Involvement of ZFPIP/Zfp462 in chromatin integrity and survival of P19 pluripotent cells

Seven Novel Variants of Weiss-Kruszka Syndrome and Phenotype Expansion

Weiss-Kruszka syndrome (WKS) is a rare genetic disorder characterized by metopic ridging, ptosis, arched eyebrows, down slanting palpebral fissures, abnormalities in the corpus callosum, cardiac malformations, and variable neurodevelopmental delay. To date, 32 individuals with a diagnosis of WKS have been reported in the literature. The syndrome is caused by a heterozygous pathogenic variant in the ZNF462 gene or a deletion of the 9p31.2 region involving ZNF462. There is significant phenotypic heterogeneity and intrafamilial variability among these patients. Our study reviewed nine patients from seven unrelated families and identified seven novel heterozygous ZNF462 variants through exome sequencing. GestaltMatcher analysis of our cohort's facial images, alongside previously published images of ZNF462 patients, demonstrated a high degree of facial similarity. Further longitudinal research is needed to delineate this rare condition's long-term health implications and adult-onset features.

Analysis of clinical phenotypes and genetic variations in two pedigrees affected with Weiss-Kruszka syndrome

BACKGROUND

Weiss-Kruszka syndrome (WSKA) is a rare autosomal dominant syndrome characterized by multiple congenital anomalies caused by variants in the zinc finger protein 462 gene (ZNF462). About 40 cases of Weiss-Kruszka syndrome have been reported worldwide, and the aim of this study was to investigate the genetic causes of three patients from two Weiss-Kruszka syndrome family pedigrees with the aim of accumulating more data on the disease.

OBJECTIVE

To explore the clinical and genetic characteristics of two pedigrees with Weiss-Kruszka syndrome.

METHODS

The clinical data and family history of patients and family members of two pedigrees with Weiss-Kruszka syndrome were collected, and the pathogenic genes of the patients were analysed by whole-exon sequencing. Suspicious variants were verified by Sanger sequencing verification and bioinformatics prediction.

RESULTS

Proband 1 has developmental delay, autistic behaviour, and abnormal electroencephalogram results. WES revealed a classical heterozygous c.6696-2 A > C splice variant of the ZNF462 gene, which was detected in neither parent. This position was conserved, and the variant was predicted to be deleterious. Minigene assays revealed that three types of aberrantly spliced mRNAs were produced. MRI of proband 2 suggested dysplasia of the corpus callosum with the formation of hemispheric cleft cysts, with a teardrop-like appearance in the lateral ventricle. WES revealed that a heterozygous c.4891 C > T:p. The Glu1631Ter nonsense variant of the ZNF462 gene was inherited from her mother. According to the guidelines of the American Society of Medical Genetics and combined with its clinical manifestations, c.6696-2 A > C and c.4891 C > T:p. Glu1631Ter was determined to be a possible pathogenic variant.

CONCLUSION

The c.6696-2 A>C and c.4891C > T:p.Glu1631Ter of the ZNF462 gene likely underlies Weiss-Kruszka syndrome in children (foetus), which enriches the variant spectrum of Chinese patients with Weiss-Kruszka syndrome and provides a basis for prenatal diagnosis and genetic counselling.

Effects of microgravity on neural crest stem cells

Exposure to microgravity (μg) results in a range of systemic changes in the organism, but may also have beneficial cellular effects. In a previous study we detected increased proliferation capacity and upregulation of genes related to proliferation and survival in boundary cap neural crest stem cells (BC) after MASER14 sounding rocket flight compared to ground-based controls. However, whether these changes were due to μg or hypergravity was not clarified. In the current MASER15 experiment BCs were exposed simultaneously to μg and 1 g conditions provided by an onboard centrifuge. BCs exposed to μg displayed a markedly increased proliferation capacity compared to 1 g on board controls, and genetic analysis of BCs harvested 5 h after flight revealed an upregulation, specifically in μg-exposed BCs, of Zfp462 transcription factor, a key regulator of cell pluripotency and neuronal fate. This was associated with alterations in exosome microRNA content between μg and 1 g exposed MASER15 specimens. Since the specimens from MASER14 were obtained for analysis with 1 week's delay, we examined whether gene expression and exosome content were different compared to the current MASER15 experiments, in which specimens were harvested 5 h after flight. The overall pattern of gene expression was different and Zfp462 expression was down-regulated in MASER14 BC μg compared to directly harvested specimens (MASER15). MicroRNA exosome content was markedly altered in medium harvested with delay compared to directly collected samples. In conclusion, our analysis indicates that even short exposure to μg alters gene expression, leading to increased BC capacity for proliferation and survival, lasting for a long time after μg exposure. With delayed harvest of specimens, a situation which may occur due to special post-flight circumstances, the exosome microRNA content is modified compared to fast specimen harvest, and the direct effects from μg exposure may be partially attenuated, whereas other effects can last for a long time after return to ground conditions.

A Nonsense Variant of ZNF462 Gene Associated With Weiss-Kruszka Syndrome-Like Manifestations: A Case Study and Literature Review

Objective: This study aims to explore the clinical characteristics and genetic basis of a patient with unilateral ptosis and unilateral hearing impairment in pedigree analysis.

