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El Makhzen N, Daimi H, Bouguenouch L, Abriel H. The burden of cystic fibrosis in North Africa. Front Genet 2024; 14:1295008. [PMID: 38269366 PMCID: PMC10806102 DOI: 10.3389/fgene.2023.1295008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 12/26/2023] [Indexed: 01/26/2024] Open
Abstract
Background: Over 200 pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene are associated with cystic fibrosis (CF)-the most prevalent autosomal recessive disease globally, the p.Phe508del variant being the most commonly observed. Main text: Recent epidemiological studies suggest a higher global prevalence of CF than previously thought. Nevertheless, comprehensive CF data remains extremely scarce among African populations, contributing to a significant information gap within the African healthcare system. Consequently, the underestimation of CF among children from African populations is likely. The goal of this article is to review the pathogenesis of CF and its prevalence in the countries of North Africa. Conclusion: The prevalence of CF in North African countries is likely underestimated due to the complexity of the disease and the lack of a timely, proper clinical and genetic investigation that allows the early identification of CF patients and thus facilitates therapeutic recommendations. Therefore, specific genetic and epidemiological studies on African individuals showing CF symptoms should be conducted to enhance the diagnostic yield of CF in Africa.
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Affiliation(s)
- Nada El Makhzen
- Ion Channels and Channelopathies Laboratory, Institute for Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Houria Daimi
- Laboratory of Human Genome and Multifactorial Diseases (LR12ES07), Faculty of Pharmacy, University of Monastir, Monastir, Tunisia
- Department of Biology, Faculty of Sciences, University of Gabes, Gabès, Tunisia
| | - Laila Bouguenouch
- Laboratory of Medical Genetics and Oncogenetics, University Hospital Hassan II, Sidi Mohamed Ben Abdellah University, Fez, Morocco
| | - Hugues Abriel
- Ion Channels and Channelopathies Laboratory, Institute for Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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Banjar HH, Tuleimat L, El Seoudi AAA, Mogarri I, Alhaider S, Nizami IY, AlMaghamsi T, Alkaf SA, Moghrabi N. Genotype patterns for mutations of the cystic fibrosis transmembrane conductance regulator gene: a retrospective descriptive study from Saudi Arabia. Ann Saudi Med 2020; 40:15-24. [PMID: 32026723 PMCID: PMC7012030 DOI: 10.5144/0256-4947.2020.15] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 07/20/2019] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Cystic fibrosis (CF) occurs in populations in Saudi Arabia and the Gulf area. Approximately 2000 known variants have been identified for the CF transmembrane conductance regulator (CTFR) gene. Screening for ten of the most common variants can detect 80% of alleles. OBJECTIVE Determine the pattern of CFTR variants in the CF population of Saudi Arabia. DESIGN A retrospective, descriptive. SETTING Tertiary care center. PATIENTS AND METHODS We examined the medical records of 396 confirmed CF patients of all age groups that were positive for a CFTR variant from the period of 1 January 1998 to 1 December 2017. MAIN OUTCOME MEASURES Zygosity, morbidity and mortality patterns of different types of CFTR variants. SAMPLE SIZE 312 families that included 396 patients. RESULTS Of 48 variants identified, 6 were novel, having not been described in the medical literature. A homozygous state was found in 283 families (90.7%) and compound heterozygosity in 23 (7.4%). Six families were heterozygous (1.9%). Median age (interquartile range) was 10.2 months (4.4 months to 5.7 years) at diagnosis and 9.7 (5.4-16.5) years at follow up. Of 396 patients, 378 patients (95.5%) survived and 18 (4.5%) died. The ten most common variants identified in descending frequency were: p.Gly473GlufsX54 in 98 alleles (16%), p.Ile1234Val in 66 alleles (11%), F508del in 64 alleles (11%), 711+1G>T in 62 alleles (10%), 3120+1G>A in 62 alleles (11%), p.His139Leuin 38 alleles (6.4%), p.Gln637Hisfs in 30 alleles (5.2%), p.Ser549Arg in 27 alleles (4.5%), p.Asn1303Lys in 14 alleles (2.3%), delExon19-21in 10 alleles (1.6%). This analysis identified 79.2% of our CFTR variants. CONCLUSION CFTR mutational patterns in our CF population are characterized by a high allelic heterogeneity. The high prevalence of homozygous variants reflects the high level of consanguinity between parents. LIMITATIONS Our CFTR screening reflected only about 80% of CF patients in Saudi Arabia. CONFLICT OF INTEREST None.
