Compound Heterozygote of Point Mutation and Chromosomal Microdeletion Involving OTUD6B Coinciding with ZMIZ1 Variant in Syndromic Intellectual Disability

Endothelial Zmiz1 modulates physiological and pathophysiological angiogenesis during retinal development

Angiogenesis is a highly coordinated process involving the control of various endothelial cell behaviors. Mechanisms for transcription factor involvement in the regulation of endothelial cell dynamics and angiogenesis have become better understood, however much remains unknown, especially the role of non-DNA binding transcriptional cofactors. Here, we show that Zmiz1, a transcription cofactor, is enriched in the endothelium and critical for embryonic vascular development, postnatal retinal angiogenesis, and pathological angiogenesis in oxygen induced retinopathy (OIR). In mice, endothelial cell-specific deletion of Zmiz1 during embryogenesis led to lethality due to abnormal angiogenesis and vascular defects. Inducible endothelial cell-specific ablation of Zmiz1 postnatally resulted in impaired retinal vascular outgrowth, decreased vascular density, and increased vessel regression. In addition, angiogenic sprouting in the superficial and deep layers of the retina was markedly reduced. Correspondingly, vascular sprouting in fibrin bead assays was significantly reduced in the absence of Zmiz1, while further in vitro and in vivo evidence also suggested deficits in EC migration. In agreement with the defective sprouting angiogenesis phenotype, gene expression analysis of isolated retinal endothelial cells revealed downregulation of tip-cell enriched genes upon inactivation of Zmiz1. Lastly, our study suggested that endothelial Zmiz1 is critical for intraretinal revascularization following hypoxia exposure in the OIR model. Taken together, these findings begin to define the previously unspecified role of endothelial Zmiz1 in physiological and pathological angiogenesis.

Biallelic OTUD6B variants associated with a Kabuki syndrome-like disorder in three siblings: A clinical report and literature review

Biallelic variants in the OTUD6B gene have been reported in the literature in association with an intellectual developmental disorder featuring dysmorphic facies, seizures, and distal limb abnormalities. Physical differences described for affected individuals suggest that the disorder may be clinically recognizable, but previous publications have reported an initial clinical suspicion for Kabuki syndrome (KS) in some affected individuals. Here, we report on three siblings with biallelic variants in OTUD6B co-segregating with neurodevelopmental delay, shared physical differences, and other clinical findings similar to those of previously reported individuals. However, clinical manifestations such as long palpebral fissures, prominent and cupped ears, developmental delay, growth deficiency, persistent fetal fingertip pads, vertebral anomaly, and seizures in the proband were initially suggestive of KS. In addition, previously unreported clinical manifestations such as delayed eruption of primary dentition, soft doughy skin with reduced sweating, and mirror movements present in our patients suggest an expansion of the phenotype, and we perform a literature review to update on current information related to OTUD6B and human gene-disease association.

Zmiz1 is a novel regulator of lymphatic endothelial cell gene expression and function

Zinc Finger MIZ-Type Containing 1 (Zmiz1), also known as ZIMP10 or RAI17, is a transcription cofactor and member of the Protein Inhibitor of Activated STAT (PIAS) family of proteins. Zmiz1 is critical for a variety of biological processes including vascular development. However, its role in the lymphatic vasculature is unknown. In this study, we utilized human dermal lymphatic endothelial cells (HDLECs) and an inducible, lymphatic endothelial cell (LEC)-specific Zmiz1 knockout mouse model to investigate the role of Zmiz1 in LECs. Transcriptional profiling of ZMIZ1-deficient HDLECs revealed downregulation of genes crucial for lymphatic vessel development. Additionally, our findings demonstrated that loss of Zmiz1 results in reduced expression of proliferation and migration genes in HDLECs and reduced proliferation and migration in vitro. We also presented evidence that Zmiz1 regulates Prox1 expression in vitro and in vivo by modulating chromatin accessibility at Prox1 regulatory regions. Furthermore, we observed that loss of Zmiz1 in mesenteric lymphatic vessels significantly reduced valve density. Collectively, our results highlight a novel role of Zmiz1 in LECs and as a transcriptional regulator of Prox1, shedding light on a previously unknown regulatory factor in lymphatic vascular biology.

