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Mention K, Cavusoglu-Doran K, Joynt AT, Santos L, Sanz D, Eastman AC, Merlo C, Langfelder-Schwind E, Scallan MF, Farinha CM, Cutting GR, Sharma N, Harrison PT. Use of adenine base editing and homology-independent targeted integration strategies to correct the cystic fibrosis causing variant, W1282X. Hum Mol Genet 2023; 32:3237-3248. [PMID: 37649273 PMCID: PMC10656707 DOI: 10.1093/hmg/ddad143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/21/2023] [Accepted: 08/12/2023] [Indexed: 09/01/2023] Open
Abstract
Small molecule drugs known as modulators can treat ~90% of people with cystic fibrosis (CF), but do not work for premature termination codon variants such as W1282X (c.3846G>A). Here we evaluated two gene editing strategies, Adenine Base Editing (ABE) to correct W1282X, and Homology-Independent Targeted Integration (HITI) of a CFTR superexon comprising exons 23-27 (SE23-27) to enable expression of a CFTR mRNA without W1282X. In Flp-In-293 cells stably expressing a CFTR expression minigene bearing W1282X, ABE corrected 24% of W1282X alleles, rescued CFTR mRNA from nonsense mediated decay and restored protein expression. However, bystander editing at the adjacent adenine (c.3847A>G), caused an amino acid change (R1283G) that affects CFTR maturation and ablates ion channel activity. In primary human nasal epithelial cells homozygous for W1282X, ABE corrected 27% of alleles, but with a notably lower level of bystander editing, and CFTR channel function was restored to 16% of wild-type levels. Using the HITI approach, correct integration of a SE23-27 in intron 22 of the CFTR locus in 16HBEge W1282X cells was detected in 5.8% of alleles, resulting in 7.8% of CFTR transcripts containing the SE23-27 sequence. Analysis of a clonal line homozygous for the HITI-SE23-27 produced full-length mature protein and restored CFTR anion channel activity to 10% of wild-type levels, which could be increased three-fold upon treatment with the triple combination of CF modulators. Overall, these data demonstrate two different editing strategies can successfully correct W1282X, the second most common class I variant, with a concomitant restoration of CFTR function.
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Affiliation(s)
- Karen Mention
- Department of Physiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
- School of Microbiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
| | - Kader Cavusoglu-Doran
- Department of Physiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
| | - Anya T Joynt
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, United States
| | - Lúcia Santos
- Department of Physiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
- Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, University of Lisboa, Campo Grande, C8 bdg, Lisboa 1749-016, Portugal
| | - David Sanz
- Department of Physiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
| | - Alice C Eastman
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, United States
| | - Christian Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, 1800 Orleans St, Baltimore, MD 21287, United States
| | - Elinor Langfelder-Schwind
- The Cystic Fibrosis Center, Lenox Hill Hospital, 100 E. 77th Street, 4E, New York, NY 10075, United States
| | - Martina F Scallan
- School of Microbiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
| | - Carlos M Farinha
- Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, University of Lisboa, Campo Grande, C8 bdg, Lisboa 1749-016, Portugal
| | - Garry R Cutting
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, United States
| | - Neeraj Sharma
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, United States
| | - Patrick T Harrison
- Department of Physiology, University College Cork, College Road, Cork, T12 K8AF, Ireland
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Ponnienselvan K, Liu P, Nyalile T, Oikemus S, Joynt AT, Kelly K, Guo D, Chen Z, Lee JM, Schiffer CA, Emerson CP, Lawson ND, Watts JK, Sontheimer EJ, Luban J, Wolfe SA. Addressing the dNTP bottleneck restricting prime editing activity. bioRxiv 2023:2023.10.21.563443. [PMID: 37904991 PMCID: PMC10614944 DOI: 10.1101/2023.10.21.563443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Prime editing efficiency is modest in cells that are quiescent or slowly proliferating where intracellular dNTP levels are tightly regulated. MMLV-reverse transcriptase - the prime editor polymerase subunit - requires high intracellular dNTPs levels for efficient polymerization. We report that prime editing efficiency in primary cells and in vivo is increased by mutations that enhance the enzymatic properties of MMLV-reverse transcriptase and can be further complemented by targeting SAMHD1 for degradation.
