A high frequency of the Cystic Fibrosis 2184insA mutation in Western Ukraine: Genotype–phenotype correlations, relevance for newborn screening and genetic testing

Functional rescue of CFTR in rectal organoids from patients carrying R334W variant by CFTR modulators and PDE4 inhibitor Roflumilast

BACKGROUND

Many disease-causing variants in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene remain uncharacterized and untreated. Restoring the function of the impaired CFTR protein is the goal of personalized medicine, particularly in patients carrying rare CFTR variants. In this study, functional defects related to the rare R334W variant were evaluated after treatment with CFTR modulators or Roflumilast, a phosphodiesterase-4 inhibitor (PDE4i).

METHODS

Rectal organoids from subjects with R334W/2184insA and R334W/2183AA > G genotypes were used to perform the Forskolin-induced swelling (FIS) assay. Organoids were left drug-untreated or treated with modulators VX-770 (I), VX-445 (E), and VX-661 (T) mixed, and their combination (ETI). Roflumilast (R) was used alone or as a combination of I + R.

RESULTS

Our data show a significant increase in FIS rate following treatment with I alone. The combined use of modulators, such as ETI, did not increase further swelling than I alone, nor in protein maturation. Treatment with R shows an increase in FIS response similar to those of I, and the combination R + I significantly increases the rescue of CFTR activity.

CONCLUSIONS

Equivalent I and ETI treatment efficacy was observed for both genotypes. Furthermore, significant organoid swelling was observed with combined I + R used that supports the recently published data describing a potentiating effect of only I in patients carrying the variant R334W and, at the same time, corroborating the role of strategies that include PDE4 inhibitors further to potentiate the effect of I for this variant.

SARS-CoV-2 viral entry and replication is impaired in Cystic Fibrosis airways due to ACE2 downregulation

As an inherited disorder characterized by severe pulmonary disease, cystic fibrosis could be considered a comorbidity for coronavirus disease 2019. Instead, current clinical evidence seems to be heading in the opposite direction. To clarify whether host factors expressed by the Cystic Fibrosis epithelia may influence coronavirus disease 2019 progression, here we describe the expression of SARS-CoV-2 receptors in primary airway epithelial cells. We show that angiotensin converting enzyme 2 (ACE2) expression and localization are regulated by Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. Consistently, our results indicate that dysfunctional CFTR channels alter susceptibility to SARS-CoV-2 infection, resulting in reduced viral entry and replication in Cystic Fibrosis cells. Depending on the pattern of ACE2 expression, the SARS-CoV-2 spike (S) protein induced high levels of Interleukin 6 in healthy donor-derived primary airway epithelial cells, but a very weak response in primary Cystic Fibrosis cells. Collectively, these data support that Cystic Fibrosis condition may be at least partially protecting from SARS-CoV-2 infection.

Systematic review of health and disease in Ukrainian children highlights poor child health and challenges for those treating refugees

Aim

Millions of Ukrainian children have been internally displaced or fled to other countries because of the Russian war. This systematic review focused on their health needs and future challenges for clinicians.

Methods

A systematic literature search of the Medline, Embase and MedRxiv databases from 1 January 2010 to 31 March 2022 identified 1628 papers on the health of Ukrainian children and 112 were relevant to this review.

Results

In 2019, under‐5 mortality was 8 per 1000 live births in Ukraine. Underweight and adverse childhood experiences, including child abuse, were frequent compared to other European countries, while childhood obesity seemed less common. Alcohol consumption was common in women of reproductive age, including during pregnancy, risking foetal alcohol syndrome. Neonatal screening programmes provided low coverage. Vaccine hesitancy was common and vaccination rates were low. Other concerns were measles, HIV, antibiotic resistance and multi‐resistant tuberculosis. Many children are expected to suffer from psychological and physical trauma due to the war. Other healthcare challenges include low COVID‐19 vaccination rates and a preference for secondary and tertiary care, rather than primary care. Many people cannot afford medication.

Conclusion

Ukrainian children often have poor health and host countries need to be aware of their needs.

Identification of 99% of CFTR gene mutations in Bulgarian-, Bulgarian Turk-, and Roma cystic fibrosis patients

Background

The spectrum and frequencies of CFTR mutations causing Cystic fibrosis (CF) varies among different populations in Europe, and beyond.

