Gene modifiers in cystic fibrosis

LMTK2 switches on canonical TGF-β1 signaling in human bronchial epithelial cells

Transforming growth factor (TGF-β1) is a critical profibrotic mediator in chronic lung disease, and there are no specific strategies to mitigate its adverse effects. Activation of TGF-β1 signaling is a multipart process involving ligands, transmembrane receptors, and transcription factors. In addition, an intricate network of adaptor proteins fine-tunes the signaling strength, duration, and activity. Namely, Smad7 recruits growth arrest and DNA damage (GADD34) protein that then interacts with the catalytic subunit of phosphoprotein phosphatase 1 (PP1c) to inactivate TGF-β receptor (TβR)-I and downregulate TGF-β1 signaling. Little is known about how TGF-β1 releases TβR-I from the GADD34-PP1c inhibition to activate its signaling. Transmembrane lemur tyrosine kinase 2 (LMTK2) is a PP1c inhibitor, and our published data showed that TGF-β1 recruits LMTK2 to the cell surface. Here, we tested the hypothesis that TGF-β1 recruits LMTK2 to inhibit PP1c, allowing activation of TβR-I. First, LMTK2 interacted with the TGF-β1 pathway in the human bronchial epithelium at multiple checkpoints. Second, TGF-β1 inhibited PP1c by an LMTK2-dependent mechanism. Third, TGF-β1 used LMTK2 to activate canonical Smad3-mediated signaling. We propose a model whereby the LMTK2-PP1c and Smad7-GADD34-PP1c complexes serve as on-and-off switches in the TGF-β1 signaling in human bronchial epithelium.NEW & NOTEWORTHY Activation of the transforming growth factor (TGF)-β1 signaling pathway is complex, involving many ligands, transmembrane receptors, transcription factors, and modulating proteins. The mechanisms of TGF-β1 signaling activation/inactivation are not fully understood. We propose for the first time a model by which transmembrane lemur tyrosine kinase 2 (LMTK2) forms a complex with phosphoprotein phosphatase 1 (PP1c) to activate TGF-β1 signaling and Smad7, growth arrest and DNA damage (GADD34), and PP1C form a complex to inactivate TGF-β1 signaling in human bronchial epithelium.

CFTR-Related Metabolic Syndrome: Genetic Variants Increasing Pancreatitis Risk in the Pediatric Puerto Rican Population

CFTR-related metabolic syndrome (CRMS) is a novel diagnosis due to widespread use of and advances in the newborn screening (NBS) process for cystic fibrosis (CF) in the United States of America, allowing for the diagnosis of asymptomatic children with CF. Before 2015, a large Puerto Rican pediatric population was not screened for CF in the NBS test. Studies have shown that patients presenting with idiopathic recurrent or chronic pancreatitis have an increased frequency of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. We present a retrospective chart review of 12 pediatric cases (n = 12) that were presented to an outpatient community clinic with clinical manifestations associated with CF. The pancreatic insufficiency prevalence (PIP) score was calculated on CFTR mutations. The mutations considered for the calculation of the PIP score were: F508del (c.1521_1523del), V201M (c.601G > A), I507del (c.1519_1521del), and L1335P (c.4004T > C). V201M mutation was classified as mild in both PIP scores, and a correlation with pancreatitis was noted. Clinical manifestations vary in cases with the V201M variant (c.601G > A). One case was diagnosed with CFTR-related disorder (CRD) and recurrent pancreatitis. It is important to consider CRMS or CRD as a differential diagnosis in the pediatric population of Puerto Rico due to the implications and increased risk of pancreatitis and other CF-related complications.