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Joynt AT, Kavanagh EW, Newby GA, Mitchell S, Eastman AC, Paul KC, Bowling AD, Osorio DL, Merlo CA, Patel SU, Raraigh KS, Liu DR, Sharma N, Cutting GR. Protospacer modification improves base editing of a canonical splice site variant and recovery of CFTR function in human airway epithelial cells. Mol Ther Nucleic Acids 2023; 33:335-350. [PMID: 37547293 PMCID: PMC10400809 DOI: 10.1016/j.omtn.2023.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 06/26/2023] [Indexed: 08/08/2023]
Abstract
Canonical splice site variants affecting the 5' GT and 3' AG nucleotides of introns result in severe missplicing and account for about 10% of disease-causing genomic alterations. Treatment of such variants has proven challenging due to the unstable mRNA or protein isoforms that typically result from disruption of these sites. Here, we investigate CRISPR-Cas9-mediated adenine base editing for such variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We validate a CFTR expression minigene (EMG) system for testing base editing designs for two different targets. We then use the EMG system to test non-standard single-guide RNAs with either shortened or lengthened protospacers to correct the most common cystic fibrosis-causing variant in individuals of African descent (c.2988+1G>A). Varying the spacer region length allowed placement of the editing window in a more efficient context and enabled use of alternate protospacer adjacent motifs. Using these modifications, we restored clinically significant levels of CFTR function to human airway epithelial cells from two donors bearing the c.2988+1G>A variant.
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Affiliation(s)
- Anya T. Joynt
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Erin W. Kavanagh
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Gregory A. Newby
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Shakela Mitchell
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Alice C. Eastman
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Kathleen C. Paul
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Alyssa D. Bowling
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Derek L. Osorio
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Christian A. Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD 21287, USA
| | - Shivani U. Patel
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD 21287, USA
| | - Karen S. Raraigh
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - David R. Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA
| | - Neeraj Sharma
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
| | - Garry R. Cutting
- Department of Genetic Medicine, Johns Hopkins University School of Medicine Baltimore, MD 21205, USA
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Abstract
Cystic fibrosis (CF) is a multiorgan disease caused by a wide variety of mutations in the cystic fibrosis transmembrane conductance regulator gene. As treatment has progressed from symptom mitigation to targeting of specific molecular defects, genetics has played an important role in identifying the proper precision therapies for each individual. Novel therapeutic approaches are focused on expanding treatment to a greater number of individuals as well as working toward a cure. This review discusses the role of genetics in our understanding of CF with a particular emphasis on how genetics informs the exciting landscape of current and novel CF therapies.