Methods

We identified 98.9% of all CFTR mutations in a representative cohort of 140 CF patients comprising 107 Bulgarian‐ (BG), 17 BG Turk‐, and 16 BG Roma cases. The compiled clinical and genotype dataset includes 110 previously analyzed patients with 30 cases currently analyzed for rare CFTR variants by massively parallel sequencing of the entire CFTR coding region and adjacent introns combined with the analysis of intra‐CFTR rearrangements.

Results

Altogether 53 different mutations, of which 15 newly identified in the BG CF population, were observed. Comparison of clinical and laboratory data between individual BG ethnic groups proved that BG Roma have a more severe nutritional status and are younger than other CF patients, as well as that the spectrum mutations differs between them.

Conclusion

This collaborative study improves genetic counselling in BG, facilitates introduction of multitier CF neonatal screening and fosters public health measures for improvement of care in the Roma CF population.

Novel mutations and deletions in cystic fibrosis in a tertiary cystic fibrosis center in Istanbul

BACKGROUND

Cystic fibrosis (CF) genotyping has garnered increased attention since the discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in 1989 led to the identification of over 1700 mutations on chromosome 7. Yet, little is known about the genetic profile of CF patients in Turkey. This study sought to determine the mutation distribution among CF patients seeking care at Marmara University.

METHODS

Two hundred fifty previously diagnosed CF patients were included in the study. CFTR gene exons 1 to 27 were amplified by a polymerase chain reaction and whole DNA sequencing was performed. Duplications and deletions were investigated by the multiplex ligation-dependent probe amplification (MLPA) technique in patients with one or two unidentified mutations in sequence analysis.

RESULTS

CFTR mutation analysis revealed 80 mutations and five large deletions were present in our study population. The five most common mutations were (delta) F508 (c.1521-1523delCTT) (28.4%), 1677delTA (c.1545-1546delTA) (6.4%), 2789 + 5G- > A (c.2657 + 5G > A) (5.8%), N1303K (c.3909C > G) (2.4%), and c.2183AA- > G (c.2051-2052delAAinsG) (4.0%). Large deletions were found in 16 patients. Four novel mutations and two novel deletions were detected in this study.

CONCLUSIONS

We have identified four novel mutations and two novel deletions using next-generation DNA sequencing and the MLPA technique and obtained an overall mutation detection rate of 91.4%. Detection of novel variants in CF patients will assist in genetic counseling and in determining appropriate patients for new therapies.

Phenotypic spectrum and genetic heterogeneity of cystic fibrosis in Sri Lanka

Background

Cystic fibrosis has been largely under-diagnosed and thus, limited data is available on the incidence of cystic fibrosis in Sri Lanka. Our aim is to describe the phenotypic and genotypic spectrum of children with cystic fibrosis in Sri Lanka.

Case presentation

This report describes 10 unrelated cystic fibrosis cases with phenotypic features of cystic fibrosis and abnormal or intermediate sweat tests. The most common phenotypic features in this sample of symptomatic patients were persistent or recurrent lower respiratory tract infections, failure to thrive and Pseudo-Bartter syndrome. Altogether 7 cystic fibrosis causing mutations were identified in 10 patients. Except delta F508 which is the commonest mutation worldwide all the other mutations detected in Sri Lankan patients are rare mutations. 1161delC and V456A detected in our patients are South Asian mutations. The other mutations such as [C.1282C > G; C.2738A > G], C.53 + 1G > C, 2184insA and a deletion encompassing exons 4 to 11 have been reported previously from European patients with cystic fibrosis.

Conclusion

These cases highlight the importance of considering the diagnosis of cystic fibrosis in children and young adults presenting with persistent respiratory tract infections associated with severe malnutrition and Pseudo-Bartter syndrome, especially in low income countries where newborn screening for cystic fibrosis is not available. The spectrum of CFTR mutations in Sri Lanka is heterogeneous and possibly linked to genetic flow from Indian subcontinent and Europe. The common mutations should be identified by sequencing the entire CFTR gene in adequate number of cystic fibrosis patients in order to design a mutation panel for common regional mutations.

Analytical parameters and validation of homopolymer detection in a pyrosequencing-based next generation sequencing system

Background

Current technologies in next-generation sequencing are offering high throughput reads at low costs, but still suffer from various sequencing errors. Although pyro- and ion semiconductor sequencing both have the advantage of delivering long and high quality reads, problems might occur when sequencing homopolymer-containing regions, since the repeating identical bases are going to incorporate during the same synthesis cycle, which leads to uncertainty in base calling. The aim of this study was to evaluate the analytical performance of a pyrosequencing-based next-generation sequencing system in detecting homopolymer sequences using homopolymer-preintegrated plasmid constructs and human DNA samples originating from patients with cystic fibrosis.

