Dataset Information

Functional Assays Are Essential for Interpretation of Missense Variants Associated with Variable Expressivity.

ABSTRACT: Missense DNA variants have variable effects upon protein function. Consequently, interpreting their pathogenicity is challenging, especially when they are associated with disease variability. To determine the degree to which functional assays inform interpretation, we analyzed 48 CFTR missense variants associated with variable expressivity of cystic fibrosis (CF). We assessed function in a native isogenic context by evaluating CFTR mutants that were stably expressed in the genome of a human airway cell line devoid of endogenous CFTR expression. 21 of 29 variants associated with full expressivity of the CF phenotype generated <10% wild-type CFTR (WT-CFTR) function, a conservative threshold for the development of life-limiting CF lung disease, and five variants had moderately decreased function (10% to ?25% WT-CFTR). The remaining three variants in this group unexpectedly had >25% WT-CFTR function; two were higher than 75% WT-CFTR. As expected, 14 of 19 variants associated with partial expressivity of CF had >25% WT-CFTR function; however, four had minimal to no effect on CFTR function (>75% WT-CFTR). Thus, 6 of 48 (13%) missense variants believed to be disease causing did not alter CFTR function. Functional studies substantially refined pathogenicity assignment with expert annotation and criteria from the American College of Medical Genetics and Genomics and Association for Molecular Pathology. However, four algorithms (CADD, REVEL, SIFT, and PolyPhen-2) could not differentiate between variants that caused severe, moderate, or minimal reduction in function. In the setting of variable expressivity, these results indicate that functional assays are essential for accurate interpretation of missense variants and that current prediction tools should be used with caution.

SUBMITTER: Raraigh KS

PROVIDER: S-EPMC5992123 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Functional Assays Are Essential for Interpretation of Missense Variants Associated with Variable Expressivity.

Raraigh Karen S KS Han Sangwoo T ST Davis Emily E Evans Taylor A TA Pellicore Matthew J MJ McCague Allison F AF Joynt Anya T AT Lu Zhongzhou Z Atalar Melis M Sharma Neeraj N Sheridan Molly B MB Sosnay Patrick R PR Cutting Garry R GR

American journal of human genetics 20180524 6

Missense DNA variants have variable effects upon protein function. Consequently, interpreting their pathogenicity is challenging, especially when they are associated with disease variability. To determine the degree to which functional assays inform interpretation, we analyzed 48 CFTR missense variants associated with variable expressivity of cystic fibrosis (CF). We assessed function in a native isogenic context by evaluating CFTR mutants that were stably expressed in the genome of a human airw ...[more]

PMID: 29805046

Similar Datasets

Project description:AimThe study aimed to develop a scalable dual-fluorescence assay in cells to enable the functional interpretation of HNF-4α missense variants identified in exome sequencing, which can be used to guide clinical diagnosis.MethodsUsing mOrange2 and GFP fluorescence proteins to track the expression of HNF-4α (HNF-4α-mOrange2) and reporter activity under the control of the HNF-1α promoter (pHNF1A-GFP), respectively, we designed a dual-fluorescence assay to evaluate the expression level, cellular localization, and transcriptional function of HNF-4α simultaneously in live cells. To assess the scalable characteristic of the assay, a small library containing five previously reported mutations and wild-type HNF-4α was constructed. Cells infected with this library were sorted into different populations through fluorescence-activated cell sorting (FACS) according to the transcription activity and expression abundance. Cloning and Sanger sequencing were used to detect the mutations of the different groups. High content screening (HCS) assay was used for the validation of individual mutants in the function and expression point of view.ResultsHNF-4α-mOrange2 exhibited nuclear localization and transactivation capability on the HNF-1α promoter as physical HNF-4α does. The expression of HNF-4α-mOrange2 shows a 6-fold induction of GFP expression compared to the control without HNF-4α-mOrange2, which was significantly abolished by the known loss-of-function mutant M373R. The different performances of wild-type and mutant M373R made them distinguishable in the FACS system, empowering the scalable capability of this assay for classifying large numbers of variants combining functional stratification and sequencing. Further application of the assay in the small library showed that three cell populations were seen grouped as Normal (same transactivation as wild type), Reducedexp_nor (reduced transactivation with normal or higher expression), and Reducedexp_low (reduced transactivation with lower expression). Subsequently, Sanger sequencing showed that wild-type HNF-4α was in the Normal group, two mutations (M373R and G79C) were enriched in the Reducedexp_nor group, and three mutations (C115S, L272P, and F83C) belonged to the Reducedexp_low group. These results were validated by further imaging data using HCS assay for individual mutation.ConclusionsOur study proposes a scalable and informative approach for the characterization of the variants in HNF-4α genes in a quantitative and high-throughput manner.