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Affiliation(s)
- Hanaa Hasan Banjar
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Lin Tuleimat
- From the Department of Medicine, Al Faisal University, Riyadh, Saudi Arabia
| | | | - Ibrahim Mogarri
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Sami Alhaider
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Imran Yaqoob Nizami
- From the Organ Transplant Center, King Faisal Specialist and Research Center, Riyadh, Saudi Arabia
| | - Talal AlMaghamsi
- From the Department of Pediatrics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Sara Andulrahman Alkaf
- From the Biostatistic Epidemiology and Scientific Computing Department, King Faisal Center for Research and Islamic Studies, Riyadh, Saudi Arabia
| | - Nabil Moghrabi
- From the Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
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Banjar H, Al-Mogarri I, Nizami I, Al-Haider S, AlMaghamsi T, Alkaf S, Al-Enazi A, Moghrabi N. Geographic distribution of cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in Saudi Arabia. Int J Pediatr Adolesc Med 2019; 8:25-28. [PMID: 33718573 PMCID: PMC7922840 DOI: 10.1016/j.ijpam.2019.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 11/18/2019] [Accepted: 12/03/2019] [Indexed: 01/17/2023]
Abstract
Introduction Cystic fibrosis (CF) has been reported before in Saudi Arabia and the Gulf area. It has been found that screening for 10 most common cystic fibrosis transmembrane conductance regulator (CFTR) mutations can detect 80% of positive CFTR cases. Objectives To determine the geographic distribution of the most common CFTR variants in 5 regions of Saudi Arabia. Methodology A retrospective chart review of all CFTR variants conducted from January 1, 1992 to December 1, 2017. Results The ten most common CFTR mutations in the Saudi population were as follows: p.Gly473GlufsX54 (17%), p.Phe508del (12%), p.Ile1234Val (12%), 3120+1G > A (11%), 711+1G > T (9%), p.His139Leu (6%), p.Gln637Hisfs (5%), p.Ser549Arg (3%), p.N1303K (3%), and delExon19-21 (2%) along with other variants 79 (20%). In terms of the highest frequency, the c.2988+1G > A (3120+1G > A) variant was found in the eastern province (7.3%) of Saudi Arabia, the c.1418delG (p.Gly473GlufsX54) variant in the northern province (6.8%), the c.579+1G > T (711+1G > T) variant in the southern province (4.8%), the c.3700A > G (p.Ile1234Val) variant in the central province (4.8%), and c.1521_1523delCTT (p.Phe508del) variant in the western province (4.3%). Conclusion The eastern and the northern provinces have the highest prevalence of CF, with the c.2988+1G > A (3120+1G > A) and c.1418delG (p.Gly473GlufsX54) variants showing the highest distribution in the Saudi CF population, which may reflect the effect of consanguinity within the same tribe. Proper family screening and counseling should be emphasized.
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Affiliation(s)
- Hanaa Banjar
- Department of Pediatrics, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia
| | - Ibrahim Al-Mogarri
- Department of Pediatrics, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia
| | - Imran Nizami
- Organ Transplant Center, (King Faisal Specialist Hospital and Research Center), Riyadh, Saudi Arabia
| | - Sami Al-Haider
- Department of Pediatrics, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia
| | - Talal AlMaghamsi
- Department of Pediatrics, King Faisal Specialist Hospital and Research Center (KFSHRC), Jeddah, Saudi Arabia
| | - Sara Alkaf
- Department of Biostatistics, Epidemiology and Scientific Computing, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia
| | - Abdulaziz Al-Enazi
- Department of Pediatrics, King Faisal Specialist Hospital and Research Center (KFSHRC), Riyadh, Saudi Arabia
| | - Nabil Moghrabi
- Department of Genetics, Molecular Diagnostic Laboratory, The Research Center, KFSHRC, Riyadh, Saudi Arabia
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Cabrini G. Innovative Therapies for Cystic Fibrosis: The Road from Treatment to Cure. Mol Diagn Ther 2019; 23:263-279. [PMID: 30478715 DOI: 10.1007/s40291-018-0372-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cystic fibrosis (CF), a life-threatening multiorgan genetic disease, is facing a new era of research and development using innovative gene-directed personalized therapies. The priority organ to cure is the lung, which suffers recurrent and chronic bacterial infection and inflammation since infancy, representing the main cause of morbidity and precocious mortality of these individuals. After the disappointing failure of gene-replacement approaches using gene therapy vectors, no single drug is presently available to repair all the CF gene defects. The impressive number of different CF gene mutations is now tackled with different chemical and biotechnological tools tailored to the specific molecular derangements, thanks to the extensive knowledge acquired over many years on the mechanisms of CF cell and organ pathology. This review provides an overview and recalls both the successes and limitations of the different experimental approaches, such as high-throughput screening on chemical libraries to discover CF gene correctors and potentiators, dual-acting compounds, read-through molecules, splicing defect repairing tools, cystic fibrosis transmembrane conductance regulator (CFTR) "amplifiers," CFTR interactome modulators and the first gene editing attempts.
