Cystic Fibrosis Transmembrane Regulator Gene Mutations Research Articles

Unmasking hereditary hemochromatosis with CFTR modulator therapy

Cystic Fibrosis (CF) is a genetic condition affecting the ability to excrete chloride, resulting in multi-system organ damage. Liver disease is one co-morbidity that affects 20-40% of people with CF. This case describes a 16-year-old male with CF (F508Del and Q493X mutations) who was started one lexacaftor/tezacaftor/ifacaftortriple CF Transmembrane Regulator (CFTR) modulator therapy. Prior to starting treatment, it was noted that he had transaminitis (AST 69, ALT 120, Total bilirubin 0.4). His liver enzymes continued to increase with therapy and at week 8 of treatment he complained of abdominal pain, body aches, and fatigue warranting further evaluation. At that time, AST and ALT were elevated at 5- and 13-times the Upper Limits of Normal (ULN) and creatinine kinase was elevated at 12-times ULN. A dose reduction led to a decrease in AST and ALT to 2 and 4-times ULN, but total and direct bilirubin increased to 2.2 mg/dl and 0.5 mg/dl, warranting a liver ultrasound and biopsy. Pathology showed fatty liver and hepatocyte iron deposition, but no indications of cirrhosis. Iron studies and genetic testing confirmed a diagnosis of HH (Homozygous HIS63ASP gene mutation). After stopping triple CFTR modulator therapy, AST and ALT continued to rise, prompting further evaluation by hepatology and hematology. Upon discontinuation of drug therapy, his lung function dropped significantly back to baseline values and respiratory symptoms returned. Discussion: Hereditary hemochromatosis gene mutations have been shown to have a gene modulating impact on CFTR gene mutations that can affect CF disease phenotype, which negatively affects pulmonary function and gastrointestinal disease. In this case, the introduction of a new medication instigated further work-up leading to the discovery of a potential alternative cause of hepatic dysfunction while attempting to optimize medications to sustain improvements in pulmonary function. Although elevated hepatic transaminases can be expected from CF and CFTR modulator therapy, further investigation may be indicated in patients with persistent elevations despite medication adjustments. This workup may lead to important considerations in balancing liver function with lung function. Keywords: cystic fibrosis; elexacaftor; tezacaftor; ivacaftor; liver transaminases; hereditary hemochromatosis.

MP38-02 CFTR GENE MUTATIONS IN SAUDI INFERTILE MEN WITH AZOOSPERMIA OR OLIGOASTHENOTERATOZOOSPERMIA

INTRODUCTION AND OBJECTIVE: Some mutations of cystic fibrosis transmembrane regulator (CFTR) gene may result in impaired spermatogenesis or cause a congenital absence of vas deferens which is manifested as isolated male infertility. The aim of this study is to examine the frequency and analyse the spectrum of CFTR gene variations in Saudi men who presented with idiopathic primary infertility. METHODS: Design and Setting: Prospective observational study conducted in King Faisal Specialist Hospital and Research Centre (Gen. Org), Jeddah, Saudi Arabia.Population: An unselected group of 50 Saudi men with idiopathic primary infertility who had either an Oligoasthenoteratozoospermia or azoospermia and presented to the andrology clinic between January 2017 and January 2019.Intervention: Genomic DNA extracted from a peripheral blood sample of each subject by a polymerase chain reaction and direct sequencing to identify all the variants of the entire coding regions and boundaries of the 27 exons of the CFTR gene. RESULTS: This study identified 10 CFTR gene mutations and polymorphisms in 7 (14%) subjects (100 chromosomes). Six subjects (12%) had two or more variants. The detected variants andpolymorphisms were: c.1408G>A, c.4389G>A, c.2562T>G, c.869+11C>T, c.2909-92G>A, c.3469-65C>A, c.1210-6delT, c.1210-6T>A, c.2988+1G>A, and c.1210-13GT>TG. CONCLUSIONS: We have shown that 14% of the study’s subjects had one or more CFTR mutation(s) and were compound in most affected patients. It seems that this frequency is higher than that in the general population. The spectrum of CFTR gene mutations in these subjects is similar to that reported worldwide.Source of Funding: King Faisal Specialist Hospital and Research Center.

