Abstract
22q11.2, 15q13.3, and 1q21.1 microdeletions attract considerable interest by conferring high risk for a range of neuropsychiatric disorders, including schizophrenia and autism. A fundamental open question is whether divergent or convergent neural mechanisms mediate this genetic pleiotropic association with the same behavioral phenotypes. We use a combination of rodent microdeletion models with high-field neuroimaging to perform a comparative whole-brain characterization of functional and structural mechanisms linked to high-risk states. Resting-state functional and structural magnetic resonance imaging data were acquired on mice carrying heterozygous microdeletions in 22q11.2 (N = 12), 15q13.3 (N = 11), and 1q21.1 (N = 11) loci. We performed network-based statistic, graph, and morphometric analyses. The three microdeletions did not share significant systems-level features. Instead, morphometric analyses revealed microcephaly in 1q21.1 and macrocephaly in 15q13.3 deletions, whereas cerebellar volume was specifically reduced in 22q11.2 deletion. In function, 22q11.2 deletion mice showed widespread cortical hypoconnectivity, accompanied by opposing hyperconnectivity in dopaminergic pathways, which was confirmed by graph analysis. 1q21.1 exhibited distinct changes in posterior midbrain morphology and function, especially in periaqueductal gray, whereas 15q13.3 demonstrated alterations in auditory/striatal system. The combination of cortical hypoconnectivity and dopaminergic hyperconnectivity and reduced cerebellum in 22q11.2 deletion mirrors key neurodevelopmental features of schizophrenia, whereas changes in midbrain and auditory/striatal morphology and topology in 1q21.1 and 15q13.3 rather indicate focal processes possibly linked to the emergence of abnormal salience perception and hallucinations. In addition to insights into pathophysiological processes in these microdeletions, our results establish the general point that microdeletions might increase risk for overlapping neuropsychiatric phenotypes through separable neural mechanisms.
Highlights
There is an increasing consensus that the current categorical classification of neuropsychiatric disorders lacks biological validity[1]
Modeling these microdeletions in animals is helpful in this context for the delineation of the essential systemslevel features contributing to the neuropsychiatric traits
Additional Region of interest (ROI) volumetry analysis allowed a comparison of regional relative brain volumes corrected for the whole-brain differences between and within the copy number variants (CNVs) groups
Summary
There is an increasing consensus that the current categorical classification of neuropsychiatric disorders lacks biological validity[1]. Schizophrenia[2,3,4], autism[5], epilepsy, attention deficit hyperactivity disorder (ADHD), and intellectual disability[6] These variants offer an excellent opportunity to determine the pathological pathways in these CNV constructs and to study the question whether pleiotropic association of different genetic variants with the same (set of) categorical phenotype is mediated by distinct or shared mechanisms, which would be of interest as final pathways linked to genetic risk for that phenotype. Low incidence rates of microdeletions[2] lead to relatively small sample sizes, limiting the ability to study their contributions to the etiology of resultant syndromes For these reasons, mouse models of CNVs are extremely valuable tools for investigating the potential causes of neuropsychiatric traits associated with deletions
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