Variants in the WDR44 WD40-repeat domain cause a spectrum of ciliopathy by impairing ciliogenesis initiation

WDR44 prevents ciliogenesis initiation by regulating RAB11-dependent vesicle trafficking. Here, we describe male patients with missense and nonsense variants within the WD40 repeats (WDR) of WDR44, an X-linked gene product, who display ciliopathy-related developmental phenotypes that we can model in zebrafish. The patient phenotypic spectrum includes developmental delay/intellectual disability, hypotonia, distinct craniofacial features and variable presence of brain, renal, cardiac and musculoskeletal abnormalities. We demonstrate that WDR44 variants associated with more severe disease impair ciliogenesis initiation and ciliary signaling. Because WDR44 negatively regulates ciliogenesis, it was surprising that pathogenic missense variants showed reduced abundance, which we link to misfolding of WDR autonomous repeats and degradation by the proteasome. We discover that disease severity correlates with increased RAB11 binding, which we propose drives ciliogenesis initiation dysregulation. Finally, we discover interdomain interactions between the WDR and NH2-terminal region that contains the RAB11 binding domain (RBD) and show patient variants disrupt this association. This study provides new insights into WDR44 WDR structure and characterizes a new syndrome that could result from impaired ciliogenesis.

BMPR1B gene in brachydactyly type 2-A family with de novo R486W mutation and a disease phenotype

Background

Brachydactylies are a group of inherited conditions, characterized mainly by the presence of shortened fingers and toes. Based on the patients’ phenotypes, brachydactylies have been subdivided into 10 subtypes. In this study, we have identified a family with two members affected by brachydactyly type A2 (BDA2). BDA2 is caused by mutations in three genes: BMPR1B, BMP2 or GDF5. So far only two studies have reported the BDA2 cases caused by mutations in the BMPR1B gene.

Methods

We employed next‐generation sequencing to identify mutations in culpable genes.

Results and Conclusion

In this paper, we report a case of BDA2 resulting from the presence of a heterozygous c.1456C>T, p.Arg486Trp variant in BMPR1B, which was previously associated with BDA2. The next generation sequencing analysis of the patients’ family revealed that the mutation occurred de novo in the proband and was transmitted to his 26‐month‐old son. Although the same variant was confirmed in both patients, their phenotypes were different with more severe manifestation of the disease in the adult.

Hypermethylation of NRG1 gene correlates with the presence of heart defects in Down's syndrome

Congenital heart defects can decrease the quality of life and life expectancy in affected individuals, and constitute a major burden for the health care systems. Endocardial cushion defects are among the most prevalent heart malformations in the general population, and are extremely frequent (approximately a 100-fold higher prevalence) in children with Down syndrome. Several genes have been proposed to be involved in the pathogenesis of these malformations, but no common pathogenic DNA variants have been identified so far. Here, we focussed on constitutive, epigenetic alterations of function of selected genes, potentially important for endocardial cushion development. We used two types of microarrays, dedicated for assessment of gene promoter methylation and whole genome expression. First, we compared the gene promoter methylation profiles between two groups of Down syndrome patients, with and without heart defects of endocardial cushion-type. Then, to determine the functional role of the detected methylation alterations, we assessed the expression of the genes of interest. We detected significant hypermethylation of the NRG1 gene promoter region in children with heart defects. NRG1 is a key factor in maturation of endocardial cushions. Supplementary gene expression assessment revealed significantly decreased activity of the ERBB3, SHC3 and SHC4 genes in children with heart defects. The above three genes are closely related to the NRG1 gene and are crucial elements of the NRG/ErbB pathway. The results of this pilot study show that hypermethylation of the NRG1 gene promoter can reflect the functional genome alteration contributing to development of congenital heart defects of endocardial cushion-type.