Project description:BackgroundThere is a paucity of data regarding the phenotype of dilated cardiomyopathy (DCM) gene variants in the general population. We aimed to determine the frequency and penetrance of DCM-associated putative pathogenic gene variants in a general adult population, with a focus on the expression of clinical and subclinical phenotype, including structural, functional, and arrhythmic disease features.MethodsUK Biobank participants who had undergone whole exome sequencing, ECG, and cardiovascular magnetic resonance imaging were selected for study. Three variant-calling strategies (1 primary and 2 secondary) were used to identify participants with putative pathogenic variants in 44 DCM genes. The observed phenotype was graded DCM (clinical or cardiovascular magnetic resonance diagnosis); early DCM features, including arrhythmia or conduction disease, isolated ventricular dilation, and hypokinetic nondilated cardiomyopathy; or phenotype-negative.ResultsAmong 18 665 individuals included in the study, 1463 (7.8%) possessed ≥1 putative pathogenic variant in 44 DCM genes by the main variant calling strategy. A clinical diagnosis of DCM was present in 0.34% and early DCM features in 5.7% of individuals with putative pathogenic variants. ECG and cardiovascular magnetic resonance analysis revealed evidence of subclinical DCM in an additional 1.6% and early DCM features in an additional 15.9% of individuals with putative pathogenic variants. Arrhythmias or conduction disease (15.2%) were the most common early DCM features, followed by hypokinetic nondilated cardiomyopathy (4%). The combined clinical/subclinical penetrance was ≤30% with all 3 variant filtering strategies. Clinical DCM was slightly more prevalent among participants with putative pathogenic variants in definitive/strong evidence genes as compared with those with variants in moderate/limited evidence genes.ConclusionsIn the UK Biobank, ≈1 of 6 of adults with putative pathogenic variants in DCM genes exhibited early DCM features potentially associated with DCM genotype, most commonly manifesting with arrhythmias in the absence of substantial ventricular dilation or dysfunction.

Project description:Recessive mutations of fibroblast growth factor 3 (FGF3) can cause LAMM syndrome (OMIM 610706), characterized by fully penetrant complete labyrinthine aplasia, microtia and microdontia.We performed a prospective molecular genetic and clinical study of families segregating hearing loss linked to FGF3 mutations. Ten affected individuals from three large Pakistani families segregating FGF3 mutations were imaged with CT, MRI, or both to detect inner ear abnormalities. We also modeled the three dimensional structure of FGF3 to better understand the structural consequences of the three missense mutations.Two families segregated reported mutations (p.R104X and p.R95W) and one family segregated a novel mutation (p.R132GfsX26) of FGF3. All individuals homozygous for p.R104X or p.R132GfsX26 had fully penetrant features of LAMM syndrome. However, recessive p.R95W mutations were associated with nearly normal looking auricles and variable inner ear structural phenotypes, similar to that reported for a Somali family also segregating p.R95W. This suggests that the mild phenotype is not entirely due to genetic background. Molecular modeling result suggests a less drastic effect of p.R95W on FGF3 function compared with known missense mutations detected in fully penetrant LAMM syndrome. Since we detected significant intrafamilial variability of the inner ear structural phenotype in the family segregating p.R95W, we also sequenced FGF10 as a likely candidate for a modifier. However, we did not find any sequence variation, pointing out that a larger sample size will be needed to map and identify a modifier. We also observed a mild to moderate bilateral conductive hearing loss in three carriers of p.R95W, suggesting either a semi-dominant effect of this mutant allele of FGF3, otitis media, or a consequence of genetic background in these three family members.We noted a less prominent dental and external ear phenotype in association with the homozygous p.R95W. Therefore, we conclude that the manifestations of recessive FGF3 mutations range from fully penetrant LAMM syndrome to deafness with residual inner ear structures and, by extension, with minimal syndromic features, an observation with implications for cochlear implantation candidacy.

Dataset Information

Functional Assays Are Essential for Interpretation of Missense Variants Associated with Variable Expressivity.

Publications

Functional Assays Are Essential for Interpretation of Missense Variants Associated with Variable Expressivity.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets