Cystic fibrosis disease modifiers: Complex genetics defines the phenotypic diversity in a monogenic disease

In many respects, genetic studies in cystic fibrosis (CF) serve as a paradigm for a human Mendelian genetic success story. From recognition of the condition as a heritable pathological entity to implementation of personalized treatments based on genetic findings, this multistep pathway of progress has focused on the genetic underpinnings of CF clinical disease. Along this path was the recognition that not all CFTR gene mutations produce the same disease and the recognition of the complex, multifactorial nature of CF genotype-phenotype relationships. The non-CFTR genetic components (gene modifiers) that contribute to variation in phenotype are the focus of this review. A multifaceted approach involving candidate gene studies, genome-wide association studies, and gene expression studies has revealed significant gene modifiers for multiple CF phenotypes. The bold challenges for the future are to integrate the findings into our understanding of CF pathogenesis and to use the knowledge to develop novel therapies

The Lamb shift in muonic hydrogen

The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the 2S1/2F=1–2P3/2F=2 energy splitting (Pohl et al., Nature, 466, 213 (2010)) in μp with an experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of rp = 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S–2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R∞ = 10 973 731.568 160 (16) m⁻¹ and the rms charge radius of the deuteron rd = 2.128 09 (31) fm

VNbCrMo refractory high-entropy alloy for nuclear applications

Refractory high-entropy alloys (RHEAs) with high melting points and low neutron absorption cross-section are sought for generation-IV fission and fusion reactors. A high throughput computational screening tool, Alloy Search and Predict (ASAP), was used to identify promising RHEA candidates from over 1 million four-element equimolar combinations. The selected VNbCrMo RHEA was further studied by CALPHAD to predict phase formation, which was compared to an experimentally produced ingot aged at 1200 °C. The VNbCrMo RHEA was found to constitute a majority bcc phase, with a 6% area fraction of C15-Laves formed at interdendritic regions, in contrast to the predictions of single-phase. The prediction of the yield strength by a model based upon edge dislocation mechanisms indicated 2.1 GPa at room temperature and 850 MPa at 1000 °C for the equimolar single bcc phase. The hardness of the alloy with C15-Laves was 748 HV (yield strength ∼2.4 GPa). Finally, the macroscopic neutron absorption cross-section was modelled for a wide range of energies. Displacements per atom per year and activation calculations, up to 1000 years after 2 years of continuous operation, in typical fusion and fission reactor scenarios were also performed using the inventory code FISPACT-II. This work gives new insight into the phase stability and performance of the VNbCrMo RHEA, which is compared with a similar design concept alloy, to assess the potential of novel RHEAs for use in advanced nuclear applications.Fil: Ferreirós, Pedro Antonio. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: von Tiedemann, S. O.. The University Of Birmingham (tub);Fil: Parkes, N.. The University Of Birmingham (tub);Fil: Gurah, D.. The University Of Birmingham (tub);Fil: King, D. J. M.. Imperial College London; Reino UnidoFil: Norman, P.. The University Of Birmingham (tub);Fil: Gilbert, M. R.. The University Of Birmingham (tub);Fil: Knowles, A. J.. Imperial College London; Reino Unid

Carrier frequencies of eleven mutations in eight genes associated with primary ciliary dyskinesia in the ashkenazi jewish population

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous, autosomal recessive disorder that results from functional and ultrastructural abnormalities of motile cilia. Patients with PCD have diverse clinical phenotypes that include chronic upper and lower respiratory tract infections, situs inversus, heterotaxy with or without congenital heart disease, and male infertility, among others. In this report, the carrier frequencies for eleven mutations in eight PCD-associated genes (DNAI1, DNAI2, DNAH5, DNAH11, CCDC114, CCDC40, CCDC65, and C21orf59) that had been found in individuals of Ashkenazi Jewish descent were investigated in order to advise on including them in existing clinical mutation panels for this population. Results showed relatively high carrier frequencies for the DNAH5 c.7502G>C mutation (0.58%), the DNAI2 c.1304G>A mutation (0.50%), and the C21orf59 c.735C>G mutation (0.48%), as well as lower frequencies for mutations in DNAI1, CCDC65, CCDC114, and DNAH11 (0.10– 0.29%). These results suggest that several of these genes should be considered for inclusion in carrier screening panels in the Ashkenazi Jewish population

