Genotype-Phenotype Comparison in POGZ-Related Neurodevelopmental Disorders by Using Clinical Scoring

JRK binds satellite III DNA and is necessary for the heat shock response

JRK is a DNA-binding protein of the pogo superfamily of transposons, which includes the well-known centromere binding protein B (CENP-B). Jrk null mice exhibit epilepsy, and growth and reproductive disorders, consistent with its relatively high expression in the brain and reproductive tissues. Human JRK DNA variants and gene expression levels are implicated in cancers and neuropsychiatric disorders. JRK protein modulates β-catenin-TCF activity but little is known of its cellular functions. Based on its homology to CENP-B, we determined whether JRK binds centromeric or other satellite DNAs. We show that human JRK binds satellite III DNA, which is abundant at the chromosome 9q12 juxtacentromeric region and on Yq12, both sites of nuclear stress body assembly. Human JRK-GFP overexpressed in HeLa cells strongly localises to 9q12. Using an anti-JRK antiserum we show that endogenous JRK co-localises with a subset of centromeres in non-stressed cells, and with heat shock factor 1 following heat shock. Knockdown of JRK in HeLa cells proportionately reduces heat shock protein gene expression in heat-shocked cells. A role for JRK in regulating the heat shock response is consistent with the mouse Jrk null phenotype and suggests that human JRK may act as a modifier of diseases with a cellular stress component.

Exploring the molecular pathways linking sleep phenotypes and POGZ-associated neurodevelopmental disorder

Pogo transposable element-derived protein with ZNF domain (POGZ) gene encodes a chromatin regulator and rare variants on this gene have been associated with a broad spectrum of neurodevelopmental disorders, such as White-Sutton syndrome. Patient clinical manifestations frequently include developmental delay, autism spectrum disorder and obesity. Sleep disturbances are also commonly observed in these patients, yet the biological pathways which link sleep traits to the POGZ-associated syndrome remain unclear. We screened for sleep implications among individuals with causative POGZ variants previously described. Sleep disturbances were observed in 52% of patients, and being obese was not observed as a risk factor for sleep problems. Next, we identified genes associated with sleep-associated traits among the POGZ regulatory targets, aiming to uncover the molecular pathways that, when disrupted by POGZ loss of function, contribute to the aetiology of sleep phenotypes in these patients. The intersect between POGZ targets and sleep-related genes was used in a pathway enrichment analysis. Relevant pathways among these overlapping genes are involved in the regulation of circadian rhythm, tau protein binding, ATPase activator activity. This study may represent the beginning for novel functional investigations on shared molecular mechanisms between sleep disturbances and rare developmental syndromes related to POGZ and its regulatory targets.

Genetic architecture of childhood speech disorder: a review

Severe speech disorders lead to poor literacy, reduced academic attainment and negative psychosocial outcomes. As early as the 1950s, the familial nature of speech disorders was recognized, implying a genetic basis; but the molecular genetic basis remained unknown. In 2001, investigation of a large three generational family with severe speech disorder, known as childhood apraxia of speech (CAS), revealed the first causative gene; FOXP2. A long hiatus then followed for CAS candidate genes, but in the past three years, genetic analysis of cohorts ascertained for CAS have revealed over 30 causative genes. A total of 36 pathogenic variants have been identified from 122 cases across 3 cohorts in this nascent field. All genes identified have been in coding regions to date, with no apparent benefit at this stage for WGS over WES in identifying monogenic conditions associated with CAS. Hence current findings suggest a remarkable one in three children have a genetic variant that explains their CAS, with significant genetic heterogeneity emerging. Around half of the candidate genes identified are currently supported by medium (6 genes) to strong (9 genes) evidence supporting the association between the gene and CAS. Despite genetic heterogeneity; many implicated proteins functionally converge on pathways involved in chromatin modification or transcriptional regulation, opening the door to precision diagnosis and therapies. Most of the new candidate genes for CAS are associated with previously described neurodevelopmental conditions that include intellectual disability, autism and epilepsy; broadening the phenotypic spectrum to a distinctly milder presentation defined by primary speech disorder in the setting of normal intellect. Insights into the genetic bases of CAS, a severe, rare speech disorder, are yet to translate to understanding the heritability of more common, typically milder forms of speech or language impairment such as stuttering or phonological disorder. These disorders likely follow complex inheritance with polygenic contributions in many cases, rather than the monogenic patterns that underly one-third of patients with CAS. Clinical genetic testing for should now be implemented for individuals with CAS, given its high diagnostic rate, which parallels many other neurodevelopmental disorders where this testing is already standard of care. The shared mechanisms implicated by gene discovery for CAS highlight potential new targets for future precision therapies.