Integrative expression analysis identifies a novel interplay between CFTR and linc-SUMF1-2 that involves CF-associated gene dysregulation

Cystic fibrosis transmembrane regulator (CFTR) is a cyclic AMP-dependent Cl− channel, and its dysfunction, due to CFTR gene mutations, causes the lethal inherited disorder cystic fibrosis (CF). To date, widespread dysregulation of certain coding genes in CF airway epithelial cells is well studied and considered as the driver of pulmonary abnormality. However, the involvement of non-coding genes, novel classes of functional RNAs with little or no protein-coding capacity, in the regulation of CF-associated gene dysregulation is poorly understood. Here, we utilized integrative analyses of human transcriptome array (HTA) and characterized 99 coding and 91 non-coding RNAs that are dysregulated in CFTR-defective CF bronchial epithelial cell line CFBE41o-. Among these genes, the expression level of linc-SUMF1-2, an intergenic non-coding RNA (lincRNA) whose function is unknown, was inversely correlated with that of WT-CFTR and consistently higher in primary human CF airway epithelial cells (DHBE-CF). Further integrative analyses under linc-SUMF1-knockdown condition determined MXRA5, SEMA5A, CXCL10, AK022877, CTGF, MYC, AREG and LAMB3 as both CFTR- and linc-SUMF1-2-dependent dysregulated gene sets in CF airway epithelial cells. Overall, our analyses reveal linc-SUMF1-2 as a dysregulated non-coding gene in CF as well as CFTR-linc-SUMF1-2 axis as a novel regulatory pathway involved in CF-associated gene dysregulation.

F508del CFTR gene mutation in patients with allergic bronchopulmonary aspergillosis

ABSTRACTObjective: The F508del mutation occurs in approximately 3.5% of Caucasian population of Northern Europe. Heterozygotes have increased risk for asthma and reduced pulmonary function. Allergic bronchopulmonary aspergillosis (ABPA) is more common in patients with cystic fibrosis (CF). We aimed to establish the frequency of F508del mutation in adult patients with ABPA. Methods: A retrospective matched case-control study of CF genotyped patients with ABPA seen at the National Aspergillosis Centre was undertaken. Key data were collected retrospectively from medical records, including respiratory comorbidities, total IgE, Aspergillus IgG and IgE, and immunoglobulins. Cystic fibrosis transmembrane regulator (CFTR) gene mutation analysis included multiplex PCR and sequencing. Results: From a cohort of 189 ABPA patients, 156 were screened for common mutations and variants in the CFTR gene. Eighteen were heterozygous for at least one CFTR mutation; 12 (7.7%) were heterozygous for the F508del, notably; 3 were heterozygous for the intron 8 5T variant; and 1 for an intronic variant of uncertain significance, c.3139 + 18C>T. Eight (67%) had asthma, 7 (58%) had CT-defined bronchiectasis, 4 (33%) hypergammaglobulinemia (>16 g/L), 3 (25%) sinusitis and 1 (8%) chronic pulmonary aspergillosis. Eight (67%) had elevated Aspergillus IgG antibodies (42–98 mg/L), and 8 (67%) had total IgE above 1,000 KIU/L. Two individuals heterozygous for the F508del mutation and the TG12T5 variant were diagnosed with CF, leading to a de novo CF discovery rate of 1.3%. Conclusions: In our ABPA patient cohort, the presence of the delta F508 mutation was higher than that seen in general population. Genetic counseling for CFTR genotyping might be appropriate for these patients.

Impact of Cystic Fibrosis Transmembrane Regulator (CFTR) gene mutations on male infertility.

Objective. The aim of this study was to evaluate the prevalence of most common mutations and intron 8 5T (IVS8-5T) polymorphism of CFTR gene in Italian: a) azoospermic males; b) non azoospermic subjects, male partners of infertile couples enrolled in assisted reproductive technology (ART) programs. Material and methods. We studied 242 subjects attending our Andrology Unit (44 azoospermic subjects and 198 non azoospermic subjects, male partners of infertile couples enrolled in ART programs). Semen analysis, molecular analysis for CFTR gene mutations and genomic variant of IVS8-5T polymorphic tract, karyotype and chromosome Y microdeletions, hormonal profile (LH, FSH, Testosterone) and seminal biochemical markers (fructose, citric acid and L-carnitine) were carried out. Results. The prevalence of the common CFTR mutations and/or the IVS8-5T polymorphism was 12.9% (4/31 cases) in secretory azoospermia, while in obstructive azoospermia was 84.6% (11/13 cases; in these, the most frequent mutations were the F508del, R117H and W1282X). Regarding the non azoospermic subjects, the prevalence of the CFTR and/or the IVS8-5T polymorphism was 11.1% (11/99 cases) in severe dyspermia, 8.1% (6/74 cases) in moderate dyspermia and finally 4.0% (1/25 cases) in normospermic subjects. Conclusions. This study confirms the highly significant prevalence of CFTR mutations in males with bilateral absence of the vas deferens or ejaculatory ducts obstruction compared with subjects with secretory azoospermia. Moreover, the significant prevalence of mutations in severely dyspermic subjects may suggest the possible involvement of CFTR even in the spermatogenic process. This could explain the unsatisfactory recovery of sperm from testicular fine needle aspiration in patients affected by genital tract blockage.

CFTR mutation/downregulation induces inflammation in mouse small intestine (902.1)

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians which is caused by the mutations of CFTR (cystic fibrosis transmembrane regulator) gene. CF presents a multitude of clinical manifestations with chronic inflammation in the lung as one of the hallmarks. In our study, we also found increased inflammation in the small intestine of CFTR DF508 mutation mice. The length of the small intestine, the thickness of the smooth muscle layer and the depth of the crypt were all increased significantly in DF508 mutants. The NF‐κB signaling pathway was found activated with the upregulation of p105/50 and increased nuclear translocation of p65. COX‐2 expression was increased significantly, which is a key player of inflammation. Further more, downregulation of CFTR in intestinal cell line Caco‐2 cells by transfection of CFTR siRNA also induced increased inflammation markers including TNFα, IL6, IL8 and IL18. Meanwhile, the mRNA of COX‐2 increased 124.84±4.26%. Both in vivo and in vitro results indicate that defect in CFTR may directly link to the activation of inflammatory pathways, such as NF‐κB and COX‐2, which may promote abnormal growth of the small intestine.

Analysis of CFTR Gene Mutations in Children with Cystic Fibrosis, First Report from North-East of Iran.

More than 1500 registered mutations in cystic fibrosis transmembrane regulator (CFTR) gene are responsible for dysfunction of an ion channel protein and a wide spectrum of clinical manifestations in patients with cystic fibrosis (CF). This study was performed to investigate the frequency of a number of well-known CFTR mutations in North Eastern Iranian CF patients. A total number of 56 documented CF patients participated in this study. Peripheral blood was obtained and DNA extraction was done by the use of routin methods. Three steps were taken for determining the target mutations: ARMS-PCR was performed for common CFTR mutations based on previous reports in Iran and neighboring countries. PCR-RFLP was done for detection of R344W and R347P, and PCR-Sequencing was performed for exon 11 in patients with unidentified mutation throughout previous steps. Samples which remained still unknown for a CFTR mutation were sequenced for exon 12. Among 112 alleles, 24 mutated alleles (21.42%) were detected: ΔF508 (10.71%), 1677delTA (3.57%), S466X (3.57%), N1303K (0.89%), G542X (0.89%), R344W (0.89%), L467F (0.89%). Eight out of 56 individuals analyzed, were confirmed as homozygous and eight samples showed heterozygous status. No mutations were detected in exon 12 of sequenced samples. Current findings suggest a selected package of CFTR mutations for prenatal, neonatal and carrier screening along with diagnosis and genetic counseling programs in CF patients of Khorasan.

Evaluating CFTR gene mutations in Adana

ABSTRACT Objective: Cystic fibrosis is the most common autosomal recessive inherited disorder seen in the white populations. It develops in result of mutations of cystic fibrosis transmembrane regulator (CFTR) gene. Rate of these mutations vary in different geographical regions. In this study, we aimed to determine the frequency of CFTR gene mutations in Adana. Methods: DNA samples of 63 subjects (21 women, 42 men) who were diagnosed as cystic fibrosis at Balcali Hospital of Cukurova University, were studied for 19 different CFTR mutations by the strip assay method which is based on reverse hybridization. Results: In cystic fibrosis diagnosed patients, 19 mutations were observed of which 9 were homozygous and 10 were heterozygous. ∆F508 frequency was found as 11.9%, and rate of homozygous was found as 66.7%. Mutation frequencies of W1282X and N1303K were found as 2.40% and 4.80% respectively and rate of homozygous mutations were 50% for both. I148T mutation frequency was found as 3.20% and all were heterozygous. For the whole 19 mutations, frequency of mutation in 63 subjects was 22.3%. Conclusion: Detection of CFTR gene mutations by the strip assay method by reverse hybridization is an easy, fast and informative method. However, due to improvability of the common mutations in probable cystic fibrosis patients because of heterogenity in this region, it is still a major problem and does not exclude cystic fibrosis diagnosis. But this problematic issue can be overcome by evaluating the whole exons of CFTR mutations by advanced molecular tecniques. Key words: CFTR, cystic fibrosis, molecular diagnosis, reverse hibridisation

Massive hepatomegaly with jaundice as a main presenting feature of cystic Fibrosis

Cystic fibrosis (CF) is a recessively inherited disease caused by mutations of the CF transmembrane conductance regulator (CFTR) gene. Patients classically present with evidence of pulmonary disease, malabsorption secondary to pancreatic insufficiency and high sweet chloride concentration. CF has can also be associated with a veriable phenotype which remains a diagnostic challenge. We report a case of a 2 year old girl with CF who initially presented with massive hepatomegaly and jaundice and was firstly suspected of a liver tumor. There was no personal or family history suggestive for CF. The diagnosis of CF liver disease was made after the results of the liver biopsy, sweat test analysis and confirmed with the existence of pathogenic mutation in the CFTR gene. Hepatomegaly and steatosis are known complications of CF but very uncommon as presenting features that lead to the diagnosis of CF. This report emphasizes the difficulty and importance of diagnosing cystic fibrosis in unusual patients.

Mutational spectrum of cystic fibrosis in the Lebanese population

Background Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasians; it is however, considered to be rare in the Arab populations. Reports of the cystic fibrosis transmembrane regulator (CFTR) mutations from Arabs, especially from the Lebanese population, are limited. Methods Twenty-two unrelated Lebanese families, with at least one child with CF, were studied. DNA extracts from blood samples of patients and parents were screened for CFTR gene mutations. Results Eleven different mutations were identified. Of the 44 alleles studied, the most common mutations were: F508del (34%), N1303K (27%), W1282X (7%), and S4X (7%). Five mutations – not previously reported in the Lebanese population – were identified; these are: S549N, G542X, 2043delG, 4016insG, and R117H-7T. Conclusions The most common CFTR mutations in addition to five mutations not previously described in the Lebanese population were identified. Identification of CFTR mutations in the Lebanese population is important for molecular investigations and genetic counseling.

