Neuroligin 2 R215H Mutant Mice Manifest Anxiety, Increased Prepulse Inhibition, and Impaired Spatial Learning and Memory

Abstract

Neuroligin 2 (NLGN2) is a postsynaptic adhesion protein that plays an essential role in synaptogenesis and function of inhibitory neuron. We previously identified a missense mutation R215H of the NLGN2 in a patient with schizophrenia. This missense mutation was shown to be pathogenic in several cell-based assays. The objective of this study was to better understand the behavioral consequences of this mutation in vivo. We generated a line of transgenic mice carrying this mutation using a recombinant-based method. The mice were subjected to a battery of behavioral tests including open field locomotor activity assay, prepulse inhibition (PPI) assay, accelerated rotarod test, novel location and novel recognition tests, elevated plus-maze (EPM) test, and Morris water maze test. The transgenic animals were viable and fertile, but the Nlgn2 R215H knock-in (KI) homozygous mice showed growth retardation, anxiety-like behavior, increased PPI, and impaired spatial learning and memory. There was no significant interaction between sex and genotype in most behavioral tests; however, we observed a significant interaction between sex and genotype in EPM test in this study. Also, we found that the Nlgn2 R215H homozygous KI mice did not express the NLGN2 protein, resembling Nlgn2 knockout mice. Our results demonstrate that Nlgn2 R215H KI homozygous mice manifest several behavioral abnormalities similar to those found in psychiatric patients carrying NLGN2 mutations, indicating that dysfunction of NLGN2 contributes to the pathogenesis of certain psychiatric symptoms commonly present in various mental disorders, not limited to schizophrenia.

GABAergic deficits and schizophrenia-like behaviors in a mouse model carrying patient-derived neuroligin-2 R215H mutation

“…The low expression level of NL2 in our R215H KI mice distinguishes our KI mice from the NL2 KO mice, which showed completely absent expression of NL2 in our Western blot analysis. Furthermore, our R215H KI mice also showed clear GABAergic deficits as expected, but it is unknown whether their KI mice have any GABAergic deficits or not [ 8 ].…”

“…Surprisingly, our former collaborator Dr. Chia-Hsiang Chen’s group recently reported that their NL2 R215H KI mice displayed an increased pre-pulse inhibition phenotype [ 8 ]. However, because the startle response of their KI mice was not reported, it makes the data difficult to compare with ours.…”

Inhibition in the amygdala anxiety circuitry

“…A nonsense variant in Nlgn2 was recently identified in a patient with severe anxiety and autism 72 , in addition to Nlgn2 mutations previously associated with schizophrenia 2 . In mice, both the deletion of Nlgn2 and a schizophrenia-associated Nlgn2 mutation, R215H, result in severe anxiety phenotypes 74 , 75 , 111 . Nlgn2 is expressed both in the BLA and (to a lesser extent) CeA of mice 74 , but interestingly appears to play very different roles in these two structures.…”

Altered Light Conditions Contribute to Abnormalities in Emotion and Cognition Through HINT1 Dysfunction in C57BL/6 Mice

“…It is generally accepted that the standard duration of the EPM is 5 min. However, based on the previous results by Chen et al ( 2017 ) and our group, we eventually decided to perform the EPM for 6 min, which should be validated in the future (Xing et al, 2013 ; Chen et al, 2017 ). Moreover, although we selected the performing time of the behavioral experiments based on published articles and our preliminary experiment, this decision may have rendered the behavioral results of the CD group incomparable with those of other similar studies.…”

“…We performed the EPM test as previously described (Pellow et al, 1985 ; Liu et al, 2014 ; Chen et al, 2017 ). Briefly, the apparatus was composed of two open arms (25 × 5 cm) and two closed arms (25 × 5 × 20 cm).…”