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.

Proteasome-Associated Syndromes: Updates on Genetics, Clinical Manifestations, Pathogenesis, and Treatment

The ubiquitin-proteasome system (UPS) has a critical role in post-translational protein modification that is essential for the maintenance of all cellular functions, including immune responses. The proteasome complex is ubiquitously expressed and is responsible for degradation of short-lived structurally abnormal, misfolded and not-needed proteins that are targeted for degradation via ubiquitin conjugation. Over the last 14 years, an increasing number of human diseases have been linked to pathogenic variants in proteasome subunits and UPS regulators. Defects of the proteasome complex or its chaperons - which have a regulatory role in the assembly of the proteasome - disrupt protein clearance and cellular homeostasis, leading to immune dysregulation, severe inflammation, and neurodevelopmental disorders in humans. Proteasome-associated diseases have complex inheritance, including monogenic, digenic and oligogenic disorders and can be dominantly or recessively inherited. In this review, we summarize the current known genetic causes of proteasomal disease, and discuss the molecular pathogenesis of these conditions based on the function and cellular expression of mutated proteins in the proteasome complex.

Clinical report and genetic analysis of a novel variant in ZMIZ1 causing neurodevelopmental disorder with dysmorphic factors and distal skeletal anomalies in a Chinese family

BACKGROUND

Neurodevelopmental disorder with dysmorphic factors and distal skeletal anomalies (NEDDFSA) is a rare and phenotypically variable disorder. The zinc finger MIZ-type containing 1 gene (ZMIZ1) is a causative gene of NEDDFSA that encodes a protein inhibitor of the activated STAT-like family transcriptional regulator. Given the rarity of reported NEDDFSA cases, new phenotypes and genotypes of this disorder are still being discovered.

OBJECTIVE

This study describes the phenotype characteristics of a Chinese NEDDFSA family caused by a novel ZMIZ1 variant.

METHODS

We reviewed the clinical phenotype of a Chinese patient with NEDDFSA and performed whole-exome sequencing (WES) of the patient's family. We simulated the potential biological harmfulness of the mutant protein. Plasmids were constructed and used for western blot and immunofluorescence assays to analyze protein expression levels.

RESULTS

The patient was a 6-month-old male infant who exhibited dysmorphic facial features, neurodevelopmental abnormalities, congenital heart disease, and previously unreported genitourinary system anomalies. WES revealed a non-frameshift deletion variant in ZMIZ1 (NM_020338.4: c.858_875del, p.Val288_Ala293del), resulting in a structural alteration in the protein's alanine-rich domain. Western blot and immunofluorescence assays indicated a significant decrease in the expression level of the mutant ZMIZ1 protein compared to the wild-type protein.

CONCLUSION

The clinical manifestations of this patient may be associated with the ZMIZ1 variant, and the structural alteration in the alanine-rich domain of the ZMIZ1 protein may contribute to a more complex disease phenotype. These results expand the genotype-phenotype correlation of ZMIZ1.

Zmiz1 is a novel regulator of lymphatic endothelial cell gene expression and function

Zinc Finger MIZ-Type Containing 1 (Zmiz1), also known as ZIMP10 or RAI17, is a transcription cofactor and member of the Protein Inhibitor of Activated STAT (PIAS) family of proteins. Zmiz1 is critical for a variety of biological processes including vascular development. However, its role in the lymphatic vasculature is unknown. In this study, we utilized human dermal lymphatic endothelial cells (HDLECs) and an inducible, lymphatic endothelial cell (LEC)-specific Zmiz1 knockout mouse model to investigate the role of Zmiz1 in LECs. Transcriptional profiling of Zmiz1-deficient HDLECs revealed downregulation of genes crucial for lymphatic vessel development. Additionally, our findings demonstrated that loss of Zmiz1 results in reduced expression of proliferation and migration genes in HDLECs and reduced proliferation and migration in vitro. We also presented evidence that Zmiz1 regulates Prox1 expression in vitro and in vivo by modulating chromatin accessibility at Prox1 regulatory regions. Furthermore, we observed that loss of Zmiz1 in mesenteric lymphatic vessels significantly reduced valve density. Collectively, our results highlight a novel role of Zmiz1 in LECs and as a transcriptional regulator of Prox1, shedding light on a previously unknown regulatory factor in lymphatic vascular biology.

