Consensus on the use and interpretation of cystic fibrosis mutation analysis in clinical practice

New technologies extend the scope of newborn blood-spot screening, but old problems remain unresolved

The potential of newborn blood-spot screening is expanding rapidly with the development of new analytical techniques and treatment methods. At the same time, some existing programmes, particularly that for congenital hypothyroidism, are coming under scrutiny because of suspicion that they are being shaped by analytical performance rather than evidence of clinical need. Screening policy varies greatly from country to country.

CONCLUSION

  Ethical and political considerations may sometimes override formal scientific decision models.

Changing epidemiology and clinical issues arising in an ageing cystic fibrosis population

Improvements in the quality and implementation of medical care for individuals with cystic fibrosis (CF) have resulted in a dramatic improvement in survival. Many of these strategies have focused on the effective management of pulmonary disease which has delayed its manifestations into later years. With an increasing number of patients surviving to later years the impact of chronic inflammation and nutritional compromise on other organ systems over a lifetime are increasingly manifest. This review highlights the changing epidemiology of the ageing CF population and the complications that may ensue.

Association of cystic fibrosis genetic modifiers with congenital bilateral absence of the vas deferens

OBJECTIVE

To investigate whether genetic modifiers of cystic fibrosis (CF) lung disease also predispose to congenital bilateral absence of the vas deferens (CBAVD) in association with cystic fibrosis transmembrane conductance regulator (CFTR) mutations. We tested the hypothesis that polymorphisms of transforming growth factor (TGF)-β1 (rs 1982073, rs 1800471) and endothelin receptor type A (EDNRA) (rs 5335, rs 1801708) are associated with the CBAVD phenotype.

DESIGN

Genotyping of subjects with clinical CBAVD.

SETTING

Outpatient and hospital-based clinical evaluation.

PATIENT(S)

DNA samples from 80 subjects with CBAVD and 51 healthy male controls from various regions of Europe. This is one of the largest genetic studies of this disease to date.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genotype analysis.

RESULT(S)

For single nucleotide polymorphism (SNP) rs 5335, we found increased frequency of the CC genotype among subjects with CBAVD. The difference was significant among Turkish patients versus controls (45.2% vs. 19.4%), and between all cases versus controls (36% vs. 15.7%). No associations between CBAVD penetrance and polymorphisms rs 1982073, rs 1800471, or rs 1801708 were observed.

CONCLUSION(S)

Our findings indicate that endothelin receptor type A polymorphism rs 5335 may be associated with CBAVD penetrance. To our knowledge, this is the first study to investigate genetic modifiers relevant to CBAVD.

Cystic fibrosis-associated liver disease

Liver disease is increasingly common in cystic fibrosis (CF). As new therapeutic options emerge, life expectancy increases and common hepatobiliary manifestations impact on quality of life and survival of CF patients. Hepatobiliary abnormalities in CF vary in nature and range from defects attributable to the underlying CFTR gene defect to those related to systemic disease and malnutrition. Today complications of liver disease represent the third most frequent cause of disease-related death in patients with CF. Here we review molecular and clinical genetics of CF, including genetic modifiers of CF-associated liver disease, and provide practical recommendations for genetic testing, diagnosis and treatment of hepatobiliary manifestations in CF.

Peripheral nerve dysfunction in patients with cystic fibrosis

The objective of this study is to investigate the frequency, magnitude, and nature of peripheral nerve dysfunction in patients with cystic fibrosis (CF). Consecutive CF patients above the age of 3 years were recruited from the pediatric gastroenterology clinic. Twenty-five patients, 14 boys and 11 girls, were included, with mean age of 10.7 +/- 5.6 years. Nerve conduction studies were performed on the peroneal and median motor nerves, and median, ulnar and sural sensory nerves on one side. Fourteen patients (56%), 9 boys and 5 girls, had abnormal findings. All abnormalities were in the sensory nerves. Ulnar sensory nerve was abnormal in 48% of patients, sural sensory nerve in 44% of patients, and median sensory nerve in 28% of patients. Amplitudes were affected in all abnormal studies, associated with prolonged latencies in 20% of sural responses, 8% of ulnar responses, and 4% of median responses. Ten patients (40%) fulfilled the minimum case definition criterion for electrodiagnostic confirmation of distal polyneuropathy. Concordant abnormalities in three nerves were found in five patients (20%). The presence of neuropathy was not related to sex, age, type of CF symptoms, body mass index, or disease duration. In conclusion, CF is associated with peripheral nerve dysfunction, which is mostly sensory with an axonal trend. Care takers of patients with CF should be aware of the potential peripheral neurologic problems associated with the disease, especially with the improving survival of these patients.

