Cystic fibrosis patients with the 3272-26A>G splicing mutation have milder disease than F508del homozygotes: a large European study

Rare Trafficking CFTR Mutations Involve Distinct Cellular Retention Machineries and Require Different Rescuing Strategies

Most of the ~2100 CFTR variants so far reported are very rare and still uncharacterized regarding their cystic fibrosis (CF) disease liability. Since some may respond to currently approved modulators, characterizing their defect and response to these drugs is essential. Here we aimed characterizing the defect associated with four rare missense (likely Class II) CFTR variants and assess their rescue by corrector drugs. We produced CFBE cell lines stably expressing CFTR with W57G, R560S, H1079P and Q1100P, assessed their effect upon CFTR expression and maturation and their rescue by VX-661/VX-445 correctors. Results were validated by forskolin-induced swelling assay (FIS) using intestinal organoids from individuals bearing these variants. Finally, knock-down (KD) of genes previously shown to rescue F508del-CFTR was assessed on these mutants. Results show that all the variants preclude the production of mature CFTR, confirming them as Class II mutations. None of the variants responded to VX-661 but the combination rescued H1079P- and Q1100P-CFTR. The KD of factors that correct F508del-CFTR retention only marginally rescued R560S- and H1079P-CFTR. Overall, data evidence that Class II mutations induce distinct molecular defects that are neither rescued by the same corrector compounds nor recognized by the same cellular machinery, thus requiring personalized drug discovery initiatives.

Allele specific repair of splicing mutations in cystic fibrosis through AsCas12a genome editing

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CFTR gene. The 3272-26A>G and 3849+10kbC>T CFTR mutations alter the correct splicing of the CFTR gene, generating new acceptor and donor splice sites respectively. Here we develop a genome editing approach to permanently correct these genetic defects, using a single crRNA and the Acidaminococcus sp. BV3L6, AsCas12a. This genetic repair strategy is highly precise, showing very strong discrimination between the wild-type and mutant sequence and a complete absence of detectable off-targets. The efficacy of this gene correction strategy is verified in intestinal organoids and airway epithelial cells derived from CF patients carrying the 3272-26A>G or 3849+10kbC>T mutations, showing efficient repair and complete functional recovery of the CFTR channel. These results demonstrate that allele-specific genome editing with AsCas12a can correct aberrant CFTR splicing mutations, paving the way for a permanent splicing correction in genetic diseases.

Genetic and phenotypic traits of children and adolescents with cystic fibrosis in Southern Brazil

Objectives:

To characterize the main identified mutations on cystic fibrosis transmembrane conductance regulator (CFTR) in a group of children and adolescents at a cystic fibrosis center and its association with the clinical and laboratorial characteristics.

Method:

Descriptive cross-sectional study including patients with cystic fibrosis who had two alleles identified with CFTR mutation. Clinical, anthropometrical, laboratorial and pulmonary function (spirometry) data were collected from patients’ records in charts and described with the results of the sample genotyping.

Results:

42 patients with cystic fibrosis were included in the study. The most frequent mutation was F508del, covering 60 alleles (71.4%). The second most common mutation was G542X (six alleles, 7.1%), followed by N1303K and R1162X mutations (both with four alleles each). Three patients (7.14%) presented type III and IV mutations, and 22 patients (52.38%) presented homozygous mutation for F508del. Thirty three patients (78.6%) suffered of pancreatic insufficiency, 26.2% presented meconium ileus, and 16.7%, nutritional deficit. Of the patients in the study, 59.52% would be potential candidates for the use of CFTR-modulating drugs.

Conclusions:

The mutations of CFTR identified more frequently were F508del and G542X. These are type II and I mutations, respectively. Along with type III, they present a more severe cystic fibrosis phenotype. More than half of the sample (52.38%) presented homozygous mutation for F508del, that is, patients who could be treated with Lumacaftor/Ivacaftor. Approximately 7% of the patients (7.14%) presented type III and IV mutations, therefore becoming candidates for the treatment with Ivacaftor.