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Affiliation(s)
- Anya T Joynt
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Garry R Cutting
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Neeraj Sharma
- McKusick-Nathans Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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Osei-Owusu IA, Norris AL, Joynt AT, Thorpe J, Cho S, Tierney E, Schmidt J, Hagopian L, Harris J, Pevsner J. Characterization of an unbalanced translocation causing 3q28qter duplication and 10q26.2qter deletion in a patient with global developmental delay and self-injury. Cold Spring Harb Mol Case Stud 2020; 6:mcs.a005884. [PMID: 33335013 PMCID: PMC7784495 DOI: 10.1101/mcs.a005884] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/08/2020] [Indexed: 01/17/2023] Open
Abstract
Chromosomal structural variation can cause severe neurodevelopmental and neuropsychiatric phenotypes. Here we present a nonverbal female adolescent with severe stereotypic movement disorder with severe problem behavior (e.g., self-injurious behavior, aggression, and disruptive and destructive behaviors), autism spectrum disorder, severe intellectual disability, attention deficit hyperactivity disorder, and global developmental delay. Previous cytogenetic analysis revealed balanced translocations present in the patient's apparently normal mother. We hypothesized the presence of unbalanced translocations in the patient due to maternal history of spontaneous abortions. Whole-genome sequencing and whole-genome optical mapping, complementary next-generation genomic technologies capable of the accurate and robust detection of structural variants, identified t(3;10), t(10;14), and t(3;14) three-way balanced translocations in the mother and der(10)t(3;14;10) and der(14)t(3;14;10) translocations in the patient. Instead of a t(3;10), she inherited a normal maternal copy of Chromosome 3, resulting in an unbalanced state of a 3q28qter duplication and 10q26.2qter deletion. Copy-imbalanced genes in one or both of these regions, such as DLG1, DOCK1, and EBF3, may contribute to the patient's phenotype that spans neurodevelopmental, musculoskeletal, and psychiatric domains, with the possible contribution of a maternally inherited 15q13.2q13.3 deletion.
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Affiliation(s)
- Ikeoluwa A Osei-Owusu
- Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Alexis L Norris
- Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Anya T Joynt
- Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | - Jeremy Thorpe
- Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA.,Program in Biochemistry, Cellular and Molecular Biology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | - Soonweng Cho
- Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | - Elaine Tierney
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Psychiatry, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Jonathan Schmidt
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Behavioral Psychology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Louis Hagopian
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Behavioral Psychology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA
| | - Jacqueline Harris
- Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA.,Department of Neurology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | - Jonathan Pevsner
- Program in Human Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Neurology, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA.,Program in Biochemistry, Cellular and Molecular Biology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.,Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
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6
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Joynt AT, Evans TA, Pellicore MJ, Davis-Marcisak EF, Aksit MA, Eastman AC, Patel SU, Paul KC, Osorio DL, Bowling AD, Cotton CU, Raraigh KS, West NE, Merlo CA, Cutting GR, Sharma N. Evaluation of both exonic and intronic variants for effects on RNA splicing allows for accurate assessment of the effectiveness of precision therapies. PLoS Genet 2020; 16:e1009100. [PMID: 33085659 PMCID: PMC7605713 DOI: 10.1371/journal.pgen.1009100] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 11/02/2020] [Accepted: 09/08/2020] [Indexed: 12/21/2022] Open
Abstract
Elucidating the functional consequence of molecular defects underlying genetic diseases enables appropriate design of therapeutic options. Treatment of cystic fibrosis (CF) is an exemplar of this paradigm as the development of CFTR modulator therapies has allowed for targeted and effective treatment of individuals harboring specific genetic variants. However, the mechanism of these drugs limits effectiveness to particular classes of variants that allow production of CFTR protein. Thus, assessment of the molecular mechanism of individual variants is imperative for proper assignment of these precision therapies. This is particularly important when considering variants that affect pre-mRNA splicing, thus limiting success of the existing protein-targeted therapies. Variants affecting splicing can occur throughout exons and introns and the complexity of the process of splicing lends itself to a variety of outcomes, both at the RNA and protein levels, further complicating assessment of disease liability and modulator response. To investigate the scope of this challenge, we evaluated splicing and downstream effects of 52 naturally occurring CFTR variants (exonic = 15, intronic = 37). Expression of constructs containing select CFTR intronic sequences and complete CFTR exonic sequences in cell line models allowed for assessment of RNA and protein-level effects on an allele by allele basis. Characterization of primary nasal epithelial cells obtained from individuals harboring splice variants corroborated in vitro data. Notably, we identified exonic variants that result in complete missplicing and thus a lack of modulator response (e.g. c.2908G>A, c.523A>G), as well as intronic variants that respond to modulators due to the presence of residual normally spliced transcript (e.g. c.4242+2T>C, c.3717+40A>G). Overall, our data reveals diverse molecular outcomes amongst both exonic and intronic variants emphasizing the need to delineate RNA, protein, and functional effects of each variant in order to accurately assign precision therapies. Genetic variants that impact pre-mRNA splicing are a common cause of genetic disease and have varying downstream molecular consequences. As a result, precision therapies that function at the protein level are not always effective for these variants and thus careful assessment is necessary. Here we evaluate RNA-level effects of 52 variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and show that study of splicing and its consequences allows for more accurate assignment of precision therapies.