S945L-CFTR molecular dynamics, functional characterization and tezacaftor/ivacaftor efficacy in vivo and in vitro in matched pediatric patient-derived cell models

Cystic Fibrosis (CF) results from over 400 different disease-causing mutations in the CF Transmembrane Conductance Regulator (CFTR) gene. These CFTR mutations lead to numerous defects in CFTR protein function. A novel class of targeted therapies (CFTR modulators) have been developed that can restore defects in CFTR folding and gating. This study aimed to characterize the functional and structural defects of S945L-CFTR and interrogate the efficacy of modulators with two modes of action: gating potentiator [ivacaftor (IVA)] and folding corrector [tezacaftor (TEZ)]. The response to these modulators in vitro in airway differentiated cell models created from a participant with S945L/G542X-CFTR was correlated with in vivo clinical outcomes of that participant at least 12 months pre and post modulator therapy. In this participants' airway cell models, CFTR-mediated chloride transport was assessed via ion transport electrophysiology. Monotherapy with IVA or TEZ increased CFTR activity, albeit not reaching statistical significance. Combination therapy with TEZ/IVA significantly (p = 0.02) increased CFTR activity 1.62-fold above baseline. Assessment of CFTR expression and maturation via western blot validated the presence of mature, fully glycosylated CFTR, which increased 4.1-fold in TEZ/IVA-treated cells. The in vitro S945L-CFTR response to modulator correlated with an improvement in in vivo lung function (ppFEV₁) from 77.19 in the 12 months pre TEZ/IVA to 80.79 in the 12 months post TEZ/IVA. The slope of decline in ppFEV1 significantly (p = 0.02) changed in the 24 months post TEZ/IVA, becoming positive. Furthermore, there was a significant improvement in clinical parameters and a fall in sweat chloride from 68 to 28 mmol/L. The mechanism of dysfunction of S945L-CFTR was elucidated by in silico molecular dynamics (MD) simulations. S945L-CFTR caused misfolding of transmembrane helix 8 and disruption of the R domain, a CFTR domain critical to channel gating. This study showed in vitro and in silico that S945L causes both folding and gating defects in CFTR and demonstrated in vitro and in vivo that TEZ/IVA is an efficacious modulator combination to address these defects. As such, we support the utility of patient-derived cell models and MD simulations in predicting and understanding the effect of modulators on CFTR function on an individualized basis.

From membrane to mineralization: the curious case of the ABCC6 transporter

ATP-binding cassette subfamily C member 6 gene/protein (ABCC6) is an ATP-dependent transmembrane transporter predominantly expressed in the liver and the kidney. ABCC6 first came to attention in human medicine when it was discovered in 2000 that mutations in its encoding gene, ABCC6, caused the autosomal recessive multisystemic mineralization disease pseudoxanthoma elasticum (PXE). Since then, the physiological and pathological roles of ABCC6 have been the subject of intense research. In the last 20 years, significant findings have clarified ABCC6 structure as well as its physiological role in mineralization homeostasis in humans and animal models. Yet, several facets of ABCC6 biology remain currently incompletely understood, ranging from the precise nature of its substrate(s) to the increasingly complex molecular genetics. Nonetheless, advances in our understanding of pathophysiological mechanisms causing mineralization lead to several treatment options being suggested or already tested in pilot clinical trials for ABCC6 deficiency. This review highlights current knowledge of ABCC6 and the challenges ahead, particularly the attempts to translate basic science into clinical practice.

Azithromycin and ciprofloxacin have a chloroquine-like effect on respiratory epithelial cells

There is interest in the use of chloroquine/hydroxychloroquine (CQ/HCQ) and azithromycin (AZT) in COVID-19 therapy. Employing cystic fibrosis respiratory epithelial cells, here we show that drugs AZT and ciprofloxacin (CPX) act as acidotropic lipophilic weak bases and confer in vitro effects on intracellular organelles similar to the effects of CQ. These seemingly disparate FDA-approved antimicrobials display a common property of modulating pH of endosomes and trans-Golgi network. We believe this may in part help understand the potentially beneficial effects of CQ/HCQ and AZT in COVID-19, and that the present considerations of HCQ and AZT for clinical trials should be extended to CPX.

Disease-modifying genetic factors in cystic fibrosis

PURPOSE OF REVIEW

To compile data from the past 10 years regarding the role of modifying genes in cystic fibrosis (CF).

RECENT FINDINGS

CF is a model disease for understanding of the action of modifying genes. Although it is a monogenic (CFTR) autosomal recessive disease, CF presents with wide phenotypic variability. In CF, variability occurs with different intensity among patients by each organ, being organ-specific, resulting from the mutual interaction of environmental and genetic factors, including CFTR mutations and various other genes, most of which are associated with inflammatory processes. In individuals, using precision medicine, gene modification studies have revealed individualized responses to drugs depending on particular CFTR mutations and modifying genes, most of which are alternative ion channels.

