Mouse models of patent ductus arteriosus (PDA) and their relevance for human PDA.

The ductus arteriosus (DA) is a unique fetal vascular shunt, which allows blood to bypass the developing lungs in utero. After birth, changes in complex signaling pathways lead to constriction and permanent closure of the DA. The persistent patency of the DA (PDA) is a common disorder in preterm infants, yet the underlying causes of PDA are not fully defined. Although limits on the availability of human DA tissues prevent comprehensive studies on the mechanisms of DA function, mouse models have been developed that reveal critical pathways in DA regulation. Over 20 different transgenic models of PDA in mice have been described, with implications for human DA biology. Similarly, we enumerate 224 human single-gene syndromes that are associated with PDA, including a small subset that consistently feature PDA as a prominent phenotype. Comparison and functional analyses of these genes provide insight into DA development and identify key regulatory pathways that may serve as potential therapeutic targets for the management of PDA.

Liver Transplantation in Children with Urea Cycle Disorders: The Importance of Minimizing Waiting Time.

Liver transplantation (LT) for children with urea cycle disorders (UCDs) is capable of correcting the enzymatic defect and preventing progressive neurologic injury. We describe the characteristics and outcomes of pediatric LT recipients with UCDs. We identified all pediatric (<18 years) LT candidates with UCDs in the United Network for Organ Sharing (UNOS) database (February 2002 to September 2020). Multivariable Cox and logistic regression were used to determine risk factors for graft loss and cognitive delay, respectively. Of 424 patients, 1.9% (8/424) experienced waitlist mortality and 95.0% underwent LT (403/424). The most frequently encountered UCDs in our cohort were ornithine transcarbamylase deficiency (46.2%), citrullinemia (20.3%), and argininosuccinic aciduria (ASA; 12.9%). The 1-, 3-, and 5-year graft survival rates were 90.4%, 86.3%, and 85.2%, respectively. Multivariable analysis showed a decreased risk of graft loss with increasing weight at LT (adjusted hazard ratio [aHR], 0.96; 95% confidence interval [CI], 0.94-0.99; P = 0.02), male sex (aHR, 0.49; 95% CI, 0.28-0.85; P = 0.01), and ASA diagnosis (aHR, 0.29; 95% CI, 0.09-0.98; P = 0.047), when adjusting for location (intensive care/hospital/home) and graft type (both P ≥ 0.65). In multivariable logistic regression, waitlist time (adjusted odds ratio [aOR], 1.10; 95% CI, 1.02-1.17; P = 0.009) and male sex (aOR, 1.71; 95% CI, 1.02-2.88; P = 0.04) were associated with increased odds of long-term cognitive delay. Waitlist duration is associated with a long-term risk of cognitive delay. Given excellent long-term outcomes, early LT evaluation should be considered in all children with UCDs to prevent progressive neurologic injury and optimize cognitive outcomes.

Pathogenic variants in USP7 cause a neurodevelopmental disorder with speech delays, altered behavior, and neurologic anomalies.

PURPOSE: Haploinsufficiency of USP7, located at chromosome 16p13.2, has recently been reported in seven individuals with neurodevelopmental phenotypes, including developmental delay/intellectual disability (DD/ID), autism spectrum disorder (ASD), seizures, and hypogonadism. Further, USP7 was identified to critically incorporate into the MAGEL2-USP7-TRIM27 (MUST), such that pathogenic variants in USP7 lead to altered endosomal F-actin polymerization and dysregulated protein recycling. METHODS: We report 16 newly identified individuals with heterozygous USP7 variants, identified by genome or exome sequencing or by chromosome microarray analysis. Clinical features were evaluated by review of medical records. Additional clinical information was obtained on the seven previously reported individuals to fully elucidate the phenotypic expression associated with USP7 haploinsufficiency. RESULTS: The clinical manifestations of these 23 individuals suggest a syndrome characterized by DD/ID, hypotonia, eye anomalies,feeding difficulties, GERD, behavioral anomalies, and ASD, and more specific phenotypes of speech delays including a nonverbal phenotype and abnormal brain magnetic resonance image findings including white matter changes based on neuroradiologic examination. CONCLUSION: The consistency of clinical features among all individuals presented regardless of de novo USP7 variant type supports haploinsufficiency as a mechanism for pathogenesis and refines the clinical impact faced by affected individuals and caregivers.