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Affiliation(s)
- Giulio Cabrini
- Laboratory of Molecular Pathology, University Hospital, Verona, Italy. .,Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.
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Abstract
Identifying mutations that cause cystic fibrosis (CF) is important for making an early, unambiguous diagnosis, which, in turn, is linked to better health and a greater life expectancy. In patients of African descent, a molecular diagnosis is often confounded by the fact that the majority of investigations undertaken to identify causative mutations have been conducted on European populations, and CF-causing mutations tend to be population specific. We undertook a survey of published data with the aim of identifying causative CF mutations in patients of African descent in the Americas. We found that 1,584 chromosomes had been tested in only 6 countries, of which 876 alleles (55.3%) still remained unidentified. There were 59 mutations identified. Of those, 41 have been shown to cause CF, 17 have no associated functional studies, and one (R117H) is of varying clinical consequence. The most common mutations identified in the patients of African descent were: ΔF508 (29.4% identified in the United States, Colombia, Brazil, and Venezuela); 3120 + 1G>A (8.4% identified in Brazil, the United States, and Colombia); G85E (3.8% identified in Brazil); 1811 + 1.6kbA>G (3.7% identified in Colombia); and 1342 - 1G>C (3.1% identified in the United States). The majority of the mutations identified (81.4%) have been described in just one country. Our findings indicate that there is a need to fully characterize the spectrum of CF mutations in the diaspora to improve diagnostic accuracy for these patients and facilitate treatment.
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Abstract
Cystic fibrosis (CF) is the most frequent lethal genetic disorder among Caucasians, but is considered to be a very rare disease in Chinese population. Here, we present an 11-year-old Chinese CF patient with disseminated bronchiectasis and salty sweat, for whom exon sequencing followed by multiplex ligation-dependent probe amplification analysis of the CFTR gene was applied for mutation screening. A homozygous deletion involving exon 20 of CFTR was observed in the patient's genome. Molecular characterization of the breakpoints indicated that both alleles of this locus had an identical novel complex rearrangement (c.3140-454_c.3367+249del931ins13, p.R1048_G1123del), leading to an in-frame removal of 76 amino acid residues in the second transmembrane domains of the CFTR protein. Although a same haplotype containing this complex rearrangement was observed on both of the maternal and paternal alleles, the parents denied any blood relationship as far as they know. Genome-wide homozygosity mapping was performed through SNP microarray and only a single homozygous interval of ~14.1 Mb at chromosome 7 containing the CFTR gene was observed, indicating the possible origin of the deletion from a common ancestor many generations ago. This study expands the mutation spectrum of CFTR in patients of Chinese origin and further emphasizes the necessity of MLPA analysis in mutation screening for CF patients.