Long-term trends in the prevalence of congenital heart defects in patients with Down syndrome in southern Poland

OBJECTIVE

Introduction: Down syndrome is one of the most common chromosomal abnormalities in humans. Patients have typical dysmorphic features and various congenital malformations. Congenital heart defects were reported as the most common of the latter, occurring in approximately 50% of the cases. The aim: We aimed to analyse the long-term trends in the prevalence of Down syndrome and related heart defects in the population of southern Poland (Krakow region).

PATIENTS AND METHODS

Material and methods: We analysed 500 consecutive patients with Down syndrome who were born from 2006 through 2017 and were diagnosed at the Department of Medical Genetics, Jagiellonian University. Next, we compared our results with the data obtained in previous regional studies.

RESULTS

Results: The prevalence of Down syndrome in the assessed period was 1.65 per 1,000 live births and was similar to the historical prevalence in our region. Cardiac malformations were detected in 57.6% of the patients and the common atrioventricular canal (CAVC) was the most frequent anomaly (35.1%). However, detailed analysis of the frequency of severe heart defects that usually require prompt surgical treatment in the course of infancy revealed that the percentage of CAVC has been significantly lower in recent years (p=0.033).

CONCLUSION

Conclusions: The prevalence of Down syndrome and the overall frequency of congenital heart defects have not significantly changed in recent years. However, the frequency of CAVC has decreased, which could be related to the technical progress in prenatal detection of this severe anomaly, and to the subsequent elective terminations of affected pregnancies. Further population studies are required to confirm the presence of this trend and elucidate its background.

Hyperoxia induces epigenetic changes in newborn mice lungs

Supplemental oxygen exposure is a risk factor for the development of bronchopulmonary dysplasia (BPD). Reactive oxygen species may damage lung tissue, but hyperoxia also has the potential to alter genome activity via changes in DNA methylation. Understanding the epigenetic potential of hyperoxia would enable further improvement of the therapeutic strategies for BPD. Here we aimed to identify hyperoxia-related alterations in DNA methylation, which could affect the activity of crucial genetic pathways involved in the development of hyperoxic lung injury. Newborn mice (n = 24) were randomized to hyperoxia (85% O₂) or normoxia groups for 14 days, followed by normoxia for the subsequent 14 days. The mice were sacrificed on day 28, and lung tissue was analyzed using microarrays developed for the assessment of genome methylation and expression profiles. The mean DNA methylation level was higher in the hyperoxia group than the normoxia group. The analysis of specific DNA fragments revealed hypermethylation of > 1000 gene promoters in the hyperoxia group, confirming the presence of the DNA-hypermethylation effect of hyperoxia. Further analysis showed significant enrichment of the TGF-β signaling pathway (p = 0.0013). The hypermethylated genes included Tgfbr1, Crebbp, and Creb1, which play central roles in the TGF-β signaling pathway and cell cycle regulation. Genome expression analysis revealed in the hyperoxia group complementary downregulation of genes that are crucial for cell cycle regulation (Crebbp, Smad2, and Smad3). These results suggest the involvement of the methylation of TGF-β pathway genes in lung tissue reaction to hyperoxia. The data also suggest that hyperoxia may be a programming factor in newborn mice.

The influence of silver additives on titania photoactivity in the photooxidation of phenol

Photodeposition of small amounts of metal silver on the surface of titanium(IV) oxide enhances its photoactivity in phenol decomposition. The applied method of in situ metal photoreduction resulted in preparing better Ag/TiO(2) systems than those already described in literature. Optimum silver loading on titania amounts to 0.5 wt%. The photoreaction, which finally leads to total phenol mineralization, proceeds via intermediate compounds. Hydroquinone, benzoquinone and catechol are the main intermediates determined quantitatively. Photooxidation of the compounds competes with the photooxidation of phenol. At higher phenol concentration, >6 x 10(-4)mol dm(-3), the rate of the photocatalytic reaction is strongly retarded. The photoreaction was conducted in a specially designed, three-phase fluidal photoreactor.