Missense mutations in TCF8 cause late-onset Fuchs corneal dystrophy and interact with FCD4 on chromosome 9p.

Fuchs corneal dystrophy (FCD) is a degenerative genetic disorder of the corneal endothelium that represents one of the most common causes of corneal transplantation in the United States. Despite its high prevalence (4% over the age of 40), the underlying genetic basis of FCD is largely unknown. Here we report missense mutations in TCF8, a transcription factor whose haploinsufficiency causes posterior polymorphous corneal dystrophy (PPCD), in a cohort of late-onset FCD patients. In contrast to PPCD-causing mutations, all of which are null, FCD-associated mutations encode rare missense changes suggested to cause loss of function by an in vivo complementation assay. Importantly, segregation of a recurring p.Q840P mutation in a large, multigenerational FCD pedigree showed this allele to be sufficient but not necessary for pathogenesis. Execution of a genome-wide scan conditioned for the presence of the 840P allele identified an additional late-onset FCD locus on chromosome 9p, whereas haplotype analysis indicated that the presence of the TCF8 allele and the disease haplotype on 9p leads to a severe FCD manifestation with poor prognosis. Our data suggest that PPCD and FCD are allelic variants of the same disease continuum and that genetic interaction between genes that cause corneal dystrophies can modulate the expressivity of the phenotype.

Evolution of technology, establishment of program, and clinical outcomes in pediatric extracorporeal membrane oxygenation: the "sickkids" experience.

Technological development has had a tremendous impact on the management of patients who require extracorporeal membrane oxygenation (ECMO). Team development and education are a vital component of a successful extracorporeal life support (ECLS) Program to reduce complications and subsequently improve clinical outcomes. We sought to review the evolution in technology, importance of team development and training, and report our experience at The Hospital for Sick Children, Toronto. There were a total of 576 ECMO runs in 534 patients (42 repeat ECMO runs) between January 1988 and June 2012. The use of ECMO for cardiac disease has increased in the last decade due to an expanded indication for ECMO in patients with single-ventricle physiology. Cardiac ECMO still remains a challenge in terms of survival (177/392, 45%). Although development of an ECLS program and team education facilitated extracorporeal cardiopulmonary resuscitation, clinical outcomes were not satisfactory (survival, 33%). The most common complications were hemorrhagic (13.8%), followed by renal (10.6%) and pulmonary dysfunction (6.9%). Advances in technology made management during ECMO safer, and the mechanical complications related to the ECMO system were 6.1%, including circuit changes due to thrombus formation, cannula repositioning, or optimization of size.

Genetic and functional dissection of HTRA1 and LOC387715 in age-related macular degeneration.

A common haplotype on 10q26 influences the risk of age-related macular degeneration (AMD) and encompasses two genes, LOC387715 and HTRA1. Recent data have suggested that loss of LOC387715, mediated by an insertion/deletion (in/del) that destabilizes its message, is causally related with the disorder. Here we show that loss of LOC387715 is insufficient to explain AMD susceptibility, since a nonsense mutation (R38X) in this gene that leads to loss of its message resides in a protective haplotype. At the same time, the common disease haplotype tagged by the in/del and rs11200638 has an effect on the transcriptional upregulation of the adjacent gene, HTRA1. These data implicate increased HTRA1 expression in the pathogenesis of AMD and highlight the importance of exploring multiple functional consequences of alleles in haplotypes that confer susceptibility to complex traits.

Toll-like receptor 3 and geographic atrophy in age-related macular degeneration.

BACKGROUND: Age-related macular degeneration is the most common cause of irreversible visual impairment in the developed world. Advanced age-related macular degeneration consists of geographic atrophy and choroidal neovascularization. The specific genetic variants that predispose patients to geographic atrophy are largely unknown. METHODS: We tested for an association between the functional toll-like receptor 3 gene (TLR3) variant rs3775291 (involving the substitution of phenylalanine for leucine at amino acid 412) and age-related macular degeneration in Americans of European descent. We also tested for the effect of TLR3 Leu and Phe variants on the viability of human retinal pigment epithelial cells in vitro and on apoptosis of retinal pigment epithelial cells from wild-type mice and Tlr3-knockout (Tlr3(-/-)) mice. RESULTS: The Phe variant (encoded by the T allele at rs3775291) was associated with protection against geographic atrophy (P=0.005). This association was replicated in two independent case-control series of geographic atrophy (P=5.43x10(-4) and P=0.002). No association was found between TLR3 variants and choroidal neovascularization. A prototypic TLR3 ligand induced apoptosis in a greater fraction of human retinal pigment epithelial cells with the Leu-Leu genotype than those with the Leu-Phe genotype and in a greater fraction of wild-type mice than Tlr3(-/-) mice. CONCLUSIONS: The TLR3 412Phe variant confers protection against geographic atrophy, probably by suppressing the death of retinal pigment epithelial cells. Since double-stranded RNA (dsRNA) can activate TLR3-mediated apoptosis, our results suggest a role of viral dsRNA in the development of geographic atrophy and point to the potential toxic effects of short-interfering-RNA therapies in the eye.