Duplicated Enhancer Region Increases Expression of CTSB and Segregates with Keratolytic Winter Erythema in South African and Norwegian Families.

Keratolytic winter erythema (KWE) is a rare autosomal-dominant skin disorder characterized by recurrent episodes of palmoplantar erythema and epidermal peeling. KWE was previously mapped to 8p23.1-p22 (KWE critical region) in South African families. Using targeted resequencing of the KWE critical region in five South African families and SNP array and whole-genome sequencing in two Norwegian families, we identified two overlapping tandem duplications of 7.67 kb (South Africans) and 15.93 kb (Norwegians). The duplications segregated with the disease and were located upstream of CTSB, a gene encoding cathepsin B, a cysteine protease involved in keratinocyte homeostasis. Included in the 2.62 kb overlapping region of these duplications is an enhancer element that is active in epidermal keratinocytes. The activity of this enhancer correlated with CTSB expression in normal differentiating keratinocytes and other cell lines, but not with FDFT1 or NEIL2 expression. Gene expression (qPCR) analysis and immunohistochemistry of the palmar epidermis demonstrated significantly increased expression of CTSB, as well as stronger staining of cathepsin B in the stratum granulosum of affected individuals than in that of control individuals. Analysis of higher-order chromatin structure data and RNA polymerase II ChIA-PET data from MCF-7 cells did not suggest remote effects of the enhancer. In conclusion, KWE in South African and Norwegian families is caused by tandem duplications in a non-coding genomic region containing an active enhancer element for CTSB, resulting in upregulation of this gene in affected individuals.

USP7 Acts as a Molecular Rheostat to Promote WASH-Dependent Endosomal Protein Recycling and Is Mutated in a Human Neurodevelopmental Disorder.

Endosomal protein recycling is a fundamental cellular process important for cellular homeostasis, signaling, and fate determination that is implicated in several diseases. WASH is an actin-nucleating protein essential for this process, and its activity is controlled through K63-linked ubiquitination by the MAGE-L2-TRIM27 ubiquitin ligase. Here, we show that the USP7 deubiquitinating enzyme is an integral component of the MAGE-L2-TRIM27 ligase and is essential for WASH-mediated endosomal actin assembly and protein recycling. Mechanistically, USP7 acts as a molecular rheostat to precisely fine-tune endosomal F-actin levels by counteracting TRIM27 auto-ubiquitination/degradation and preventing overactivation of WASH through directly deubiquitinating it. Importantly, we identify de novo heterozygous loss-of-function mutations of USP7 in individuals with a neurodevelopmental disorder, featuring intellectual disability and autism spectrum disorder. These results provide unanticipated insights into endosomal trafficking, illuminate the cooperativity between an ubiquitin ligase and a deubiquitinating enzyme, and establish a role for USP7 in human neurodevelopmental disease.

Neuropathy target esterase impairments cause Oliver-McFarlane and Laurence-Moon syndromes.

BACKGROUND: Oliver-McFarlane syndrome is characterised by trichomegaly, congenital hypopituitarism and retinal degeneration with choroidal atrophy. Laurence-Moon syndrome presents similarly, though with progressive spinocerebellar ataxia and spastic paraplegia and without trichomegaly. Both recessively inherited disorders have no known genetic cause. METHODS: Whole-exome sequencing was performed to identify the genetic causes of these disorders. Mutations were functionally validated in zebrafish pnpla6 morphants. Embryonic expression was evaluated via in situ hybridisation in human embryonic sections. Human neurohistopathology was performed to characterise cerebellar degeneration. Enzymatic activities were measured in patient-derived fibroblast cell lines. RESULTS: Eight mutations in six families with Oliver-McFarlane or Laurence-Moon syndrome were identified in the PNPLA6 gene, which encodes neuropathy target esterase (NTE). PNPLA6 expression was found in the developing human eye, pituitary and brain. In zebrafish, the pnpla6 curly-tailed morphant phenotype was fully rescued by wild-type human PNPLA6 mRNA and not by mutation-harbouring mRNAs. NTE enzymatic activity was significantly reduced in fibroblast cells derived from individuals with Oliver-McFarlane syndrome. Intriguingly, adult brain histology from a patient with highly overlapping features of Oliver-McFarlane and Laurence-Moon syndromes revealed extensive cerebellar degeneration and atrophy. CONCLUSIONS: Previously, PNPLA6 mutations have been associated with spastic paraplegia type 39, Gordon-Holmes syndrome and Boucher-Neuhäuser syndromes. Discovery of these additional PNPLA6-opathies further elucidates a spectrum of neurodevelopmental and neurodegenerative disorders associated with NTE impairment and suggests a unifying mechanism with diagnostic and prognostic importance.