p.Ser1235Arg should no longer be considered as a cystic fibrosis mutation: results from a large collaborative study

Among the 1700 mutations reported in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, a missense mutation, p.Ser1235Arg, is a relatively frequent finding. To clarify its clinical significance, we collected data from 104 subjects heterozygous for the mutation p.Ser1235Arg from the French CF network, addressed for various indications including classical CF, atypical phenotypes or carrier screening in subjects with or without a family history. Among them, 26 patients (5 having CF, 10 CBAVD (congenital bilateral absence of the vas deferens) and 11 with CF-like symptoms) and 14 healthy subjects were compound heterozygous for a second CFTR mutation. An exhaustive CFTR gene analysis identified a second mutation in cis of p.Ser1235Arg in all CF patients and in 81.8% CBAVD patients. Moreover, epidemiological data from >2100 individuals found a higher frequency of p.Ser1235Arg in the general population than in CF or CBAVD patients. These data, added to the fact that in silico analysis and functional assays suggest a benign nature of this substitution, give several lines of evidence against an association of p.Ser1235Arg with CF or CBAVD.

Pulmonary exacerbations in cystic fibrosis with negative bacterial cultures

BACKGROUND

Pulmonary exacerbations are a major cause of morbidity in cystic fibrosis (CF) and likely contribute to lung function decline. Exacerbations are often associated with characteristic airway bacteria [CF related bacteria (CFRB)]. However, some patients do not have CFRB detected by culture during exacerbations.

OBJECTIVES

We sought to determine the proportion of airway cultures negative for CFRB during pulmonary exacerbations, and to characterize patients who were CFRB-negative versus CFRB-positive.

METHODS

We performed a retrospective study of patients with CF admitted for a pulmonary exacerbation. Patients were classified as CFRB-positive or CFRB-negative based on admission airway cultures. Demographics, clinical presentation, lung function, history of chronic Pseudomonas aeruginosa infection and improvement in lung function with treatment were compared between groups.

MAIN RESULTS

There were 672 admissions for exacerbation involving 211 patients over 5 years. Seventeen percent were classified as CFRB-negative. Forty-one percent of bronchoalveolar lavage (BAL), 32% of throat and 10% of sputum samples were CFRB-negative. Among patients capable of expectorating sputum, the CFRB-negative group was younger, less likely to have chronic P. aeruginosa, had higher lung function and body mass index (BMI), and had a lower systemic inflammatory response on admission compared to those with CFRB-positive cultures. The two groups had similar numbers of patients with three or more signs and symptoms of a pulmonary exacerbation (88% vs. 92%). Both groups returned to baseline lung function following treatment.

CONCLUSIONS

A significant number of patients with CF and pulmonary exacerbation did not have typical CFRB detected by culture. Patients without CFRB still had characteristic signs and symptoms of pulmonary exacerbation and responded to treatment. Understanding the causes of illness in these patients may improve the diagnosis and treatment of pulmonary exacerbations in CF.

Genetic counselling issues in cystic fibrosis

Cystic fibrosis is a chronic condition for which genetic testing offers much for the individuals affected in terms of an early diagnosis and offers timely additional information for families with regard to family planning and prenatal testing. Genetic counselling encompasses a range of clinical issues for families and forms a complementary resource for clinicians caring for people with cystic fibrosis. This review will discuss the range of genetic information readily available to patients and families through genetic counselling.

Cystic fibrosis transmembrane conductance regulator modulators for personalized drug treatment of cystic fibrosis: progress to date

This article considers the issue of personalized drug discovery for the orphan disease cystic fibrosis (CF) to deliver a candidate for therapeutic development. CF is a very complicated disease due to numerous anomalies of the gene leading to progressive severity and morbidity. Despite extensive research efforts, 20 years after the cloning of the CF gene, CF patients are still waiting for a curative treatment as prescribed medications still target the secondary manifestations of the disease rather than the gene or the CF transmembrane conductance regulator (CFTR) protein. New therapeutics aimed at improving mutant CFTR functions, also known as 'protein repair therapy' are nevertheless hoped and predicted to replace some of the currently used therapy, while improving the quality of life as well as life expectancy of CF patients. Although there is substantial variability in the cost of treating CF between countries, a protein repair therapy should also alleviate the financial burden of medical costs for CF patients and their families. Finding new drugs or rediscovering old ones for CF is critically dependent on the delivery of molecular and structural information on the CFTR protein, on its mutated version and on the network of CFTR-interacting proteins. The expertise needed to turn compounds into marketable drugs for CF will depend on our ability to provide biological information obtained from pertinent models of the disease and on our success in transferring safe molecules to clinical trials. Predicting a drug-induced response is also an attractive challenge that could be rapidly applied to patients.