SUMMARY

Studies of modifying genes in CF allow: understanding of clinical variability among patients with the same CFTR genotype; evaluation of precision medicine; understanding of environmental and genetic effects at the organ level; understanding the involvement of genetic variants in inflammatory responses; improvements in genetic counseling; understanding the involvement of genetic variants in inflammatory responses in lung diseases, such as asthma; and understanding the individuality of the person with the disease.

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.

Early childhood lung function is a stronger predictor of adolescent lung function in cystic fibrosis than early Pseudomonas aeruginosa infection

OBJECTIVE

Pseudomonas aeruginosa has been suggested as a major determinant of poor pulmonary outcomes in cystic fibrosis (CF), although other factors play a role. Our objective was to investigate the association of early childhood Pseudomonas infection on differences in lung function in adolescence with CF.

METHODS

Two populations of subjects with CF were studied: from the Gene Modifier Study (GMS), 346 F508del homozygotes with severe vs. mild adolescent lung disease, and from the Colorado Newborn Screen Study (NBS) 172 subjects diagnosed with CF by newborn screening. Associations of Pseudomonas infection and lung function in early childhood with lung function in adolescence were investigated using multivariate linear regression analyses.

RESULTS

Among GMS subjects, those with severe adolescent lung disease had worse lung function in childhood (FEV1 25 percentage points lower) compared to subjects with mild adolescent lung disease, regardless of early childhood Pseudomonas status. Among NBS subjects, those with lowest adolescent lung function had significantly lower early childhood lung function and faster rate of decline in FEV1 than subjects with highest adolescent lung function; early Pseudomonas infection was not associated with rate of FEV1 decline. The strongest predictor of adolescent lung function was early childhood lung function. Subjects with a higher percentage of cultures positive for Pseudomonas before age 6 or a lower BMI at 2-4 years old also had lower adolescent lung function, though these associations were not as strong as with early childhood lung function.

CONCLUSIONS

In separate analyses of two distinct populations of subjects with CF, we found a strong correlation between lower lung function in early childhood and adolescence, regardless of early childhood Pseudomonas status. Factors in addition to early Pseudomonas infection have a strong impact on lung function in early childhood in CF. Further exploration may identify novel underlying genetic or environmental factors that predispose children with CF to early loss of lung function.

Impaired defenses of neonatal mouse alveolar macrophage with cftr deletion are modulated by glutathione and TGFβ1

Our understanding of the intrinsic effects of cystic fibrosis (CF) transmembrane conductance regulator (cftr) deletion on resident neonatal alveolar macrophage (AM) remains limited. We previously demonstrated that diminished glutathione (GSH) or excessive AM transforming growth factor beta one (TGFβ1) contributes to AM dysfunction in a variety of disease states. In this study, using a gut-corrected cftr neonatal knockout (KO) mouse model and a siRNA-manipulated macrophage-like cell line (THP-1 cell), we hypothesized (1) that cftr mutation alone increases neonatal AM oxidant stress and cellular TGFβ1 signaling via altered GSH, thereby impairing cellular function, and (2) that exogenous GSH attenuates AM alterations and dysfunction in the KO AM In neonatal KO mice, the baseline bronchoalveolar lavage fluid demonstrated a near doubling in mixed disulfides (P ≤ 0.05) and oxidized GSSG (P ≤ 0.05) without concurrent inflammation compared to WT littermates. KO AM demonstrated diminished AM thiols (P ≤ 0.05), increased AM mitochondrial ROS (P ≤ 0.05), increased AM TGFβ1 (P ≤ 0.05) with increased TGFβ1 signaling (P ≤ 0.05), and impaired phagocytosis (P ≤ 0.05). KO AM mitochondrial ROS was modulated by exogenous GSH (P ≤ 0.05). Conversely, TGFβ1 was reduced (P ≤ 0.05) and impaired phagocytosis was rescued (P ≤ 0.05) by exogenous GSH in the KO AM These results suggest that an altered neonatal AM phenotype may contribute to the initiation of lung inflammation/infection in the CF lung. Modulation of the AM in the neonatal CF lung may potentially alter progression of disease.