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Affiliation(s)
- Anya T. Joynt
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Taylor A. Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Matthew J. Pellicore
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Emily F. Davis-Marcisak
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Melis A. Aksit
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Alice C. Eastman
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Shivani U. Patel
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Kathleen C. Paul
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Derek L. Osorio
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Alyssa D. Bowling
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Calvin U. Cotton
- Departments of Pediatrics, Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Karen S. Raraigh
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Natalie E. West
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Christian A. Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Garry R. Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail: (GRC); (NS)
| | - Neeraj Sharma
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail: (GRC); (NS)
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7
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McCague AF, Raraigh KS, Pellicore MJ, Davis-Marcisak EF, Evans TA, Han ST, Lu Z, Joynt AT, Sharma N, Castellani C, Collaco JM, Corey M, Lewis MH, Penland CM, Rommens JM, Stephenson AL, Sosnay PR, Cutting GR. Correlating Cystic Fibrosis Transmembrane Conductance Regulator Function with Clinical Features to Inform Precision Treatment of Cystic Fibrosis. Am J Respir Crit Care Med 2020; 199:1116-1126. [PMID: 30888834 DOI: 10.1164/rccm.201901-0145oc] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rationale: The advent of precision treatment for cystic fibrosis using small-molecule therapeutics has created a need to estimate potential clinical improvements attributable to increases in cystic fibrosis transmembrane conductance regulator (CFTR) function. Objectives: To derive CFTR function of a variety of CFTR genotypes and correlate with key clinical features (sweat chloride concentration, pancreatic exocrine status, and lung function) to develop benchmarks for assessing response to CFTR modulators. Methods: CFTR function assigned to 226 unique CFTR genotypes was correlated with the clinical data of 54,671 individuals enrolled in the Clinical and Functional Translation of CFTR (CFTR2) project. Cross-sectional FEV1% predicted measurements were plotted by age at which measurement was obtained. Shifts in sweat chloride concentration and lung function reported in CFTR modulator trials were compared with function-phenotype correlations to assess potential efficacy of therapies. Measurements and Main Results: CFTR genotype function exhibited a logarithmic relationship with each clinical feature. Modest increases in CFTR function related to differing genotypes were associated with clinically relevant improvements in cross-sectional FEV1% predicted over a range of ages (6-82 yr). Therapeutic responses to modulators corresponded closely to predictions from the CFTR2-derived relationship between CFTR genotype function and phenotype. Conclusions: Increasing CFTR function in individuals with severe disease will have a proportionally greater effect on outcomes than similar increases in CFTR function in individuals with mild disease and should reverse a substantial fraction of the disease process. This study provides reference standards for clinical outcomes that may be achieved by increasing CFTR function.