Post-intensive care syndrome following cardiothoracic critical care: Feasibility of a complex intervention.

OBJECTIVES: To describe the long-term outcomes of cardiac intensive care unit patients and their primary caregivers, and to explore the feasibility of implementing a complex intervention, designed to support problems associated with post-intensive care syndrome and post-intensive care syndrome-family, in the year following discharge from the cardiac intensive care unit. DESIGN: A complex multidisciplinary rehabilitation programme, delivered as a quality improvement initiative, in a single centre in the West of Scotland. Outcomes were measured using surveys of health related quality of life, self efficacy, anxiety, depression, pain, caregiver strain, and insomnia. PARTICIPANTS: Patients and their caregivers were invited to participate 12 weeks after hospital discharge. Twenty-seven patients and 23 caregivers attended the programme. RESULTS: Over 90% of patients had problems in at least one quality of life domain at baseline, 41% of patients had symptoms of anxiety and 22% had symptoms of depression. During the baseline visit, caregiver strain was present in 20% of caregivers, 57% had symptoms of anxiety, and 35% had symptoms of depression. Improvements in outcomes were seen in both patients and caregivers at 1-year follow-up. The programme was implemented, and iterative learning obtained about the content and the operationalization of the service, in order to understand feasibility. CONCLUSION: This small-scale quality improvement project has demonstrated that this complex multidisciplinary rehabilitation programme is feasible and has positive implications for patients following discharge from the cardiac intensive care unit, and their caregivers.

The functional intraoperative pulmonary blood flow study is a more sensitive predictor than preoperative anatomy for right ventricular pressure and physiologic tolerance of ventricular septal defect closure after complete unifocalization in patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collaterals.

BACKGROUND: The objective was to determine if intraoperative pulmonary artery (PA) flow studies after complete unifocalization correlate with postrepair hemodynamics for pulmonary atresia (PA), ventricular septal defects (VSD), and major aortopulmonary collaterals. METHODS AND RESULTS: Twenty patients (median age, 8 months; weight, 7.9 kg) underwent unifocalization between 2003 and 2008. A functional PA flow study was achieved by cannulating the unifocalized central PA before intracardiac repair and increasing flow incrementally to 2.5 L/min per m(2). Mean PA pressure (mPAP) was measured. The intent was to close the VSD for a mPAP of <30 mm Hg. Right ventricular systolic pressure (RVSP) and systemic systolic pressure were recorded. Total incorporated pulmonary segments, pulmonary segment artery ratio (ratio of incorporated segments to 18), and total neopulmonary artery index (the sum of major aortopulmonary collaterals and native PA index) were calculated. The VSD was successfully closed in 18 patients (90%). One attempted closure required an intraoperative fenestration. The study mPAP correlated with RVSP (rho=0.72; P=0.0027) and RVSP/systemic systolic pressure (rho=0.67; P=0.0063). Total neopulmonary artery index had a nonsignificant negative correlation with RVSP (rho=-0.42; P=0.079). Total incorporated pulmonary segments and pulmonary segment artery ratio were not correlated. Flow study mPAP had the highest accuracy in predicting successful VSD closure: area under the receiver-operator curve (0.83) versus total neopulmonary artery index (0.42), pulmonary segments (0.35), and pulmonary segment artery ratio (0.33). CONCLUSIONS: The intraoperative pulmonary flow study predicted postoperative physiology significantly better than did standard anatomic measures. Conventional measures should be used with caution when determining the possibility for complete repair.

Cavopulmonary support with a microaxial pump for the failing Fontan physiology.