Patients with cystic fibrosis having a residual function mutation: Data from the Italian registry

BACKGROUND

CFTR mutations permitting residual function (RF) of the CFTR protein are disease-causing. These mutations are associated with a pneumopathy that is delayed in onset and is slower in progression than are more common forms of cystic fibrosis (CF), although the disease may become severe in some patients. RF mutations are among the most frequent in Italy, thus encouraging investigation of their prevalence and associated phenotypes.

METHODS

Data from the Italian Registry were used to compare patients with at least one RF mutation with those homozygous for F508del.

RESULTS

A total of 806 patients bearing at least one RF mutation were identified among 5204 registered patients (15.5%). The RF patients were older than the F508del homozygotes (median age 26.0 years vs 19.8 years, respectively), with a higher median age at diagnosis (6.3 years vs 0.2 years, respectively) and a lower median sweat chloride value (76.0 mmol/L vs 100.0 mmol/L, respectively). In the RF group, lung infections and comorbidities were less prevalent than those in the F508del homozygotes, while better FEV₁ and nutritional status were observed at all ages. Within the RF group, RF/F508del subjects showed more severe pneumopathy than did patients with RF/other mutations. In particular, the 3849 + 10kbC → T/F508del subjects had worse FEV₁ and a higher prevalence of lung infections than did patients with other genotypes.

CONCLUSIONS

Patients with RF mutations are numerous in Italy and have a milder disease phenotype than do F508del homozygotes. Inside the RF group, F508del heterozygotes and, in particular, 3849 + 10kbC → T/F508del patients showed more severe pneumopathy.

Systematic Computational Identification of Variants That Activate Exonic and Intronic Cryptic Splice Sites

We developed a variant-annotation method that combines sequence-based machine-learning classification with a context-dependent algorithm for selecting splice variants. Our approach is distinctive in that it compares the splice potential of a sequence bearing a variant with the splice potential of the reference sequence. After training, classification accurately identified 168 of 180 (93.3%) canonical splice sites of five genes. The combined method, CryptSplice, identified and correctly predicted the effect of 18 of 21 (86%) known splice-altering variants in CFTR, a well-studied gene whose loss-of-function variants cause cystic fibrosis (CF). Among 1,423 unannotated CFTR disease-associated variants, the method identified 32 potential exonic cryptic splice variants, two of which were experimentally evaluated and confirmed. After complete CFTR sequencing, the method found three cryptic intronic splice variants (one known and two experimentally verified) that completed the molecular diagnosis of CF in 6 of 14 individuals. CryptSplice interrogation of sequence data from six individuals with X-linked dyskeratosis congenita caused by an unknown disease-causing variant in DKC1 identified two splice-altering variants that were experimentally verified. To assess the extent to which disease-associated variants might activate cryptic splicing, we selected 458 pathogenic variants and 348 variants of uncertain significance (VUSs) classified as high confidence from ClinVar. Splice-site activation was predicted for 129 (28%) of the pathogenic variants and 75 (22%) of the VUSs. Our findings suggest that cryptic splice-site activation is more common than previously thought and should be routinely considered for all variants within the transcribed regions of genes.

Novel personalized therapies for cystic fibrosis: treating the basic defect in all patients

Cystic fibrosis (CF) is the most common genetic life-shortening condition in Caucasians. Despite being a multi-organ disease, CF is classically diagnosed by symptoms of acute/chronic respiratory disease, with persistent pulmonary infections and mucus plugging of the airways and failure to thrive. These multiple symptoms originate from dysfunction of the CF transmembrane conductance regulator (CFTR) protein, a channel that mediates anion transport across epithelia. Indeed, establishment of a definite CF diagnosis requires proof of CFTR dysfunction, commonly through the so-called sweat Cl(-) test. Many drug therapies, including mucolytics and antibiotics, aim to alleviate the symptoms of CF lung disease. However, new therapies to modulate defective CFTR, the basic defect underlying CF, have started to reach the clinic, and several others are in development or in clinical trials. The novelty of these therapies is that, besides targeting the basic defect underlying CF, they are mutation specific. Indeed, even this monogenic disease is influenced by a large number of different genes and biological pathways as well as by environmental factors that are difficult to assess. Accordingly, every person with CF is unique and so functional assessment of patients' tissues ex vivo is key for diagnosing and predicting the severity of this disease. Of note, such assessment will also be crucial to assess drug responses, in order to effectively treat all CF patients. It is not because it is a monogenic disorder that personalized treatment for CF is much easier than for complex disorders.

