ABCMdb

PMID: 9271620

Kerem E, Nissim-Rafinia M, Argaman Z, Augarten A, Bentur L, Klar A, Yahav Y, Szeinberg A, Hiba O, Branski D, Corey M, Kerem B
A missense cystic fibrosis transmembrane conductance regulator mutation with variable phenotype.
Pediatrics. 1997 Sep;100(3):E5., [PubMed]

Sentences

No. Mutations Sentence Comment

20 ABCC7 p.Gly85Glu Thus, the G85E mutation cannot be classified either as a severe or as a mild mutation. Login to comment 33 ABCC7 p.Gly85Glu Pancreatic status was suggested to be the best parameter in differentiating between the two groups.17 The G85E mutation is a missense mutation result- From the *Department of Pediatrics, Cystic Fibrosis (CF) Clinic, Shaare Zedek Medical Center, Jerusalem, Israel; and the ‡Department of Genetics, Hebrew University, Jerusalem; the §Department of Paediatrics, CF Clinic, Chaim Sheba Medical Center, Tel Hashomer, Israel; the ʈDepartment of Paediatrics, CF Clinic, Rambam Medical Center, Haifa; the ¶Department of Paediatrics, Bikur Cholim Hospital, Jerusalem, Israel; and the #Research Institute, Hospital for Sick Children, Toronto, Canada. Login to comment 39 ABCC7 p.Gly85Glu 3 September 1997 ing from a substitution of glutamic acid for glycine at amino acid 85. Login to comment 42 ABCC7 p.Gly85Glu Two patients, 1 with PI and the other with PS and exceptionally mild lung disease, were previously reported.18,19 Thus, for further determination of the correlation between the G85E mutation and disease phenotype a larger cohort of patients was required. Login to comment 63 ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Hybridization to RT-PCR Products 50 ␮L of each differential RT-PCR reaction were subjected to electrophoresis and were subsequently blotted and hybridized to the exon 3 oligonucleotide G85E-N 5ЈGTTCTATGGAATCTTT 3Ј that identified the normal sequence, washed at 42°C, and to G85E-M 5ЈGTTCTATGAAATCTTT 3Ј that identified the G85E mutation, washed at 40°C. Login to comment 70 ABCC7 p.Gly85Glu To assess the severity of disease presentation of the patients carrying the G85E mutation, we compared their clinical parameters with those of two groups of patients. Login to comment 71 ABCC7 p.Trp1282* The first was comprised of 40 patients homozygous or compound heterozygous for the W1282X and ⌬F508 mutations, both associated with severe disease presentation.2,3 In the second group were 20 patients carrying the 3849ϩ10kb C-ϾT mutation, which is associated with higher frequency of PS and a milder phenotype.7,8 Statistical Analysis Mean values of continuous variables were compared using analysis of variance and Student`s t test. Login to comment 75 ABCC7 p.Gly85Glu RESULTS Twelve CF patients were found to carry the G85E mutation, 9 were Arab, 8 from the same extended family (Table 1, patients 1 to 4 and 6 to 9), and 3 were Jews from Turkish origin (patients 10 to 12). Login to comment 76 ABCC7 p.Trp1282* ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Six patients were homozygous for the G85E mutation and 6 were compound heterozygote for the G85E and the ⌬F508, W1282X or the 3849ϩ10kb C-ϾT mutations. Login to comment 77 ABCC7 p.Gly85Glu All the studied chromosomes carrying the G85E mutation had the 7T variant in the polythymidine tract at the branch/acceptor site in intron 8. Login to comment 78 ABCC7 p.Gly85Glu The clinical parameters of the patients carrying the G85E mutation are presented in Table 1. Login to comment 79 ABCC7 p.Gly85Glu It shows a high variability in the age at diagnosis among patients carrying the G85E. Login to comment 85 ABCC7 p.Gly85Glu One had 3 children homozygous for the G85E mutation (Table 1, patients 1 to 3). Login to comment 89 ABCC7 p.Gly85Glu The second family had 2 children compound heterozygous for G85E and ⌬F508 mutations (Table 1, patients 7 and 8). Login to comment 92 ABCC7 p.Trp1282* ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Comparison of the patients carrying the G85E mutation with patients carrying the ⌬F508 and/or W1282X mutations previously associated with PI and the more severe disease (group 1) or with patients carrying the 3849ϩ10kb C-ϾT previously associated with higher frequency of PS and a milder disease (group 2), revealed that the mean age at diagnosis and age at assessment in the group of patients