ABCMdb

PMID: 20949073

Hinzpeter A, Aissat A, Sondo E, Costa C, Arous N, Gameiro C, Martin N, Tarze A, Weiss L, de Becdelievre A, Costes B, Goossens M, Galietta LJ, Girodon E, Fanen P
Alternative splicing at a NAGNAG acceptor site as a novel phenotype modifier.
PLoS Genet. 2010 Oct 7;6(10). pii: e1001153., [PubMed]

Sentences

No. Mutations Sentence Comment

2 ABCC7 p.Glu831* We identified such a mechanism as the origin of the mild to asymptomatic phenotype observed in cystic fibrosis patients homozygous for the E831X mutation (2623G.T) in the CFTR gene. Login to comment 34 ABCC7 p.Glu831* Results/Discussion Family pedigree In this study, we focused on the rare E831X mutation (2623G.T) which affects the first nucleotide of exon 14a which forms part of one of the two NAGNAG acceptor sites detected in the CFTR gene. Login to comment 35 ABCC7 p.Glu831* We had the opportunity to study a consanguineous family of Turkish origin which included three patients (Figure 1A) homozygous for the E831X mutation (Figure 1B). Login to comment 73 ABCC7 p.Glu831* The resulting proteins would be either truncated after the regulatory domain (CFTR-E831X, Figure 4C) or missing one amino acid (CFTR-DE831, Figure 4D), respectively. Login to comment 79 ABCC7 p.Glu831* Stably expressed CFTR-E831X protein was detected as a single band at the expected size (Figure 5A, right panel), while transiently expressed CFTR-DE831 showed a normal maturation profile with the presence of both bands B and C (Figure 5A, lower left panel). Login to comment 80 ABCC7 p.Glu831* Immunostaining of transiently transfected HeLa cells confirmed a processing defect in both the CFTR-del831-873 and CFTR-E831X mutant proteins as they could only be detected in intracellular compartments close to the nucleus, whereas both CFTR-WT and CFTR-DE831 showed clear cell surface staining (Figure 5B). Login to comment 81 ABCC7 p.Glu831* Finally, functional assays showed the absence of CFTR-dependent anion transport in cells expressing either CFTR-del831-873 or CFTR-E831X. Login to comment 84 ABCC7 p.Glu831* Phenotypes associated with the E831X mutation CF was suspected in the first year of life in patient III10 (Figure 1A) due to recurrent bronchitis, and this was confirmed by a positive sweat test (70 mmol/L). Login to comment 85 ABCC7 p.Glu831* The patient was tested and found to be homozygous for the nonsense mutation E831X. Login to comment 88 ABCC7 p.Glu831* The female patient married her first cousin who was found to be an E831X carrier. Login to comment 89 ABCC7 p.Glu831* Their son (IV1) is homozygous for the E831X mutation. Login to comment 91 ABCC7 p.Gly551Asp Interestingly, this mutation was first described in a female CF patient carrying the severe missense substitution G551D on the other allele. Login to comment 92 ABCC7 p.Glu831* E831X was considered as a severe mutation because she presented with meconium ileus at birth, a neonate pulmonary infection and an elevated sweat test [16]. Login to comment 97 ABCC7 p.Glu831* Subsequently, E831X was reported to be the allele present in cohorts of men with Figure 2. Login to comment 120 ABCC7 p.Glu831* These clinical observations and our data bring the deleterious nature of the E831X mutation into question; but how can the minor functional CFTR-DE831 isoform lead to such mild phenotypes? Login to comment 142 ABCC7 p.Glu831* Alternative splicing at the NAGNAG site generates mRNA including the stop codon encoding truncated CFTR-E831X (C), and mRNA lacking the stop codon leading to CFTR-DE831 (D). Login to comment 145 ABCA4 p.Gly863Ala This mutation (2588G.C) was shown to produce two isoforms leading to either an indel of Gly863 or to a missense defect, Gly863Ala, by shifting the NAGNAG motif from an implausible sequence (TAGGAG) into a plausible sequence (TAGCAG). Login to comment 158 ABCC7 p.Glu831* Western blot analysis of HEK293 cells stably expressing CFTR-WT or CFTR-E831X (right panel). Login to comment 187 ABCC7 p.Glu831* Phenotypes associated with E831X mutations. Login to comment 188 ABCC7 p.Gly551Asp ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Glu831* ABCC7 p.Asp110His Age at diagnosis, gender: M, F Ethnic origin Genotype Sweat test* (mmol/l) Phenotype References Birth, F - E831X/G551D 100 Early childhood: MI, PI, and lung infections Adulthood: PI and no pulmonary symptoms 15 Twins 13y, M Turkish E831X/591del18 89/94 Recurrent nasal polyps 16 Adult, M Turkish E831X/D110H - CBAVD 17 Adult, M Turkish E831X/1677delTA - CBAVD 17 Adult, M Turkish E831X/DF508 92/94 CBAVD PS and mild lung disease 18 Adult, M Portuguese E831X/DF508 - CBAVD 19 First year, F - E831X/DF508 100 PS and no lung involvement French registry First year, M Turkish E831X/E831X 70 PS and mild lung disease This study III10 Adult, F Turkish E831X/E831X 70 PS and no lung involvement This study III5 Neonatal diagnosis, M Turkish E831X/E831X 74 PS and mild lung disease This study IV1 Abbreviations: CBAVD, congenital bilateral absence of the vas deferens; MI, meconium ileus; PI, pancreatic insufficiency; PS, pancreatic sufficiency. Login to comment 206 ABCC7 p.Glu831* HEK293 cells stably expressing CFTR-WT or CFTR-E831X were selected using Zeocin (50 mg/mL). Login to comment 207 ABCC7 p.Glu831* Constructs and mutagenesis CFTR-WT cDNA was subcloned in pTracer [30] and CFTR-E831X, CFTR-DE831 and CFTR-del-831-873 were generated by site-directed mutagenesis (Stratagene) and each construct was sequenced. Login to comment 223 ABCC7 p.Glu831* Cells stably expressing CFTR-E831X or CFTR-WT were lysed in 1X RIPA buffer and samples containing 30 mg total protein were analyzed by Western blot. Login to comment 301 ABCC7 p.Glu831* Di Girgenti C, Virruso L, Messineo R, Cannuscio A, Termini L, et al. (2008) From ''evocative`` symptoms to genotype deltaF508/E831X. Login to comment