Fine characterization of the recurrent c.1584+18672A>G deep-intronic mutation in the cystic fibrosis transmembrane conductance regulator gene

Splicing mutations account for approximately 12% of the 1,890 cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations described in cystic fibrosis (CF). However, their impact on pre-mRNA processing frequently remains unclear. An interesting opportunity to study CFTR transcripts in vivo involves the use of RNA from nasal brushings. Through this approach we previously identified a deep-intronic mutation (c.1584+18672A>G) that activates a 104-base pair (bp) out-of-frame pseudoexon by creating a donor splice site. The screening of 230 patients with CF identified c.1584+18672A>G in three additional individuals, demonstrating that it is a recurrent, and potentially overlooked, mutation among Italian patients. Haplotype analysis suggests that it originated from at least two independent events. To characterize the mutation further, a genomic region, including the activated pseudoexon and surrounding intronic sequences, was cloned into an expression vector and transfected into HeLa cells. RT-PCR analysis identified two alternative splicing products, produced by the activation of two different cryptic acceptor splice sites. One included the 104-bp pseudoexon (78.7% of transcripts), and the other led to the inclusion of a 65-bp pseudoexon (21.3% of mRNAs). The allele-specific measurement of wild-type and aberrant splicings from the nasal-brushing RNA of the three probands with genotype F508del/c.1584+18672A>G demonstrated: (1) a low level of pseudoexon inclusion in the F508del transcript (not containing the splicing mutation); (2) residual wild-type splicing in the c.1584+18672A>G mRNA; (3) the degradation of aberrant transcripts; and (4) the relative strength of the different cryptic splice sites. Interestingly, the residual wild-type splicing detected in transcripts bearing the c.1584+18672A>G mutation correlates well with the milder clinical phenotype of patients.

Measurements of CFTR-mediated Cl- secretion in human rectal biopsies constitute a robust biomarker for Cystic Fibrosis diagnosis and prognosis

Background

Cystic Fibrosis (CF) is caused by ∼1,900 mutations in the CF transmembrane conductance regulator (CFTR) gene encoding for a cAMP-regulated chloride (Cl⁻) channel expressed in several epithelia. Clinical features are dominated by respiratory symptoms, but there is variable organ involvement thus causing diagnostic dilemmas, especially for non-classic cases.

Methodology/Principal Findings

To further establish measurement of CFTR function as a sensitive and robust biomarker for diagnosis and prognosis of CF, we herein assessed cholinergic and cAMP-CFTR-mediated Cl⁻ secretion in 524 freshly excised rectal biopsies from 118 individuals, including patients with confirmed CF clinical diagnosis (n = 51), individuals with clinical CF suspicion (n = 49) and age-matched non-CF controls (n = 18). Conclusive measurements were obtained for 96% of cases. Patients with “Classic CF”, presenting earlier onset of symptoms, pancreatic insufficiency, severe lung disease and low Shwachman-Kulczycki scores were found to lack CFTR-mediated Cl⁻ secretion (<5%). Individuals with milder CF disease presented residual CFTR-mediated Cl⁻ secretion (10–57%) and non-CF controls show CFTR-mediated Cl⁻ secretion ≥30–35% and data evidenced good correlations with various clinical parameters. Finally, comparison of these values with those in “CF suspicion” individuals allowed to confirm CF in 16/49 individuals (33%) and exclude it in 28/49 (57%). Statistical discriminant analyses showed that colonic measurements of CFTR-mediated Cl⁻ secretion are the best discriminator among Classic/Non-Classic CF and non-CF groups.

Conclusions/Significance

Determination of CFTR-mediated Cl⁻ secretion in rectal biopsies is demonstrated here to be a sensitive, reproducible and robust predictive biomarker for the diagnosis and prognosis of CF. The method also has very high potential for (pre-)clinical trials of CFTR-modulator therapies.

