Neurodevelopmental disorder-associated ZBTB20 gene variants affect dendritic and synaptic structure

Investigating the Role of the Zinc Finger Protein ZC2HC1C on Autism Spectrum Disorder Susceptibility

Background and Objectives: Zinc finger proteins are important transcription factors that regulate gene expression and play a critical role in neurodevelopment including autism spectrum disorders (ASDs). They are involved in a variety of cellular processes, including cell proliferation, differentiation, and apoptosis. Materials and Methods: Whole-exome sequencing (WES) analysis on a patient diagnosed with ASD. Results: Sequencing identified a homozygous insertion causing a stop codon, resulting in the removal of several functional domains including the zinc finger C2HC/C3H type of the ZC2HC1C protein. To date, no MIM entry has been assigned to the detected gene. In silico predictions described the variant as likely pathogenic, indicating an autosomal recessive inheritance pattern. In this study, we hypothesize that this homozygous mutation disrupts protein function and may represent a susceptibility gene for autism. The parents and the patient's sister were healthy and carry the variant in the heterozygous condition. This gene is expressed in brain tissues showing high expression in both the choroid plexus (ChP) and midbrain, whose dysfunctions, as reported, may lead to ASD. Moreover, predictive pathway analyses indicated the probable involvement of this gene in primary cilia development. This process has been frequently linked to neurodevelopmental impairments, such as autism, as documented in previous studies. Conclusions: Further analyses are needed via in vitro functional assays or by ZC2HC1C gene knockout to validate its functional role.

The HDL-Mimetic Peptide 4F Mitigates Vascular and Cortical Amyloid Pathology and Associated Neuroinflammation in a Transgenic Mouse Model of Cerebral Amyloid Angiopathy and Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide. Despite recent advances, more effective and safer treatment options for AD are needed. Cerebral amyloid angiopathy (CAA) is one of the key pathological hallmarks of AD characterized by amyloid-β (Aβ) deposition in the cerebral vasculature and is associated with intracerebral hemorrhage, cerebrovascular dysfunction, and cognitive impairment. CAA is also considered to underlie the main adverse effect of recently FDA-approved anti-Aβ immunotherapies, namely the amyloid-related imaging abnormalities (ARIA). Substantial evidence has shown that elevated levels of high-density lipoprotein (HDL) and its main protein component, APOA-I, are associated with reduced CAA and superior cognitive function. 4F is an APOA-I/HDL-mimetic peptide and its clinical safety and activity have been demonstrated in human trials for cardiovascular diseases. The present study investigates whether treatment with 4F modulates CAA and associated cognitive deficits and neuropathologies in the well-established Tg-SwDI mouse model of CAA/AD. Age/sex-matched Tg-SwDI mice received daily treatments of 4F or vehicle (PBS), respectively, by intraperitoneal injections for 12 weeks. The results showed that 4F treatment reduced overall Aβ plaque deposition and CAA, and attenuated CAA-associated microgliosis, without significantly affecting total levels of Aβ, astrocytosis, and behavioral function. Unbiased transcriptomic analysis revealed a heightened inflammatory state in the brain of SwDI mice and that 4F treatment reversed the overactivation of vascular cells, in particular vascular smooth muscle cells, relieving cerebrovascular inflammation in CAA/AD mice. Our study provides experimental evidence for the therapeutic potential of 4F to mitigate CAA and associated pathologies in AD.

Role of FPR2 antagonism in alleviating social isolation-induced depression and protecting blood-brain barrier integrity

