Williams syndrome is an epigenome-regulator disease

Clinical phenotypes study of 231 children with Williams syndrome in China: A single-center retrospective study

BACKGROUND

Williams syndrome (WS) is a multisystem neurodevelopmental disorder caused by microdeletions in 7q11.23. This study aims to characterize the clinical phenotypes of Chinese children with WS to help for the early diagnosis and intervention of this disease.

METHODS

231 children diagnosed with WS were retrospectively recruited to the study. Clinical data were analyzed to obtain the incidence of different clinical phenotypes. The occurrence of phenotypes and the influence of gender and age on the incidence of different phenotypes were analyzed.

RESULTS

All WS exhibited facial dysmorphism (100.0%). The majority had neurodevelopmental disorder (91.8%), hoarseness (87.4%) and cardiovascular anomalies (85.7%). The incidence of short stature (46.9%), inguinal hernia (47.2%), hypercalciuria (29.10%), hypercalcemia (9.1%), subclinical hypothyroidism (26.4%) and hypothyroidism (7.4%) were relatively higher. Gender differences were found in supravalvular aortic stenosis (SVAS, p < .001), ventricular septal defect (VSD, p < .05), inguinal hernia (p < .001), superior pulmonary stenosis (SVPS, p < .05) and neurodevelopmental disorder (p < .05). The incidence of neurodevelopmental disorder in WS increased with age (p < .05) while cardiovascular anomalies (p < .001), short stature (p < .001), hypercalciuria (p < .001) and hypercalcemia (p < .01) decreased with age.

CONCLUSIONS

Facial dysmorphism, neurodevelopmental disorder, hoarseness and cardiovascular anomalies were the most common phenotypes. Genetic testing should be suggested to confirm the diagnosis for children with the above abnormalities. Gender and age should be taken into account when making diagnosis and intervention.

Quantity as a Fish Views It: Behavior and Neurobiology

An ability to estimate quantities, such as the number of conspecifics or the size of a predator, has been reported in vertebrates. Fish, in particular zebrafish, may be instrumental in advancing the understanding of magnitude cognition. We review here the behavioral studies that have described the ecological relevance of quantity estimation in fish and the current status of the research aimed at investigating the neurobiological bases of these abilities. By combining behavioral methods with molecular genetics and calcium imaging, the involvement of the retina and the optic tectum has been documented for the estimation of continuous quantities in the larval and adult zebrafish brain, and the contributions of the thalamus and the dorsal-central pallium for discrete magnitude estimation in the adult zebrafish brain. Evidence for basic circuitry can now be complemented and extended to research that make use of transgenic lines to deepen our understanding of quantity cognition at genetic and molecular levels.

Epigenetic reprogramming converts human Wharton's jelly mesenchymal stem cells into functional cardiomyocytes by differential regulation of Wnt mediators

Background

Lineage commitment of mesenchymal stem cells (MSCs) to cardiac differentiation is controlled by transcription factors that are regulated by epigenetic events, mainly histone deacetylation and promoter DNA methylation. Here, we studied the differentiation of human Wharton’s jelly MSCs (WJMSCs) into the cardiomyocyte lineage via epigenetic manipulations.

Methods

We introduced these changes using inhibitors of DNA methyl transferase and histone deacetylase, DC301, DC302, and DC303, in various combinations. We characterized for cardiogenic differentiation by assessing the expression of cardiac-specific markers by immunolocalization, quantitative RT-PCR, and flow cytometry. Cardiac functional studies were performed by FURA2AM staining and Greiss assay. The role of Wnt signaling during cardiac differentiation was analyzed by quantitative RT-PCR. In-vivo studies were performed in a doxorubicin-induced cardiotoxic mouse model by injecting cardiac progenitor cells. Promoter methylation status of the cardiac transcription factor Nkx2.5 and the Wnt antagonist, secreted frizzled-related protein 4 (sFRP4), after cardiac differentiation was studied by bisulfite sequencing.