Renal impairment in children with cystic fibrosis

BACKGROUND

Due to the improvement in life expectancy in cystic fibrosis (CF), co-morbidities such as renal function impairment may be more frequent.

AIM

To determine the prevalence of renal disease in children with CF and to identify associated risk factors.

METHODS

A single-center retrospective study analyzing the genetic, clinical and therapeutic characteristics of 112 children. The estimated glomerular filtration rate (GFR), microalbuminuria and lithiasic risk factors were assessed.

RESULTS

The median calculated GFR (Schwartz) was 123, 161 and 155ml/min/1.73m(2) in children aged 1, 6 and 15years, respectively. The cumulative dose of aminoglycosides was not correlated to GFR. Microalbuminuria was present in 22/38 patients. Hyperoxaluria was observed in 58/83 patients and was associated with a severe genotype, pancreas insufficiency and liver disease. Hypercalciuria, hyperuricuria and hypocitraturia were identified in 16/87, 15/83 and 57/76 patients, respectively.

CONCLUSION

Renal impairment in CF has various presentations. There appears to be low levels of renal impairment in children with CF. However, the risk of oxalocalcic urolithiasis is enhanced, and GFR may be underestimated by the Schwartz formula. Further studies using measured GFR techniques are thus warranted.

Independent contribution of common CFTR variants to chronic pancreatitis

OBJECTIVE

We have assessed whether CFTR gene has a major impact on chronic pancreatitis (CP) pathogenesis than that provided by the CFTR mutations. For this aim, we have evaluated clinical parameters, CFTR mutations, and 3 potential regulatory CFTR variants (coding single-nucleotide polymorphisms): c.1540A>G, c.2694T>G, and c.4521G>A.

METHODS

CFTR gene analysis was performed in a cohort of 136 CP patients and 93 controls from Spanish population using current scanning techniques (single-strand conformation polymorphism/heteroduplex, denaturing gradient gel electrophoresis, and denaturing high-performance liquid chromatography) and direct sequencing.

RESULTS

A higher frequency of CFTR mutations were observed in patients (39%) than in controls (15%; P < or = 0.001), differences being mostly attributable to the prevalence of the cystic fibrosis (CF)-causing mutations (P = 0.009). The analysis of variants has shown statistically significant differences between patients and controls for c.4521G>A (Pcorrected = 0.036). Furthermore, the multi-marker analysis revealed that the 1540A;2694G;4521A (AGA) haplotype was more prevalent in CP than controls (Pcorrected = 0.042). Remarkably, this association was unrelated to CF-causing mutations (P = 0.006).

CONCLUSIONS

Our results corroborate the higher susceptibility of CF carriers to CP and, furthermore, suggest that the AGA haplotype could contribute to an increased risk in the development of CP irrespective of other CF-causing mutations.

[Genetic mutation databases: stakes and perspectives for orphan genetic diseases]

New technologies, which constantly become available for mutation detection and gene analysis, have contributed to an exponential rate of discovery of disease genes and variation in the human genome. The task of collecting and documenting this enormous amount of data in genetic databases represents a major challenge for the future of biological and medical science. The Locus Specific Databases (LSDBs) are so far the most efficient mutation databases. This review presents the main types of databases available for the analysis of mutations responsible for genetic disorders, as well as open perspectives for new therapeutic research or challenges for future medicine. Accurate and exhaustive collection of variations in human genomes will be crucial for research and personalized delivery of healthcare.

Cystic Fibrosis Foundation practice guidelines for the management of infants with cystic fibrosis transmembrane conductance regulator-related metabolic syndrome during the first two years of life and beyond

Through early detection, newborn screening (NBS)(1) for cystic fibrosis (CF) offers the opportunity for early intervention and improved outcomes. NBS programs screen for hypertrypsinogenemia, and most also identify mutations in the CF transmembrane conductance regulator (CFTR) gene. Individuals identified by NBS are diagnosed with CF if they have an elevated sweat chloride level or if they have inherited 2 disease-causing mutations in the CFTR gene. Mutations in the CFTR gene can cause CF, but not all CFTR mutations are disease-causing. The term CFTR-related metabolic syndrome (CRMS) is proposed to describe infants identified by hypertrypsinogenemia on NBS who have sweat chloride values <60 mmol/L and up to 2 CFTR mutations, at least 1 of which is not clearly categorized as a "CF-causing mutation," thus they do not meet CF Foundation guidelines for the diagnosis of CF. With what is now near-universal CF NBS in the United States, an increasing number of infants with CRMS are being identified. Given our inadequate knowledge of the natural history of CRMS, standards for diagnosis, monitoring, and treatment are absent. This document aims to help guide the monitoring and care of individuals with CRMS while our knowledge base on appropriate management evolves.