Primary ciliary dyskinesia: Recent advances in diagnostics, genetics, and characterization of clinical disease

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous recessive disorder of motile cilia that leads to oto-sino-pulmonary diseases and organ laterality defects in approximately 50% of cases. The estimated incidence of PCD is approximately 1 per 15,000 births, but the prevalence of PCD is difficult to determine, primarily because of limitations in diagnostic methods that focus on testing ciliary ultrastructure and function. Diagnostic capabilities have recently benefitted from (1) documentation of low nasal nitric oxide production in PCD and (2) discovery of biallelic mutations in multiple PCD-causing genes. The use of these complementary diagnostic approaches shows that at least 30% of patients with PCD have normal ciliary ultrastructure. More accurate identification of patients with PCD has also allowed definition of a strong clinical phenotype, which includes neonatal respiratory distress in >80% of cases, daily nasal congestion and wet cough starting soon after birth, and early development of recurrent/chronic middle-ear and sinus disease. Recent studies, using advanced imaging and pulmonary physiologic assessments, clearly demonstrate early onset of lung disease in PCD, with abnormal air flow mechanics by age 6-8 years that is similar to cystic fibrosis, and age-dependent onset of bronchiectasis. The treatment ofPCDis not standardized, and there are no validated PCD-specific therapies. Most patients with PCD receive suboptimal management, which should include airway clearance, regular surveillance of pulmonary function and respiratory microbiology, and use of antibiotics targeted to pathogens. The PCD Foundation is developing a network of clinical centers, which should improve diagnosis and management of PCD

Nonantagonistic interactions between the sexes revealed by the ecological consequences of reproductive traits

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73504/1/j.1420-9101.2004.00779.x.pd

Mucus clearance and lung function in cystic fibrosis with hypertonic saline

BACKGROUND: Abnormal homeostasis of the volume of airway surface liquid in patients with cystic fibrosis is thought to produce defects in mucus clearance and airway defense. Through osmotic forces, hypertonic saline may increase the volume of airway surface liquid, restore mucus clearance, and improve lung function. METHODS: A total of 24 patients with cystic fibrosis were randomly assigned to receive treatment with inhaled hypertonic saline (5 ml of 7 percent sodium chloride) four times daily with or without pretreatment with amiloride. Mucus clearance and lung function were measured during 14-day baseline and treatment periods. RESULTS: Long-term inhalation of hypertonic saline without pretreatment with amiloride (i.e., with placebo pretreatment) resulted in a sustained (≥8 hours) increase in 1-hour rates of mucus clearance, as compared with those with amiloride pretreatment (14.0±2.0 vs. 7.0±1.5 percent, respectively; P = 0.02) and increased 24-hour rates of mucus clearance over baseline. Furthermore, inhalation of hypertonic saline with placebo improved the forced expiratory volume in one second (FEV 1) between the baseline period and the treatment period (mean difference, 6.62 percent; 95 percent confidence interval, 1.6 to 11.7; P = 0.02), whereas hypertonic saline with amiloride did not improve FEV 1 (mean difference, 2.9 percent; 95 percent confidence interval, -2.2 to 8.0; P = 0.23). Forced vital capacity (FVC), the forced expiratory flow between 25 and 75 percent of FVC (FEF 25-75), and respiratory symptoms also significantly improved in patients treated with hypertonic saline and placebo, whereas the residual volume as a proportion of total lung capacity (RV:TLC) did not change in either group. A comparison of the changes in lung function in the two groups showed no significant difference. In vitro data suggested that sustained hydration of airway surfaces was responsible for the sustained improvement in mucus clearance, whereas inhibition of osmotically driven water transport by amiloride accounted for the observed loss of clinical benefit. CONCLUSIONS: In patients with cystic fibrosis, inhalation of hypertonic saline produced a sustained acceleration of mucus clearance and improved lung function. This treatment may protect the lung from insults that reduce mucus clearance and produce lung disease