Refining the continuum of CFTR-associated disorders in the era of newborn screening

Clinical heterogeneity in cystic fibrosis (CF) often causes diagnostic uncertainty in infants without symptoms and in older patients with milder phenotypes. We performed a cross-sectional evaluation of a comprehensive set of clinical and laboratory descriptors in a physician-defined cohort (N = 376; Children's Hospital of Wisconsin and the American Family Children's Hospital CF centers in Milwaukee and Madison, WI, USA) to determine the robustness of categorizing CF (N = 300), cystic fibrosis transmembrane conductance regulator (CFTR)-related disorder (N = 19), and CFTR-related (CRMS) metabolic syndrome (N = 57) according to current consensus guidelines. Outcome measures included patient demographics, clinical measures, sweat chloride levels, CFTR genotype, age at diagnosis, airway microbiology, pancreatic function, infection, and nutritional status. The CF cohort had a significantly higher median sweat chloride level (105 mmol/l) than CFTR-related disorder patients (43 mmol/l) and CFTR-related metabolic syndrome patients (35 mmol/l; p ≤ 0.001). Patient groups significantly differed in pancreatic sufficiency, immunoreactive trypsinogen levels, sweat chloride values, genotype, and positive Pseudomonas aeruginosa cultures (p ≤ 0.001). An automated classification algorithm using recursive partitioning demonstrated concordance between physician diagnoses and consensus guidelines. Our analysis suggests that integrating clinical information with sweat chloride levels, CFTR genotype, and pancreatic sufficiency provides a context for continued longitudinal monitoring of patients for personalized and effective treatment.

The Evolution of Cystic Fibrosis Care

Cystic fibrosis (CF) is the most common life-limiting inherited illness of whites. Most of the morbidity and mortality in CF stems from impaired mucociliary clearance leading to chronic, progressive airways obstruction and damage. Significant progress has been made in the care of patients with CF, with advances focused on improving mucociliary clearance, minimizing inflammatory damage, and managing infections; these advances include new antimicrobial therapies, mucolytic and osmotic agents, and antiinflammatory treatments. More recently, researchers have targeted disease-causing mutations using therapies to promote gene transcription and improve channel function, which has led to impressive physiologic changes in some patients. As we develop more advanced, allele-directed therapies for the management of CF, it will become increasingly important to understand the specific genetic and environmental interactions that cause the significant heterogeneity of lung disease seen in the CF population. This understanding of CF endotypes will allow for more targeted, personalized therapies for future patients. This article reviews the genetic and molecular basis of CF lung disease, the treatments currently available, and novel therapies that are in development.

Downregulation of CFTR promotes epithelial-to-mesenchymal transition and is associated with poor prognosis of breast cancer

The epithelial-to-mesenchymal transition (EMT), a process involving the breakdown of cell-cell junctions and loss of epithelial polarity, is closely related to cancer development and metastatic progression. While the cystic fibrosis transmembrane conductance regulator (CFTR), a Cl(-) and HCO3(-) conducting anion channel expressed in a wide variety of epithelial cells, has been implicated in the regulation of epithelial polarity, the exact role of CFTR in the pathogenesis of cancer and its possible involvement in EMT process have not been elucidated. Here we report that interfering with CFTR function either by its specific inhibitor or lentiviral miRNA-mediated knockdown mimics TGF-β1-induced EMT and enhances cell migration and invasion in MCF-7. Ectopic overexpression of CFTR in a highly metastatic MDA-231 breast cancer cell line downregulates EMT markers and suppresses cell invasion and migration in vitro, as well as metastasis in vivo. The EMT-suppressing effect of CFTR is found to be associated with its ability to inhibit NFκB targeting urokinase-type plasminogen activator (uPA), known to be involved in the regulation of EMT. More importantly, CFTR expression is found significantly downregulated in primary human breast cancer samples, and is closely associated with poor prognosis in different cohorts of breast cancer patients. Taken together, the present study has demonstrated a previously undefined role of CFTR as an EMT suppressor and its potential as a prognostic indicator in breast cancer.