Cystic Fibrosis Foundation evidence-based guidelines for management of infants with cystic fibrosis

Newborn screening for cystic fibrosis (CF) offers the opportunity for early medical and nutritional intervention that can lead to improved outcomes. Management of the asymptomatic infant diagnosed with CF through newborn screening, prenatal diagnosis, or sibling screening is different from treatment of the symptomatically diagnosed individual. The focus of management is on maintaining health by preventing nutritional and respiratory complications. The CF Foundation convened a committee to develop recommendations based on a systematic review of the evidence and expert opinion. These guidelines encompass monitoring and treatment recommendations for infants diagnosed with CF and are intended to help guide families, primary care providers, and specialty care centers in the care of infants with CF.

Inconclusive cystic fibrosis neonatal screening results: long-term psychosocial effects on parents

AIM

Cystic Fibrosis (CF) Newborn Screening occasionally identifies neonates where a CF diagnosis can neither be confirmed nor excluded. To assess how parents of these infants cope with this ambiguous situation.

METHODS

Parents of 11 children with Ambiguous Diagnosis (group AD) were compared with parents of 11 children diagnosed with CF through neonatal screening [group Cystic Fibrosis Diagnosis (CFD)] and with parents of 11 Healthy Control children (group HC) matched for gender and age.

RESULTS

The emotional reaction to the inconclusive result was less pronounced in AD than in CFD (p = 0.003), and AD parents considered their infants as healthy as controls. Parents' anxiety about their child's health is stronger in CFD than in AD (p < 0.05) and HC (p < 0.001). Long-term emotional distress was rated similarly in AD and CFD, and greater than in HC (p = 0.0003). The parent/child relationship was less influenced in AD than in the CF group (p = 0.03). Seven AD and CFD parents changed their family planning projects.

CONCLUSION

Inconclusive neonatal screening results appear to be understood and associated with lower anxiety levels than CF diagnosis. Concern about the child's health is similar to healthy controls and lower than in parents of CF children.

Cystic fibrosis: exploiting its genetic basis in the hunt for new therapies

Cystic fibrosis (CF) is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel expressed in epithelial cells throughout the body. In the lungs, absence or dysfunction of CFTR results in altered epithelial salt and water transport eventuating in impaired mucociliary clearance, chronic infection and inflammation, and tissue damage. CF lung disease is the major cause of morbidity and mortality in CF despite the many therapies aimed at reducing it. However, recent technological advances combined with two decades of research driven by the discovery of the CFTR gene have resulted in the development and clinical testing of novel therapies aimed at the principal underlying defect in CF, thereby ushering in a new age of therapy for CF.

Clinical phenotype of cystic fibrosis patients with the G551D mutation

BACKGROUND

Data on whether the phenotype of cystic fibrosis (CF) patients with compound heterozygocity for G551D (Gly551Asp) differs from patients with F508del (Phe508del) homozygous mutations is divergent.

AIM

We hypothesized that CF patients with the G551D mutation would have less severe disease than F508del homozygotes.

DESIGN

We compared the clinical phenotype of adult patients with a G551D mutation with adult patients homozygous for F508del and those with the missense mutation R117H (Arg117His). Compound heterozygotes for the G551D and R117H were analysed separately.

METHODS

Data were collected for 101 adult CF patients. Group 1-4 represents in order F508del homozygote patients (n = 61), those with the G551D mutation and a more severe mutation (n = 13), those with R117H mutation and a more severe mutation (n = 23) and also those compound for both the R117H and G551D mutations (n = 4).

RESULTS

Our findings have shown that adult patients with the G551D mutation and a second severe mutation have a milder clinical phenotype than F508del homozygous adult patients. Higher FEV(1) and body mass index and less impaired glucose tolerance was demonstrated in the patients with G551D and R117H compared to F508del homozygotes. There was a reduced yearly rate of decline of FEV(1) (P < 0.05), infection with Pseudomonas aeruginosa along with reduced burden of care. Compound heterozygosity for G551D and R117H mutations was associated with normal spirometry, body mass index, no chronic infection and no symptoms.