Social isolation (SI) is a prevalent issue in modern society, particularly exacerbated during the COVID-19 pandemic, and it is a significant contributor to depressive disorders. Inflammation-related markers are upregulated in patients with major depressive disorder (MDD) unresponsive to first-line selective serotonin reuptake inhibitor (SSRI) antidepressants. This study investigates the role of formyl peptide receptor 2 (FPR2), a G-protein coupled receptor expressed in central and peripheral immune cells, in SI-induced depression. We developed a mouse model of SI by housing mice individually for three weeks. SI mice exhibited increased capillary-associated microglia (CAMs) with upregulated FPR2 expression in the prefrontal cortex (PFC) and hippocampus compared to group-housed controls. Notably, subcutaneous administration of the FPR2 antagonist WRW4 alleviated depressive and anxiety-like behaviors in SI mice, reducing microglial activation and neuronal damage. WRW4 treatment decreased CAM numbers and their FPR2 expression. RNA sequencing revealed that SI primarily induced changes in genes associated with blood-brain barrier (BBB) function, followed by alterations in genes related to hormone activity, immune activation, and neuronal function. Transcriptomic changes in brain endothelial cells from SI mice resembled those observed in animal models of several neurological disorders and in MDD patients. WRW4 treatment partially reversed these transcriptomic alterations and restored compromised BBB integrity. Additionally, intracerebroventricular (ICV) injection of WRW4 also alleviated depressive and anxiety-like behaviors in SI mice. Finally, our analysis of public transcriptome databases indicates FPR2 upregulation in the orbital ventral PFC of MDD patients and peripheral blood mononuclear cells of those in severe depressive episodes. These findings suggest that the pharmacological targeting of FPR2 may rescue SI-induced pathology in mice by protecting BBB integrity.

Sex- and Substance-Specific Associations of Circadian-Related Genes with Addiction in the UK Biobank Cohort Implicate Neuroplasticity Pathways

BACKGROUND/OBJECTIVES

The circadian clockwork is implicated in the etiology of addiction, with circadian rhythm disruptions bidirectionally linked to substance abuse, but the molecular mechanisms that underlie this connection are not well known.

METHODS

Here, we use machine learning to reveal sex- and substance-specific associations with addiction in variants from 51 circadian-related genes (156,702 SNPs) in 98,800 participants from a UK Biobank cohort. We further analyze SNP associations in a subset of the cohort for substance-specific addictions (alcohol, illicit drugs (narcotics), and prescription drugs (opioids)).

RESULTS

We find robust (OR > 10) and novel sex-specific and substance-specific associations with variants in synaptic transcription factors (ZBTB20, CHRNB3) and hormone receptors (RORA), particularly in individuals addicted to narcotics and opioids. Circadian-related gene variants associated with male and female addiction were non-overlapping; variants in males primarily involve dopaminergic pathways, while variants in females factor in metabolic and inflammation pathways, with a novel gene association of female addiction with DELEC1, a gene of unknown function.

CONCLUSIONS

Our findings underscore the complexity of genetic pathways associated with addiction, involving core clock genes and circadian-regulated pathways, and reveal novel circadian-related gene associations that will aid the development of targeted, sex-specific therapeutic interventions for substance abuse.

Resolution of severe neurobehavioral difficulties in an individual with Primrose syndrome with sertraline

Primrose syndrome (PS) is a rare genetic disease characterized by developmental delay, intellectual disability, sensorineural hearing loss, and dysmorphic features. PS is caused by de novo pathogenic variants in the ZBTB20 gene, which encodes a transcription factor modulating neurogenesis. We describe resolution with sertraline of neurobehavioral difficulties in a 17-year-old Hispanic male with PS with de novo heterozygous c.1916G > A (p.C639Y) variant of ZBTB20. Neurobehavioral difficulties included aggression towards self and others, irritability, tearfulness, and mood liability that did not respond to behavioral interventions or aripiprazole. Treatment with sertraline, a medication indicated for psychiatric disorders including anxiety and depression, led to the resolution of neurobehavioral difficulties after 2 weeks of initiation of medication. The treatment course suggests that selective serotonin reuptake inhibitors, such as sertraline, may be a useful tool for neurobehavioral difficulties in PS over antipsychotics that are accompanied by complex side effect profiles, and suggest that anxiety is the primary cause of the neurobehavioral difficulties in this patient.

