Myhre syndrome is caused by dominant-negative dysregulation of SMAD4 and other co-factors.

Myhre syndrome is a connective tissue disorder characterized by congenital cardiovascular, craniofacial, respiratory, skeletal, and cutaneous anomalies as well as intellectual disability and progressive fibrosis. It is caused by germline variants in the transcriptional co-regulator SMAD4 that localize at two positions within the SMAD4 protein, I500 and R496, with I500 V/T/M variants more commonly identified in individuals with Myhre syndrome. Here we assess the functional impact of SMAD4-I500V variant, identified in two previously unpublished individuals with Myhre syndrome, and provide novel insights into the molecular mechanism of SMAD4-I500V dysfunction. We show that SMAD4-I500V can dimerize, but its transcriptional activity is severely compromised. Our data show that SMAD4-I500V acts dominant-negatively on SMAD4 and on receptor-regulated SMADs, affecting transcription of target genes. Furthermore, SMAD4-I500V impacts the transcription and function of crucial developmental transcription regulator, NKX2-5. Overall, our data reveal a dominant-negative model of disease for SMAD4-I500V where the function of SMAD4 encoded on the remaining allele, and of co-factors, are perturbed by the continued heterodimerization of the variant, leading to dysregulation of TGF and BMP signaling. Our findings not only provide novel insights into the mechanism of Myhre syndrome pathogenesis but also extend the current knowledge of how pathogenic variants in SMAD proteins cause disease.

Functional genomics and gene-environment interaction highlight the complexity of congenital heart disease caused by Notch pathway variants.

Congenital heart disease (CHD) is the most common birth defect and brings with it significant mortality and morbidity. The application of exome and genome sequencing has greatly improved the rate of genetic diagnosis for CHD but the cause in the majority of cases remains uncertain. It is clear that genetics, as well as environmental influences, play roles in the aetiology of CHD. Here we address both these aspects of causation with respect to the Notch signalling pathway. In our CHD cohort, variants in core Notch pathway genes account for 20% of those that cause disease, a rate that did not increase with the inclusion of genes of the broader Notch pathway and its regulators. This is reinforced by case-control burden analysis where variants in Notch pathway genes are enriched in CHD patients. This enrichment is due to variation in NOTCH1. Functional analysis of some novel missense NOTCH1 and DLL4 variants in cultured cells demonstrate reduced signalling activity, allowing variant reclassification. Although loss-of-function variants in DLL4 are known to cause Adams-Oliver syndrome, this is the first report of a hypomorphic DLL4 allele as a cause of isolated CHD. Finally, we demonstrate a gene-environment interaction in mouse embryos between Notch1 heterozygosity and low oxygen- or anti-arrhythmic drug-induced gestational hypoxia, resulting in an increased incidence of heart defects. This implies that exposure to environmental insults such as hypoxia could explain variable expressivity and penetrance of observed CHD in families carrying Notch pathway variants.

Heterozygous loss of WBP11 function causes multiple congenital defects in humans and mice.

The genetic causes of multiple congenital anomalies are incompletely understood. Here, we report novel heterozygous predicted loss-of-function (LoF) and predicted damaging missense variants in the WW domain binding protein 11 (WBP11) gene in seven unrelated families with a variety of overlapping congenital malformations, including cardiac, vertebral, tracheo-esophageal, renal and limb defects. WBP11 encodes a component of the spliceosome with the ability to activate pre-messenger RNA splicing. We generated a Wbp11 null allele in mouse using CRISPR-Cas9 targeting. Wbp11 homozygous null embryos die prior to E8.5, indicating that Wbp11 is essential for development. Fewer Wbp11 heterozygous null mice are found than expected due to embryonic and postnatal death. Importantly, Wbp11 heterozygous null mice are small and exhibit defects in axial skeleton, kidneys and esophagus, similar to the affected individuals, supporting the role of WBP11 haploinsufficiency in the development of congenital malformations in humans. LoF WBP11 variants should be considered as a possible cause of VACTERL association as well as isolated Klippel-Feil syndrome, renal agenesis or esophageal atresia.

NAD Deficiency, Congenital Malformations, and Niacin Supplementation.