Nasal polyposis in lung transplant recipients with cystic fibrosis

BACKGROUND

Chronic rhinosinusitis with nasal polyposis is common in patients with cystic fibrosis (CF). There are still many open questions regarding factors related to this condition. Furthermore, the prevalence of nasal polyposis and its implications for the outcomes in lung transplant recipients with cystic fibrosis are unknown.

METHODS

All CF patients who underwent lung transplantation at our centre between November 1992 and December 2009 were included. Nasal polyp status was determined endoscopically at time sinus surgery and its relationships to gender, age at lung transplantation, Liou raw score, body mass index, FEV1%predicted, diabetes mellitus, pre-transplant pseudomonas colonisation of the sinuses and the lungs, pre-transplant corticosteroid use and type of mutation of the CFTR gene were analysed. The post-transplant survival times and the incidence of bronchiolitis obliterans syndrome in patients with or without nasal polyposis were compared.

RESULTS

Nasal polyps were found in 19% (17 patients) of the 89 lung transplant recipients, whose data was available for statistical analysis. None of the factors analysed was related to the nasal polyp status. The post-transplant survival times and the incidence of bronchiolitis obliterans syndrome did not significantly differ between patients with or without nasal polyposis.

CONCLUSIONS

CF-related nasal polyposis occurs in a relevant fraction of lung transplant recipients. A specific effect of nasal polyposis on post-transplant outcome could not be confirmed. Nevertheless, there was a trend to NP recurrence in patients with post-transplant sinonasal pseudomonas colonisation and is a tendency of less chronic rejection in CF patients with nasal polyps.

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

It is often challenging for the clinician interested in cystic fibrosis (CF) to interpret molecular genetic results, and to integrate them in the diagnostic process. The limitations of genotyping technology, the choice of mutations to be tested, and the clinical context in which the test is administered can all influence how genetic information is interpreted. This paper describes the conclusions of a consensus conference to address the use and interpretation of CF mutation analysis in clinical settings. Although the diagnosis of CF is usually straightforward, care needs to be exercised in the use and interpretation of genetic tests: genotype information is not the final arbiter of a clinical diagnosis of CF or CF transmembrane conductance regulator (CFTR) protein related disorders. The diagnosis of these conditions is primarily based on the clinical presentation, and is supported by evaluation of CFTR function (sweat testing, nasal potential difference) and genetic analysis. None of these features are sufficient on their own to make a diagnosis of CF or CFTR-related disorders. Broad genotype/phenotype associations are useful in epidemiological studies, but CFTR genotype does not accurately predict individual outcome. The use of CFTR genotype for prediction of prognosis in people with CF at the time of their diagnosis is not recommended. The importance of communication between clinicians and medical genetic laboratories is emphasized. The results of testing and their implications should be reported in a manner understandable to the clinicians caring for CF patients.

High incidence of the CFTR mutations 3272-26A→G and L927P in Belgian cystic fibrosis patients, and identification of three new CFTR mutations (186-2A→G, E588V, and 1671insTATCA)

We have analyzed 143 unrelated Belgian patients with a positive diagnosis of cystic fibrosis (CF) for mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. An initial screening for 29 CFTR mutations led to mutation identification in 89.9% of the tested chromosomes. Subsequently an extensive analysis of the CFTR gene was performed by denaturating gradient gel electrophoresis (DGGE) in those patients with at least one unknown mutation after preliminary screening. In addition to 10 previously reported mutations we identified 2 new mutations 186-2A-->G and E588V. A third new mutation 1671insTATCA was identified during routine screening for DeltaF508. Two mutations were detected with a higher frequency than expected: 3272-26A-->G, which is the second most common mutation after DeltaF508 in our CF population with a frequency of 3.8%, and L927P (2.4%). The clinical data is presented for the mutations 186-2A-->G, E588V, 3272-26A-->G and L927P. The mutation data are useful for the Belgian population to supplement the initial screening set of mutations.