The Evolution of Ultraconserved Elements in Vertebrates

Ultraconserved elements were discovered two decades ago, arbitrarily defined as sequences that are identical over a length ≥ 200 bp in the human, mouse, and rat genomes. The definition was subsequently extended to sequences ≥ 100 bp identical in at least three of five mammalian genomes (including dog and cow), and shown to have undergone rapid expansion from ancestors in fish and strong negative selection in birds and mammals. Since then, many more genomes have become available, allowing better definition and more thorough examination of ultraconserved element distribution and evolutionary history. We developed a fast and flexible analytical pipeline for identifying ultraconserved elements in multiple genomes, dedUCE, which allows manipulation of minimum length, sequence identity, and number of species with a detectable ultraconserved element according to specified parameters. We suggest an updated definition of ultraconserved elements as sequences ≥ 100 bp and ≥97% sequence identity in ≥50% of placental mammal orders (12,813 ultraconserved elements). By mapping ultraconserved elements to ∼200 species, we find that placental ultraconserved elements appeared early in vertebrate evolution, well before land colonization, suggesting that the evolutionary pressures driving ultraconserved element selection were present in aquatic environments in the Cambrian-Devonian periods. Most (>90%) ultraconserved elements likely appeared after the divergence of gnathostomes from jawless predecessors, were largely established in sequence identity by early Sarcopterygii evolution-before the divergence of lobe-finned fishes from tetrapods-and became near fixed in the amniotes. Ultraconserved elements are mainly located in the introns of protein-coding and noncoding genes involved in neurological and skeletomuscular development, enriched in regulatory elements, and dynamically expressed throughout embryonic development.

Molecular Organization and Regulation of the Mammalian Synapse by the Post-Translational Modification SUMOylation

Neurotransmission occurs within highly specialized compartments forming the active synapse where the complex organization and dynamics of the interactions are tightly orchestrated both in time and space. Post-translational modifications (PTMs) are central to these spatiotemporal regulations to ensure an efficient synaptic transmission. SUMOylation is a dynamic PTM that modulates the interactions between proteins and consequently regulates the conformation, the distribution and the trafficking of the SUMO-target proteins. SUMOylation plays a crucial role in synapse formation and stabilization, as well as in the regulation of synaptic transmission and plasticity. In this review, we summarize the molecular consequences of this protein modification in the structural organization and function of the mammalian synapse. We also outline novel activity-dependent regulation and consequences of the SUMO process and explore how this protein modification can functionally participate in the compartmentalization of both pre- and post-synaptic sites.

De novo missense variants in ZBTB47 are associated with developmental delays, hypotonia, seizures, gait abnormalities, and variable movement abnormalities

The collection of known genetic etiologies of neurodevelopmental disorders continues to increase, including several syndromes associated with defects in zinc finger protein transcription factors (ZNFs) that vary in clinical severity from mild learning disabilities and developmental delay to refractory seizures and severe autism spectrum disorder. Here we describe a new neurodevelopmental disorder associated with variants in ZBTB47 (also known as ZNF651), which encodes zinc finger and BTB domain-containing protein 47. Exome sequencing (ES) was performed for five unrelated patients with neurodevelopmental disorders. All five patients are heterozygous for a de novo missense variant in ZBTB47, with p.(Glu680Gly) (c.2039A>G) detected in one patient and p.(Glu477Lys) (c.1429G>A) identified in the other four patients. Both variants impact conserved amino acid residues. Bioinformatic analysis of each variant is consistent with pathogenicity. We present five unrelated patients with de novo missense variants in ZBTB47 and a phenotype characterized by developmental delay with intellectual disability, seizures, hypotonia, gait abnormalities, and variable movement abnormalities. We propose that these variants in ZBTB47 are the basis of a new neurodevelopmental disorder.