BACKGROUND: Congenital malformations can be manifested as combinations of phenotypes that co-occur more often than expected by chance. In many such cases, it has proved difficult to identify a genetic cause. We sought the genetic cause of cardiac, vertebral, and renal defects, among others, in unrelated patients. METHODS: We used genomic sequencing to identify potentially pathogenic gene variants in families in which a person had multiple congenital malformations. We tested the function of the variant by using assays of in vitro enzyme activity and by quantifying metabolites in patient plasma. We engineered mouse models with similar variants using the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 system. RESULTS: Variants were identified in two genes that encode enzymes of the kynurenine pathway, 3-hydroxyanthranilic acid 3,4-dioxygenase (HAAO) and kynureninase (KYNU). Three patients carried homozygous variants predicting loss-of-function changes in the HAAO or KYNU proteins (HAAO p.D162*, HAAO p.W186*, or KYNU p.V57Efs*21). Another patient carried heterozygous KYNU variants (p.Y156* and p.F349Kfs*4). The mutant enzymes had greatly reduced activity in vitro. Nicotinamide adenine dinucleotide (NAD) is synthesized de novo from tryptophan through the kynurenine pathway. The patients had reduced levels of circulating NAD. Defects similar to those in the patients developed in the embryos of Haao-null or Kynu-null mice owing to NAD deficiency. In null mice, the prevention of NAD deficiency during gestation averted defects. CONCLUSIONS: Disruption of NAD synthesis caused a deficiency of NAD and congenital malformations in humans and mice. Niacin supplementation during gestation prevented the malformations in mice. (Funded by the National Health and Medical Research Council of Australia and others.).

Revealing hidden genetic diagnoses in the ocular anterior segment disorders.

PURPOSE: Ocular anterior segment disorders (ASDs) are clinically and genetically heterogeneous, and genetic diagnosis often remains elusive. In this study, we demonstrate the value of a combined analysis protocol using phenotypic, genomic, and pedigree structure data to achieve a genetic conclusion. METHODS: We utilized a combination of chromosome microarray, exome sequencing, and genome sequencing with structural variant and trio analysis to investigate a cohort of 41 predominantly sporadic cases. RESULTS: We identified likely causative variants in 54% (22/41) of cases, including 51% (19/37) of sporadic cases and 75% (3/4) of cases initially referred as familial ASD. Two-thirds of sporadic cases were found to have heterozygous variants, which in most cases were de novo. Approximately one-third (7/22) of genetic diagnoses were found in rarely reported or recently identified ASD genes including PXDN, GJA8, COL4A1, ITPR1, CPAMD8, as well as the new phenotypic association of Axenfeld-Rieger anomaly with a homozygous ADAMTS17 variant. The remainder of the variants were in key ASD genes including FOXC1, PITX2, CYP1B1, FOXE3, and PAX6. CONCLUSIONS: We demonstrate the benefit of detailed phenotypic, genomic, variant, and segregation analysis to uncover some of the previously "hidden" heritable answers in several rarely reported and newly identified ocular ASD-related disease genes.

Identification of clinically actionable variants from genome sequencing of families with congenital heart disease.

PURPOSE: Congenital heart disease (CHD) affects up to 1% of live births. However, a genetic diagnosis is not made in most cases. The purpose of this study was to assess the outcomes of genome sequencing (GS) of a heterogeneous cohort of CHD patients. METHODS: Ninety-seven families with probands born with CHD requiring surgical correction were recruited for genome sequencing. At minimum, a proband-parents trio was sequenced per family. GS data were analyzed via a two-tiered method: application of a high-confidence gene screen (hcCHD), and comprehensive analysis. Identified variants were assessed for pathogenicity using the American College of Medical Genetics and Genomics-Association for Molecular Pathology (ACMG-AMP) guidelines. RESULTS: Clinically relevant genetic variants in known and emerging CHD genes were identified. The hcCHD screen identified a clinically actionable variant in 22% of families. Subsequent comprehensive analysis identified a clinically actionable variant in an additional 9% of families in genes with recent disease associations. Overall, this two-tiered approach provided a clinically relevant variant for 31% of families. CONCLUSIONS: Interrogating GS data using our two-tiered method allowed identification of variants with high clinical utility in a third of our heterogeneous cohort. However, association of emerging genes with CHD etiology, and development of novel technologies for variant assessment and interpretation, will increase diagnostic yield during future reassessment of our GS data.

KBG syndrome: An Australian experience.

In 2011, heterozygous mutations in the ANKRD11 gene were identified in patients with KBG syndrome. Since then, 100 cases have been described with the expansion of the clinical phenotype. Here we present 18 KBG affected individuals from 13 unrelated families, 16 with pathogenic mutations in the ANKRD11 gene. Consistent features included intellectual disability, macrodontia, and the characteristic broad forehead with hypertelorism, and a prominent nasal bridge. Common features included hand anomalies, cryptorchidism, and a large number of palate abnormalities. Distinctive findings in this series included malrotation of the abdominal viscera, bilateral inguinal herniae in two patients, basal ganglia calcification and the finding of osteopenia in three patients. Nine novel heterozygous variants were found and the genotype-phenotype correlation was explored. This report highlights the need for thorough examination and investigation of the dental and skeletal systems. The results confirm the specificity of ANKRD11 mutations in KBG and further evidence for this transcription repressor in neural, cardiac, and skeletal development. The description of further cases of KBG syndrome is needed to further delineate this condition, in particular the specific neurological and behavioral phenotype.