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7
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Stewart C, Pepper MS. Cystic fibrosis on the African continent. Genet Med 2015; 18:653-62. [DOI: 10.1038/gim.2015.157] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 09/17/2015] [Indexed: 01/11/2023] Open
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Mutesa L, Azad AK, Verhaeghe C, Segers K, Vanbellinghen JF, Ngendahayo L, Rusingiza EK, Mutwa PR, Rulisa S, Koulischer L, Cassiman JJ, Cuppens H, Bours V. Genetic analysis of Rwandan patients with cystic fibrosis-like symptoms: identification of novel cystic fibrosis transmembrane conductance regulator and epithelial sodium channel gene variants. Chest 2008; 135:1233-1242. [PMID: 19017867 DOI: 10.1378/chest.08-2246] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND The defect in chloride and sodium transport in cystic fibrosis (CF) patients is a consequence of CF transmembrane conductance regulator (CFTR) loss of function and an abnormal interaction between CFTR and the epithelial sodium channel (ENaC). A few patients were described with CF-like symptoms, a single CFTR mutation, and an ENaC mutation. METHODS To study African patients with CF-like symptoms and to relate the disease to gene mutations of both CFTR and ENaC genes, we collected clinical data and DNA samples from 60 African patients with a CF phenotype. The CFTR gene was first analyzed in all patients by denaturing high-performance liquid chromatography followed by direct sequencing; whereas, the sodium channel non-voltage-gated 1 alpha (SCNN1A), sodium channel non-voltage-gated 1 beta (SCNN1B), and sodium channel non-voltage-gated 1 gamma (SCNN1G) subunits of the ENaC gene were analyzed by sequencing in the five patients who carried only one CF mutation. The frequency of all identified ENaC variants was established in a control group of 200 healthy individuals and in the 55 CF-like patients without any CFTR mutation. RESULTS Three CFTR mutants, including one previously undescribed missense mutation (p.A204T), and a 5T/7T variant were identified in five patients. ENaC gene sequencing in these five patients detected the following eight ENaC variants: c.72T>C and p.V573I in SCNN1A; p.V348M, p.G442V, c.1473 + 28C>T, and p.T577T in SCNN1B; and p.S212S and c.1176 + 30G>C in SCNN1G. In the 55 CF-like patients without any CFTR mutation, we identified five of these eight ENaC variants, including the frequent p.G442V polymorphism, but we did not detect the presence of the p.V348M, p.T577T, and c.1176 + 30G>C ENaC variants. Moreover, these last three ENaC variants, p.V348M, p.T577T, and c.1176 + 30G>C, were not found in the control group. CONCLUSION Our data suggest that CF-like syndrome in Africa could be associated with CFTR and ENaC mutations.
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Affiliation(s)
- Léon Mutesa
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium
| | - Abul Kalam Azad
- Department of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Catherine Verhaeghe
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium
| | - Karin Segers
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium
| | - Jean-François Vanbellinghen
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium
| | - Louis Ngendahayo
- Department of Pathology, Centre Hospitalier Universitaire-Butare, National University of Rwanda, Butare, Rwanda
| | - Emmanuel Kamanzi Rusingiza
- Department of Pediatrics, Centre Hospitalier Universitaire-Kigali, National University of Rwanda, Kigali, Rwanda
| | - Philippe Rutwaza Mutwa
- Department of Pediatrics, Centre Hospitalier Universitaire-Kigali, National University of Rwanda, Kigali, Rwanda
| | - Stephen Rulisa
- Department of Pediatrics, Centre Hospitalier Universitaire-Kigali, National University of Rwanda, Kigali, Rwanda
| | - Lucien Koulischer
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium
| | | | - Harry Cuppens
- Department of Human Genetics, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Vincent Bours
- Department of Human Genetics, Centre Hospitalier Universitaire-Sart-Tilman, Grappe Interdisciplinaire de Genoprotéomique Appliquée-Research, University of Liège, Liège, Belgium.