Differential Expression of the β3 Subunit of Voltage-Gated Ca2+ Channel in Mesial Temporal Lobe Epilepsy

The purpose of this study was to identify and validate new putative lead drug targets in drug-resistant mesial temporal lobe epilepsy (mTLE) starting from differentially expressed genes (DEGs) previously identified in mTLE in humans by transcriptome analysis. We identified consensus DEGs among two independent mTLE transcriptome datasets and assigned them status as "lead target" if they (1) were involved in neuronal excitability, (2) were new in mTLE, and (3) were druggable. For this, we created a consensus DEG network in STRING and annotated it with information from the DISEASES database and the Target Central Resource Database (TCRD). Next, we attempted to validate lead targets using qPCR, immunohistochemistry, and Western blot on hippocampal and temporal lobe neocortical tissue from mTLE patients and non-epilepsy controls, respectively. Here we created a robust, unbiased list of 113 consensus DEGs starting from two lists of 3040 and 5523 mTLE significant DEGs, respectively, and identified five lead targets. Next, we showed that CACNB3, a voltage-gated Ca2+ channel subunit, was significantly regulated in mTLE at both mRNA and protein level. Considering the key role of Ca2+ currents in regulating neuronal excitability, this suggested a role for CACNB3 in seizure generation. This is the first time changes in CACNB3 expression have been associated with drug-resistant epilepsy in humans, and since efficient therapeutic strategies for the treatment of drug-resistant mTLE are lacking, our finding might represent a step toward designing such new treatment strategies.

Transcription Factor Zbtb20 as a Regulator of Malignancy and Its Practical Applications

Zbtb20 (zinc finger and BTB domain-containing protein 20) is a transcription factor with a zinc finger DNA binding domain and a BTB domain responsible for protein-protein interaction. Recently, this TF has received attention because new data showed its pivotal involvement in normal neural development and its regulatory effects on proliferation and differentiation in different tissues. Zbtb20 was shown to increase proliferation and migration and confer resistance to apoptosis in the contexts of many malignant tumors like hepatocellular carcinoma, non-small-cell lung carcinoma, gastric adenocarcinoma, glioblastoma multiforme, breast cancer, and acute myeloid leukemia. The involvement of Zbtb20 in tumor biology is best studied in hepatocellular carcinoma, where it is a promising candidate as an immunohistochemical tumor marker or may be used in patient screening. Here we review the current data connecting Zbtb20 with malignant tumors.

Age-Associated Changes in Endothelial Transcriptome and Epigenetic Landscapes Correlate With Elevated Risk of Cerebral Microbleeds

Background Stroke is a leading global cause of human death and disability, with advanced aging associated with elevated incidences of stroke. Despite high mortality and morbidity of stroke, the mechanisms leading to blood-brain barrier dysfunction and development of stroke with age are poorly understood. In the vasculature of brain, endothelial cells (ECs) constitute the core component of the blood-brain barrier and provide a physical barrier composed of tight junctions, adherens junctions, and basement membrane. Methods and Results We show, in mice, the incidents of intracerebral bleeding increases with age. After isolating an enriched population of cerebral ECs from murine brains at 2, 6, 12, 18, and 24 months, we studied age-associated changes in gene expression. The study reveals age-dependent dysregulation of 1388 genes, including many involved in the maintenance of the blood-brain barrier and vascular integrity. We also investigated age-dependent changes on the levels of CpG methylation and accessible chromatin in cerebral ECs. Our study reveals correlations between age-dependent changes in chromatin structure and gene expression, whereas the dynamics of DNA methylation changes are different. Conclusions We find significant age-dependent downregulation of the Aplnr gene along with age-dependent reduction in chromatin accessibility of promoter region of the Aplnr gene in cerebral ECs. Aplnr is associated with positive regulation of vasodilation and is implicated in vascular health. Altogether, our data suggest a potential role of the apelinergic axis involving the ligand apelin and its receptor to be critical in maintenance of the blood-brain barrier and vascular integrity.