Results

By induction with DC301 and DC302, WJMSCs differentiated into cardiomyocyte-like structures with an upregulation of Wnt antagonists, sFRP3 and sFRP4, and Dickkopf (Dkk)1 and Dkk3. The cardiac function enhancer, vinculin, and DDX20, a DEAD-box RNA helicase, were also upregulated in differentiated cardiomyocytes. Additionally, bisulfite sequencing revealed, for the first time in cardiogenesis, that sFRP4 is activated by promoter CpG island demethylation. In vivo, these MSC-derived cardiac progenitors could not only successfully engraft to the site of cardiac injury in mice with doxorubicin-induced cardiac injury, but also form functional cardiomyocytes and restore cardiac function.

Conclusion

The present study unveils a link between Wnt inhibition and epigenetic modification to initiate cardiac differentiation, which could enhance the efficacy of stem cell therapy for ischemic heart disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0638-7) contains supplementary material, which is available to authorized users.

DNA damage response defect in Williams-Beuren syndrome

Williams-Beuren syndrome (WBS, no. OMIM 194050) is a rare multisystem genetic disorder caused by a microdeletion on chromosome 7q11.23 and characterized by cardiovascular malformations, mental retardation, and a specific facial dysmorphism. Recently, we reported that a series of non-Hodgkin's lymphoma occurs in children with WBS and thus hypothesized that a predisposition to cancer may be associated with this genetic disorder. The aim of the present study was to ascertain the role played by three genes hemizygously deleted in WBS (RFC2, GTF2I and BAZ1B) in DNA damage response pathways. Cell proliferation, cell cycle analysis, γ-H2A.X induction, and expression of DNA damage response proteins were investigated upon exposure to genotoxic treatments in WBS patient-derived primary fibroblasts and in the 293T cell line treated with specific siRNAs targeting RFC2, GTF2I and BAZ1B. An impaired hydroxyurea-induced phosphorylation of CHK1 was observed in the WBS cells. However, this defective DNA damage response was not associated with an increased sensitivity to genotoxic agents. In addition, depletion of RFC2, GTF2I and BAZ1B using specific siRNAs did not have a significant impact on the DNA damage response in 293T cells. Our results highlight that the ATR-dependent DNA damage response is impaired in WBS patient cells but is also dispensable for viability when these cells undergo a genotoxic stress. The mechanism by which the ATR pathway is impaired in WBS warrants elucidation through further investigation.

PTH and Vitamin D

PTH and Vitamin D are two major regulators of mineral metabolism. They play critical roles in the maintenance of calcium and phosphate homeostasis as well as the development and maintenance of bone health. PTH and Vitamin D form a tightly controlled feedback cycle, PTH being a major stimulator of vitamin D synthesis in the kidney while vitamin D exerts negative feedback on PTH secretion. The major function of PTH and major physiologic regulator is circulating ionized calcium. The effects of PTH on gut, kidney, and bone serve to maintain serum calcium within a tight range. PTH has a reciprocal effect on phosphate metabolism. In contrast, vitamin D has a stimulatory effect on both calcium and phosphate homeostasis, playing a key role in providing adequate mineral for normal bone formation. Both hormones act in concert with the more recently discovered FGF23 and klotho, hormones involved predominantly in phosphate metabolism, which also participate in this closely knit feedback circuit. Of great interest are recent studies demonstrating effects of both PTH and vitamin D on the cardiovascular system. Hyperparathyroidism and vitamin D deficiency have been implicated in a variety of cardiovascular disorders including hypertension, atherosclerosis, vascular calcification, and kidney failure. Both hormones have direct effects on the endothelium, heart, and other vascular structures. How these effects of PTH and vitamin D interface with the regulation of bone formation are the subject of intense investigation.