CONCLUSION

Mutations on different chromosomes are not independent of each other for the overall impact on the amount of functional CFTR. This study suggests that patients with the G551D mutation and a second severe mutation have a milder clinical phenotype than F508del homozygous patients, but the phenotype is not as mild as patients with the R117H mutation.

An MBL2 haplotype and ABCB4 variants modulate the risk of liver disease in cystic fibrosis patients: a multicentre study

BACKGROUND

Cystic fibrosis is the most common lethal recessive disorder among Caucasians. Over 1500 mutations have been identified in cystic fibrosis transmembrane conductance regulator disease-gene so far. A large variability of the clinical phenotype has been observed both in cystic fibrosis patients bearing the same genotype, and in affected sibpairs. Thus, genes inherited independently from cystic fibrosis transmembrane conductance regulator could modulate the clinical expression of cystic fibrosis.

METHODS

We analysed some putative modifier genes of liver cystic fibrosis phenotype (serpin 1, hemochromatosis, transferrin receptor 2, ferroportin 1, mannose binding lectin and adenosine triphospate-binding cassette subfamily B member 4) in 108 unrelated cystic fibrosis patients with and without liver involvement.

RESULTS

HYPD mannose binding lectin haplotype was significantly (p<0.05) more frequent in cystic fibrosis patients with liver disease versus those without liver disease. This haplotype already related to a more severe pulmonary cystic fibrosis phenotype, is associated to a reduced MBL immunological activity. The c.834-66G>T variant of adenosine triphospate-binding cassette subfamily B member 4 gene was significantly (p<0.05) less frequent in cystic fibrosis patients with liver disease as compared to those with no liver disease.

CONCLUSIONS

The HYPD mannose binding lectin haplotype may predispose a subgroup of cystic fibrosis patients to a more severe liver involvement impairing the local defence mechanisms whereas the c.834-66G>T adenosine triphospate-binding cassette subfamily B member 4 variant may enhance the activity of the protein and thus exert a protective effect toward liver disease.

Rescue of CF airway epithelial cell function in vitro by a CFTR potentiator, VX-770

Cystic fibrosis (CF) is a fatal genetic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), a protein kinase A (PKA)-activated epithelial anion channel involved in salt and fluid transport in multiple organs, including the lung. Most CF mutations either reduce the number of CFTR channels at the cell surface (e.g., synthesis or processing mutations) or impair channel function (e.g., gating or conductance mutations) or both. There are currently no approved therapies that target CFTR. Here we describe the in vitro pharmacology of VX-770, an orally bioavailable CFTR potentiator in clinical development for the treatment of CF. In recombinant cells VX-770 increased CFTR channel open probability (P(o)) in both the F508del processing mutation and the G551D gating mutation. VX-770 also increased Cl(-) secretion in cultured human CF bronchial epithelia (HBE) carrying the G551D gating mutation on one allele and the F508del processing mutation on the other allele by approximately 10-fold, to approximately 50% of that observed in HBE isolated from individuals without CF. Furthermore, VX-770 reduced excessive Na(+) and fluid absorption to prevent dehydration of the apical surface and increased cilia beating in these epithelial cultures. These results support the hypothesis that pharmacological agents that restore or increase CFTR function can rescue epithelial cell function in human CF airway.

Non-classic cystic fibrosis associated with D1152H CFTR mutation

BACKGROUND

Limited knowledge exists on phenotypes associated with the D1152H cystic fibrosis transmembrane conductance regulator (CFTR) mutation.

METHODS

Subjects with a D1152H allele in trans with another CFTR mutation were identified using the French Cystic Fibrosis Registry. Phenotypic characteristics were compared with those of pancreatic insufficient (PI) and pancreatic sufficient (PS) cystic fibrosis (CF) subjects in the Registry (CF cohort).

RESULTS

Forty-two subjects with D1152H alleles were identified. Features leading to diagnosis included chronic sinopulmonary disease (n = 25), congenital absence of the vas deferens (n = 11), systematic neonatal screening (n = 4), and genetic counseling (n = 2). Median age at diagnosis was 33 [interquartile range (IQR, 24-41)] years in D1152H subjects. Median sweat chloride concentrations were 43.5 (39-63) mmol/l in D1152H subjects and were markedly lower than in PI and PS CF subjects (p < 0.05). Bronchiectasis was present in 67% of D1152H subjects, but Pseudomonas aeruginosa colonization and pancreatic insufficiency were present in <30% of subjects. Estimated rates of decline in forced expiratory volume in 1 s (FEV(1)) were lower in D1152H subjects vs PI CF subjects (p < 0.05). None of the D1152H subjects identified since 1999 had died or required lung transplantation.