Pharmacokinetics and Pharmacodynamics of Linezolid in Children With Cystic Fibrosis

Alternative antimicrobial regimens are needed for treatment of methicillin-resistant Staphylococcus aureus (MRSA)-associated pulmonary exacerbations in children with cystic fibrosis (CF). There are no published pharmacokinetic (PK) and pharmacodynamic (PD) data for linezolid in children with CF. (1) To determine the PK and PD profile of linezolid among children with CF; (2) to characterize the effect of linezolid on MRSA infection; (3) to determine the effect of age and CF transmembrane regulator (CFTR) gene mutations on drug clearance. Linezolid clearance is enhanced in children with CF requiring a higher dosage regimen. Age and CFTR gene mutations affect drug clearance. This was a retrospective cohort study; medical records of children with MRSA-associated pulmonary exacerbations treated with linezolid (10 mg/kg/dose IV every 8h) were reviewed. Linezolid peak and trough concentrations in serum were determined by high performance liquid chromatography, PK profiles determined using standard noncompartmental method, and PD indices were evaluated. 10 children (mean +/- SD, 10.2 +/- 5.5 years) received 14 courses of linezolid at 10 +/- 0.4 mg/kg/dose every 8h for 15.4 +/- 3.2 days. Seven had homozygous DeltaF508 CFTR mutation. Peak and trough linezolid concentrations varied widely (range, 8.4-20.5 and 0.1-11.5 mcg/mL respectively). The PK profile of children <10 years differed significantly from older patients (>or=10 years). The PK indices of children with homozygous DeltaF508 differed marginally from those with heterozygous CFTR mutations, but there were too few subjects to allow separation of age and CFTR mutations effect. No patient achieved the target PD ratio of AUC/MIC >80. MRSA persisted in sputum or throat culture after treatment with linezolid. Additional PK and PD data are needed to optimize linezolid therapy in children with cystic fibrosis; it is likely that higher doses will be needed.

CFTR gene mutations in pancreatitis: Frequency and clinical manifestations in an Austrian patient cohort

Mutations in the gene encoding the cystic fibrosis transmembrane regulator (CFTR) are over-represented in patients with chronic pancreatitis: 13-37% of pancreatitis patients are heterozygous for CFTR mutations, compared with the carrier estimate of 3.2% in the central European population. The aim of the current study was to investigate the association between clinical manifestations of pancreatitis and CFTR carrier status. A cohort of 133 pancreatitis patients was recruited in a confined geographical region (Tyrol-Western Austria) and analysed for the 30 most common CFTR gene mutations in Europe by multiplex PCR and gene sequencing. Pancreatitis was classified as acute or chronic according to the criteria of the Japan Pancreas Society (JPS) and etiological factors included in the TIGAR-O classification, namely toxic, idiopathic, genetic, autoimmune, recurrent and obstructive causes were assessed. The overall frequency of CFTR mutations in the patient cohort was 11.2%. In patients classified as 'idiopathic definitive chronic pancreatitis' (JPS criteria), the frequency of mutations was 12.7%, whereas patients with 'acute pancreatitis' or 'possible chronic pancreatitis' (JPS criteria) had a frequency of CFTR mutations of 10% and 9.1%, respectively. The frequency of CFTR mutations is highest in patients with definitive chronic pancreatitis and may therefore be regarded as a risk factor for the development of CP. However, multiple etiological factors for pancreatitis are present in the majority of patients. Mutation analysis of the CFTR gene therefore appears to be of limited diagnostic and prognostic value in the management of chronic pancreatitis.

Increased frequency of cystic fibrosis transmembrane conductance regulator gene mutations in infertile males

To investigate the frequency of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene in males with reduced sperm quality before intracytoplasmic sperm injection (ICSI). The nine most frequent cystic-fibrosis-causing mutations in the German population and IVS8T alleles were analyzed. University-based centers for reproductive medicine and clinical genetics. An unselected group of 597 males with oligo-, astheno-, terato-, crypto-, oligoasthenoteratozoospermia, or azoospermia, which underwent pre-ICSI genetic counseling over a 5-year period. Blood samples were collected from the patients during genetic counseling. Frequency of mutations of CFTR gene in infertile males. A heterozygous CFTR mutation was observed in 34 of 597 patients (5.70%). None of the patients had two CFTR mutations. Given that our mutation panel recognizes about 82% of heterozygotes, it can be assumed that the frequency of CFTR heterozygotes in our cohort is about 6.94%. The frequency of CFTR mutations in our cohort did not correlate with a reduced sperm count. The frequency of cystic fibrosis in the German population is 1:3300. Thus, a CFTR heterozygosity of 3.42% can be estimated. This indicates that in our cohort of infertile males, the frequency of CFTR heterozygosity is twofold higher than in the general population (P<.0001).