Results

In the plasmid system average correct genotyping was 95.8% in 4-mers, 87.4% in 5-mers and 72.1% in 6-mers. Despite the experienced low genotyping accuracy in 5- and 6-mers, it was possible to generate amplicons with more than a 90% adequate detection rate in every homopolymer tract. When homopolymers in the CFTR gene were sequenced average accuracy was 89.3%, but varied in a wide range (52.2 – 99.1%). In all but one case, an optimal amplicon-sequencing primer combination could be identified. In that single case (7A tract in exon 14 (c.2046_2052)), none of the tested primer sets produced the required analytical performance.

Conclusions

Our results show that pyrosequencing is the most reliable in case of 4-mers and as homopolymer length gradually increases, accuracy deteriorates. With careful primer selection, the NGS system was able to correctly genotype all but one of the homopolymers in the CFTR gene. In conclusion, we configured a plasmid test system that can be used to assess genotyping accuracy of NGS devices and developed an accurate NGS assay for the molecular diagnosis of CF using self-designed primers for amplification and sequencing.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4544-x) contains supplementary material, which is available to authorized users.

Comprehensive genetic study of cystic fibrosis in Slovak patients in 25 years of genetic diagnostics

INTRODUCTION

Cystic fibrosis (CF) has one of the longest histories in hereditary disease molecular diagnostics. However, identification of causative mutations in the CFTR gene is complicated by over 2000 currently identified mutations; with more still being discovered. Knowledge of mutation spectrum may improve effective routine diagnostics and is obligatory in mutation-specific treatment.

OBJECTIVES

This study presents comprehensive mutation screening of the CFTR gene; with 275 unrelated, clinically confirmed and treated cystic fibrosis (CF) patients diagnosed in 25 years genetic testing in Slovakia.

METHODS

Detection of the most common CFTR mutations was performed by ELUCIGENE 29 and ELUCIGENE CF EU2 kits. HRM and dHPLC mutation screening methods with subsequent Sanger sequencing were applied for minor mutation screening, and MLPA analysis for deletion/duplication detection.

RESULTS

A total of 70 different mutations were identified, from which the most common mutation F508del accounted for 60.36% of all disease alleles and 8 mutations have currently been observed only in Slovak patients. Two large deletions identified on chromosomes 2 and 22 were further characterized to identify breakpoints. Based on mutation screening results and neonatal screening we estimated incidence in Slovakian newborns at approximately 1:6000-7000.

CONCLUSION

In our study, we identified mutations in 98.54% of all disease chromosomes, while 86.54% were identified using ELUCIGENE kits, 0.54% by MLPA analysis and 11.46% by sequencing analysis. Knowledge of the mutation spectrum in genetically diagnosed patients improves possibilities of genetic counseling and cascade screening in the affected families and Slovak population.

A Clinical and Molecular Survey of 62 Cystic Fibrosis Patients from Umbria (Central Italy) Disclosing a High Frequency (2.4%) of the 2184insA Allele: Implications for Screening

Genetic testing strategies and counseling in cystic fibrosis (CF) can be problematic due to its extreme allelic heterogeneity and the difficult clinical interpretation of rare variants. Since in a previous survey of Italian CF patients, Umbria (a small region with about 900,000 inhabitants) was excluded due to the low number of chromosomes tested (<50), we have performed a comprehensive retrospective clinical and molecular survey of 62 CF patients coming from this region. We have summarized all the genotypic and phenotypic data in a table, and we interviewed the older patients in order to obtain a comprehensive overview of their conditions. We found that the c.2052_2053insA (2184insA) variant, a class I mutation with high frequency in Eastern Europe but very rare in Italy, is the fourth most frequent allele in Umbria. The 2184insA variant was not included in the first-level regional screening, and we therefore suggest the implementation of this variant in the future.

Molecular Analysis of Cystic Fibrosis Patients in Hungary - An Update to the Mutational Spectrum

BACKGROUND

In this study the authors present an update to the CFTR mutation profile in Hungary, utilizing data from a selected cohort of 45 cystic fibrosis (CF) patients from different regions of the country.

METHODS

Depending on the preceding analysis, four different mutation detection methods were used. A commercial assay targeting the most common CF-causing mutations was performed as the first test followed by an allele specific PCR for CFTRdele2,3(21kb), Sanger sequencing and MLPA analysis of the coding region of the CFTR gene.