Investigation of the possible role of a novel gene, DPCD, in primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is an autosomal recessive disease caused by mutations that affect the proper function of cilia. Recently, deletion of DNA polymerase λ (Poll) in mice produced a phenotype characteristic of PCD (Kobayashi et al., 2002, Mol. Cell. Biol. 22:2769-2776). Because it is unclear how a mutation in a DNA polymerase would result in a specific defect in axonemes, the targeting construct was examined further. Analysis of the genomic region surrounding the Poll gene revealed an uncharacterized gene, named Dpcd, that is predicted to be transcribed from the opposite strand relative to Poll. The deletion of Poll would also remove the first exon of Dpcd. Because it is possible that the PCD phenotype observed is due to the absence of either gene, the expression of these genes during ciliogenesis of human airway epithelial cells was examined. Northern analysis demonstrated that DPCD expression increases during ciliated cell differentiation; the expression of POLL decreases. To examine directly whether DPCD is mutated in cases of human PCD, the complete coding sequence of DPCD was sequenced from 51 unrelated PCD patients. No disease-causing mutations were confirmed; however, one variant could not be excluded. Therefore, DPCD remains a novel candidate gene for PCD

In vivo airway surface liquid Cl- analysis with solid-state electrodes

The pathogenesis of cystic fibrosis (CF) airways disease remains controversial. Hypotheses that link mutations in CFTR and defects in ion transport to CF lung disease predict that alterations in airway surface liquid (ASL) isotonic volume, or ion composition, are critically important. ASL [Cl-] is pivotal in discriminating between these hypotheses, but there is no consensus on this value given the difficulty in measuring [Cl-] in the "thin" ASL (∼30 μm) in vivo. Consequently, a miniaturized solid-state electrode with a shallow depth of immersion was constructed to measure ASL [Cl-] in vivo. In initial experiments, the electrode measured [Cl-] in physiologic salt solutions, small volume (7.6 μl) test solutions, and in in vitro cell culture models, with ≥93% accuracy. Based on discrepancies in reported values and/or absence of data, ASL Cl- measurements were made in the following airway regions and species. First, ASL [Cl-] was measured in normal human nasal cavity and averaged 117.3 ± 11.2 mM (n = 6). Second, ASL [Cl-] measured in large airway (tracheobronchial) regions were as follows: rabbit trachea and bronchus = 114.3 ± 1.8 mM; (n = 6) and 126.9 ± 1.7 mM; (n = 3), respectively; mouse trachea = 112.8 ± 4.2 mM (n = 13); and monkey bronchus = 112.3 ± 10.9 mM (n = 3). Third, Cl- measurements were made in small (1-2 mm) diameter airways of the rabbit (108.3 ± 7.1 mM, n = 5) and monkey (128.5 ± 6.8 mM, n = 3). The measured [Cl-], in excess of 100 mM throughout all airway regions tested in multiple species, is consistent with the isotonic volume hypothesis to describe ASL physiology

Increasing concentration of inhaled saline with or without amiloride: Effect on mucociliary clearance in normal subjects

Mucociliary clearance is determined by ciliary activity and rheology of airway surface liquid. To test the hypothesis that mucociliary clearance would increase after inhalation of an osmotically active agent that would increase the volume of airway surface liquid, we measured mucociliary clearance in 16 normal subjects after inhalation of varying tonicities of saline alone, and after pretreatment with a Na+ channel blocker (amiloride). Subjects inhaled vehicle (0.12% saline) or amiloride, followed by inhalation of 0.12, 0.9, or 7% saline. Subsequently, mucociliary clearance rates were measured by γ scintigraphy of inhaled 99mTc Fe2O3. Mucociliary clearance of whole and peripheral lung was increased (approximately two-fold) after inhalation of increasing concentrations of saline (p < 0.04). Pretreatment with amiloride increased mucociliary clearance rates (approximately twofold) after inhalation of 0.12 and 0.9% saline (p < 0.05), but not 7% saline. The rates of mucociliary clearance by pretreatment with amiloride and 7% saline alone (approximately 1.4% per minute) approached the rapid mucocillary clearance rates (approximately 2.0% per minute) reported in systemic pseudohypoaldosteronism, which has loss-of-function mutations of the epithelial Na+ channel and an increased volume of airway surface liquid. We conclude that maneuvers that increase the volume of airway surface liquid are associated with increased rates of mucociliary clearance in normal subjects