rs1800086
Variant summary
Our verdict is Uncertain significance. Variant got 1 ACMG points: 2P and 1B. PM1BS2_Supporting
The NM_000492.4(CFTR):c.1052C>G(p.Thr351Ser) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00018 in 1,614,014 control chromosomes in the GnomAD database, including 2 homozygotes. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).
Frequency
Consequence
NM_000492.4 missense
Scores
Clinical Significance
Conservation
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ACMG classification
Verdict is Uncertain_significance. Variant got 1 ACMG points.
Transcripts
RefSeq
Gene | Transcript | HGVSc | HGVSp | Effect | Exon rank | MANE | Protein | UniProt |
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CFTR | NM_000492.4 | c.1052C>G | p.Thr351Ser | missense_variant | Exon 8 of 27 | ENST00000003084.11 | NP_000483.3 |
Ensembl
Frequencies
GnomAD3 genomes AF: 0.000223 AC: 34AN: 152164Hom.: 0 Cov.: 32
GnomAD3 exomes AF: 0.000183 AC: 46AN: 251162Hom.: 0 AF XY: 0.000169 AC XY: 23AN XY: 135728
GnomAD4 exome AF: 0.000176 AC: 257AN: 1461732Hom.: 2 Cov.: 31 AF XY: 0.000171 AC XY: 124AN XY: 727178
GnomAD4 genome AF: 0.000223 AC: 34AN: 152282Hom.: 0 Cov.: 32 AF XY: 0.000148 AC XY: 11AN XY: 74472
ClinVar
Submissions by phenotype
Cystic fibrosis Uncertain:5Benign:1
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This alteration is classified as likely benign based on a combination of the following: seen in unaffected individuals, population frequency, intact protein function, lack of segregation with disease, co-occurrence, RNA analysis, in silico models, amino acid conservation, lack of disease association in case-control studies, and/or the mechanism of disease or impacted region is inconsistent with a known cause of pathogenicity. -
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This imprecision led to the belief that this variant is pathogenic. Despite this variant has been classified and reclassified over the course of time as pathogenic and lately as likely pathogenic (by Mendelics and Invitae), new functional evidence has shown that this variant does not alter CFTR function even when located in the same allele (in cis) as NM_000492.4(CFTR):2552G>T; p.Arg851Leu) and in trans with the most common pathogenic variant p.Phe508del (NM_000492.4(CFTR):1521_1523delCTT). Although in a pathogenic range due to its very low frequency in public databases (1000 Genomes, GnomAd Exons, GnomAd Genomes, etc., in people from different ethnicities), the aminoacid change promoted by this missense variant is practically synonymous for both amino acids residues are polar uncharged (at physiological pH), conserving the hydroxyl group in the side chain of this amino acid, basically having absent to little impact in the CFTR protein. Also, there is another missense variant in the same nucleotide position which has been classified as having uncertain significance (NM_000492.4(CFTR):c.1052C>T; p.Thr351Ile). Besides, prediction tools do not fully agree when predicting the deleteriousness of this variant. Therefore, the controversial data existing to date regarding this variant leads to the classification of uncertain significance. Brief Medical History: the patient was diagnosed with NBS and treated with pancreatic enzymes until the age of 2-3 y.o. The mother decided to stop giving any medication. Since then, the patient presented normal thrive and growth, normal stature, and was eutrophic throughout her life, which would not be expected given the patient's genotype. The patient is now 22 y.o. and has no history of chronic lung infections nor exacerbations or any other features compatible with Cystic Fibrosis. Sweat chloride tests have always been within borderline range (30-59 mM). Also, the patient is pancreatic-sufficient. In January 2020, the patient provided stool samples. Fecal elastase-1 levels in feces samples are within the normal range of the assay, which is a biomarker of pancreatic exocrine sufficiency. Other biochemical and hematological measurements to verify liver function were also normal throughout the patient's life. -
This sequence change replaces threonine, which is neutral and polar, with serine, which is neutral and polar, at codon 351 of the CFTR protein (p.Thr351Ser). This variant is present in population databases (rs1800086, gnomAD 0.07%). This missense change has been observed in individual(s) with pancreatitis, congenital absence of the vas deferens (CAVD), and mild or atypical cysitic fibrosis (PMID: 2395135, 9272157, 15858154, 16128988, 23670503). ClinVar contains an entry for this variant (Variation ID: 53174). Invitae Evidence Modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) indicates that this missense variant is expected to disrupt CFTR protein function with a positive predictive value of 95%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
not provided Uncertain:5
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PP3, PM2 -
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The CFTR c.1052C>G; p.Thr351Ser variant (rs1800086) is reported in the literature in individuals affected with cystic fibrosis (Schrijver 2005) or a CFTR-related disorder (CFTR-RD; de Cid 2010, Larriba 2005, Masson 2013). While a few CFTR-RD patients also carried a pathogenic CFTR variant (Masson 2013), the p.Thr351Ser variant has been reported on the same chromosome as other CFTR variants, so the contribution to disease is uncertain (Bienvenu 2010, Dal'Maso 2013, Trujillano 2013). This variant is reported in ClinVar (Variant ID: 53174). It is found in the general population with an overall allele frequency of 0.017% (48/282554 alleles) in the Genome Aggregation Database (v2.1.1). In vitro functional analyses showed no significant difference in splicing, protein synthesis/folding or chloride secretion compared to wildtype (Bergougnoux 2023). Computational analyses predict that this variant is deleterious (REVEL: 0.773). Due to conflicting information, the clinical significance of the p.Thr351Ser variant is uncertain at this time. References: Bergougnoux A et al. The multi-faceted nature of 15 CFTR exonic variations: Impact on their functional classification and perspectives for therapy. J Cyst Fibros. 