Loss of POGZ alters neural differentiation of human embryonic stem cells

Role of LEDGF/p75 (PSIP1) in oncogenesis. Insights in molecular mechanism and therapeutic potential

Aberrant gene expression due to dysfunction in proteins involved in transcriptional regulation is a hallmark of tumor development. Indeed, targeting transcriptional regulators represents an emerging approach in cancer therapeutics. Lens epithelium-derived growth factor (LEDGF/p75, PSIP1) is a co-transcriptional activator that tethers several proteins to the chromatin. LEDGF/p75 has been implicated in diseases such as HIV infection and KMT2A-rearranged leukemia. Notably, LEDGF/p75 is upregulated in various human cancers including prostate and breast cancer. In this review, we discuss the essential role of LEDGF/p75 in different malignancies and explore its mechanistic contribution to tumorigenesis revealing its potential as a therapeutic target for chemotherapy.

Denovo variants in POGZ and YY1 genes: The novel mega players for neurodevelopmental syndromes in two unrelated consanguineous families

Novel denovo variants of exome sequences are major cause of pathogenic neurodevelopmental disorders with a dominant genetic mechanism that emphasize their heterogeneity and complex phenotypes. White Sutton syndrome and Gabriele-de-Vries syndrome are congenital neuro-impairments with overlap of severe intellectual disability, microcephaly, convulsions, seizures, delayed development, dysmorphism of faces, retinal diseases, movement disorders and autistic traits. POGZ gene codes for pogo transposable element-derived zinc-finger protein and YY1 gene regulates transcription, chromatin, and RNA-binding proteins that have been associated with White Sutton and Gabriele-de-Vries syndromes, in recent data. We present probands of two unrelated consanguineous families with complicated, unexplained neurocognitive syndromic characteristics clinically undiagnosed. Objectives of the study were to identify altered genetics and protein characteristics underlying molecular pathological pathways in both the patients. Whole exome sequencing identifies novel, denovo missense variant NM_015100.4: c.776 C>T (p. Pro259Leu) in exons 19 of POGZ gene and non-frameshift variant NM_003403.5: c.141_143delGGA (p. Glu47del) in exon 1 of YY1 gene for White Sutton syndrome in eight years five-month-old girl and Gabriele-de-Vries syndrome in seven years eight months old boy residing in Rawalpindi and Chakwal districts of Punjab, Pakistan respectively. Protein modelling for identified variants predicts size and conformation modifications in mutated amino acid residues that lead to damaging effects in the conserved domains expressed as neurological pathophysiology. The present study widens the diversely ethnic and highly inbred gene pool of Punjab, Pakistan population for spontaneously originated deleterious mutations and contributes to the continuously expanding phenotypic canvas. Molecular genetic identification and personalized diagnosis for the patients suffering from complicated neurodevelopmental phenotypes, for better care, management of day-to-day activities and prolonged life span are the utmost hopes.

A novel nonsense variant in POGZ expanding the spectrum of White-Sutton syndrome: A case report

White-Sutton Syndrome (WHSUS) is a rare neurodevelopmental genetic disorder with an autosomal dominant mode of inheritance. Truncating mutations in pogo transposable element with zinc finger domain (POGZ) gene have been reported in cases of WHSUS. In this article, we present the first diagnosed case of WHSUS in Lebanon. The 10-month-old infant presented with failure to thrive, chronic diarrhea, vomiting and recurrent upper respiratory tract infections. Molecular testing was performed showing a novel nonsense variant in the POGZ gene: c.1135C > T p.(Arg379∗). With a relatively mild form of the disease, our findings suggest that WHSUS patients may present heterogenous clinical features.

O-GlcNAc transferase congenital disorder of glycosylation (OGT-CDG): Potential mechanistic targets revealed by evaluating the OGT interactome

O-GlcNAc transferase (OGT) is the sole enzyme responsible for the post-translational modification of O-GlcNAc on thousands of target nucleocytoplasmic proteins. To date, nine variants of OGT that segregate with OGT Congenital Disorder of Glycosylation (OGT-CDG) have been reported and characterized. Numerous additional variants have been associated with OGT-CDG, some of which are currently undergoing investigation. This disorder primarily presents with global developmental delay and intellectual disability (ID), alongside other variable neurological features and subtle facial dysmorphisms in patients. Several hypotheses aim to explain the etiology of OGT-CDG, with a prominent hypothesis attributing the pathophysiology of OGT-CDG to mutations segregating with this disorder disrupting the OGT interactome. The OGT interactome consists of thousands of proteins, including substrates as well as interactors that require noncatalytic functions of OGT. A key aim in the field is to identify which interactors and substrates contribute to the primarily neural-specific phenotype of OGT-CDG. In this review, we will discuss the heterogenous phenotypic features of OGT-CDG seen clinically, the variable biochemical effects of mutations associated with OGT-CDG, and the use of animal models to understand this disorder. Furthermore, we will discuss how previously identified OGT interactors causal for ID provide mechanistic targets for investigation that could explain the dysregulated gene expression seen in OGT-CDG models. Identifying shared or unique altered pathways impacted in OGT-CDG patients will provide a better understanding of the disorder as well as potential therapeutic targets.

