants of proper synapse efficacy. The balance of excitatory and inhibitory synaptic transmission (E-I balance) stabilizes synaptic activity, and dysregulation of the E-I balance has been implicated in neurodevelopmental disorders, including autism spectrum disorders. However, the molecular mechanisms underlying the E-I balance remain to be elucidated. Here, using single-cell transcriptomics, immunohistochemistry, and electrophysiology approaches to murine CA1 pyramidal neurons obtained from organotypic hippocampal slice cultures, we investigate neuroligin (Nlgn) genes that encode a family of postsynaptic adhesion molecules known to shape excitatory and inhibitory synaptic function. We demonstrate that the NLGN3 protein differentially regulates inhibitory synaptic transmission in a splice isoform-dependent manner at hippocampal CA1 synapses. We also found that distinct subcellular localizations of the NLGN3 isoforms contribute to the functional differences observed among these isoforms. Finally, results from single-cell RNA-Seq analyses revealed that Nlgn1 and Nlgn3 are the major murine Nlgn genes and that the expression levels of the Nlgn splice isoforms are highly diverse in CA1 pyramidal neurons. Our results delineate isoform-specific effects of Nlgn genes on the E-I balance in the murine hippocampus.

Highlights

Neuroligin proteins (NLGNs) were the first identified binding partners of a-latrotoxin receptors, neurexin proteins (NRXs), and localize at postsynaptic sites to regulate synapse maturation and function [1]
As paired-pulse ratio (PPR) inversely correlates with presynaptic release probability, these results suggest that overexpression of NLGN3D and 3A2 can modulate presynaptic release probability
We demonstrated that NLGN3 regulates inhibitory synaptic transmission and excitatory and inhibitory synapse localization in a splice isoform–dependent manner

Summary

Introduction

Neuroligin proteins (NLGNs) were the first identified binding partners of a-latrotoxin receptors, neurexin proteins (NRXs), and localize at postsynaptic sites to regulate synapse maturation and function [1]. We assess the function of NLGN3 splice isoforms on excitatory and inhibitory synaptic transmission in CA1 pyramidal neurons in mouse organotypic slice cultures. To examine the potential roles of NLGN3 splice isoforms on excitatory and inhibitory synapse function, we biolistically transfected the Nlgn3 splice isoform genes in CA1 pyramidal cells of organotypic hippocampal slice cultures (Fig. 1).

Results

Conclusion