Heterozygosity for Nuclear Factor One X in mice models features of Malan syndrome.

EBioMedicine 39 (2019) 388–400 Contents lists available at ScienceDirect EBioMedicine journal homepage: www.ebiomedicine.com Research paper Heterozygosity for Nuclear Factor One X in mice models features of Malan syndrome Sabrina Oishi a, Danyon Harkins a, Nyoman D. Kurniawan b, Maria Kasherman a,c, Lachlan Harris a,d, Oressia Zalucki a, Richard M. Gronostajski e, Thomas H.J. Burne f,g, Michael Piper a,f,⁎ a The School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia The Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD 4072, Australia Griffith Institute for Drug Discovery, Griffith University, Brisbane, QLD 4111, Australia d The Francis Crick Institute, 1 Midland Road, King's Cross, London, United Kingdom e Department of Biochemistry, Program in Genetics, Genomics and Bioinformatics, Center of Excellence in Bioinformatics and Life Sciences, State University of New York at Buffalo, Buffalo, NY 14203, USA f The Queensland Brain Institute, The University of Queensland, Brisbane, QLD 4072, Australia g Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, Brisbane, QLD 4076, Australia b c a r t i c l e i n f o Article history: Received 21 September 2018 Received in revised form 16 November 2018 Accepted 20 November 2018 Available online 29 November 2018 Keywords: NFIX Malan syndrome Macrocephaly Intellectual disability a b s t r a c t Background: Nuclear Factor One X (NFIX) haploinsufficiency in humans results in Malan syndrome, a disorder characterized by overgrowth, macrocephaly and intellectual disability. Although clinical assessments have determined the underlying symptomology of Malan syndrome, the fundamental mechanisms contributing to the enlarged head circumference and intellectual disability in these patients remains undefined. Methods: Here, we used Nfix heterozygous mice as a model to investigate these aspects of Malan syndrome. Volumetric magnetic resonance imaging (MRI) was used to calculate the volumes of 20 brain sub regions. Diffusion tensor MRI was used to perform tractography-based analyses of the corpus callosum, hippocampal commissure, and anterior commissure, as well as structural connectome mapping of the whole brain. Immunohistochemistry examined the neocortical cellular populations. Two behavioral assays were performed, including the active place avoidance task to assess spatial navigation and learning and memory function, and the 3-chambered sociability task to examine social behaviour. Findings: Adult Nfix+/− mice exhibit significantly increased brain volume (megalencephaly) compared to wildtypes, with the cerebral cortex showing the highest increase. Moreover, all three forebrain commissures, in particular the anterior commissure, revealed significantly reduced fractional anisotropy, axial and radial diffusivity, and tract density intensity. Structural connectome analyses revealed aberrant connectivity between many crucial brain regions. Finally, Nfix+/− mice exhibit behavioral deficits that model intellectual disability. Interpretation: Collectively, these data provide a significant conceptual advance in our understanding of Malan syndrome by suggesting that megalencephaly underlies the enlarged head size of these patients, and that disrupted cortical connectivity may contribute to the intellectual disability these patients exhibit. Fund: Australian Research Council (ARC) Discovery Project Grants, ARC Fellowship, NYSTEM and Australian Postgraduate Fellowships. © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). 1. Introduction Malan syndrome (MIM #614753) is caused by mutations in the Nuclear Factor One-X (NFIX) gene in humans [1]. Heterozygous NFIX deletions or nonsense/missense mutations in the DNA-binding/ dimerization domain (exon 2/3) of NFIX (MIM #164005), located at ⁎ Corresponding author at: The School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia. E-mail address: (M. Piper). chromosome 19p13.2, results in loss of protein function, which is referred to as NFIX haploinsufficiency [1–4]. The clinical features of Malan syndrome include prenatal and childhood overgrowth, developmental delays, macrocephaly (head circumference N2 standard deviation from the corresponding age of the population), intellectual disability, and autistic-like traits [1,5]. Patients also exhibit advanced bone age and stereotypical craniofacial features [1,5]. Recently, a review of Malan syndrome patients summarized that while the majority (60 out of 79 cases) of patients had macrocephaly, neuroimaging showed relatively normal brain structure in most patients with the occasional https://doi.org/10.1016/j.ebiom.2018.11.044 2352-3964/© 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). S. Oishi et al. / EBioMedicine 39 (2019) 388–400 Research in context Evidence before this study Nuclear Factor One X (NFIX) haploinsufficiency in humans results in Malan syndrome, a disorder characterized by overgrowth, macrocephaly and intellectual disability. Although clinical assessments have determined the underlying symptomology of Malan syndrome, the fundamental mechanisms contributing to their enlarged head circumference and intellectual disability in these patients remains undefined. Added value of the study This study used Nfix heterozygous mice as a model to investigate these aspects of Malan syndrome. Using magnetic resonance imaging, this study reveals that brain volume (termed as megalencephaly) is significantly increased within adult Nfix+/− mice, most markedly within the cerebral cortex. Moreover, using diffusion magnetic resonance imaging and tractography-based analyses, we reveal microstructural deficits within major forebrain commissures and aberrant connectivity between many crucial brain regions. Finally, we demonstrate that Nfix+/− mice exhibit cortically-mediated behavioral deficits that model intellectual disability. Implications of all the available evidence Collectively, these data suggest that the macrocephaly exhibited within Malan syndrome likely arises from megalencephaly, as well as providing insights into the structural and behavioral correlates underlying the intellectual disability of these patients. In summary, this study models brain structure and behavior in Nfix heterozygous mice to provide a significant conceptual advance in our understanding of the factors underlying Malan syndrome. These findings suggest that future assessments of Malan syndrome patients could include high-resolution neuroimaging, such as DTMRI and tractography, to identify megalencephaly and aberrant brain connectivity. non-specific abnormality such as enlarged ventricles, small callosal bodies, and cortical dysplasia [5]. Macrocephal (...truncated)