Recurrence of split hand/foot malformation, cleft lip/palate, and severe urogenital abnormalities due to germline mosaicism for TP63 mutation.

We describe two sibling fetuses with urogenital abnormalities detected by prenatal ultrasound, in which post-delivery examination showed split hand and foot malformation, and bilateral cleft lip and palate. These findings are consistent with ectrodactyly-ectodermal dysplasia-cleft lip with or without cleft palate syndrome (EEC). Both fetuses were found to have the same missense mutation in TP63 (c.1051G > A; p.D351N). Parental clinical examinations and lymphocyte DNA analyses were normal. This report illustrates the potential severity of urogenital defects in TP63-related disorders, which may be detectable with fetal ultrasonography. It highlights the need to counsel for the possibility of germline mosaicism in TP63-associated disorders. © 2016 Wiley Periodicals, Inc.

Nebulised deoxyribonuclease for viral bronchiolitis in children younger than 24 months.

BACKGROUND: Bronchiolitis is one of the most common respiratory problems in the first year of life. The sputum of infants with bronchiolitis has increased deoxyribonucleic acid (DNA) content, leading to mucous plugging and airway obstruction. Recombinant human deoxyribonuclease (rhDNase), an enzyme that digests extracellular DNA, might aid the clearance of mucus and relieve peripheral airway obstruction. OBJECTIVES: To determine the effect of nebulised rhDNase on the severity and duration of viral bronchiolitis in children younger than 24 months of age in the hospital setting. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2012, Issue 7 which includes the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to July Week 4, 2012), EMBASE (1974 to August 2012) and LILACS (1982 to August 2012). SELECTION CRITERIA: Randomised controlled trials (RCTs) using nebulised rhDNase alone or with concomitant therapy in children younger than 24 months of age hospitalised with acute bronchiolitis. DATA COLLECTION AND ANALYSIS: Two review authors independently performed literature searches, assessed trial quality and extracted data. We obtained unpublished data from trial authors. We used Review Manager 5.1 to pool treatment effects expressed as the mean difference (MD) or standardised mean difference (SMD) with 95% confidence intervals (CI). MAIN RESULTS: Three RCTs (333 participants) were identified, two of which were multicentre trials comprising only participants positive for respiratory syncytial virus (RSV). The other trial enrolled participants clinically diagnosed with bronchiolitis from a hospital in Italy. All studies used 2.5 mL (1 mg/mL) of nebulised rhDNase compared with placebo either as a daily or a twice daily dose. Adjunctive therapy included nebulised salbutamol, steroids, supplemental oxygen, intravenous fluids or tube feeding, nasal washing, nasal decongestants and antibiotics.Overall, nebulised rhDNase showed no benefit in clinically meaningful outcomes. Meta-analysis favoured the control group with a shorter duration of hospital stay (MD 0.50; 95% CI 0.10 to 0.90, P = 0.01) and better clinical score improvement (SMD -0.24; 95% CI -0.50 to 0.01, P = 0.06). The largest trial showed no difference in supplemental oxygen use or intensive care unit (ICU) admission.In one RCT, four out of 11 patients in the treatment group had atelectasis. Two of these patients showed distinctive clinical improvement after nebulised rhDNase.There was no significant difference in adverse events. These included temporary desaturation, temporary coughing, increased coughing, facial rash, hoarseness, dyspnoea and bad taste, reported in a total of 11 patients from both treatment groups. AUTHORS' CONCLUSIONS: The results based on the three included studies in this review did not support the use of nebulised rhDNase in children under 24 months of age hospitalised with acute bronchiolitis. In these patients, treatment did not shorten the length of hospitalisation or improve clinical outcomes. It might have a role in severe bronchiolitis complicated by atelectasis, but further clinical studies would need to be performed.

A new era of genetic testing in congenital heart disease: A review.

Genetic and genomic testing in pediatric CHD is becoming increasingly routine, and can have important psychosocial, clinical and reproductive implications. In this paper we highlight important challenges and considerations when providing genetics consults and testing in pediatric CHD and illustrate the role of a dedicated CHD genetics clinic. Key lessons include that a) a genetic diagnosis can have clinical utility that justifies testing early in life, b) adequate genetic counselling is crucial to ensure families are supported, understand the range of possible results, and are prepared for new or unexpected health information, and c) further integration of the clinical genetics and cardiology workflows will be required to effectively manage the burgeoning information arising from genetic testing. Our experience demonstrates that a dedicated CHD genetics clinic is a valuable addition to a multidisciplinary team providing care to children with CHD.