Splicing modulation as a modifier of the CFTR function

A significant fraction of CF-causing mutations affects pre-mRNA splicing. These mutations can generate both aberrant and correct transcripts, the level of which varies among different patients. An inverse correlation was found between this level and disease severity, suggesting a role for splicing regulation as a genetic modifier. Subsequent studies showed that overexpression of splicing factors modulated the level of correctly spliced RNA, transcribed from minigenes carrying CF-causing splicing mutations. Overexpression of splicing factors also modulated the level of normal CFTR transcripts, transcribed from the endogenous CFTR allele carrying splicing mutations, in CF-derived epithelial cells. Several of the factors promoted higher level of correct CFTR transcripts. The increased level of normal transcripts led to activation of the CFTR channel and restoration of its function. Restoration was also obtained by sodium butyrate, a histone deacetylase inhibitor, known to up-regulate the expression of splicing factors. These results highlight the role of the splicing machinery as a modifier of disease severity in patients carrying splicing mutations and shed a new light on the therapeutic potential of splicing modulation for genetic diseases caused by splicing mutations.

Paternity in men with cystic fibrosis: a retrospective survey in France

BACKGROUND

Because more patients reach adulthood, new questions as "what about having a child and/or paternity responsibility?" arose.

METHOD

We performed a retrospective investigation based on the French CF registry. The context of the paternity and the health status of fathers were recorded. A comparison with clinical status of non-father patients and a compilation of follow-up data to evaluate its impact were done.

RESULTS

Forty-eight men had 69 children. One fourth was said to be natural conceptions, 69% needed assisted reproduction techniques. No child had CF. Clinical status of men was satisfactory: mean BMI was 20.9 kg/m(2) and mean FEV(1) and FVC were 50.5% and 69.2% of predicted, respectively. When matched to CF non-fathers, few significant differences appeared. More non-fathers were F508del/F508del (p=0.03). Fathers' sputum cultures were positive for non-Pseudomonas aeruginosa strain (p=0.05), including Staphylococcus aureus (p=0.01). Mean age at diagnosis was higher, and based on minor evidence of sterility as first symptom leading to the diagnosis of CF (p=0.01) or aspergillosis (p=0.03). The 3-year follow-up showed no degradation of the clinical status.

CONCLUSION

Men having paternity responsibility over children did not differ from the CF male population and neither did it seem to have an impact on the disease course.

Cystic Fibrosis--clinical features of a sample of Portuguese patients

Even though there have been rapid advances in the comprehension of molecular determinants of Cystic Fibrosis, this disease continues to be one of the most common lethal recessive diseases in the Caucasian population worldwide. The reality of Portuguese patients is still greatly unknown, due to the lack of studies published in reference to our population. The objectives of this study were: clinical evaluation of a group of Portuguese patients with Cystic Fibrosis, with two identified mutations; comparing the clinical presentation of a group of homozygous patients for the F508del mutation with patients that are not homozygous for this mutation. A group of patients, followed in Pediatric Pneumology Consultations of S. João Hospital, were characterised in terms of phenotype and were classified according to criteria of severity. All of the patients in this group presented class I and/or II mutations, classically associated with a more severe phenotype. In conformity with the severe genotype, all patients presented a phenotype of pancreatic insufficiency but with greater variability of pulmonary manifestations. Significant variations were not found in terms of age at diagnosis, presenting forms and disease severity between F508del homozygous patients and the other patients. On the other hand, patients with the same genotype (homozygous F508del) presented different spectrums of clinical manifestations and phenotype severity. Just as much, or even more than the genotype characterisation, the time period of evolution of the disease and external factors, namely being subjected to infectious stimulus, interfere in the severity of the phenotype, at a certain moment in time.

Processing of CFTR: traversing the cellular maze--how much CFTR needs to go through to avoid cystic fibrosis?

Biosynthesis of the cystic fibrosis transmembrane conductance regulator (CFTR), like other proteins aimed at the cell surface, involves transport through a series of membranous compartments, the first of which is the endoplasmic reticulum (ER), where CFTR encounters the appropriate environment for folding, oligomerization, maturation, and export from the ER. After exiting the ER, CFTR has to traffic through complex pathways until it reaches the cell surface. Although not yet fully understood, the fine details of these pathways are starting to emerge, partially through identification of an increasing number of CFTR-interacting proteins (CIPs) and the clarification of their roles in CFTR trafficking and function. These aspects of CFTR biogenesis/degradation and by membrane traffic and CIPs are discussed in this review. Following this description of complex pathways and multiple checkpoints to which CFTR is subjected in the cell, the basic question remains of how much CFTR has to overcome these barriers and be functionally expressed at the plasma membrane to avoid CF. This question is also discussed here.

