High resolution magnetic resonance imaging for characterization of the neuroligin-3 knock-in mouse model associated with autism spectrum disorder.

Manoj Kumar,Edward S Brodkin,Charles Kenworthy,Harish Poptani,Stephen Pickup,James C Gee,Ranjit Ittyerah,Ted Abel,Wei-Ting Hwang,Jeffery T Duda,Valerie W Hu

doi:10.1371/journal.pone.0109872

Abstract

Autism spectrum disorders (ASD) comprise an etiologically heterogeneous set of neurodevelopmental disorders. Neuroligin-3 (NL-3) is a cell adhesion protein that mediates synapse development and has been implicated in ASD. We performed ex-vivo high resolution magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI) and behavioral (social approach and zero maze) tests at 3 different time points (30, 50 and 70 days-of-age) on NL-3 and wild-type littermates to assess developmental brain abnormalities in NL-3 mice. MRI data were segmented in 39 different gray and white matter regions. Volumetric measurements, along with DTI indices from these segmented regions were also performed. After controlling for age and gender, the NL-3 knock-in animals demonstrated significantly reduced sociability and lower anxiety-related behavior in comparison to their wild type littermates. Significantly reduced volume of several white and gray matter regions in the NL-3 knock-in mice were also observed after considering age, gender and time point as covariates. These findings suggest that structural changes in the brain of NL-3 mice are induced by the mutation in the NL-3 gene. No significant differences in DTI indices were observed, which suggests that the NL-3 mutation may not have a profound effect on water diffusion as detected by DTI. The volumetric and DTI studies aid in understanding the biology of disrupting function on an ASD risk model and may assist in the development of imaging biomarkers for ASD.

Highlights

Autism spectrum disorder (ASD) comprises a complex and etiologically heterogeneous group of neurodevelopmental disorders with an unknown unifying pathogenesis
The NL-3 animals spent 8.7 seconds less time sniffing the stimulus mouse in comparison to their wild type littermates (p = 0.019) (Figure 2A)
We observed significantly lower volume from 6 brain regions and higher volume from the pons and medulla in NL-3 knock-in mice compared to the wild type littermates after considering age and gender as covariates

Summary

Introduction

Autism spectrum disorder (ASD) comprises a complex and etiologically heterogeneous group of neurodevelopmental disorders with an unknown unifying pathogenesis. The etiology of ASD is unknown in most cases, but monogenic heritable forms exist that have provided insights into ASD pathogenesis and have led to the notion of autism as a ‘synapse disorder’ [4]. The point mutation at the amino acid position 451 (R451C) caused a decrease in the amount of NL-3 in patients with ASD. The same point mutation was introduced in a mouse to generate the NL-3 R451C knock-in mouse model of ASD [6]. The NL-3 knock-in mice have been reported to exhibit behavioral symptoms similar to those observed in human ASD [6]. A subsequent study did not observe behavioral phenotypes relevant to ASD in this model, and raised concerns about the relevance of the model to ASD [8]

Methods

Results

Conclusion