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Affiliation(s)
- Allison F McCague
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Karen S Raraigh
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | | | | | - Taylor A Evans
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Sangwoo T Han
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Zhongzhou Lu
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Anya T Joynt
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Neeraj Sharma
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
| | - Carlo Castellani
- 2 Cystic Fibrosis Center, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Joseph M Collaco
- 3 Eudowood Division of Pediatric Respiratory Sciences, School of Medicine
| | | | | | | | - Johanna M Rommens
- 7 Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Anne L Stephenson
- 8 Department of Respirology, Adult Cystic Fibrosis Program, St. Michael's Hospital, Toronto, Ontario, Canada
| | - Patrick R Sosnay
- 9 Pulmonary and Critical Care Medicine, School of Medicine, Johns Hopkins University, Baltimore, Maryland
| | - Garry R Cutting
- 1 McKusick-Nathans Institute of Genetic Medicine, School of Medicine
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Aksit MA, Bowling AD, Evans TA, Joynt AT, Osorio D, Patel S, West N, Merlo C, Sosnay PR, Cutting GR, Sharma N. Decreased mRNA and protein stability of W1282X limits response to modulator therapy. J Cyst Fibros 2019; 18:606-613. [PMID: 30803905 DOI: 10.1016/j.jcf.2019.02.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/14/2019] [Accepted: 02/14/2019] [Indexed: 12/13/2022]
Abstract
BACKGROUND Cell-based studies have shown that W1282X generates a truncated protein that can be functionally augmented by modulators. However, modulator treatment of primary cells from individuals who carry two copies of W1282X generates no functional CFTR. To understand the lack of response to modulators, we investigated the effect of W1282X on CFTR RNA transcript levels. METHODS qRT-PCR and RNA-seq were performed on primary nasal epithelial (NE) cells of a previously studied individual who is homozygous for W1282X, her carrier parents and control individuals without nonsense variants in CFTR. RESULTS CFTR RNA bearing W1282X in NE cells shows a steady-state level of 4.2 ± 0.9% of wild-type (WT) CFTR RNA in the mother and 12.4 ± 1.3% in the father. NMDI14, an inhibitor of nonsense-mediated mRNA decay (NMD), restored W1282X mRNA to almost 50% of WT levels in the parental NE cells. RNA-seq of the NE cells homozygous for W1282X showed that CFTR transcript level was reduced to 1.7% of WT (p-value: 4.6e-3). Negligible truncated CFTR protein was generated by Flp-In 293 cells stably expressing the W1282X EMG even though CFTR transcript was well above levels observed in the parents and proband. Finally, we demonstrated that NMD inhibition improved the stability and response to correctors of W1282X-CFTR protein expressed in the Flp-In-293 cells. CONCLUSION These results show that W1282X can cause substantial degradation of CFTR mRNA that has to be addressed before efforts aimed at augmenting CFTR protein function can be effective.
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Affiliation(s)
- M A Aksit
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - A D Bowling
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - T A Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - A T Joynt
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - D Osorio
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - S Patel
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - N West
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - C Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - P R Sosnay
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, United States
| | - G R Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - N Sharma
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
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9
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Sharma N, Evans TA, Pellicore MJ, Davis E, Aksit MA, McCague AF, Joynt AT, Lu Z, Han ST, Anzmann AF, Lam ATN, Thaxton A, West N, Merlo C, Gottschalk LB, Raraigh KS, Sosnay PR, Cotton CU, Cutting GR. Capitalizing on the heterogeneous effects of CFTR nonsense and frameshift variants to inform therapeutic strategy for cystic fibrosis. PLoS Genet 2018; 14:e1007723. [PMID: 30444886 PMCID: PMC6267994 DOI: 10.1371/journal.pgen.1007723] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 11/30/2018] [Accepted: 09/28/2018] [Indexed: 12/18/2022] Open
Abstract
CFTR modulators have revolutionized the treatment of individuals with cystic fibrosis (CF) by improving the function of existing protein. Unfortunately, almost half of the disease-causing variants in CFTR are predicted to introduce premature termination codons (PTC) thereby causing absence of full-length CFTR protein. We hypothesized that a subset of nonsense and frameshift variants in CFTR allow expression of truncated protein that might respond to FDA-approved CFTR modulators. To address this concept, we selected 26 PTC-generating variants from four regions of CFTR and determined their consequences on CFTR mRNA, protein and function using intron-containing minigenes expressed in 3 cell lines (HEK293, MDCK and CFBE41o-) and patient-derived conditionally reprogrammed primary nasal epithelial cells. The PTC-generating variants fell into five groups based on RNA and protein effects. Group A (reduced mRNA, immature (core glycosylated) protein, function <1% (n = 5)) and Group B (normal mRNA, immature protein, function <1% (n = 10)) variants were unresponsive to modulator treatment. However, Group C (normal mRNA, mature (fully glycosylated) protein, function >1% (n = 5)), Group D (reduced mRNA, mature protein, function >1% (n = 5)) and Group E (aberrant RNA splicing, mature protein, function > 1% (n = 1)) variants responded to modulators. Increasing mRNA level by inhibition of NMD led to a significant amplification of modulator effect upon a Group D variant while response of a Group A variant was unaltered. Our work shows that PTC-generating variants should not be generalized as genetic 'nulls' as some may allow generation of protein that can be targeted to achieve clinical benefit.