Markedly elevated neonatal immunoreactive trypsinogen levels in the absence of cystic fibrosis gene mutations is not an indication for further testing

Aims: To investigate the immunoreactive trypsinogen (IRT) values above the usual 99th centile laboratory cut-off and determine the value of offering further testing to those infants with a markedly elevated...

A Proinflammatory, Antiapoptotic Phenotype Underlies the Susceptibility to Acute Pancreatitis in Cystic Fibrosis Transmembrane Regulator (−/−) Mice

A Proinflammatory, Antiapoptotic Phenotype Underlies the Susceptibility to Acute Pancreatitis in Cystic Fibrosis Transmembrane Regulator (−/−) Mice

Gender-sensitive association of CFTR gene mutations and 5T allele emerging from a large survey on infertility

Human infertility in relation to mutations affecting the cystic fibrosis transmembrane regulator (CFTR) gene has been investigated by different authors. The role of additional variants, such as the possible forms of the thymidine allele (5T, 7T and 9T) of the acceptor splice site of intron 8, has in some instances been considered. However, a large-scale analysis of the CFTR gene and number of thymidine residues, alone and in combination, in the two sexes had not yet been addressed. This was the aim of this study. Two groups were compared, a control group of 20,532 subjects being screened for perspective reproduction, and the patient group represented by 1854 idiopathically infertile cases. Analyses involved PCR-based CFTR mutations assessment, reverse dot-blot IVS8-T polymorphism analyses, denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. The expected 5T increase in infertile men was predominantly owing to the 5/9 genotypic class. The intrinsic rate of 5T fluctuated only slightly among groups, but some gender-related differences arose when comparing their association. Infertile men showed a significantly enriched 5T + CFTR mutation co-presence, distributed in the 5/9 and 5/7 classes. In contrast, females, from both the control and the infertile groups, showed a trend towards a pronounced reduction of such association. The statistical significance of the difference between expected and observed double occurrence of 5T + CFTR traits in women suggests, in line with other reports in the literature, a possible survival-hampering effect. Moreover, regardless of the 5T status, CFTR mutations appear not to be involved in female infertility. These results underline the importance of (i) assessing large sample populations and (ii) considering separately the two genders, whose genotypically opposite correlations with these phenomena may otherwise tend to mask each other.

Diagnosis of CF despite normal or borderline sweat chloride

Research over the last 20 years has identified the CF gene and its product, the cystic fibrosis transmembrane regulator (CFTR), has defined the physiologic functions of CFTR as a chloride channel and regulator of other channels including the sodium channel, and has identified numerous CFTR gene mutations in patients with cystic fibrosis. In addition, this research has provided additional diagnostic tests, including CFTR gene mutation analysis and evaluation of CFTR function using nasal potential difference testing. While these diagnostic tests have expanded our ability to diagnose cystic fibrosis in patients with borderline sweat chloride values, inappropriate use and/or interpretation of these studies can lead to the incorrect conclusion that a particular patient does (or does not) have cystic fibrosis. The results of these studies must be considered with other clinical information and diagnostic studies to determine if a patient fulfills the diagnostic criteria for cystic fibrosis. Advances in our understanding of the spectrum of CFTR gene mutations and CFTR physiologic function have changed our approach to diagnosing cystic fibrosis. In the past, the presence of clinical features of cystic fibrosis or a family history prompted sweat chloride testing; and, the diagnosis of cystic fibrosis was made if two or more sweat chloride determinations were elevated (greater than 60mmol/L). Rarely, a patient with prominent clinical features of cystic fibrosis but borderline or normal sweat chloride values was identified and may have been labelled as “CF variant”. Extensive evaluations of several patients with clinical features of CF

Adenosine triphosphate-binding cassette superfamily transporter gene expression in severe male infertility.