The number of patients with the failing Fontan physiology is increasing. We tested a novel in situ microaxial pump (Impella) to support the failing atrio-pulmonary Fontan circulation in an acute pig model. A Fontan model was established in eight juvenile pigs by connecting the right atrium to the main pulmonary artery after tricuspid valve destruction. The Impella pump was inserted retrograde from the distal main pulmonary artery into the right atrium. Hemodynamics, blood gas, and echocardiographic data were compared among baseline, pure Fontan physiology (10 minutes), and mechanically assisted Fontan physiology (up to 12 hours). The Impella system generated a blood flow of 75-85 ml/kg/minute in six animals, and 55-65 ml/kg/minute in two animals. The mechanically assisted Fontan attained a significantly higher mean blood pressure (39.6 ± 7 vs. 24.7 ± 3.3 mm Hg, p < 0.01), lower central venous pressure (5 ± 2.4 vs. 12.8 ± 1.7 mm Hg, p < 0.01), and higher mixed venous saturation (60.4 ± 10.8 vs. 23.4 ± 8.4 mm Hg, p < 0.01) compared with pure Fontan physiology. Cardiac output and stroke volume were similar during baseline and mechanically assisted Fontan (p = not significant). This acute pig study demonstrated the feasibility of mechanical circulatory support in the failing Fontan physiology. The in situ microaxial pump maintained cardiac output while increasing blood pressure and reducing venous pressure.

Foam formation and acute air emboli with the maquet paediatric Quadrox I: a word of caution.

We report 3 cases of significant foam formation in the venous reservoir with the Maquet Quadrox-I oxygenator and VHK 31 000 reservoir system. All the 3 patients required maximal suction return during procedures, causing pressurization of reservoir and foam formation. Two patients experienced systemic air emboli, which were dealt with by means of retrograde cerebral perfusion and hypothermia with no neurological sequela. These events emphasize the importance of device selection in high-risk patients as well as crisis management.

TTC21B contributes both causal and modifying alleles across the ciliopathy spectrum.

Ciliary dysfunction leads to a broad range of overlapping phenotypes, collectively termed ciliopathies. This grouping is underscored by genetic overlap, where causal genes can also contribute modifier alleles to clinically distinct disorders. Here we show that mutations in TTC21B, which encodes the retrograde intraflagellar transport protein IFT139, cause both isolated nephronophthisis and syndromic Jeune asphyxiating thoracic dystrophy. Moreover, although resequencing of TTC21B in a large, clinically diverse ciliopathy cohort and matched controls showed a similar frequency of rare changes, in vivo and in vitro evaluations showed a significant enrichment of pathogenic alleles in cases (P < 0.003), suggesting that TTC21B contributes pathogenic alleles to ∼5% of ciliopathy cases. Our data illustrate how genetic lesions can be both causally associated with diverse ciliopathies and interact in trans with other disease-causing genes and highlight how saturated resequencing followed by functional analysis of all variants informs the genetic architecture of inherited disorders.

Linkage of a mild late-onset phenotype of Fuchs corneal dystrophy to a novel locus at 5q33.1-q35.2.

PURPOSE: To identify the disease locus associated with autosomal dominant Fuchs corneal dystrophy (FCD) in a large family and to compare the progression of severity in families mapped to the FCD1 and FCD2 loci. METHODS: Seventeen individuals in a large family were examined by slit lamp biomicroscopy. Blood samples were collected, DNA was extracted, and a genome-wide scan was performed with a microarray SNP chip. After initial generation of a genome-wide, two-point LOD score, linkage was confirmed and the critical interval was established by genotyping of short tandem repeat (STR) microsatellite markers. RESULTS: A genome-wide linkage scan localized the disease interval to the long arm of chromosome 5, with a maximum two-point parametric LOD score of 3.41. Haplotype analyses refined the critical interval to 5q33.1-q35.2, spanning a 27-Mb (29-cM) region. Clinical examination of affected individuals in this family revealed an early onset of FCD at approximately age 40, after which progression of the disease was significantly attenuated compared to the FCD1- and FCD2-linked families. CONCLUSIONS: Late-onset FCD is linked to a novel locus on 5q33.1-q35.2 and is associated with a milder severity in age at onset and rate of progression than the FCD1 and FCD2 loci. Correlation of individual genotypes with unique rates of disease progression will provide important tools for disease management, as well as for identifying the underlying genetic lesion, offer insight into the pathomechanism of FCD.