Loss of Zmiz1 in mice leads to impaired cortical development and autistic-like behaviors.

De novo mutations in transcriptional regulators are emerging as key risk factors contributing to the etiology of neurodevelopmental disorders. Human genetic studies have recently identified ZMIZ1 and its de novo mutations as causal of a neurodevelopmental syndrome strongly associated with intellectual disability, autism, ADHD, microcephaly, and other developmental anomalies. However, the role of ZMIZ in brain development or how ZMIZ1 mutations cause neurological phenotypes is unknown. Here, we generated a forebrain-specific Zmiz1 mutant mouse model that develops brain abnormalities, including cortical microcephaly, corpus callosum dysgenesis, and abnormal differentiation of upper-layer cortical neurons. Behaviorally, Zmiz1 mutant mice show alterations in motor activity, anxiety, communication, and social interactions with strong sex differences, resembling phenotypes associated with autism. Molecularly, Zmiz1 deficiency leads to transcriptomic changes disrupting neurogenesis, neuron differentiation programs, and synaptic signaling. We identified Zmiz1-mediated downstream regulation of key neurodevelopmental factors, including Lhx2, Auts2, and EfnB2. Importantly, reactivation of the EfnB2 pathway by exogenous EFNB2 recombinant protein rescues the dendritic outgrowth deficits in Zmiz1 mutant cortical neurons. Overall, our in vivo findings provide insight into Zmiz1 function in cortical development and reveal mechanistic underpinnings of ZMIZ1 syndrome, thereby providing valuable information relevant to future studies on this neurodevelopmental disorder.

Zmiz1 is a novel regulator of brain development associated with autism and intellectual disability.

Neurodevelopmental disorders (NDDs) are a class of pathologies arising from perturbations in brain circuit formation and maturation with complex etiological triggers often classified as environmental and genetic. Neuropsychiatric conditions such as autism spectrum disorders (ASD), intellectual disability (ID), and attention deficit hyperactivity disorders (ADHD) are common NDDs characterized by their hereditary underpinnings and inherent heterogeneity. Genetic risk factors for NDDs are increasingly being identified in non-coding regions and proteins bound to them, including transcriptional regulators and chromatin remodelers. Importantly, de novo mutations are emerging as important contributors to NDDs and neuropsychiatric disorders. Recently, de novo mutations in transcriptional co-factor Zmiz1 or its regulatory regions have been identified in unrelated patients with syndromic ID and ASD. However, the role of Zmiz1 in brain development is unknown. Here, using publicly available databases and a Zmiz1 mutant mouse model, we reveal that Zmiz1 is highly expressed during embryonic brain development in mice and humans, and though broadly expressed across the brain, Zmiz1 is enriched in areas prominently impacted in ID and ASD such as cortex, hippocampus, and cerebellum. We investigated the relationship between Zmiz1 structure and pathogenicity of protein variants, the epigenetic marks associated with Zmiz1 regulation, and protein interactions and signaling pathways regulated by Zmiz1. Our analysis reveals that Zmiz1 regulates multiple developmental processes, including neurogenesis, neuron connectivity, and synaptic signaling. This work paves the way for future studies on the functions of Zmiz1 and highlights the importance of combining analysis of mouse models and human data.

Characterization and manipulation of Corticothalamic neurons in associative cortices using Syt6-Cre transgenic mice.

Corticothalamic interactions between associative cortices and higher order thalamic nuclei are involved in high-cognitive functions such as decision-making and working memory. Corticothalamic neurons (CTn) in the prefrontal cortex and other associative areas have been much less studied than their counterparts in the primary sensory areas. The availability of characterized transgenic tools to study CTn in associative areas will facilitate their study and contribute to overcome the scarcity of data about their properties, network dynamics, and contribution to cognitive functions. Here, we characterized the Syt6-Cre (KI148Gsat/Mmud) transgenic mouse line, by tracking expression of a Cre-mediated reporter. In this line, Cre-reporter is strongly expressed in the prefrontal, motor, cingulate, and retrosplenial cortices, as well as in other brain areas including the cerebellum and the olfactory tubercle. Cortical expression starts embryonically and reaches the adult expression pattern by postnatal day 15. In the cortex, Cre-reporter is expressed by layer 6-CTn and by layer 5-CTn to a lesser extent. We quantified Syt6-Cre+ CTn axon varicosities to estimate the distribution and density of putative corticothalamic driver and modulator inputs to thalamic nuclei in the medial, midline, intralaminar, anterior, and motor groups. Also, we characterized the effect of optogenetic stimulation of Syt6-Cre+ neurons in the activity of the prefrontal cortex. CTn stimulation in the prefrontal cortex induces an oscillatory activity in the local field potential that resembles the cortical downstates typically observed during slow-wave sleep or quiet wake.