Copper phenotype in Alzheimer's disease: dissecting the pathway

Alzheimer's disease (AD) is the most common form of dementia. Several hypotheses have been put forward to explain the basis of disease onset and progression. Unfortunately, none of these seems to clarify the complexity of the pathogenesis. In fact, diverse and independent pathogenetic pathways can be disrupted at the same time, and each contributes to disease etiology. In recent years, researchers have begun studying biometals more deeply. A number of studies have shown that metal dyshomeostasis may enhance AD onset and progression. Specifically, different authors have hypothesized that alterations in metal metabolism are associated with an increased in metal-related oxidative stress and beta-amyloid oligomer formation and precipitation. Studies conducted in vivo, in vitro, in living patients and in silico studies have demonstrated that local and systemic defects in copper metabolism are characteristic signs of AD. This strongly supports the hypothesis that copper pathways may be disrupted by the disease. More specifically, a copper phenotype can be proposed for AD, based on defects found in genes involved in copper metabolism. In this review, we describe copper dyshomeostasis in AD patients and attempt to explain the basis of the AD copper phenotype. Dissecting copper pathways, we highlight mechanisms which may be at the basis of the disease. We also discuss various associated translation outcomes.

Apolipoprotein E genotype and neurological disease onset in Niemann-Pick disease, type C1

Niemann-Pick disease, type C1 (NPC1) is a lipid storage disorder that results in progressive neurological impairment. The NPC1 phenotype is extremely variable and at the individual level is likely influenced by other genetic traits. In addition to residual function of NPC1 protein, we hypothesize that modifier genes, as frequently observed with other autosomal recessive diseases, influence the NPC phenotype. The NPC1 phenotype includes progressive dementia, and the NPC pathology has some overlap with the pathology of Alzheimer disease (AD). Thus, we examined apolipoprotein E (ApoE) and microtubule-associated protein tau (MAPT) polymorphisms in a cohort of 15 NPC1 patients with well characterized longitudinal disease progression. Although we did not find any correlations between disease severity and tau polymorphisms, we found significant associations between ApoE polymorphisms and phenotypic severity. Specifically, ApoE4 and ApoE2 alleles were associated, respectively, with increased and decreased disease severity in this cohort of NPC1 patients. These data support the hypothesis that ApoE may play a role in modulating NPC1 neuropathology.

Recommendations for the classification of diseases as CFTR-related disorders

Several diseases have been clinically or genetically related to cystic fibrosis (CF), but a consensus definition is lacking. Here, we present a proposal for consensus guidelines on cystic fibrosis transmembrane conductance regulator (CFTR)-related disorders (CFTR-RDs), reached after expert discussion and two dedicated workshops. A CFTR-RD may be defined as "a clinical entity associated with CFTR dysfunction that does not fulfil diagnostic criteria for CF". The utility of sweat testing, mutation analysis, nasal potential difference, and/or intestinal current measurement for the differential diagnosis of CF and CFTR-RD is discussed. Algorithms which use genetic and functional diagnostic tests to distinguish CF and CFTR-RDs are presented. According to present knowledge, congenital bilateral absence of vas deferens (CBAVD), acute recurrent or chronic pancreatitis and disseminated bronchiectasis, all with CFTR dysfunction, are CFTR-RDs.

[Pancreatitis in cystic fibrosis: association with genotype and pancreatic status]

INTRODUCTION

Pancreatitis is an uncommon complication of cystic fibrosis (CF). Either single or recurrent acute episodes can occur and it occasionally may follow a protracted course with relentless destruction of the pancreas. Moreover mild mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) have been found in many cases of idiopathic chronic pancreatitis. We describe a group of patients with CF who had one or more episodes of pancreatitis. We have estimated its prevalence in a large population of patients with CF across Spain.

METHODS

A retrospective descriptive study was conducted by collecting the demographic, clinical and laboratory data, pancreatic status and genotype of CF patients who attended the CF Units in 5 Spanish hospitals.