Droplet-based transcriptome profiling of individual synapses

Synapses are crucial structures that mediate signal transmission between neurons in complex neural circuits and display considerable morphological and electrophysiological heterogeneity. So far we still lack a high-throughput method to profile the molecular heterogeneity among individual synapses. In the present study, we develop a droplet-based single-cell (sc) total-RNA-sequencing platform, called Multiple-Annealing-and-Tailing-based Quantitative scRNA-seq in Droplets, for transcriptome profiling of individual neurites, primarily composed of synaptosomes. In the synaptosome transcriptome, or 'synaptome', profiling of both mouse and human brain samples, we detect subclusters among synaptosomes that are associated with neuronal subtypes and characterize the landscape of transcript splicing that occurs within synapses. We extend synaptome profiling to synaptopathy in an Alzheimer's disease (AD) mouse model and discover AD-associated synaptic gene expression changes that cannot be detected by single-nucleus transcriptome profiling. Overall, our results show that this platform provides a high-throughput, single-synaptosome transcriptome profiling tool that will facilitate future discoveries in neuroscience.

Postnatal age-differential ASD-like transcriptomic, synaptic, and behavioral deficits in Myt1l-mutant mice

Myelin transcription factor 1 like (Myt1l), a zinc-finger transcription factor, promotes neuronal differentiation and is implicated in autism spectrum disorder (ASD) and intellectual disability. However, it remains unclear whether Myt1l promotes neuronal differentiation in vivo and its deficiency in mice leads to disease-related phenotypes. Here, we report that Myt1l-heterozygous mutant (Myt1l-HT) mice display postnatal age-differential ASD-related phenotypes: newborn Myt1l-HT mice, with strong Myt1l expression, show ASD-like transcriptomic changes involving decreased synaptic gene expression and prefrontal excitatory synaptic transmission and altered righting reflex. Juvenile Myt1l-HT mice, with markedly decreased Myt1l expression, display reverse ASD-like transcriptomes, increased prefrontal excitatory transmission, and largely normal behaviors. Adult Myt1l-HT mice show ASD-like transcriptomes involving astrocytic and microglial gene upregulation, increased prefrontal inhibitory transmission, and behavioral deficits. Therefore, Myt1l haploinsufficiency leads to ASD-related phenotypes in newborn mice, which are temporarily normalized in juveniles but re-appear in adults, pointing to continuing phenotypic changes long after a marked decrease of Myt1l expression in juveniles.

Differential Methylation Profile in Fragile X Syndrome-Prone Offspring Mice after in Utero Exposure to Lactobacillus Reuteri

Environmental factors such as diet, gut microbiota, and infections have proven to have a significant role in epigenetic modifications. It is known that epigenetic modifications may cause behavioral and neuronal changes observed in neurodevelopmental disabilities, including fragile X syndrome (FXS) and autism (ASD). Probiotics are live microorganisms that provide health benefits when consumed, and in some cases are shown to decrease the chance of developing neurological disorders. Here, we examined the epigenetic outcomes in offspring mice after feeding of a probiotic organism, Lactobacillus reuteri (L. reuteri), to pregnant mother animals. In this study, we tested a cohort of Western diet-fed descendant mice exhibiting a high frequency of behavioral features and lower FMRP protein expression similar to what is observed in FXS in humans (described in a companion manuscript in this same GENES special topic issue). By investigating 17,735 CpG sites spanning the whole mouse genome, we characterized the epigenetic profile in two cohorts of mice descended from mothers treated and non-treated with L. reuteri to determine the effect of prenatal probiotic exposure on the prevention of FXS-like symptoms. We found several genes involved in different neurological pathways being differentially methylated (p ≤ 0.05) between the cohorts. Among the key functions, synaptogenesis, neurogenesis, synaptic modulation, synaptic transmission, reelin signaling pathway, promotion of specification and maturation of neurons, and long-term potentiation were observed. The results of this study are relevant as they could lead to a better understanding of the pathways involved in these disorders, to novel therapeutics approaches, and to the identification of potential biomarkers for early detection of these conditions.