2023 May;22(3):515-524. PMID: 36567205. Bienvenu T et al. Cystic fibrosis transmembrane conductance regulator channel dysfunction in non-cystic fibrosis bronchiectasis. Am J Respir Crit Care Med. 2010 May 15;181(10):1078-84. PMID: 20167849. Dal'Maso VB et al. Diagnostic contribution of molecular analysis of the cystic fibrosis transmembrane conductance regulator gene in patients suspected of having mild or atypical cystic fibrosis. J Bras Pneumol. 2013 Mar-Apr;39(2):181-9. PMID: 23670503. de Cid R et al. Independent contribution of common CFTR variants to chronic pancreatitis. Pancreas. 2010 Mar;39(2):209-15. PMID: 19812525. Larriba S et al. Molecular evaluation of CFTR sequence variants in male infertility of testicular origin. Int J Androl. 2005 Oct;28(5):284-90. PMID: 16128988. Masson E et al. A conservative assessment of the major genetic causes of idiopathic chronic pancreatitis: data from a comprehensive analysis of PRSS1, SPINK1, CTRC and CFTR genes in 253 young French patients. PLoS One. 2013 Aug;8(8):e73522. PMID: 23951356. Schrijver I et al. Diagnostic testing by CFTR gene mutation analysis in a large group of Hispanics: novel mutations and assessment of a population-specific mutation spectrum. J Mol Diagn. 2005 May;7(2):289-99. PMID: 15858154. Trujillano D et al. Next generation diagnostics of cystic fibrosis and CFTR-related disorders by targeted multiplex high-coverage resequencing of CFTR. J Med Genet. 2013 Jul;50(7):455-62. PMID: 23687349. -
CFTR-related disorder Pathogenic:1Uncertain:1Benign:1
This variant was observed as part of a predisposition screen in an ostensibly healthy population. A literature search was performed for the gene, cDNA change, and amino acid change (where applicable). Publications were found based on this search. The evidence from the literature, in combination with allele frequency data from public databases where available, was sufficient to rule this variant out of causing disease. Therefore, this variant is classified as benign. -
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The CFTR c.1052C>G variant is predicted to result in the amino acid substitution p.Thr351Ser. This variant has been reported in the heterozygous state in an individual with idiopathic chronic pancreatitis, an individual with CBAVD, and in an individual with clinical manifestations consistent with the spectrum of CF (Table S1, Masson. 2013. PubMed ID: 23951356; Larriba et al. 2005 PubMed ID: 16128988; Schrijver et al. 2005. PubMed ID: 15858154). This variant has also been reported in the compound heterozygous state with a p.Phe508del variant in an individual with CBAVD (Doerk et al. 1997. Table 3 PubMed ID: 9272157) and in the homozygous state (and in cis with another CFTR variant) in an individual with a CFTR-related disorder ( Table S3, Trujillano. 2013. PubMed ID: 23687349). In one individual with CF, this variant was one of three identified, and was in cis with a p.Phe508del variant (Dal'Maso et al. 2013 Table 3 PubMed ID: 23670503). To our knowledge, no functional or family studies are available to confirm the pathogenicity of the c.1052C>G change. This variant is reported in 0.068% of alleles in individuals of Ashkenazi Jewish descent in gnomAD. At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -
not specified Uncertain:1
Variant summary: CFTR c.1052C>G (p.Thr351Ser) results in a conservative amino acid change located in the ABC transporter type 1, transmembrane domain (IPR036640) of the encoded protein sequence. Four of five in-silico tools predict a damaging effect of the variant on protein function. The variant allele was found at a frequency of 0.00019 in 251542 control chromosomes. This frequency is not significantly higher than estimated for a pathogenic variant in CFTR causing Cystic Fibrosis (0.00019 vs 0.013), allowing no conclusion about variant significance. c.1052C>G has been reported in the literature in individuals affected with Cystic Fibrosis, CBAVD, chronic pancreatitis and diffuse bronchiectasis, without strong evidence of causality (Mercier_1993, Dork_1997, Schrijver_2005, Bienvenu_2010, de Cid_2010, Dal Maso_2013, Masson_2013, Trujillano_2013, Grangeia_2018, Rispoli_2020, da Silva Filho_2021, Dermine_2024). These reports do not provide unequivocal conclusions about association of the variant with Cystic Fibrosis. At-least two co-occurrences in cis with other pathogenic variants have been reported (e.g. CFTR c.3484C>T, p.Arg1162X; CFTR c.1521_1523del, p.Phe508del) (Mercier_1993, Dal Maso_2013), providing supporting evidence for a benign role. One of these reports was in an obligate carrier father of an individual with CF (in cis with p.Arg1162X, Mercier_1993) while the other was in an individual reportedly affected with CF who harbored a non-informative genotype attributed to a synonymous variant (p.Pro1290=) in trans (in cis with p.Phe508del, Del Maso_2013). At least two publications report experimental evidence evaluating an impact on protein function (Bergougnoux_2023, Bihler_2024). The variant did not show any deleterious impact on mRNA or protein expression and Western blot results were not suggestive of a folding defect. However, the most pronounced variant effect resulted in approximately 46% of normal chloride channel conductance relative to wild type (e.g. Bihler_2024). The following publications have been ascertained in the context of this evaluation (PMID: 36567205, 20167849, 38388235, 33572515, 23670503, 38657903, 20059485, 9272157, 18716917, 29589582, 16128988, 23951356, 8477260, 25735457, 32185651, 15858154, 23687349, 32819855, 19812525). ClinVar contains an entry for this variant (Variation ID: 53174). Based on the evidence outlined above, the variant was classified as uncertain significance. -
Computational scores
Source:
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at