Cystic fibrosis transmembrane regulator (CFTR), multidrug-resistant (MDR)1, and multidrug resistance-associated (MRP) proteins belong to the ATP-binding cassette (ABC) transporter superfamily. A compensatory regulation of MDR1 and CFTR gene expression has been observed in CFTR knockout rodent intestine and in an epithelial cell line of human colon, whereas a high homology and similar anion binding site are shared by MRP and CFTR proteins. To provide better insight into the relationship among the expression behavior in vivo of the three genes in human testis, analysis of MDR1 and MRP gene expression in testicular biopsies was performed and related to the presence of CFTR gene mutations in congenital absence of the vas deferens (CAVD: n = 20) and non-CAVD (n = 30) infertile patients with azoospermia or severe oligozoospermia. A CFTR mutation analysis performed in both groups of patients supported the involvement of CFTR gene mutations in CAVD phenotype (85%) and in defective spermatogenesis (19%). Quantitative reverse transcription-polymerase chain reaction analysis of testicular tissue showed a CFTR-independent MDR1 and MRP gene expression in human testis, suggesting that the mechanisms underlying CFTR gene regulation in testis are different from those in intestine. These findings should contribute to the understanding of patterns of in vivo expression of CFTR, MDR1, and MRP genes in CFTR-related infertility.

Basal Nucleotide Levels, Release, and Metabolism in Normal and Cystic Fibrosis Airways

Cystic fibrosis (CF) is a syndrome caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. Despite advances in our understanding of the molecular pathogenesis of CF, the link between CFTR gene mutations and the pathogenesis of CF lung disease remains poorly defined. CFTR has been assigned a number of putative functions that may contribute to innate airway defense, including the regulation of adenosine 5'-triphosphate (ATP) release into the extracellular environment. Because extracellular ATP and uridine 5'-triphosphate (UTP) may regulate airway mucociliary clearance via interaction with luminal P2Y2 receptors, the loss of CFTR-mediated nucleotide release could explain the defect in CF airway defense. We tested the physiologic importance of CFTR-mediated nucleotide release in vivo by directly measuring levels of ATP and UTP in nasal airway surface liquid from normal and CF subjects. Because these basal nucleotide levels reflect the net activities of nucleotide release and metabolic pathways, we also measured constitutive rates of nucleotide release and metabolism on well-differentiated normal and CF airway cultures in vitro. The measurement of ATP release rates were paralleled by in vivo studies employing continuous nasal perfusion in normal and CF subjects. Finally, the regulation of ATP release by isoproterenol and methacholine-stimulated submucosal gland secretion was tested. These studies revealed that steady-state ATP and UTP levels were similar in normal (470 +/- 131 nM and 37 +/- 7 nM, respectively) and CF (911 +/- 199 nM and 33 +/- 12 nM, respectively) subjects. The rates of both ATP release and metabolism were also similar in normal and CF airway epithelia both in vitro and in vivo. Airway submucosal glands did not secrete nucleotides, but rather, secreted a soluble nucleotidase in response to cholinergic stimuli. The concentration of ATP in airway surface liquid is in a range that is relevant for the activation of airway nucleotide receptors. However, despite this finding that suggests endogenous nucleotides may be important for the regulation of mucociliary clearance, our data do not support a role for CFTR in regulating extracellular nucleotide concentrations on airway surfaces.

Pancréatite aiguë récidivante et mutation hétérozygote du gène CFTR. À propos d'un cas

Recurrent pancreatitis is seldom associated with CFTR (Cystic Fibrosis Transmembrane Regulator) gene mutation. A 17-year-old boy presented with isolated idiopathic pancreatitis. CFTR gene mutations study revealed delta F508 heterozygous mutation. Mutations for the CFTR gene should be explored in case of recurrent pancreatitis.