An epigenetic circuit controls neurogenic programs during neocortex development

The production and expansion of intermediate progenitors (IPs) are essential for neocortical neurogenesis during development and over evolution. Here, we have characterized an epigenetic circuit that precisely controls neurogenic programs, particularly properties of IPs, during neocortical development. The circuit comprises a long non-coding RNA (LncBAR) and the BAF (SWI/SNF) chromatin-remodeling complex, which transcriptionally maintains the expression of Zbtb20. LncBAR knockout neocortex contains more deep-layer but fewer upper-layer projection neurons. Intriguingly, loss of LncBAR promotes IP production, but paradoxically prolongs the duration of the cell cycle of IPs during mid-later neocortical neurogenesis. Moreover, in LncBAR knockout mice, depletion of the neural progenitor pool at embryonic stage results in fewer adult neural progenitor cells in the subventricular zone of lateral ventricles, leading to a failure in adult neurogenesis to replenish the olfactory bulb. LncBAR binds to BRG1, the core enzymatic component of the BAF chromatin-remodeling complex. LncBAR depletion enhances association of BRG1 with the genomic locus of, and suppresses the expression of, Zbtb20, a transcription factor gene known to regulate both embryonic and adult neurogenesis. ZBTB20 overexpression in LncBAR-knockout neural precursors reverses compromised cell cycle progressions of IPs.

ZBTB20 is crucial for the specification of a subset of callosal projection neurons and astrocytes in the mammalian neocortex

Neocortical progenitor cells generate subtypes of excitatory projection neurons in sequential order followed by the generation of astrocytes. The transcription factor zinc finger and BTB domain-containing protein 20 (ZBTB20) has been implicated in regulation of cell specification during neocortical development. Here, we show that ZBTB20 instructs the generation of a subset of callosal projections neurons in cortical layers II/III in mouse. Conditional deletion of Zbtb20 in cortical progenitors, and to a lesser degree in differentiating neurons, leads to an increase in the number of layer IV neurons at the expense of layer II/III neurons. Astrogliogenesis is also affected in the mutants with an increase in the number of a specific subset of astrocytes expressing GFAP. Astrogliogenesis is more severely disrupted by a ZBTB20 protein containing dominant mutations linked to Primrose syndrome, suggesting that ZBTB20 acts in concert with other ZBTB proteins that were also affected by the dominant-negative protein to instruct astrogliogenesis. Overall, our data suggest that ZBTB20 acts both in progenitors and in postmitotic cells to regulate cell fate specification in the mammalian neocortex.

Next-generation gene panel testing in adolescents and adults in a medical neuropsychiatric genetics clinic

Intellectual disability (ID) encompasses a clinically and genetically heterogeneous group of neurodevelopmental disorders that may present with psychiatric illness in up to 40% of cases. Despite the evidence for clinical utility of genetic panels in pediatrics, there are no published studies in adolescents/adults with ID or autism spectrum disorder (ASD). This study was approved by our institutional research ethics board. We retrospectively reviewed the medical charts of all patients evaluated between January 2017 and December 2019 in our adult neuropsychiatric genetics clinic at the McGill University Health Centre (MUHC), who had undergone a comprehensive ID/ASD gene panel. Thirty-four patients aged > 16 years, affected by ID/ASD and/or other neuropsychiatric/behavioral disorders, were identified. Pathogenic or likely pathogenic variants were identified in one-third of our cohort (32%): 8 single-nucleotide variants in 8 genes (CASK, SHANK3, IQSEC2, CHD2, ZBTB20, TREX1, SON, and TUBB2A) and 3 copy number variants (17p13.3, 16p13.12p13.11, and 9p24.3p24.1). The presence of psychiatric/behavioral disorders, regardless of the co-occurrence of ID, and, at a borderline level, the presence of ID alone were associated with positive genetic findings (p = 0.024 and p = 0.054, respectively). Moreover, seizures were associated with positive genetic results (p = 0.024). One-third of individuals presenting with psychiatric illness who met our red flags for Mendelian diseases have pathogenic or likely pathogenic variants which can be identified using a comprehensive ID/ASD gene panel (~ 2500 genes) performed on an exome backbone.