CONCLUSIONS

When present in trans with a CF-causing mutation, D1152H causes significant pulmonary disease, but all subjects had prolonged survival.

Amniotic fluid digestive enzyme analysis is useful for identifying CFTR gene mutations of unclear significance

BACKGROUND

The large number of CFTR [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)] mutations and the existence of variants of unclear significance complicate the prenatal diagnosis of cystic fibrosis (CF). The aim of this study was to determine whether the pattern of amniotic fluid digestive enzymes (AF-DEs) could be correlated with the severity of CFTR mutations.

METHODS

The AF-DE pattern (gamma-glutamyltranspeptidase, aminopeptidase M, and the intestinal isoform of alkaline phosphatase) was retrospectively analyzed in 43 AF samples. All fetuses presented 2 CFTR mutations, which were classified according to the severity of the disease: CF/CF (n = 38); CF/CFTR-related disorders (n = 1); and CF/unknown variant (n = 4). The relationships between clinical CF status, CFTR mutations, and AF-DE pattern were studied.

RESULTS

Of 38 severely affected CF fetuses, an "obstructive" AF-DE pattern was observed in 15 of 15 samples collected before 22 weeks, irrespective of the CFTR mutation (diagnostic sensitivity, 100%; diagnostic specificity, 99.8%). In the 23 fetuses evaluated after 22 weeks, the AF-DE pattern was abnormal in 7 cases and noncontributive in 16 (diagnostic sensitivity, 30.4%; diagnostic specificity, 99.8%). Of the 5 questionable cases (F508del/N1224K, F508del/L73F, 3849+10kbC>T/G1127E, F508del/S1235R, F508del/G622D), all were CF symptom free at 2-4 years of follow-up. The AF-DE pattern (<22 weeks) was typical in 3 cases but abnormal in the last 2 cases.

CONCLUSIONS

AF-DE analysis is of value for prenatal CF diagnosis in classic forms of CF and could be helpful in nonclassic CF.

Human cystic fibrosis embryonic stem cell lines derived on placental mesenchymal stromal cells

This study describes the production of two new human embryonic stem cell (hESC) lines affected by cystic fibrosis. These cell lines are heterozygous compounds, each a carrier of the DF508 mutations associated either with E585X or with 3849+10 kb C-->T. The derivation process was performed on irradiated human placental mesenchymal stromal cells and designed to minimize contact with xeno-components. This new source of feeder cells is easy to obtain and devoid of ethical concerns. The cells have a great capacity to proliferate which reduces the need for continuous preparation of new feeder cell lines. In addition, three normal hESC lines were obtained in the same conditions. The five stem cell lines retained hESC-specific features, including an unlimited and undifferentiated proliferation capacity, marker expression and the maintenance of stable karyotype. They also demonstrated pluripotency in vitro, forming cell lineages of the three germ layers, as indicated by immunolocalization of beta-tubulin, alpha-fetoprotein and actin. These new genetic cell lines represent an important in-vitro tool to study the physiological processes underlying this genetic disease, drug screening, and tissue engineering.

Application of pyrosequencing to the identification of sequence variations in the cystic fibrosis transmembrane conductance regulator gene

BACKGROUND

A high number of mutations associated with cystic fibrosis have been identified in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, most of which are rare and, therefore, hamper extensive molecular diagnosis. In couples undergoing prenatal diagnosis where no mutation is found in one or both partners, additional analysis of intragenic polymorphisms may allow for the identification of fetal alleles associated with cystic fibrosis.

METHODS

We developed novel, rapid and accurate assays for CFTR genotype determination using pyrosequencing technology; a simple, automated and reliable technique with low cost.

RESULTS

Assays were optimized for the identification of the seven most frequent CFTR mutations (p.DeltaF508, p.N1303K, p.G542X, c.2183AA>G, c.1717-1G>A, p.W1282X, p.R1162X) in the Italian population and two common intragenic polymorphisms (rs213950 and rs1800136). Blind validation on 15 known control samples, typed for each sequence variation, allowed correct identification of all 135 genotypes.

CONCLUSIONS

We demonstrated that this procedure is highly specific for the identification of individual CFTR sequence variations associated with cystic fibrosis, allowing both population screening and prenatal diagnosis.

