ClinVar Genomic variation as it relates to human health

PharmGKB Level of Evidence 1A: Level 1A clinical annotations describe variant-drug combinations that have variant-specific prescribing guidance available in a current clinical guideline annotation or an FDA-approved drug label annotation. Annotations of drug labels or clinical guidelines must give prescribing guidance for specific variants (e.g. CYP2C9*3, HLA-B*57:01) or provide mapping from defined allele functions to diplotypes and phenotypes to be used as supporting evidence for a level 1A clinical annotation. Level 1A clinical annotations must also be supported by at least one publication in addition to a clinical guideline or drug label with variant-specific prescribing guidance.

Variant summary: CFTR c.1055G>A (p.Arg352Gln) results in a conservative amino acid change in 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 2.4e-05 in 251124 control chromosomes (gnomAD). c.1055G>A has been reported in the literature in multiple individuals affected with Cystic Fibrosis (e.g. Dupuis_2015, Shackelton_1994, Sosnay_2013). These data indicate that the variant is very likely to be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function, and demonstrated that the variant leads to defective chloride channel function (Sosnay 2013). Four clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014 without evidence for independent evaluation, and all of them classified the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic.

NM_000492.3(CFTR):c.1055G>A(R352Q) is classified as pathogenic in the context of cystic fibrosis and is associated with the non-classic form of disease. Sources cited for classification include the following: PMID 18456578 and 23974870. Classification of NM_000492.3(CFTR):c.1055G>A(R352Q) is based on the following criteria: This is a well-established pathogenic variant in the literature that has been observed more frequently in patients with clinical diagnoses than in healthy populations. Please note: this variant was assessed in the context of healthy population screening.‚Äã

Previously reported disease-causing CFTR variant. See www.CFTR2.org for phenotype information.

The CFTR c.1055G>A; p.Arg352Gln variant (rs121908753) is reported in the literature in several individuals affected with cystic fibrosis (Masson 2013, Ooi 2012, Sosnay 2013). This variant is also reported in ClinVar (Variation ID: 7198), and is only observed on six alleles in the Genome Aggregation Database, indicating it is not a common polymorphism. The arginine at codon 352 is highly conserved, and computational analyses predict that this variant is deleterious (REVEL: 0.804). Additionally, functional assays demonstrate reduced protein function (Van Goor 2014). Based on available information, this variant is considered to be pathogenic. References 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(8):e73522. PMID: 23951356. Ooi CY et al. Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations in pancreatitis. J Cyst Fibros. 2012 Sep;11(5):355-62. PMID: 22658665. Sosnay PR et al. Defining the disease liability of variants in the cystic fibrosis transmembrane conductance regulator gene. Nat Genet. 2013 Oct;45(10):1160-7. PMID: 23974870. Van Goor F et al. Effect of ivacaftor on CFTR forms with missense mutations associated with defects in protein processing or function. J Cyst Fibros. 2014 Jan;13(1):29-36. PMID: 23891399.

The variant was found in a symptomatic patient. Analysis of this variant using bioinformatics tools for the prediction of the effect of amino acid changes on protein structure and function yielded predictions that this variant is damaging. The variant occurs with multiple lone recessive pathogenic variants in the same gene. Functional studies have shown that this variant has a deleterious effect on protein function.

This sequence change replaces arginine, which is basic and polar, with glutamine, which is neutral and polar, at codon 352 of the CFTR protein (p.Arg352Gln). This variant is present in population databases (rs121908753, gnomAD 0.01%). This missense change has been observed in individual(s) with cystic fibrosis (PMID: 7544319, 20522854, 27086061, 28646244). ClinVar contains an entry for this variant (Variation ID: 7198). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt CFTR protein function with a positive predictive value of 80%. For these reasons, this variant has been classified as Pathogenic.

PS3, PM3_Supporting, PP3, PM1, PM2

The p.R352Q pathogenic mutation (also known as c.1055G>A), located in coding exon 8 of the CFTR gene, results from a G to A substitution at nucleotide position 1055. The arginine at codon 352 is replaced by glutamine, an amino acid with highly similar properties. This mutation was first reported in an individual with pancreatic sufficient cystic fibrosis (CF) and an unknown variant on the other chromosome (Cremonesi L et al. Hum. Mutat., 1992;1:314-9). In two additional studies, p.R352Q was reported in conjunction with p.F508del in an individual with CF and an individual with idiopathic chronic pancreatitis (Zitkiewicz E et al. PLoS ONE, 2014 Mar;9:e89094; Steiner B et al. Hum. Mutat., 2011 Aug;32:912-20). This mutation is associated with pancreatic sufficiency and elevated sweat chloride levels (Sosnay PR et al. Nat. Genet., 2013 Oct;45:1160-7). In a functional study using a Xenopus laevis oocyte model, alterations affecting the positive charge at codon 352 (p.R352A, p.R352E, p.R352Q) were observed to alter pore structure by disrupting the interaction between R352 and D993 (Cui G et al. J. Membr. Biol., 2008 Mar;222:91-106). Based on the supporting evidence, this alteration is interpreted as a disease-causing mutation.

The observed frameshift variant c.3871del(p.Ala1291ProfsTer39) in the ATP7B gene has not been reported previously as a pathogenic variant nor as a benign variant, to our knowledge. This variant is absent in the gnomAD Exomes. This variant causes a frameshift starting with codon Alanine 1291, changes this amino acid to Proline residue, and creates a premature Stop codon at position 39 of the new reading frame, denoted p.Ala1291ProfsTer39. This variant is predicted to cause loss of normal protein function through protein truncation. Loss of function variants have been previously reported to be disease causing. For these reasons, this variant has been classified as Likely Pathogenic.