carrying the G85E mutation were not significantly different from those in group 1, but significantly lower than in group 2 (P ϭ .001 for age of diagnosis, P ϭ .04 for age at assessment; Table 2). Login to comment 93 ABCC7 p.Gly85Glu Likewise, mean sweat chloride levels in patients carrying the G85E mutation was similar to group 1, and significantly higher than group 2 (P ϭ .001; Table 2). Login to comment 94 ABCC7 p.Trp1282* ABCC7 p.Gly85Glu Thus, it seems that patients carrying the G85E mutation have similarly severe disease as patients carrying the ⌬F508 and/or W1282X mutations. Login to comment 95 ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu However, the F test of equal variance was significantly different between these groups: the range of age at diagnosis and sweat chloride levels were much broader for the G85E group than for group 1 (P Ͻ .0001), and sweat chloride was more variable in the G85E mutation than in group 2 (P ϭ .002). Login to comment 97 ABCC7 p.Gly85Glu Clinical Data of CF Patients Carrying the G85E Mutation Patient No. Login to comment 98 ABCC7 p.Trp1282* ABCC7 p.Trp1282* ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Genotype Sex Age at Diagnosis Sweat Chloride meq/l Mode of Presentation Current Age Pancreatic Status FEV1 % Predicted Weight Percentile Sputum Culture 1* G85E/G85E F 9 mo 143 Respir ϩ GI Died 13 y PI NA Ͻ3 Klebsiela 2* G85E/G85E M 2 mo 184 Respir Died 10 y PI NA Ͻ3 H influenzae 3* G85E/G85E M 12 y 54 Liver 13 y PS 82 Ͻ3 H influenzae 4 G85E/G85E F 6 mo 157 Respir ϩ GI Died 6 y PI 20 Ͻ3 P aeruginosa 5 G85E/G85E F 2 mo 90 Respir ϩ GI 4 mo PI NA Ͻ3 H influenzae 6 G85E/G85E F 3 mo 97 Respir ϩ GI 6 yr PS 86 35 H influenzae ϩ Staph 7† G85E/⌬F508 M 6 mo 158 GI Died 11 y PI NA 3 NA 8† G85E/⌬F508 M 10 y 108 Screening 12 y PS 83 80 Staph 9 G85E/⌬F508 M 5 mo NA Respir ϩ GI 18 y PI 50 Ͻ3 P aeruginosa ϩ Staph 10 G85E/W1282X F 7 mo 117 Respir 20 y PI 65 50 P aeruginosa 11 G85E/W1282X F 19 y 82 Pancreatitis ϩ Respir 34 y PI 22 50 P aeruginosa 12 G85E/3849 ϩ 10KB M 5 mo 54 Respir 10 y PI 65 97 P aeruginosa * and † Patients are siblings, respectively. Login to comment 101 ABCC7 p.Trp1282* ABCC7 p.Trp1282* ABCC7 p.Trp1282* ABCC7 p.Trp1282* ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Comparison of Clinical Data Between CF Patients Carrying the G85E Mutations and Patients Homozygous or Compound Heterozygous for Two Severe Mutations (W1282X and ⌬F508) and Those Carry a Milder Mutation (3849ϩ10kb C-ϾT) Variable G85E W1282X/W1282X ⌬F508/⌬F508 W1282X/⌬F508 3849 ϩ 10kb C-ϾT n 12 40 21 Age at diagnosis* 3.7 Ϯ 6.3 0.7 Ϯ 1.8࿣ 13.2 Ϯ 7.8 Sweat chloride (mmol/L)* 119 Ϯ 38 111 Ϯ 12࿣ 71 Ϯ 18¶ Died, n 4 2 2 Pancreatic sufficiency, %§ 25 0 79 Meconium ileus, %§ 0 33 0 Current age, y† 12.8 Ϯ 8.5 10.8 Ϯ 7.0 19.8 Ϯ 8.8 Weight (percentile)‡ 28 Ϯ 34 24 Ϯ 24 50 Ϯ 34 Forced expiratory volume in 1 second (% predicted) 55 Ϯ 26 (n ϭ 7) 66 Ϯ 28 (n ϭ 24) 55 Ϯ 21 (n ϭ 19) * P Ͻ .0001, † P Ͻ .001, ‡ P Ͻ .01 analysis of variance for three means. Login to comment 103 ABCC7 p.Gly85Glu ࿣ P Ͻ .0001 F test of equal variance compared with G85E. Login to comment 104 ABCC7 p.Gly85Glu ¶ P Ͻ .01 F test of equal variance compared with G85E. Login to comment 105 ABCC7 p.Gly85Glu Of the patients carrying the G85E mutation, 25% had PS significantly higher than in group 1 (0%), and significantly lower than in group 2 (80%) (P Ͻ .001; Table 2). Login to comment 106 ABCC7 p.Gly85Glu Furthermore, similar to the patients in group 2, none of the patients carrying the G85E mutation had meconium ileus, whereas a third of the patients from group 1 had meconium ileus (P ϭ .002). Login to comment 107 ABCC7 p.Gly85Glu The nutritional status of patients carrying the G85E mutation was poor. Login to comment 109 ABCC7 p.Gly85Glu However, 58% of the patients carrying the G85E mutation were under the third percentile of weight, compared with 25% of the group 1 patients (P ϭ .02), and 20% of group 2 (0.05). Login to comment 114 ABCC7 p.Gly85Glu ABCC7 p.Gly85Glu Levels of Correctly Spliced CFTR RNA Transcribed From the G85E Allele in Respiratory Epithelium We next studied the possibility that the variability in pulmonary function found among our patients carrying the G85E mutation is associated with the level of exon 9 skipping that leads to the