Increased prevalence of risk factors for morbidity and mortality in the US Hispanic CF population

Hispanic ethnicity is an independent risk factor for increased morbidity and mortality in cystic fibrosis (CF) patients. In order to compare the prevalence of risk factors for morbidity and mortality between the Hispanic CF population and the non-Hispanic CF population, we performed a cross-sectional study of patients in the 2004 Cystic Fibrosis Foundation Patient Registry. Among 22,714 CF patients, 1,511 were identified as ethnic Hispanic. Hispanic patients were diagnosed earlier (2.8 vs. 3.3 years, P = 0.005) and acquired Pseudomonas aeruginosa at a younger age (6.6 years vs. 10 years, P < 0.001). FEV(1) was lower for Hispanic patients (81.5% vs. 87% predicted for those under 18 years old [P < 0.001] and 2.1 L vs. 2.3 L for those 18 years and older [P = 0.01]). Hispanic patients had similar or better nutritional status. Hispanic patients were more likely to be diagnosed with liver disease (OR 1.31 [1.1, 1.56]) but less likely to be diagnosed with depression (OR 0.53 [0.39, 0.68]), bone and joint disease (OR 0.55 [0.41, 0.71]), or CF-related diabetes (OR 0.53 [0.43, 0.62]). Hispanic patients had lower median income by zip code ($41,930 vs. $47,341; P < 0.001), a higher rate of government insurance (55.2% vs. 32.0%; P < 0.001), and greater percentage of mothers with less than a high school education (26.7% vs. 6.5%; P < 0.001). We conclude that there is an increased prevalence of important risk factors for morbidity and mortality in the Hispanic CF population.

A Novel Approach to CFTR Mutation Testing by Pyrosequencing-Based Assay Panels Adapted to Ethnicities

Background: Cystic fibrosis (CF) is a common autosomal recessive genetic disorder caused by a variety of sequence alterations in the CFTR gene [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)]. Because the relative prevalence of mutations strongly depends on the ethnic background, first-level testing of CF as defined by recent consensus recommendations ought to be adaptable to the ethnicity of patients.

Methods: We therefore developed and implemented a diagnostic approach to first-level testing for CF based on published mutation frequencies and Pyrosequencing (PSQ) technology that we complemented with standard procedures of mutation detection at the second level.

Results: The current test system of PSQ assays for 46 target CF mutations [including CFTRdele2,3 (21 kb) and 1342-6 (T)n (5T/7T/9T)] permits recombinations of single assays to optimize sensitivities for certain ethnicities. By easy expansion of the original mutation panel, the first-level test sensitivities with other ethnic groups would be increased, provided that the mutation frequencies are known. The test was validated with our local, ethnically mixed, but mainly German population (155 patients). The mutation-detection rate for the 92 patients whose CF was confirmed by the sweat test was 89.0% for the patients of German descent (73 of the 92 patients) and 73.7% for the patients of any other origin (19 of the 92 patients). Ethnicity-adapted testing panels for our foreign CF patients would increase the sensitivities for the respective groups by approximately 5%.

Conclusions: PSQ-based genotyping is a reliable, convenient, highly flexible, and inexpensive alternative to conventional methods for first-level testing of CFTR, facilitating flexible adaptation of the analyzed mutation panel to any local ethnic group.

Cystic fibrosis

Cystic fibrosis is the most common lethal genetic disease in white populations. The outlook for patients with the disease has improved steadily over many years, largely as a result of earlier diagnosis, more aggressive therapy, and provision of care in specialised centres. Researchers now have a more complete understanding of the molecular-biological defect that underlies cystic fibrosis, which is leading to new approaches to treatment. One of these treatments, hypertonic saline, is already in use, whereas others are in advanced stages of development. We review clinical care for cystic fibrosis and discuss recent advances in the understanding of its pathogenesis, implementation of screening of neonates, and development of therapies aimed at treating the basic defect.

Three novel CFTR polymorphic repeats improve segregation analysis for cystic fibrosis

BACKGROUND

Molecular diagnosis for cystic fibrosis (CF) is based on the direct identification of mutations in the CFTR gene [cystic fibrosis transmembrane conductance regulator (ATP-binding cassette sub-family C, member 7)] (detection rate about 90% with scanning procedures) and on segregation analysis of intragenic polymorphisms for carrier and prenatal diagnosis in about 20% of CF families in which 1 or both causal mutations are unknown.