Real-Time Analysis of Neuronal Cell Cultures for CNS Drug Discovery

The ability to screen for agents that can promote the development and/or maintenance of neuronal networks creates opportunities for the discovery of novel agents for the treatment of central nervous system (CNS) disorders. Over the past 10 years, advances in robotics, artificial intelligence, and machine learning have paved the way for the improved implementation of live-cell imaging systems for drug discovery. These instruments have revolutionized our ability to quickly and accurately acquire large standardized datasets when studying complex cellular phenomena in real-time. This is particularly useful in the field of neuroscience because real-time analysis can allow efficient monitoring of the development, maturation, and conservation of neuronal networks by measuring neurite length. Unfortunately, due to the relative infancy of this type of analysis, standard practices for data acquisition and processing are lacking, and there is no standardized format for reporting the vast quantities of data generated by live-cell imaging systems. This paper reviews the current state of live-cell imaging instruments, with a focus on the most commonly used equipment (IncuCyte systems). We provide an in-depth analysis of the experimental conditions reported in publications utilizing these systems, particularly with regard to studying neurite outgrowth. This analysis sheds light on trends and patterns that will enhance the use of live-cell imaging instruments in CNS drug discovery.

Abnormal cell sorting and altered early neurogenesis in a human cortical organoid model of Protocadherin-19 clustering epilepsy

Introduction

Protocadherin-19 (PCDH19)-Clustering Epilepsy (PCE) is a developmental and epileptic encephalopathy caused by loss-of-function variants of the PCDH19 gene on the X-chromosome. PCE affects females and mosaic males while male carriers are largely spared. Mosaic expression of the cell adhesion molecule PCDH19 due to random X-chromosome inactivation is thought to impair cell-cell interactions between mutant and wild type PCDH19-expressing cells to produce the disease. Progress has been made in understanding PCE using rodent models or patient induced pluripotent stem cells (iPSCs). However, rodents do not faithfully model key aspects of human brain development, and patient iPSC models are limited by issues with random X-chromosome inactivation.

Methods

To overcome these challenges and model mosaic PCDH19 expression in vitro, we generated isogenic female human embryonic stem cells with either HA-FLAG-tagged PCDH19 (WT) or homozygous PCDH19 knockout (KO) using genome editing. We then mixed GFP-labeled WT and RFP-labeled KO cells and generated human cortical organoids (hCOs).

Results

We found that PCDH19 is highly expressed in early (days 20-35) WT neural rosettes where it co-localizes with N-Cadherin in ventricular zone (VZ)-like regions. Mosaic PCE hCOs displayed abnormal cell sorting in the VZ with KO and WT cells completely segregated. This segregation remained robust when WT:KO cells were mixed at 2:1 or 1:2 ratios. PCE hCOs also exhibited altered expression of PCDH19 (in WT cells) and N-Cadherin, and abnormal deep layer neurogenesis. None of these abnormalities were observed in hCOs generated by mixing only WT or only KO (modeling male carrier) cells.

Discussion

Our results using the mosaic PCE hCO model suggest that PCDH19 plays a critical role in human VZ radial glial organization and early cortical development. This model should offer a key platform for exploring mechanisms underlying PCE-related cortical hyperexcitability and testing of potential precision therapies.

Discriminative features in White-Sutton syndrome: literature review and first report in Iran

White-Sutton Syndrome is one of the rare neurodevelopmental disorder inherited in an autosomal dominant manner, mainly caused by de novo mutations in the POGZ gene and shows many phenotypic signs such as intellectual disability, Autism Spectrum Disorder and other spectra. About 70 patients with this syndrome have been reported worldwide. In this paper, we have described different phenotypic features of the White-Sutton Syndrome with a brief review of recent literatures. Finally, we have reported an Iranian male with intellectual disability and visual impairment. We have explained the clinical symptoms of the patient and have compared the patient's phenotype with existing data from individuals with White-Sutton Syndrome. The results of Whole Exome Sequencing test, performed for the patient, declared the presence of a de novo mutation in POGZ gene and confirmed the White-Sutton Syndrome diagnosis.

Protocol for selecting single human pluripotent stem cells using a modified micropipetter

Single-cell clonal selection is a critical procedure for generating a homogeneous population of human pluripotent stem cells. Here, we present a protocol that repurposes the STRIPPER Micropipetter, normally used for in vitro fertilization, to pick single stem cells. We describe steps for tool and reagent preparation, single-cell picking, and colony passaging. We then detail procedures for amplification and analysis. Our protocol does not require cell sorting and produces homogenous clonal cultures with more than 50% survival rate. For complete details on the use and execution of this protocol, please refer to Deng et al.1.

Congenital hypogonadotropic hypogonadism in a patient with a de novo POGZ mutation

OBJECTIVE

Congenital hypogonadotropic hypogonadism (CHH) is a rare, genetically heterogeneous reproductive disorder caused by gonadotropin-releasing hormone (GnRH) deficiency. Approximately half of CHH patients also have decreased or absent sense of smell, that is, Kallmann syndrome (KS). We describe a patient with White-Sutton syndrome (developmental delay and autism spectrum disorder) and KS due to a heterozygous de novo mutation in POGZ (c.2857C>T, p.(Gln953*)), a gene encoding pogo transposable element derived with zinc finger domain, which acts as a transcriptomic regulator of neuronal networks.

DESIGN AND METHODS

We modeled the role of POGZ in CHH by generating 2 clonal human pluripotent stem cell lines with CRISPR/Cas9, carrying either the heterozygous patient mutation (H11 line) or a homozygous mutation (c.2803-2906del; p.E935Kfs*7 encoding a truncated POGZ protein; F6del line).

RESULTS

During the differentiation to GnRH neurons, neural progenitors derived from F6del line displayed severe proliferation defect, delayed wound-healing capacity, downregulation of intermediate progenitor neuron genes TBR1 and TBR2, and immature neuron markers PAX6 and TUBB3 and gave rise to fewer neurons with shorter neurites and less neurite branch points compared to the WT and H11 lines (P < .005). Both lines, however, could be successfully differentiated to GnRH neurons.

CONCLUSIONS

In conclusion, this is the first report on the overlap between White-Sutton syndrome and CHH. POGZ mutations do not hinder GnRH neuron formation but may cause CHH/KS by affecting the size and motility of the anterior neural progenitor pool and neurite outgrowth.