Methods: The clinical data of the child and his father were collected. The genomic DNA of the patient and his relatives were extracted from their peripheral blood samples and subjected to trio-whole-exome sequencing (trio-WES) and copy number variation analysis. Sanger sequencing was used to verify the potential variant.

Results: The sequencing analysis identified a heterozygous nonsense variant c.6431C > A (p.Ser2144*) in the ZNF462 gene (NM_021224.6) in the child and his father, whereas the locus in his asymptomatic mother, brother, and grandparents was found to be the wild type, which is an autosomal dominant inheritance. The new genetic variant has not been previously reported in the ClinVar and HGMD databases and the Genome Aggregation Database (gnomAD).

Conclusion: This is the first incidence of Weiss–Kruszka syndrome relating to the nonsense variant in the ZNF462 gene in China. The finding from this study is novel in its expansion of the variant spectrum of the ZNF462 gene and clarifies the genetic etiology of the patient and his father.

Acute lymphoblastic leukemia in a child with Weiss-Kruszka syndrome: Casual or causal association?

Weiss-Kruszka syndrome is a recently described genetic disorder characterized by craniofacial features, ptosis, dysgenesis of the corpus callosum, and neurodevelopmental impairment. It is caused by heterozygous loss-of-function variants
in ZNF462 gene. During the time, the original phenotype was expanded, including several complications, sensorineural hearing loss, congenital hypogonadotropic hypogonadism with anosmia and complete growth hormone deficiency associated with empty sella syndrome. Here we report the first case of Weiss-Kruszka syndrome, associated to a de novo 9q31.1q31.3 microdeletion showing an acute lymphoblastic leukemia. A speculation on the contribution of our case to the phenotypic expansion of WSKA is here discussed. More clinical and functional studies are needed to elucidate this association. A possible expansion of the WSKA phenotype is discussed.

Zinc finger proteins orchestrate active gene silencing during embryonic stem cell differentiation

Transcription factors and chromatin remodeling proteins control the transcriptional variability for ESC lineage commitment. During ESC differentiation, chromatin modifiers are recruited to the regulatory regions by transcription factors, thereby activating the lineage-specific genes or silencing the transcription of active ESC genes. However, the underlying mechanisms that link transcription factors to exit from pluripotency are yet to be identified. In this study, we show that the Ctbp2-interacting zinc finger proteins, Zfp217 and Zfp516, function as linkers for the chromatin regulators during ESC differentiation. CRISPR-Cas9-mediated knock-outs of both Zfp217 and Zfp516 in ESCs prevent the exit from pluripotency. Both zinc finger proteins regulate the Ctbp2-mediated recruitment of the NuRD complex and polycomb repressive complex 2 (PRC2) to active ESC genes, subsequently switching the H3K27ac to H3K27me3 during ESC differentiation for active gene silencing. We therefore suggest that some zinc finger proteins orchestrate to control the concise epigenetic states on active ESC genes during differentiation, resulting in natural lineage commitment.

Phenotype delineation of ZNF462 related syndrome

Zinc finger protein 462 (ZNF462) is a relatively newly discovered vertebrate specific protein with known critical roles in embryonic development in animal models. Two case reports and a case series study have described the phenotype of 10 individuals with ZNF462 loss of function variants. Herein, we present 14 new individuals with loss of function variants to the previous studies to delineate the syndrome of loss of function in ZNF462. Collectively, these 24 individuals present with recurring phenotypes that define a multiple congenital anomaly syndrome. Most have some form of developmental delay (79%) and a minority has autism spectrum disorder (33%). Characteristic facial features include ptosis (83%), down slanting palpebral fissures (58%), exaggerated Cupid's bow/wide philtrum (54%), and arched eyebrows (50%). Metopic ridging or craniosynostosis was found in a third of study participants and feeding problems in half. Other phenotype characteristics include dysgenesis of the corpus callosum in 25% of individuals, hypotonia in half, and structural heart defects in 21%. Using facial analysis technology, a computer algorithm applying deep learning was able to accurately differentiate individuals with ZNF462 loss of function variants from individuals with Noonan syndrome and healthy controls. In summary, we describe a multiple congenital anomaly syndrome associated with haploinsufficiency of ZNF462 that has distinct clinical characteristics and facial features.

Transcription of Satellite DNAs in Mammals

Centromeric and pericentric regions have long been regarded as transcriptionally inert portions of chromosomes. A number of studies in the past 10 years disproved this dogma and provided convincing evidence that centromeric and pericentric sequences are transcriptionally active in several biological contexts.In this chapter, we provide a comprehensive picture of the various contexts (cell growth and differentiation, stress, effect of chromatin organization) in which these sequences are expressed in mouse and human cells and discuss the possible functional implications of centromeric and pericentric sequences activation and/or of the resulting noncoding RNAs. Moreover, we provide an overview of the molecular mechanisms underlying the activation of centromeric and pericentromeric sequences as well as the structural features of encoded RNAs.