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Paracchini V, Seia M, Coviello D, Porcaro L, Costantino L, Capasso P, Degiorgio D, Padoan R, Corbetta C, Claut L, Costantini D, Colombo C. Molecular and clinical features associated with CFTR gene rearrangements in Italian population: identification of a new duplication and recurrent deletions. Clin Genet 2008; 73:346-52. [PMID: 18279436 DOI: 10.1111/j.1399-0004.2007.00957.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Cystic fibrosis (CF) is mainly caused by small deletions or missense mutations in the CFTR gene. The CF mutation database lists more than 35 large rearrangements that may escape detection using polymerase chain reaction-base techniques. The Innogenetics assay, the denaturing high-performance liquid chromatography and sequencing screening showed a mutation detection rate of 92.6% in our population. We report here the results of multiplex ligation-dependent probe amplification (MLPA) screening for CFTR gene rearrangements, performed on the unidentified alleles of our CF patients. Our sample population consists of 692 non-related Italian CF patients (for a total of 1384 alleles), followed at CF Centres in the Lombardia Region. MLPA analysis was performed in 49 patients who still had one or two unidentified alleles (for a total of 52 unidentified alleles) after extensive analysis of CFTR gene. All patients who were studied had the classical form of CF. We characterized nine different deletions and a new duplication. The deletion of exons 22-23 (7/82) was the most frequent in our cohort. The search for deletion/duplications of the CFTR gene has made it possible to reach a 94.1% detection rate, with an improvement (1.6%) of the carrier detection rate in the Italian population.
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Affiliation(s)
- V Paracchini
- Medical Genetics Laboratory, Fondazione IRCCS Policlinico, Mangiagalli, Regina Elena, Milan, Italy
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Hantash FM, Redman JB, Goos D, Kammesheidt A, McGinniss MJ, Sun W, Strom CM. Characterization of a recurrent novel large duplication in the cystic fibrosis transmembrane conductance regulator gene. J Mol Diagn 2007; 9:556-60. [PMID: 17690208 PMCID: PMC1975096 DOI: 10.2353/jmoldx.2007.060141] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Recently, DNA rearrangements in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have been described with increasing frequency. These large DNA rearrangements are not detected using conventional methods of DNA sequencing, single-strand conformational polymorphism, or denaturing high-performance liquid chromatography. We and others have described methods to detect such rearrangements in the CFTR gene. With one exception, all rearrangements reported thus far are single or multiple exon deletions, whereas only one report has described a large duplication. We describe here the detection and characterization of a novel large duplication in the CFTR gene. This duplication, referred to as gIVS6a + 415_IVS10 + 2987Dup26817bp, was detected in a classic CF female patient whose other mutation was DeltaF508. The duplication was inherited paternally. The duplication encompassed exons 6b to 10 and occurred on the IVS8-11TG/IVS8-7T/G1540 haplotype. This large duplication is predicted to result in the production of a truncated CFTR protein lacking the terminal part of NBD1 domain and beyond and thus can be considered a null allele. The combination of the DeltaF508 and gIVS6a + 415_IVS10 + 2987Dup26817bp mutation probably causes the severe CF phenotype in this patient. We designed a simple polymerase chain reaction test to detect the duplication, and we further detected the same duplication from another independent laboratory. The duplication breakpoint is identical in all three patients, suggesting a likely founder mutation.
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Affiliation(s)
- Feras M Hantash
- Quest Diagnostics Nichols Institute, Molecular Genetics, 33608 Ortega Hwy, San Juan Capistrano, CA 92690, USA.
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Kammesheidt A, Kharrazi M, Graham S, Young S, Pearl M, Dunlop C, Keiles S. Comprehensive genetic analysis of the cystic fibrosis transmembrane conductance regulator from dried blood specimens – Implications for newborn screening. Genet Med 2006; 8:557-62. [PMID: 16980811 DOI: 10.1097/01.gim.0000237793.19868.97] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE In the United States, approximately 1/3,700 babies is born with cystic fibrosis each year. The >1,300 documented sequence variants pose a challenge for detection of cystic fibrosis through genetic screening. To investigate whether comprehensive characterization of the cystic fibrosis gene is feasible using dried newborn blood specimens, we modified the whole blood Ambry Test: CF and determined its sensitivity by testing DNA from individuals with cystic fibrosis who still had unknown mutations after commercial mutation panel testing. METHODS DNA from 42 archived newborn dried blood specimens of affected Hispanic, African-American and Caucasian individuals in California was analyzed by temporal temperature gradient electrophoresis screening and targeted sequencing, and by gross deletion analysis. RESULTS Excluding two specimens that could not be analyzed due to poor DNA quality, we report a 100% sensitivity and clinical detection rate in the remaining 40 patients. Eighty-three mutations representing 40 different variants were detected, including 8 novel mutations. CONCLUSIONS This study demonstrates the feasibility of temporal temperature gradient electrophoresis-based full sequence analysis and targeted sequencing from DNA in newborn blood specimens. The Ambry Test: CF, as an additional step in cystic fibrosis newborn screening models, can be used to dramatically reduce the number of cystic fibrosis carrier sweat test referrals.