Homozygous loss of DIAPH1 is a novel cause of microcephaly in humans.

The combination of family-based linkage analysis with high-throughput sequencing is a powerful approach to identifying rare genetic variants that contribute to genetically heterogeneous syndromes. Using parametric multipoint linkage analysis and whole exome sequencing, we have identified a gene responsible for microcephaly (MCP), severe visual impairment, intellectual disability, and short stature through the mapping of a homozygous nonsense alteration in a multiply-affected consanguineous family. This gene, DIAPH1, encodes the mammalian Diaphanous-related formin (mDia1), a member of the diaphanous-related formin family of Rho effector proteins. Upon the activation of GTP-bound Rho, mDia1 generates linear actin filaments in the maintenance of polarity during adhesion, migration, and division in immune cells and neuroepithelial cells, and in driving tangential migration of cortical interneurons in the rodent. Here, we show that patients with a homozygous nonsense DIAPH1 alteration (p.Gln778*) have MCP as well as reduced height and weight. diap1 (mDia1 knockout (KO))-deficient mice have grossly normal body and brain size. However, our histological analysis of diap1 KO mouse coronal brain sections at early and postnatal stages shows unilateral ventricular enlargement, indicating that this mutant mouse shows both important similarities as well as differences with human pathology. We also found that mDia1 protein is expressed in human neuronal precursor cells during mitotic cell division and has a major impact in the regulation of spindle formation and cell division.

Renal teratogens.

In utero exposure to certain drugs early in pregnancy may adversely affect nephrogenesis. Exposure to drugs later in pregnancy may affect the renin-angiotensin system, which could have an impact on fetal or neonatal renal function. Reduction in nephron number and renal function could have adverse consequences for the child several years later. Data are limited on the information needed to guide decisions for patients and providers regarding the use of certain drugs in pregnancy. The study of drug nephroteratogenicity has not been systematized, a large, standardized, global approach is needed to evaluate the renal risks of in utero drug exposures.

Brief report: Risk of adverse fetal outcomes associated with immunosuppressive medications for chronic immune-mediated diseases in pregnancy.

OBJECTIVE: To assess the risk of adverse fetal outcomes following exposure to individual immunosuppressive drugs in pregnant women with chronic immune-mediated diseases. METHODS: Health plan data were obtained from the Tennessee Medicaid and Kaiser Permanente Northern California and Southern California claims databases, with linkage to both vital records and medical records. Women with inflammatory arthropathies, those with systemic lupus erythematosus, and those with inflammatory bowel disease who filled prescriptions for immunosuppressive treatments during pregnancy were included. Major congenital malformations, fetal deaths, and life-threatening neonatal complications were identified from the electronic data and validated with medical record review. RESULTS: The cohort included 608 infants, including 437 with exposure to immunosuppressive drugs during the mother's pregnancy (402 during the first trimester, and 35 during the second and third trimester only) and 171 whose mothers filled prescriptions for immunosuppressive treatments before, but not during, pregnancy. There were 25 pregnancies (4.1% of the cohort) with confirmed major congenital malformations, and 10 fetal deaths (1.6% of the cohort). Among 113 preterm infants with exposures during pregnancy, 23 (20.4%) had life-threatening neonatal complications, and among 485 term infants, 10 (2.1%) had life-threatening complications. Compared to the reference group (treatment before, but not during, pregnancy), the risk ratios (RRs) for adverse fetal outcomes associated with immunosuppressive treatments (by exposure category) during pregnancy included the following: methotrexate (RR 1.39, 95% confidence interval [95% CI] 0.43-4.53), tumor necrosis factor inhibitors (RR 0.98, 95% CI 0.38-2.55), hydroxychloroquine (RR 1.33, 95% CI 0.69-2.55), and other immunosuppressive medications (RR 0.98, 95% CI 0.48-1.98). CONCLUSION: In this study, there was no evidence of a large increase in risk of adverse fetal outcomes from first-trimester exposure to immunosuppressive medications, although the confidence intervals for the risk ratios were wide. Further studies will be needed as use of these medications increases over time.

TM4SF20 ancestral deletion and susceptibility to a pediatric disorder of early language delay and cerebral white matter hyperintensities.

White matter hyperintensities (WMHs) of the brain are important markers of aging and small-vessel disease. WMHs are rare in healthy children and, when observed, often occur with comorbid neuroinflammatory or vasculitic processes. Here, we describe a complex 4 kb deletion in 2q36.3 that segregates with early childhood communication disorders and WMH in 15 unrelated families predominantly from Southeast Asia. The premature brain aging phenotype with punctate and multifocal WMHs was observed in ~70% of young carrier parents who underwent brain MRI. The complex deletion removes the penultimate exon 3 of TM4SF20, a gene encoding a transmembrane protein of unknown function. Minigene analysis showed that the resultant net loss of an exon introduces a premature stop codon, which, in turn, leads to the generation of a stable protein that fails to target to the plasma membrane and accumulates in the cytoplasm. Finally, we report this deletion to be enriched in individuals of Vietnamese Kinh descent, with an allele frequency of about 1%, embedded in an ancestral haplotype. Our data point to a constellation of early language delay and WMH phenotypes, driven by a likely toxic mechanism of TM4SF20 truncation, and highlight the importance of understanding and managing population-specific low-frequency pathogenic alleles.

Correlation of heart rate and cardiac dysfunction in Duchenne muscular dystrophy.

Sinus tachycardia is common in cases of Duchenne muscular dystrophy (DMD). The authors hypothesized that an elevated heart rate would herald cardiomyopathy onset. A retrospective case-control study was performed with 55 DMD boys and 150 age-matched control boys. The variables were age, heart rate, shortening fraction, and left ventricular end-diastolic dimension. Cardiomyopathy was defined as a shortening fraction less than 28%. The DMD boys had a higher initial heart rate with no baseline echocardiographic evidence of cardiomyopathy. The control subjects showed a statistically significant age-related decline in heart rate (p = 0.001) but not the DMD boys. Cardiomyopathy developed in 17 of the 55 DMD boys over a period of 4.6 ± 1.6 years. The DMD upper and lower heart rate groups were similar in age, follow-up time, and initial shortening fraction, yet cardiomyopathy developed in 14 (42%) of 33 upper quartile boys but only 3 (14%) of 22 lower quartile DMD boys (odds ratio, 6.5 (95% confidence interval, 1.15-18.92; p < 0.05). Compared with the control subjects, the DMD boys had a higher resting heart rate and a lack of age-related heart rate decline. The DMD boys in the upper heart rate quartile were more likely to progress to cardiomyopathy than those in the lower quartiles. This study establishes heart rate elevation as a statistically significant risk factor for cardiomyopathy. Further studies may define heart rate cutoffs for early pharmacologic intervention for incipient cardiomyopathy.

A balanced t(10;15) translocation in a male patient with developmental language disorder.

We report the clinical and cytogenetic findings on a male child with developmental language disorder, no physical abnormalities, and a balanced t(10;15)(q24.1;q21.1) translocation. As the child's parents are unavailable for investigations, it is unclear whether the translocation is inherited or de novo. Fluorescence in situ hybridization (FISH) analyses were carried out using specific RP11-BAC clones mapping near 15q21.1 and 10q24.1 to refine the location of the breakpoints. The breakpoint on 15q21.1 interrupts the SEMA6D gene and the breakpoint on 10q24.1 is located between the ENTPD1 and CCNJ genes. The SEMA6D gene was further investigated in samples of individuals with developmental language disorders and controls; this investigation offered further evidence of the involvement of SEMA6D with developmental language disorders.

Investigation of 95 variants identified in a genome-wide study for association with mortality after acute coronary syndrome.

BACKGROUND: Genome-wide association studies (GWAS) have identified new candidate genes for the occurrence of acute coronary syndrome (ACS), but possible effects of such genes on survival following ACS have yet to be investigated. METHODS: We examined 95 polymorphisms in 69 distinct gene regions identified in a GWAS for premature myocardial infarction for their association with post-ACS mortality among 811 whites recruited from university-affiliated hospitals in Kansas City, Missouri. We then sought replication of a positive genetic association in a large, racially diverse cohort of myocardial infarction patients (N = 2284) using Kaplan-Meier survival analyses and Cox regression to adjust for relevant covariates. Finally, we investigated the apparent association further in 6086 additional coronary artery disease patients. RESULTS: After Cox adjustment for other ACS risk factors, of 95 SNPs tested in 811 whites only the association with the rs6922269 in MTHFD1L was statistically significant, with a 2.6-fold mortality hazard (P = 0.007). The recessive A/A genotype was of borderline significance in an age- and race-adjusted analysis of the entire combined cohort (N = 3095; P = 0.052), but this finding was not confirmed in independent cohorts (N = 6086). CONCLUSIONS: We found no support for the hypothesis that the GWAS-identified variants in this study substantially alter the probability of post-ACS survival. Large-scale, collaborative, genome-wide studies may be required in order to detect genetic variants that are robustly associated with survival in patients with coronary artery disease.

Genetic risk score does not correlate with body mass index of Latina women in a clinical trial.

Obesity disproportionately affects Latina women. Common genetic variants are convincingly associated with body mass index (BMI) and may be used to create genetic risk scores (GRS) for obesity that could define genetically influenced forms of obesity and alter response to clinical trial interventions. The objective of this study was (1) to identify the frequency and effect size of common obesity genetic variants in Latina women; (2) to determine the clinical utility of a GRS for obesity with Latina women participating in a community-based clinical trial. DNA from 85 Latina women was genotyped for eight genetic variants previously associated with BMI in Caucasians, but not yet assessed in Latina populations. The main outcome measure was the correlation of GRS (sum of eight risk alleles) with BMI, waist circumference, and percent body fat. A majority (83%) of participants had a BMI ≥25. Frequency of loci near FTO, MC4R, and GNPDA2 were lower in Latinas than Caucasians. Association of each locus with BMI was lower in Latinas compared to Caucasians with no significant correlations with BMI. We conclude that an eight locus GRS has no clinical utility for explaining obesity or predicting response to intervention in Latina women participating in a clinical trial.

Common polymorphisms in human lysyl oxidase genes are not associated with the adolescent idiopathic scoliosis phenotype.

BACKGROUND: Although adolescent idiopathic scoliosis affects approximately 3% of adolescents, the genetic contributions have proven difficult to identify. Work in model organisms, including zebrafish, chickens, and mice, has implicated the lysyl oxidase family of enzymes in the development of scoliosis. We hypothesized that common polymorphisms in the five human lysyl oxidase genes (LOX, LOXL1, LOXL2, LOXL3, and LOXL4) may be associated with the phenotype of adolescent idiopathic scoliosis. METHODS: This was a case-control genetic association study. A total of 112 coding and tag SNPs in LOX, LOXL1, LOXL2, LOXL3, and LOXL4 were genotyped in a discovery cohort of 138 cases and 411 controls. Genotypes were tested for association with adolescent idiopathic scoliosis by logistic regression with a two degree of freedom genotypic model and gender as a covariate. Fourteen SNPs with p < 0.1 in the discovery phase were genotyped in an independent replication cohort of 400 cases and 506 controls. RESULTS: No evidence for significant association was found between coding or tag SNPs in LOX, LOXL1, LOXL2, LOXL3, and LOXL4 and the phenotype of adolescent idiopathic scoliosis. CONCLUSIONS: Despite suggestive evidence in model organisms, common variants and known coding SNPs in the five human lysyl oxidase genes do not confer increased genotypic risk for adolescent idiopathic scoliosis. The above methodology does not address rare variants or individually private mutations in these genes, and future research may focus on this area.

Vaccines are not associated with metabolic events in children with urea cycle disorders.