Novel biallelic variants affecting the OTU domain of the gene OTUD6B associate with severe intellectual disability syndrome and molecular dynamics simulations

Intellectual developmental disorder with dysmorphic facies, seizures, and distal limb anomalies (IDDFSDA) is an autosomal recessive multisystem disorder caused by compound heterozygous or homozygous variants in the gene OTUD6B. Herein, we describe novel pathogenic compound heterozygous variants in OTUD6B identified via whole-exome sequencing in an index case exhibited the severe IDDFSDA phenotype. The potential pathogenicity of the novel frameshift and missense variants in the index case was investigated using in silico tools. The truncating frameshift variant in one allele was predicted to undergo degradation via nonsense-mediated decay of the mRNA molecule. To predict the severity of the damage to the protein caused by the missense variant in the other allele and its effects on phenotypic severity was further investigated together with a previously reported first homozygous missense variant in the same domain in another patient with a less severe IDDFSDA phenotype using structural modeling and molecular dynamics (MD) simulations for the first time. Based on these analyzes, it is anticipated that Tyr216Cys in the earlier reported case with less severe IDDFSDA will lead to localized destabilization, whereas Ile274Arg in the presented index case with the severe IDDFSDA phenotype will lead to significant distortion in the overall fold of OTUD6B. Our findings suggest that compound LOF and ultrarare missense variants may be contribute to the underlying variability expressivity associated with this disorder. In conclusion, our findings support that the clinical severity could be related with the predicted functional severity of the variations in OTUD6B. However, additional functional studies are required.

A de Novo ZMIZ1 Pathogenic Variant for Neurodevelopmental Disorder With Dysmorphic Facies and Distal Skeletal Anomalies

Background: Neurodevelopmental disorder with dysmorphic facies and distal skeletal anomalies (NEDDFSA) is a rare syndromic disorder characterized by global neurodevelopmental delay, early-onset hypotonia, poor overall growth, poor speech/language ability, and additional common phenotypes such as eye anomalies, joint hypermobility, and skeletal anomalies of the hands and feet. NEDDFSA is caused by heterozygous pathogenic variants in the ZMIZ1 gene on chromosome 10q22.3 with autosomal dominant (AD) mode of inheritance. All the 32 reported cases with variants in ZMIZ1 gene had a genetic background in Caucasian, Hispanic, North African, and Southeastern Asian. Until now, there are no reports of Chinese patients with ZMIZ1 pathogenic variants.

Methods: A 5-year-old girl was found to have the characteristic phenotypes of NEDDFSA. Array-Comparative Genomic Hybridization (array-CGH) and whole exome sequencing (WES) were applied for the trio of this female patient. Sanger sequencing was used to verify the selected variants. A comprehensive molecular analysis was carried out by protein structure prediction, evolutionary conservation, motif scanning, tissue-specific expression, and protein interaction network to elucidate pathogenicity of the identified ZMIZ1 variants.

Results: The karyotype was 46, XX with no micro-chromosomal abnormalities identified by array-CGH. There were 20 variants detected in the female patient by WES. A de novo heterozygous missense variant (c.2330G > A, p.Gly777Glu, G777E) was identified in the exon 20 of ZMIZ1. No variants of ZMIZ1 were identified in the non-consanguineous parents and her healthy elder sister. It was predicted that G777E was pathogenic and detrimental to the spatial conformation of the MIZ/SP-RING zinc finger domain of ZMIZ1.

Conclusion: Thus far, only four scientific articles reported deleterious variants in ZMIZ1 and most of the cases were from Western countries. This is the first report about a Chinese patient with ZMIZ1 variant. It will broaden the current knowledge of ZMIZ1 variants and variable clinical presentations for clinicians and genetic counselors.