A Low-Cost and Simple Genetic Screening for Cystic Fibrosis Provided by the Brazilian Public Health System

Pancreatic Insufficiency in a Child with p.Gly542* and c.2657+5G>A Heterozygote CFTR: A Case Report

Cystic fibrosis is a monogenic and autosomal recessive disease. It is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator gene responsible for encoding the CFTR protein. Involvement of the gastrointestinal and respiratory systems is the main clinical manifestation. In this case, we report a heterozygous CFTR patient harboring class I (p.Gly542*) and class V (c.2657+5G>A) mutations. The importance of this case report lies in the clinical features because the patient, aged 3 years, presented with early exocrine pancreatic insufficiency, which can be considered atypical, as most individuals with this genotype are pancreatic sufficient or develop pancreatic insufficiency later in life. This report aims at presenting the tests requested that contributed to the patient's diagnosis, as well as at understanding the association between these mutations and their phenotypic presentation. Interpretation of the genotype-phenotype relationship represents a challenge, as genetic analysis alone is not sufficient to clearly predict severity of the disease. This is because the significant phenotypic heterogeneity existing among patients with the same genotype may exert socioeconomic and sociocultural influences, or by the action of CFTR modifiers, such as environmental and modifying genes, which can alter the protein's function and exert an impact on the individual's phenotype.

Cystic Fibrosis: Systems Biology Analysis from Homozygous p.Phe508del Variant Patients' Samples Reveals Perturbations in Tissue-Specific Pathways

Cystic fibrosis (CF) is an autosomal recessive disorder, caused by diverse genetic variants for the CF transmembrane conductance regulator (CFTR) protein. Among these, p.Phe508del is the most prevalent variant. The effects of this variant on the physiology of each tissue remains unknown. This study is aimed at predicting cell signaling pathways present in different tissues of fibrocystic patients, homozygous for p.Phe508del. The study involved analysis of two microarray datasets, E-GEOD-15568 and E-MTAB-360 corresponding to the rectal and bronchial epithelium, respectively, obtained from the ArrayExpress repository. Particularly, differentially expressed genes (DEGs) were predicted, protein-protein interaction (PPI) networks were designed, and centrality and functional interaction networks were analyzed. The study reported that p.Phe508del-mutated CFTR-allele in homozygous state influenced the whole gene expression in each tissue differently. Interestingly, gene ontology (GO) term enrichment analysis revealed that only “neutrophil activation” was shared between both tissues; however, nonshared DEGs were grouped into the same GO term. For further verification, functional interaction networks were generated, wherein no shared nodes were reported between these tissues. These results suggested that the p.Phe508del-mutated CFTR-allele in homozygous state promoted tissue-specific pathways in fibrocystic patients. The generated data might further assist in prediction diagnosis to define biomarkers or devising therapeutic strategies.

Next-Generation Sequencing for Molecular Diagnosis of Cystic Fibrosis in a Brazilian Cohort

Cystic fibrosis (CF), an autosomal recessive genetic disease, is recognized as one of the most prevalent diseases in Caucasian populations. Epidemiological data show that the incidence of CF varies between countries and ethnic groups in the same region. CF occurs due to pathogenic variants in the gene encoding cystic fibrosis transmembrane conductance regulator (CFTR), located on chromosome 7q31.2. To date, more than 2,000 variants have been registered in the CFTR database. The study of these variants leads to the diagnosis and the possibility of a specific treatment for each patient through precision medicine. In this study, complete screening of CFTR was performed through next-generation sequencing (NGS) to gain insight into the variants circulating in the population of Rio de Janeiro and to provide patient access to treatment through genotype-specific therapies. Samples from 93 patients with an inconclusive molecular diagnosis were subjected to full-length screening of CFTR using an Illumina NGS HiSeq platform. Among these patients, 46 had two pathogenic variants, whereas 12 had only one CFTR variant. Twenty-four variants were not part of our routine screening. Of these 24 variants, V938Gfs∗37 had not been described in the CF databases previously. This research achieved a molecular diagnosis of the patients with CF and identification of possible molecular candidates for genotype-specific treatments.

[Rare diseases on the agenda for innovation in health: progress and challenges with cystic fibrosis]

The article proposes to discuss the many complexities involved in the incorporation of new health technologies for rare diseases, with a central focus on the case of cystic fibrosis. Cystic fibrosis was chosen because it is a autosomal recessive genetic disorder, considered the most common of the rare diseases. The disease has also benefited greatly from investments in research in the field of molecular biology, mainly in the United States, but also among European research groups, which resulted in the registration and marketing of four new drugs. These new drugs act for the first time on the basic defect in cystic fibrosis. From a perspective that views rare diseases as a field of research woven among many others, the article aims to problematize cystic fibrosis from a more person-centered approach, the duality of witnessing from afar the molecularization of life, the emergence of last-generation drugs that interrupt, at the molecular level, the cascade of errors and thus the symptoms and evolution of the disease. The article aims to bring various elements to the debate that traverse the complex local reality of Brazilian cystic fibrosis patients in a global context of technological innovation and with a break in the treatment paradigm. Based on the field of rare diseases, including the presentation of cystic fibrosis in the age of precision medicine, alongside discussions on biopolitics in a context of health innovation and high-cost drugs, the article aims to shed light on the current challenges and possibilities.

Cystic Fibrosis: A Simple and Customized Strategy for Genetic Screening Able to Detect Over 90% of Identified Mutated Alleles in Brazilian Newborns

INTRODUCTION

The incorporation of molecular genetic testing into cystic fibrosis (CF) screening programs increases the specificity of the diagnostic strategy and has the potential to decrease the rate of false- positive results. In this sense, our objective was to develop a genotyping assay that could detect 25 pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene with high sensitivity and that could be incorporated into the routine of newborn screening, complementing the current existing protocol used in our public health institution.

METHODS

A mini-sequencing assay was standardized using single-base extension in a previously genotyped control sample. This strategy was validated in a Brazilian cohort of CF patients by Sanger sequencing.

RESULTS

The inclusion of the 25 variants in the current newborn screening program increased the identification rates of two alleles from 33 to 52.43% in CF patients. This new approach was able to detect a total of 37 variants, which represents 93.01% of all mutated alleles described in the last CF Brazilian Register.

CONCLUSIONS

Mini-sequencing for the simultaneous detection of 25 CFTR gene variants improves the screening of Brazilian newborns and decreases the number of inconclusive cases. This method uses minimal hands-on time and is suited for rapid screening, which reduces sample processing costs.

Cystic fibrosis year in review 2018, part 2

Cystic fibrosis (CF) research and case reports were robust in the year 2018. This report summarizes publications related the multisystem effects of CF, pulmonary exacerbations, new and expanded therapies other than cystic fibrosis transmembrane conductance regulator modulator studies, and patient-reported priorities and outcomes.