Multiple Functions of the Eya Phosphotyrosine Phosphatase

Eyes absent (Eya), a protein conserved from plants to humans and best characterized as a transcriptional coactivator, is also the prototype for a novel class of eukaryotic aspartyl protein tyrosine phosphatases. This minireview discusses recent breakthroughs in elucidating the substrates and cellular events regulated by Eya's tyrosine phosphatase function and highlights some of the complexities, new questions, and surprises that have emerged from efforts to understand how Eya's unusual multifunctionality influences developmental regulation and signaling.

Bromodomains and their pharmacological inhibitors

Over 60 bromodomains belonging to proteins with very different functions have been identified in humans. Several of them interact with acetylated lysine residues, leading to the recruitment and stabilization of protein complexes. The bromodomain and extra-terminal domain (BET) proteins contain tandem bromodomains which bind to acetylated histones and are thereby implicated in a number of DNA-centered processes, including the regulation of gene expression. The recent identification of inhibitors of BET and non-BET bromodomains is one of the few examples in which effective blockade of a protein-protein interaction can be achieved with a small molecule. This has led to major strides in the understanding of the function of bromodomain-containing proteins and their involvement in diseases such as cancer and inflammation. Indeed, BET bromodomain inhibitors are now being clinically evaluated for the treatment of hematological tumors and have also been tested in clinical trials for the relatively rare BRD-NUT midline carcinoma. This review gives an overview of the newest developments in the field, with a focus on the biology of selected bromodomain proteins on the one hand, and on reported pharmacological inhibitors on the other, including recent examples from the patent literature.

Development of neurodevelopmental disorders: a regulatory mechanism involving bromodomain-containing proteins

Neurodevelopmental disorders are classified as diseases that cause abnormal functions of the brain or central nervous system. Children with neurodevelopmental disorders show impaired language and speech abilities, learning and memory damage, and poor motor skills. However, we still know very little about the molecular etiology of these disorders. Recent evidence implicates the bromodomain-containing proteins (BCPs) in the initiation and development of neurodevelopmental disorders. BCPs have a particular domain, the bromodomain (Brd), which was originally identified as specifically binding acetyl-lysine residues at the N-terminus of histone proteins in vitro and in vivo. Other domains of BCPs are responsible for binding partner proteins to form regulatory complexes. Once these complexes are assembled, BCPs alter chromosomal states and regulate gene expression. Some BCP complexes bind nucleosomes, are involved in basal transcription regulation, and influence the transcription of many genes. However, most BCPs are involved in targeting. For example, some BCPs function as a recruitment platform or scaffold through their Brds-binding targeting sites. Others are recruited to form a complex to bind the targeting sites of their partners. The regulation mediated by these proteins is especially critical during normal and abnormal development. Mutant BCPs or dysfunctional BCP-containing complexes are implicated in the initiation and development of neurodevelopmental disorders. However, the pathogenic molecular mechanisms are not fully understood. In this review, we focus on the roles of regulatory BCPs associated with neurodevelopmental disorders, including mental retardation, Fragile X syndrome (FRX), Williams syndrome (WS), Rett syndrome and Rubinstein-Taybi syndrome (RTS). A better understanding of the molecular pathogenesis, based upon the roles of BCPs, will lead to screening of targets for the treatment of neurodevelopmental disorders.

Epigenetic modifications of stem cells: a paradigm for the control of cardiac progenitor cells

Stem cells of all types are characterized by the ability to self-renew and to differentiate. Multiple lines of evidence suggest that both maintenance of stemness and lineage commitment, including determination of the cardiomyogenic lineage, are tightly controlled by epigenetic mechanisms such as DNA methylation, histone modifications, and ATP-dependent chromatin remodeling. Epigenetic mechanisms are intrinsically reversible, interdependent, and highly dynamic in regulation of chromatin structure and specific gene transcription programs, thereby contributing to stem cell homeostasis. Here, we review the current understanding of epigenetic mechanisms involved in regulation of stem cell self-renewal and differentiation and in the control of cardiac progenitor cell commitment during heart development. Further progress in this area will help to decipher the epigenetic landscape in stem and progenitor cells and facilitate manipulation of stem cells for regenerative applications.