RESULTS

The overall number of CF patients under follow-up in the five centres was 520, of which 17 cases with pancreatitis were identified. The prevalence of pancreatitis in this population was 3.3%, higher than previously reported. Noticeably eight of the 17 patients (47.06%) had pancreatic insufficiency. This appears to be, partly, in contrast with that classically found, as this complication is usually associated with patients with a certain level of pancreatic reserve. No associations with genotype, age, gender or other factors were found.

CONCLUSIONS

The prevalence of pancreatitis in our CF patients was higher than that found in other CF populations, and was not limited to patients with pancreatic sufficiency. It occurred mostly in teenagers and young adults often with mild pulmonary disease. The CF genotype was variable. The course of the patients should be carefully monitored, and further information on the long-term outcome of larger cohorts of patients is needed.

Plasma lipidomics reveals potential prognostic signatures within a cohort of cystic fibrosis patients

Cystic fibrosis (CF) is associated with abnormal lipid metabolism. We have recently shown variations in plasma levels of several phosphatidylcholine (PC) and lysophopshatidylcholine (LPC) species related to disease severity in CF patients. Here our goal was to search for blood plasma lipid signatures characteristic of CF patients bearing the same mutation (F508del) and different phenotypes, and to study their correlation with forced expiratory volume in 1 s (FEV1) and Pseudomonas aeruginosa chronic infection, evaluated at the time of testing (t = 0) and three years later (t = 3). Samples from 44 F508del homozygotes were subjected to a lipidomic approach based on LC-ESI-MS. Twelve free fatty acids were positively correlated with FEV1 at t = 0 (n = 29). Four of them (C20:3n-9, C20:5n-3, C22:5n-3, and C22:6n-3) were also positively correlated with FEV1 three years later, along with PC(32:2) and PC(36:4) (n = 31). Oleoylethanolamide (OEA) was negatively correlated with FEV1 progression (n = 17). Chronically infected patients at t = 0 showed lower PC(32:2), PC(38:5), and C18:3n-3 and higher cholesterol, cholesterol esters, and triacylglycerols (TAG). Chronically infected patients at t = 3 showed significantly lower levels of LPC(18:0). These results suggest a potential prognostic value for some lipid signatures in, to our knowledge, the first longitudinal study aimed at identifying lipid biomarkers for CF.

Relationship between cystic fibrosis respiratory tract bacterial communities and age, genotype, antibiotics and Pseudomonas aeruginosa

Polymicrobial bronchopulmonary infections in cystic fibrosis (CF) cause progressive lung damage and death. Although the arrival of Pseudomonas aeruginosa often heralds a more rapid rate of pulmonary decline, there is significant inter-individual variation in the rate of decline, the causes of which remain poorly understood. By coupling culture-independent methods with ecological analyses, we discovered correlations between bacterial community profiles and clinical disease markers in respiratory tracts of 45 children with CF. Bacterial community complexity was inversely correlated with patient age, presence of P. aeruginosa and antibiotic exposure, and was related to CF genotype. Strikingly, bacterial communities lacking P. aeruginosa were much more similar to each other than were those containing P. aeruginosa, regardless of antibiotic exposure. This suggests that community composition might be a better predictor of disease progression than the presence of P. aeruginosa alone and deserves further study.

Pathology of gastrointestinal organs in a porcine model of cystic fibrosis

Cystic fibrosis (CF), which is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), is characterized by multiorgan pathology that begins early in life. To better understand the initial stages of disease, we studied the gastrointestinal pathology of CFTR-/- pigs. By studying newborns, we avoided secondary changes attributable to environmental interactions, infection, or disease progression. Lesions resembling those in humans with CF were detected in intestine, pancreas, liver, gallbladder, and cystic duct. These organs had four common features. First, disease was accelerated compared with that in humans, which could provide a strategy to discover modifying factors. Second, affected organs showed variable hyperplastic, metaplastic, and connective tissue changes, indicating that remodeling was a dynamic component of fetal life. Third, cellular inflammation was often mild to moderate and not always present, which raises new questions as to the role of cellular inflammation in early disease pathogenesis. Fourth, epithelial mucus-producing cells were often increased, producing a striking accumulation of mucus with a layered appearance and resilient structure. Thus, mucus cell hyperplasia and mucus accumulation play prominent roles in early disease. Our findings also have implications for CF lung disease, and they lay the foundation for a better understanding of CF pathogenesis.