A novel missense mutation P1290S at exon-20 of the CFTR gene in a Portuguese patient with congenital bilateral absence of the vas deferens

OBJECTIVE

To report a novel cystic fibrosis transmembrane conductance regulator (CFTR) gene missense mutation in a compound heterozygote with congenital bilateral absence of the vas deferens (CBAVD).

DESIGN

Descriptive, controlled study.

SETTING

Tertiary academic hospital genetics laboratory and private in vitro fertilization (IVF) clinic.

PATIENT(S)

One 46-year-old man with CBAVD and no clinical cystic fibrosis (CF) phenotype as indicated by the advanced age at diagnosis, absence of chronic airways and gastrointestinal disease, and normal pancreatic function and sweat chloride concentration. Genomic blood DNA from the patient's parents was analyzed to perform family studies, and 109 fertile men, 32 patients with CBAVD, 15 children carriers of one CFTR mutation, and 5 patients with CF were used to rule out polymorphism.

INTERVENTION(S)

Clinical evaluation and treatment, genetical screenings.

MAIN OUTCOME MEASURE(S)

Clinical data, biochemical assays, spermiogram analysis, testicle biopsy, intracytoplasmic sperm injection (ICSI) outcome, and CFTR whole gene mutation screening and IVS8T polymorphism.

RESULT(S)

The DNA analysis revealed a 7T/7T homozygote at IVS8-T, with a 4000C-->T change (P1290S) in exon 20 of the CFTR gene, which was inherited from the patient's father. It was associated with a 3272-26A-->G mutation in the other allele that was inherited from his mother.

CONCLUSION(S)

The novel P1290S missense CFTR mutation causes an amino acid change in a highly conserved region of the CFTR protein that controls channel opening. Pathogenicity is suggested by development of CBAVD in association with a mild CFTR mutation.

Identification and characterization of hepsin/-TM, a non-transmembrane hepsin isoform

Type II transmembrane serine proteases (TTSPs), including hepsin, are a new class of cell surface catalytic enzymes. In the present study, a non-transmembrane isoform of hepsin, named hepsin/-TM that originates from alternative splicing, was identified. Unlike the transmembrane hepsin isoform, this non-transmembrane isoform was distributed within the cytoplasm. Real-time PCR experiments revealed that while hepsin was expressed in all tested human tissues, hepsin/-TM was restricted in kidney, brain and lung tissues. Significantly, hepsin/-TM was not expressed in liver where hepsin was originally identified. However, hepsin/-TM was highly expressed in brain where hepsin was expressed at a relatively lower level. Moreover, these two isoforms showed different expression patterns in a number of colon adenocarcinoma cell lines. In addition, in contrast to hepsin, expression of hepsin/-TM in vivo does not exert any apparent inhibitory effect on mammalian cell growth.

Diagnosis of cystic fibrosis in adults with diffuse bronchiectasis

We assessed the contribution of the sweat test, genotyping and nasal potential difference (NPD) in the diagnosis of cystic fibrosis (CF) in adults with diffuse bronchiectasis (DB). Among 601 adults referred for DB from 1992 to 2001, 46 were diagnosed with CF. The sweat test was positive in 37 patients and normal or intermediate in nine patients. Two CF mutations were identified in 18 patients (39%) by screening for 31 mutations and in 36 patients (78%) after complete genetic analysis. NPD was suggestive of CF in 71% of the patients. The combination of the sweat test and genetic analysis led to the diagnosis of CF in 45 patients. In the nine patients with normal or intermediate sweat test, the diagnosis was confirmed by screening for 31 mutations in five, by complete genetic screening in three, and by NPD in the remaining patient. Searching for CF should start with sweat test. If the sweat test is normal or intermediate, screening for 31 mutations may help to diagnose CF. A complete genetic analysis is indicated when only one mutation is detected and/or when other clinical features, such as obstructive azoospermia or pancreatic insufficiency, are suggestive of CF. NPD measurement is indicated in controversial cases.