BACKGROUND: Despite the success of childhood immunizations in prevention of infectious diseases, questions remain about the safety of vaccines in medically fragile children with inborn errors of metabolism such as urea cycle disorders (UCDs). Patients with UCDs are subject to hyperammonemic episodes (HAEs) after infection, fever, or other stressors. OBJECTIVE: We sought to assess the risk of HAEs that required urgent care or hospitalization after routine vaccinations in pediatric patients with underlying UCDs. METHODS: This was a retrospective investigation of vaccine safety in children with UCDs within the longitudinal Rare Diseases Clinical Research Consortium for UCD. Postvaccination exposure periods were defined as 7 or 21 days after any immunization. The association of vaccines and HAEs was modeled by using conditional Poisson regression, adjusting for age, and using a self-controlled case series method including all patients with ≥1 HAE and with any vaccine exposure. RESULTS: The study enrolled 169 children younger than 18 years. Of these children, 74 had records of at least 1 HAE and at least 1 vaccination. With adjustment for age, there was no increase in relative incidence of HAEs in either the 7-day (1.31 [95% confidence interval (CI): 0.80-2.13]) or 21-day (1.05 [95% CI: 0.74-1.47]) exposure period after vaccination compared with HAEs outside of the vaccination periods. No vaccine type was associated with significantly more HAEs. CONCLUSIONS: We found no statistically significant association between childhood immunizations and HAEs in children with UCDs. The results support the safety of immunization in this medically vulnerable population.

Variation in recovery: Role of gender on outcomes of young AMI patients (VIRGO) study design.

BACKGROUND: Among individuals with ischemic heart disease, young women with an acute myocardial infarction (AMI) represent an extreme phenotype associated with an excess mortality risk. Although women younger than 55 years of age account for less than 5% of hospitalized AMI events, almost 16 000 deaths are reported annually in this group, making heart disease a leading killer of young women. Despite a higher risk of mortality compared with similarly aged men, young women have been the subject of few studies. METHODS AND RESULTS: Variation in Recovery: Role of Gender on Outcomes of Young AMI Patients (VIRGO) is a large, observational study of the presentation, treatment, and outcomes of young women and men with AMI. VIRGO will enroll 2000 women, 18 to 55 years of age, with AMI and a comparison cohort of 1000 men with AMI from more than 100 participating hospitals. The aims of the study are to determine sex differences in the distribution and prognostic importance of biological, demographic, clinical, and psychosocial risk factors; to determine whether there are sex differences in the quality of care received by young AMI patients; and to determine how these factors contribute to sex differences in outcomes (including mortality, hospitalization, and health status). Blood serum and DNA for consenting participants will be stored for future studies. CONCLUSIONS: VIRGO will seek to identify novel and prognostic factors that contribute to outcomes in this young AMI population. Results from the study will be used to develop clinically useful risk-stratification models for young AMI patients, explain sex differences in outcomes, and identify targets for intervention.

Lack of association between the Trp719Arg polymorphism in kinesin-like protein-6 and coronary artery disease in 19 case-control studies.

OBJECTIVES: We sought to replicate the association between the kinesin-like protein 6 (KIF6) Trp719Arg polymorphism (rs20455), and clinical coronary artery disease (CAD). BACKGROUND: Recent prospective studies suggest that carriers of the 719Arg allele in KIF6 are at increased risk of clinical CAD compared with noncarriers. METHODS: The KIF6 Trp719Arg polymorphism (rs20455) was genotyped in 19 case-control studies of nonfatal CAD either as part of a genome-wide association study or in a formal attempt to replicate the initial positive reports. RESULTS: A total of 17,000 cases and 39,369 controls of European descent as well as a modest number of South Asians, African Americans, Hispanics, East Asians, and admixed cases and controls were successfully genotyped. None of the 19 studies demonstrated an increased risk of CAD in carriers of the 719Arg allele compared with noncarriers. Regression analyses and fixed-effects meta-analyses ruled out with high degree of confidence an increase of ≥2% in the risk of CAD among European 719Arg carriers. We also observed no increase in the risk of CAD among 719Arg carriers in the subset of Europeans with early-onset disease (younger than 50 years of age for men and younger than 60 years of age for women) compared with similarly aged controls as well as all non-European subgroups. CONCLUSIONS: The KIF6 Trp719Arg polymorphism was not associated with the risk of clinical CAD in this large replication study.