The Potential Role of miRNAs as Predictive Biomarkers in Neurodevelopmental Disorders

Neurodevelopmental disorders are defined as a set of abnormal brain developmental conditions marked by the early childhood onset of cognitive, behavioral, and functional deficits leading to memory and learning problems, emotional instability, and impulsivity. Autism spectrum disorder, attention-deficit/hyperactivity disorder, Tourette syndrome, fragile X syndrome, and Down's syndrome are a few known examples of neurodevelopmental disorders. Although they are relatively common in both developed and developing countries, very little is currently known about their underlying molecular mechanisms. Both genetic and environmental factors are known to increase the risk of neurodevelopmental disorders. Current diagnostic and screening tests for neurodevelopmental disorders are not reliable; hence, individuals with neurodevelopmental disorders are often diagnosed in the later stages. This negatively affects their prognosis and quality of life, prompting the need for a better diagnostic biomarker. Recent studies on microRNAs and their altered regulation in diseases have shed some light on the possible role they could play in the development of the central nervous system. This review attempts to elucidate our current understanding of the role that microRNAs play in neurodevelopmental disorders with the hope of utilizing them as potential biomarkers in the future.

SUMOylation controls the neurodevelopmental function of the transcription factor Zbtb20

SUMOylation is a dynamic post-translational protein modification that primarily takes place in cell nuclei, where it plays a key role in multiple DNA-related processes. In neurons, the SUMOylation-dependent control of a subset of neuronal transcription factors is known to regulate various aspects of nerve cell differentiation, development, and function. In an unbiased screen for endogenous SUMOylation targets in the developing mouse brain, based on a His₆ -HA-SUMO1 knock-in mouse line, we previously identified the transcription factor Zinc finger and BTB domain-containing 20 (Zbtb20) as a new SUMO1-conjugate. We show here that the three key SUMO paralogues SUMO1, SUMO2, and SUMO3 can all be conjugated to Zbtb20 in vitro in HEK293FT cells, and we confirm the SUMOylation of Zbtb20 in vivo in mouse brain. Using primary hippocampal neurons from wild-type and Zbtb20 knock-out (KO) mice as a model system, we then demonstrate that the expression of Zbtb20 is required for proper nerve cell development and neurite growth and branching. Furthermore, we show that the SUMOylation of Zbtb20 is essential for its function in this context, and provide evidence indicating that SUMOylation affects the Zbtb20-dependent transcriptional profile of neurons. Our data highlight the role of SUMOylation in the regulation of neuronal transcription factors that determine nerve cell development, and they demonstrate that key functions of the transcription factor Zbtb20 in neuronal development and neurite growth are under obligatory SUMOylation control.

C2H2-Type Zinc Finger Proteins in Brain Development, Neurodevelopmental, and Other Neuropsychiatric Disorders: Systematic Literature-Based Analysis

Neurodevelopmental disorders (NDDs) are multifaceted pathologic conditions manifested with intellectual disability, autistic features, psychiatric problems, motor dysfunction, and/or genetic/chromosomal abnormalities. They are associated with skewed neurogenesis and brain development, in part through dysfunction of the neural stem cells (NSCs) where abnormal transcriptional regulation on key genes play significant roles. Recent accumulated evidence highlights C₂H₂-type zinc finger proteins (C₂H₂-ZNFs), the largest transcription factor family in humans, as important targets for the pathologic processes associated with NDDs. In this review, we identified their significant accumulation (74 C₂H₂-ZNFs: ~10% of all human member proteins) in brain physiology and pathology. Specifically, we discuss their physiologic contribution to brain development, particularly focusing on their actions in NSCs. We then explain their pathologic implications in various forms of NDDs, such as morphological brain abnormalities, intellectual disabilities, and psychiatric disorders. We found an important tendency that poly-ZNFs and KRAB-ZNFs tend to be involved in the diseases that compromise gross brain structure and human-specific higher-order functions, respectively. This may be consistent with their characteristic appearance in the course of species evolution and corresponding contribution to these brain activities.