translation of a nonfunctional CFTR protein. Login to comment 115 ABCC7 p.Gly85Glu The level of aberrantly spliced CFTR RNA transcribed in respiratory epithelial cells from the G85E allele was analyzed using semiquantitative nondifferential RT-PCR. Login to comment 116 ABCC7 p.Gly85Glu The RT-PCR was performed on respiratory epithelial cells from 3 patients who carried at least one G85E allele (patients 3, 8, and 9). Login to comment 118 ABCC7 p.Gly85Glu The results showed that the level of transcripts lacking exon 9 transcribed from the G85E allele was 55 Ϯ 3% for patient 3, 49 Ϯ 2% for patient 8, and 35 Ϯ 4% for patient 9. Login to comment 121 ABCC7 p.Gly85Glu Thus, the level of aberrantly spliced transcripts could not explain the variable pulmonary function among patients carrying the G85E mutation. Login to comment 122 ABCC7 p.Gly85Glu DISCUSSION This study demonstrates high variability of clinical presentation among patients carrying the G85E mutation. Login to comment 123 ABCC7 p.Gly85Glu Thus, the G85E mutation cannot be classified either as a severe or as a mild mutation. Login to comment 126 ABCC7 p.Trp1282* ABCC7 p.Asn1303Lys ABCC7 p.Gly542* Several genotype-phenotype studies including the CF genotype-phenotype consortium have shown that there are mutations like the ⌬F508,2,6,11 W1282X,3,6 G542X,6 N1303K,4,6 and R533X5,6 in which Ͼ95% of the patients had PI2-10 whereas others like the 3849ϩ10kb C-ϾT,7,8 A455E15 Fig 1. Login to comment 129 ABCC7 p.Trp1282* ABCC7 p.Trp1282* ABCC7 p.Trp1282* Severe: ⌬F508/⌬F508, W1282X/W1282X, ⌬F508/W1282X. Login to comment 131 ABCC7 p.Gly85Glu The incidence of PS among the patients carrying the G85E mutation (25%), suggests that it cannot be classified either as a PI- or PS-associated mutation. Login to comment 132 ABCC7 p.Gly85Glu Slightly elevated, borderline, or even normal values of sweat chloride were previously reported among patients carrying at least one copy of the splicing mutation 3849ϩ10kb C-ϾT.7,8,15 Two of the patients in our study, carrying the G85E mutation, had borderline sweat chloride levels, whereas the others had typically high levels. Login to comment 133 ABCC7 p.Gly85Glu Furthermore, as shown in Table 2, it seems that the G85E patients present to medical attention at a later age than the patients in the severe group. Login to comment 134 ABCC7 p.Gly85Glu However, again this is attributable to the wide range of the age of diagnosis among the G85E patients, and not attributable to a milder disease course. Login to comment 136 ABCC7 p.Gly85Glu Thus, the results of our analysis show that the G85E mutation is associated with variable disease presentation in all the studied parameters. Login to comment 139 ABCC7 p.Gly85Glu The mechanism causing the variability seen among the patients carrying the G85E mutation is unknown. Login to comment 141 ABCC7 p.Gly85Glu Sequence variations within the CFTR gene that modulate the CF phenotype have been reported in 2 CF patients.29,30 However, in our study 8 patients were from the same extended family, carrying the same G85E allele, as evidenced by extended haplotype analysis using polymorphic markers in the CFTR locus (data not shown). Login to comment 146 ABCC7 p.Arg117His ABCC7 p.Arg117His ABCC7 p.Arg117His The 5T allele is associated with the lowest levels of normal splicing of exon 9, and high levels of exon 9 skipping leading to a nonfunctional chloride channel.32 Furthermore, the 5T allele was shown to affect the disease severity of patients carrying the mutation R117H.33 In patients carrying the R117H mutation when the allele also contained the 5T variant the phenotype was mild CF, whereas in patients carrying R117H together with the 7T variant the phenotype was male infertility only. Login to comment 147 ABCC7 p.Gly85Glu In our study all the G85E chromosomes contained the 7T variant. Login to comment 148 ABCC7 p.Gly85Glu In addition, the level of RNA transcripts lacking exon 9, transcribed from the G85E allele, varied among different individuals. Login to comment 153 ABCC7 p.Gly85Glu Further understanding the mechanisms underlying the disease variability found among patients carrying the G85E mutation will contribute to our understanding of the genotype-phenotype association and disease variability in CF. Login to comment