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Affiliation(s)
- Neeraj Sharma
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Taylor A. Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Matthew J. Pellicore
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Emily Davis
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Melis A. Aksit
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Allison F. McCague
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Anya T. Joynt
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Zhongzhu Lu
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Sangwoo T. Han
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Arianna F. Anzmann
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Anh-Thu N. Lam
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Abigail Thaxton
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Natalie West
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Christian Merlo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Laura B. Gottschalk
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Karen S. Raraigh
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Patrick R. Sosnay
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Calvin U. Cotton
- Departments of Pediatrics, Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Garry R. Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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10
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Han ST, Rab A, Pellicore MJ, Davis EF, McCague AF, Evans TA, Joynt AT, Lu Z, Cai Z, Raraigh KS, Hong JS, Sheppard DN, Sorscher EJ, Cutting GR. Residual function of cystic fibrosis mutants predicts response to small molecule CFTR modulators. JCI Insight 2018; 3:121159. [PMID: 30046002 DOI: 10.1172/jci.insight.121159] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 06/12/2018] [Indexed: 12/24/2022] Open
Abstract
Treatment of individuals with cystic fibrosis (CF) has been transformed by small molecule therapies that target select pathogenic variants in the CF transmembrane conductance regulator (CFTR). To expand treatment eligibility, we stably expressed 43 rare missense CFTR variants associated with moderate CF from a single site in the genome of human CF bronchial epithelial (CFBE41o-) cells. The magnitude of drug response was highly correlated with residual CFTR function for the potentiator ivacaftor, the corrector lumacaftor, and ivacaftor-lumacaftor combination therapy. Response of a second set of 16 variants expressed stably in Fischer rat thyroid (FRT) cells showed nearly identical correlations. Subsets of variants were identified that demonstrated statistically significantly higher responses to specific treatments. Furthermore, nearly all variants studied in CFBE cells (40 of 43) and FRT cells (13 of 16) demonstrated greater response to ivacaftor-lumacaftor combination therapy than either modulator alone. Together, these variants represent 87% of individuals in the CFTR2 database with at least 1 missense variant. Thus, our results indicate that most individuals with CF carrying missense variants are (a) likely to respond modestly to currently available modulator therapy, while a small fraction will have pronounced responses, and (b) likely to derive the greatest benefit from combination therapy.
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Affiliation(s)
- Sangwoo T Han
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Andras Rab
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Matthew J Pellicore
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Emily F Davis
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Allison F McCague
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Taylor A Evans
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Anya T Joynt
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Zhongzhou Lu
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Zhiwei Cai
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Karen S Raraigh
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Jeong S Hong
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - David N Sheppard
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Eric J Sorscher
- Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Garry R Cutting
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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11
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Raraigh KS, Han ST, Davis E, Evans TA, Pellicore MJ, McCague AF, Joynt AT, Lu Z, Atalar M, Sharma N, Sheridan MB, Sosnay PR, Cutting GR. Functional Assays Are Essential for Interpretation of Missense Variants Associated with Variable Expressivity. Am J Hum Genet 2018; 102:1062-1077. [PMID: 29805046 DOI: 10.1016/j.ajhg.2018.04.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 03/30/2018] [Indexed: 12/22/2022] Open
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.
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