Donor mannose-binding lectin deficiency increases the likelihood of clinically significant infection after liver transplantation

BACKGROUND

Mannose-binding lectin (MBL) is an important mediator of innate immunity and is synthesized primarily by the liver. Low MBL levels are common, are due primarily to polymorphisms in the gene encoding MBL (MBL2), and are associated with an increased risk of infection, particularly when immunity is compromised. We report a large, retrospective study that examined the association between MBL status and clinically significant infection following orthotopic liver transplantation.

METHODS

One hundred two donor-recipient orthotopic liver transplantation pairs were studied. Five polymorphisms in the promoter and coding regions of MBL2 were examined. MBL levels were measured, using the mannan-binding and C4-deposition assays, in serum samples obtained before and after transplantation. Associations between MBL status, as assessed by serum MBL levels and MBL2 genotype, and time to first clinically significant infection (CSI) after transplantation were examined in survival analysis with consideration of competing risks.

RESULTS

The median duration of follow-up after orthotopic liver transplantation was 4 years. Thirty-six percent of recipients developed CSI after transplantation. The presence of MBL2 coding mutations in the donor was significantly associated with CSI in the recipient; the cumulative incidence function of infection was 55% in recipients of deficient livers, compared with 32% for recipients of wild-type livers (P = .002). Infection was not associated with recipient MBL2 genotype. Low MBL levels after orthotopic liver transplantation levels (mannan-binding <1 microg/mL or C4 deposition <0.2 C4 U/microL) were also associated with CSI (cumulative incidence function, 52% vs. 20%, P = .003; and cumulative incidence function, 54% vs. 24%, P = .007, respectively). In multivariate analysis, mutation in the MBL2 coding region of the donor (hazard ratio, 2.8; P = .005) and the use of cytomegalovirus prophylaxis (hazard ratio, 2.6; P = .005) were independently associated with CSI.

CONCLUSIONS

Recipients of MBL-deficient livers have almost a 3-fold greater likelihood of developing CSI and may benefit from MBL replacement.

Ligation dependent allele specific quantification (LASQ) of CFTR cDNA on the LightCycler using MLPA hybridization probes

BACKGROUND

As for Cystic Fibrosis (CF) and many other hereditary diseases there is still a lack in understanding the relationship between genetic (e.g. allelic) and phenotypic diversity. Therefore methods which allow fine quantification of allelic proportions of mRNA transcripts are of high importance.

METHODS

We used either genomic DNA (gDNA) or total RNA extracted from nasal cells as starting nucleic acid template for our assay. The subjects included in this study were 9 CF patients compound heterozygous for the F508del mutation and each one F508del homozygous and one wild type homozygous respectively. We established a novel ligation based quantification method which allows fine quantification of the allelic proportions of ss and ds CFTR cDNA. To verify reliability and accuracy of this novel assay we compared it with semiquantitative fluorescent PCR (SQF-PCR).

RESULTS

We established a novel assay for allele specific quantification of gene expression which combines the benefits of the specificity of the ligation reaction and the accuracy of quantitative real-time PCR. The comparison with SQF-PCR clearly demonstrates that LASQ allows fine quantification of allelic proportions.

CONCLUSION

This assay represents an alternative to other fine quantitative methods such as ARMS PCR and Pyrosequencing.

Genome-wide association studies: potential next steps on a genetic journey

Genome-wide association studies have successfully identified numerous loci at which common variants influence disease risk or quantitative traits. Despite these successes, the variants identified by these studies have generally explained only a small fraction of the heritable component of disease risk, and have not pinpointed with certainty the causal variant(s) at the associated loci. Furthermore, the mechanisms of action by which associated loci influence disease or quantitative phenotypes are often unclear, because we do not know through which gene(s) the associated variants exert their effects or because these gene(s) are of unknown function or have no clear connection to known disease biology. Thus, the initial set of genome-wide association studies serve as a starting point for future genetic and functional studies. We outline possible next steps that may help accelerate progress from genetic studies to the biological knowledge that can guide the development of predictive, preventive, or therapeutic measures.