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Saxena SK, Kaur S, George C. Rab4GTPase modulates CFTR function by impairing channel expression at plasma membrane. Biochem Biophys Res Commun 2006; 341:184-91. [PMID: 16413502 DOI: 10.1016/j.bbrc.2005.12.170] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 12/24/2005] [Indexed: 10/25/2022]
Abstract
Cystic fibrosis (CF), an autosomal recessive disorder, is caused by the disruption of biosynthesis or the function of a membrane cAMP-activated chloride channel, CFTR. CFTR regulatory mechanisms include recruitment of channel proteins to the cell surface from intracellular pools and by protein-protein interactions. Rab proteins are small GTPases involved in regulated trafficking controlling vesicle docking and fusion. Rab4 controls recycling events from endosome to the plasma membrane, fusion, and degradation. The colorectal cell line HT-29 natively expresses CFTR and responds to cAMP stimulation with an increase in CFTR-mediated currents. Rab4 over-expression in HT-29 cells inhibits both basal and cAMP-stimulated CFTR-mediated currents. GTPase-deficient Rab4Q67L and GDP locked Rab4S22N both inhibit channel activity, which appears characteristically different. Active status of Rab4 was confirmed by GTP overlay assay, while its expression was verified by Western blotting. The pull-down and immunoprecipitation experiments suggest that Rab4 physically interacts with CFTR through protein-protein interaction. Biotinylation with cell impermeant NHS-Sulfo-SS-Biotin implies that Rab4 impairs CFTR expression at cell surface. The enhanced cytosolic CFTR indicates that Rab4 expression restrains CFTR appearance at the cell membrane. The study suggests that Rab4 regulates the channel through multiple mechanisms that include protein-protein interaction, GTP/GDP exchange, and channel protein trafficking. We propose that Rab4 is a dynamic molecule with a significant role in CFTR function.
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Affiliation(s)
- Sunil K Saxena
- Center for Cell and Molecular Biology, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ 07030, USA.
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Hantash FM, Redman JB, Starn K, Anderson B, Buller A, McGinniss MJ, Quan F, Peng M, Sun W, Strom CM. Novel and recurrent rearrangements in the CFTR gene: clinical and laboratory implications for cystic fibrosis screening. Hum Genet 2005; 119:126-36. [PMID: 16362824 DOI: 10.1007/s00439-005-0082-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2005] [Accepted: 09/15/2005] [Indexed: 11/29/2022]
Abstract
Because standard techniques used to detect mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene do not detect single or multiple exonic rearrangements, the importance of such rearrangements may be underestimated. Using an in-house developed, single-tube, semi-quantitative fluorescent PCR (SQF PCR) assay, we analyzed 36 DNA samples submitted for extensive CFTR sequencing and identified ten samples with rearrangements. Of 36 patients with classic CF, 10 (28%) harbored various deletions in the CFTR gene, accounting for 14% of CF chromosomes. A deletion encompassing the CFTR promoter and exons 1 and 2 was detected in a sample from one proband, and in the maternal DNA as well. In another family, a deletion of the promoter and exon 1 was detected in three siblings. In both of these cases, the families were African American and the 3120+1G > A splice site mutation was also identified. These promoter deletions have not been previously described. In a third case, a deletion of exons 17a, 17b, and 18 was identified in a Caucasian female and the same mutation was detected in the paternal DNA. In the other seven cases, we identified the following deletions: exons 2 and 3 (n = 2); exons 4, 5, and 6a; exons 17a and 17b; exons 22 and 23; and exons 22, 23, and 24 (n = 2). In our series, the frequency of CFTR rearrangements in classic CF patients, when only one mutation was identified by extensive DNA sequencing, was >60% (10/16). Screening for exon deletions and duplications in the CFTR gene would be beneficial in classic CF cases, especially when only one mutation is identified by standard methodologies.
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Affiliation(s)
- Feras M Hantash
- Department of Molecular Genetics, Quest Diagnostics Nichols Institute, San Juan Capistrano, CA, USA.
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