RESULTS

In our recent study 27 different mutations were detected, including 2 novel ones (c.1037_1038insA and c.1394C>T). Besides F508del (c.1521_1523delCTT), the following mutations were found at a frequency of ≥ 4.0%: W1282X (c.3846G>A), N1303K (c.3909C>G), CFTRdele2,3(21kb) (c.54-5940_273+10250del21kb) and 2184insA (c.2052_2053insA). In addition, four mutations (G542X, Y1092X, 621+1G>T, and 2143delT) were found in more than one allele.

CONCLUSIONS

The updated database of Hungarian mutations not only enables to increase the efficiency of the existing diagnostic approach, but also provides a further refined basis for the introduction of the molecular newborn screening (NBS) program in Hungary.

CFTR mutations spectrum and the efficiency of molecular diagnostics in Polish cystic fibrosis patients

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane regulator gene (CFTR). In light of the strong allelic heterogeneity and regional specificity of the mutation spectrum, the strategy of molecular diagnostics and counseling in CF requires genetic tests to reflect the frequency profile characteristic for a given population. The goal of the study was to provide an updated comprehensive estimation of the distribution of CFTR mutations in Polish CF patients and to assess the effectiveness of INNOLiPA_CFTR tests in Polish population. The analyzed cohort consisted of 738 patients with the clinically confirmed CF diagnosis, prescreened for molecular defects using INNOLiPA_CFTR panels from Innogenetics. A combined efficiency of INNOLiPA CFTR_19 and CFTR_17_TnUpdate tests was 75.5%; both mutations were detected in 68.2%, and one mutation in 14.8% of the affected individuals. The group composed of all the patients with only one or with no mutation detected (109 and 126 individuals, respectively) was analyzed further using a mutation screening approach, i.e. SSCP/HD (single strand conformational polymorphism/heteroduplex) analysis of PCR products followed by sequencing of the coding sequence. As a result, 53 more mutations were found in 97 patients. The overall efficiency of the CF allele detection was 82.5% (7.0% increase compared to INNOLiPA tests alone). The distribution of the most frequent mutations in Poland was assessed. Most of the mutations repetitively found in Polish patients had been previously described in other European populations. The most frequent mutated allele, F508del, represented 54.5% of Polish CF chromosomes. Another eight mutations had frequencies over 1%, 24 had frequencies between 1 and 0.1%; c.2052-2053insA and c.3468+2_3468+3insT were the most frequent non-INNOLiPA mutations. Mutation distribution described herein is also relevant to the Polish diaspora. Our study also demonstrates that the reported efficiency of mutation detection strongly depends on the diagnostic experience of referring health centers.

Newborn screening for cystic fibrosis: Polish 4 years' experience with CFTR sequencing strategy

Newborn screening for cystic fibrosis (NBS CF) in Poland was started in September 2006. Summary from 4 years' experience is presented in this study. The immunoreactive trypsin/DNA sequencing strategy was implemented. The group of 1,212,487 newborns were screened for cystic fibrosis during the programme. We identified a total of 221 CF cases during this period, including, 4 CF cases were reported to be omitted by NBS CF. Disease incidence in Poland based on the programme results was estimated as 1/4394 and carrier frequency as 1/33. The frequency of the F508del was similar (62%) to population data previously reported. This strategy allowed us to identify 29 affected infants with rare genotypes. The frequency of some mutations (eg, 2184insA, K710X) was assessed in Poland for the first time. Thus, sequencing assay seems to be accurate method for screening programme using blood spots in the Polish population.

Newborn screening for cystic fibrosis

PURPOSE OF REVIEW

Newborn screening for cystic fibrosis (CF) is now universal in the US and many other countries. The rapid expansion of screening has resulted in numerous publications identifying new challenges for healthcare providers. This review provides an overview of these publications and includes ideas on managing these challenges.

RECENT FINDINGS

Most CF newborn screening algorithms involve DNA mutation analysis. As screening has expanded, new challenges have been identified related to carrier detection and inconclusive diagnoses. Early descriptions of infants with CF-related metabolic syndrome (CRMS) indicate that the natural history of this condition cannot be predicted. Early identification has also provided an opportunity to better understand the pathophysiology of CF. However, few studies have been conducted in infants with CF to determine optimal therapy and recommendations are largely anecdotal.

SUMMARY

Newborn screening provides an opportunity to identify and begin treatment early in individuals with CF. Whereas a single, optimal approach to screening does not exist, all programs can benefit from new findings regarding sweat testing, carrier detection, early pathophysiology, and clinical outcomes.