METHODS

We identified 3 novel intragenic polymorphic repeats (IVS3polyA, IVS4polyA, and IVS10CA repeats) in the CFTR gene and developed and validated a procedure based on the PCR followed by capillary electrophoresis for large-scale analysis of these polymorphisms and the 4 previously identified microsatellites (IVS1CA, IVS8CA, IVS17bTA, and IVS17bCA repeats) in a single run. We validated the procedure for both single- and 2-cell samples (for a possible use in preimplantation diagnosis), and on a large number of CF patients bearing different genotypes and non-CF controls.

RESULTS

The allelic distribution and heterozygosity results suggest that the 3 novel polymorphisms strongly contribute to carrier and prenatal diagnosis of CF in families in which 1 or both causal mutations have not been identified. At least 1 of the 4 previously identified microsatellites was informative in 78 of 100 unrelated CF families; at least 1 of all 7 polymorphisms was informative in 98 of the families. Finally, the analysis of haplotypes for the 7 polymorphisms revealed that most CF mutations are associated with different haplotypes, suggesting multiple slippage events but a single origin for most CFTR mutations.

CONCLUSIONS

The analysis of the 7 polymorphisms is a rapid and efficient tool for routine carrier, prenatal, and preimplantation diagnosis of CF.

Hepatobiliary disease in patients with cystic fibrosis

PURPOSE OF REVIEW

This review explores the recent advances in knowledge regarding hepatobiliary disease in patients with cystic fibrosis.

RECENT FINDINGS

Hepatobiliary abnormalities associated with cystic fibrosis are varied in nature and range from defects attributable to the underlying genetic defect to those related to systemic disease and malnutrition. Novel research into the underlying pathogenesis of cystic fibrosis liver disease and the primary role of cystic fibrosis transmembrane conductance regulator in biliary secretory epithelium is presented. This work has been fostered by the development of new animal models of cystic fibrosis transmembrane conductance regulator dysfunction. Of the wide range of hepatobiliary complications associated with cystic fibrosis the most clinically relevant problem is progression of focal biliary cirrhosis to multilobular cirrhosis with its attendant complications of portal hypertension and potentially end-stage liver disease. However, recent studies suggest that liver transplantation may not improve survival in patients with cystic fibrosis and significant portal hypertension.

SUMMARY

Hepatobiliary disease is a common finding in patients with cystic fibrosis; the pathogenesis is multifactorial in nature. As new therapeutic strategies emerge, life expectancy will continue to increase as will the impact of liver disease on quality of life and survival of patients with cystic fibrosis. This review will discuss novel insights into pathogenesis as well as diagnostic and management options.

Clinical practice and genetic counseling for cystic fibrosis and CFTR-related disorders

Cystic fibrosis transmembrane conductance regulator-related disorders encompass a disease spectrum from focal male reproductive tract involvement in congenital absence of the vas deferens to multiorgan involvement in classic cystic fibrosis. The reproductive, gastrointestinal, and exocrine manifestations of cystic fibrosis transmembrane conductance regulator deficiency are correlated with CFTR genotype, whereas the respiratory manifestations that are the main cause of morbidity and mortality in cystic fibrosis are less predictable. Molecular genetic testing of CFTR has led to new diagnostic strategies and will enable targeting of molecular therapies now in development. Older diagnostic methods that measure sweat chloride and nasal potential difference nonetheless remain important because of their sensitivity and specificity. In addition, the measurement of immunoreactive trypsinogen and the genotyping of CFTR alleles are key to newborn screening programs because of low cost. The multiorgan nature of cystic fibrosis leads to a heavy burden of care, thus therapeutic regimens are tailored to the specific manifestations present in each patient. The variability of cystic fibrosis lung disease and the variable expressivity of mild CFTR alleles complicate genetic counseling for this autosomal recessive disorder. Widespread implementation of newborn screening programs among populations with significant cystic fibrosis mutation carrier frequencies is expected to result in increasing demands on genetic counseling resources.

Best practice guidelines for molecular genetic diagnosis of cystic fibrosis and CFTR-related disorders--updated European recommendations

The increasing number of laboratories offering molecular genetic analysis of the CFTR gene and the growing use of commercial kits strengthen the need for an update of previous best practice guidelines (published in 2000). The importance of organizing regional or national laboratory networks, to provide both primary and comprehensive CFTR mutation screening, is stressed. Current guidelines focus on strategies for dealing with increasingly complex situations of CFTR testing. Diagnostic flow charts now include testing in CFTR-related disorders and in fetal bowel anomalies. Emphasis is also placed on the need to consider ethnic or geographic origins of patients and individuals, on basic principles of risk calculation and on the importance of providing accurate laboratory reports. Finally, classification of CFTR mutations is reviewed, with regard to their relevance to pathogenicity and to genetic counselling.