Population screening for cystic fibrosis: knowledge and emotional consequences 18 months later

We assessed cystic fibrosis (CF) knowledge and emotional consequences of CF population testing 18 months after screening was offered. Questionnaires were sent to 593 individuals and 353 responded (59.5%). All respondents had sound knowledge of CF disease, although carriers were more likely to correctly state the pattern of CF inheritance and CF carrier rate in Australia. Eleven of 47 carriers falsely believed they were only very likely to be carriers, while nearly a third of test-negative individuals falsely believed they were definitely not carriers. Imprecise recall of the meaning of results may be due to memory loss over time, simplification of result meaning and minimization of risk. The Health Orientation Scale (HOS) was used to assess emotional consequences of CF carrier testing 18 months after testing. Both carriers and test-negative individuals thought most carriers would experience more negative feelings than most non-carriers. Carriers experienced less positive feelings about their test result compared to non-carriers. Interestingly, the carriers' own feelings about their result were more positive compared to how they thought most carriers would feel. These results suggest that carriers experience minimal adverse psychological effects, although a negative social stigma may be attached to carrying the CF gene mutation.

Cystic fibrosis in Greece: molecular diagnosis, haplotypes, prenatal diagnosis and carrier identification amongst high-risk individuals

Cystic fibrosis (CF) mutation analysis on 437 CF patients, characterized 80 different mutations (20 so far specific to our population) accounting for 91% of CF genes and generating 103 different genotypes. Eight mutations were common [F508del (53.4%), 621+1G>T (5.7%), G542X (3.9%), N1303K (2.6%), 2789+5G>A (1.7%), 2183AA>G (1.4%), E822X (1.4%), R1158X (1%)], 12 showed frequencies between 0.5% and 1%, while the remaining (60) were very rare (1 to 3 alleles). Denaturing gradient gel electrophoresis (DGGE) screening of 12 exons (3, 4, 7, 10, 11, 13, 14b, 16, 17b 20 and 21) detected 85.5% of CF alleles. Haplotypes for eight diallelic and three microsatellite markers have been characterized for the common, a few rare and novel Greek mutations. Results of 165 prenatal diagnoses (including 49 due to bowel hyperechogenicity), testing a total of 41 different parental genotypes, are reported. One hundred and sixteen prenatal tests resulted in 22 affected, 59 heterozygous, 34 normal fetuses and one incomplete diagnosis. Of the 49 echogenic bowel fetuses, 3 were heterozygotes. Carrier screening was initiated, with emphasis on individuals and couples in high-risk groups - with a family history of CF, one partner with CF, and couples with male infertility seeking in vitro fertilization (IVF). Mutation analysis on 672 individuals (120 couples, 91 unaffected CF siblings, 283 CF family relatives and 58 general population subjects), identified a total of 176 heterozygotes and 7 couples where both partners were CF heterozygotes. Prenatal diagnosis was performed in 4 cases and 3 were counseled on the availability of a prenatal test.

Five percent of normal cystic fibrosis transmembrane conductance regulator mRNA ameliorates the severity of pulmonary disease in cystic fibrosis

Estimates of the level of transcripts from the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene required to develop a CF phenotype range from 4-20% of normal. Due to the importance of obtaining reliable data on this issue for therapeutic strategies, we developed a novel polymerase chain reaction-based method to quantify CFTR transcripts and applied it to the analysis of nasal epithelium RNA of five patients with CF and the 3272-26A>G/F508del genotype. We calculated that 8.2 +/- 0.84% of the total CFTR RNA present in these five patients is normal full-length CFTR mRNA. We then demonstrated (in nasal samples from F508del carriers, n = 30) that the abundance of full-length F508del CFTR transcripts is reduced compared with wild-type transcripts, and estimated that the average ratio of F508del/wild-type transcripts is 0.87 +/- 0.06. To determine the amount of full-length transcripts relative to levels found in normal individuals, we corrected for the lower abundance of the F508del transcripts and calculated that the five patients with CF have, on average, 4.7 +/- 0.45% of the normal level of wild-type CFTR mRNA. Because these patients have mild CF compared with F508del homozygotes, this CFTR mRNA level appears to be sufficient to avoid the severe complications of the disease.