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.

White-Sutton syndrome and congenital heart disease: case report and literature review

BACKGROUND

White-Sutton syndrome is an autosomal dominant neurodevelopmental disorder caused by heterozygous mutation in POGZ (Pogo Transposable Element Derived with ZNF Domain). This syndrome is characterized by delayed psychomotor development apparent in infancy and abnormal facial features. To date, 80 cases have been reported in the literature; however, the phenotypic characterizations remain incomplete.

CASE PRESENTATION

We herein describe a 2-year-old girl harboring a novel frameshift de novo POGZ variant: c.2746del (p.Thr916ProfsTer12). This patient presented with multisystem abnormalities affecting the digestive tract and neurological functioning, as well as congenital heart disease, which involved an atrial septal defect (18 × 23 × 22 mm) with pulmonary arterial hypertension (42 mmHg). The relationship between congenital heart disease and White-Sutton syndrome as described in both the GeneReview and OMIM databases (#616,364) remains unclear. A review of the current literature revealed 18 cases of White-Sutton syndrome with POGZ variants and congenital heart disease, and we summarize their clinical features in this study.

CONCLUSIONS

Our findings based on the present case and those in the literature indicate a relationship between POGZ mutation and congenital heart disease.

NGS-driven molecular diagnosis of heterogeneous hereditary neurological disorders reveals novel and known variants in disease-causing genes

Hereditary neurological disorders (HNDs) are a clinically and genetically heterogeneous group of disorders. These disorders arise from the impaired function of the central or peripheral nervous system due to aberrant electrical impulses. More than 600 various neurological disorders, exhibiting a wide spectrum of overlapping clinical presentations depending on the organ(s) involved, have been documented. Owing to this clinical heterogeneity, diagnosing these disorders has been a challenge for both clinicians and geneticists and a large number of patients are either misdiagnosed or remain entirely undiagnosed. Contribution of genetics to neurological disorders has been recognized since long; however, the complete picture of the underlying molecular bases are under-explored. The aim of this study was to accurately diagnose 11 unrelated Pakistani families with various HNDs deploying NGS as a first step approach. Using exome sequencing and gene panel sequencing, we successfully identified disease-causing genomic variants these families. We report four novel variants, one each in, ECEL1, NALCN, TBR1 and PIGP in four of the pedigrees. In the rest of the seven families, we found five previously reported pathogenic variants in POGZ, FA2H, PLA2G6 and CYP27A1. Of these, three families segregate a homozygous 18 bp in-frame deletion of FA2H, indicating a likely founder mutation segregating in Pakistani population. Genotyping for this mutation can help low-cost population wide screening in the corresponding regions of the country. Our findings not only expand the existing repertoire of mutational spectrum underlying neurological disorders but will also help in genetic testing of individuals with HNDs in other populations.

A Novel POGZ Variant in a Patient with Intellectual Disability and Obesity

White–Sutton syndrome is a rare type of autosomal dominant neurodevelopmental disorder caused by mutations, mostly de novo, in the POGZ gene. No more than 120 patients have been described so far in the literature. Common clinical manifestations include intellectual disability, developmental delay, autism spectrum disorder, other behavioral abnormalities, sleeping problems, hyperactivity and visual problems. We describe a 20-year-old male patient from Colombia who presented with delayed psychomotor development, intellectual disability, obesity, sleep difficulties, hypotonia, hypogonadism, gynecomastia, visual abnormalities and several facial dysmorphisms. Genetic testing showed a novel heterozygous frameshift variant (c.3308del; p.Leu1103Profs*19) in the POGZ gene (NM_015100.3). This is the first report of a diagnosed patient with WHSUS in Colombia.