High-efficiency TadA cytosine base editors for precise modelling of human disease variants.

Genetic Variant Reinterpretation: Economic and Population Health Management Challenges.

Expanding base editing scope to near-PAMless with engineered CRISPR/Cas9 variants in plants

Genetic Counseling and Testing for Pulmonary Arterial Hypertension in the United States

Genomic screening of the general adult population: key concepts for assessing net benefit with systematic evidence reviews.

Targeted base editing enables safe and efficient knockout of ELANE for the treatment of ELANE-associated severe congenital neutropenia

A Multimodality Approach to Assessing Factor I Genetic Variants in Atypical Hemolytic Uremic Syndrome

Background: Racial/ethnic disparities in minority access to genetic testing have perpetuated a higher likelihood of identifying an uncertain result in minority populations. Methods :Patient data was obtained from the Informed Genetics Annotated Patient Registry (iGAP), an IRB-approved multi-center longitudinal, observational study designed to capture genetic and genomic test results and their utilization and impact on treatment practices and outcomes. Patients self-declare race/ethnicity. Genetic panels contained between 1 and 148 genes and variant classification was determined by the performing genetic testing companies and reported as negative, variant of uncertain significance (VUS),likely-pathogenic, or pathogenic. Descriptive statistics were used to assess and compare data of these populations and germline genetic testing results indicating variant of uncertain significance. Results: The three racial/ethnic groups have similar percentages of BRCA1 and BRCA2pathogenic variants. However, Caucasians have considerably more pathogenic variants in lesser penetrant genes [see Table 1]. Conclusions: Racial/ethnic groups vary by volume of lesser penetrant genes with Caucasians having the highest numbers. Correlation by SNP heritage assignment may lead to a better understanding of these differences. Gene NameAshkenazi PV% Askenazi PVs% of PV subjects AshkenaziAshkenazi VUS%VUS Ashkenazi VUS% of subjects VUS AshkenaziAsian% Asian PVs% of PV subjects AsianAsian VUS%VUS Asian mutations% of subjects VUS AsianBlack/African% Black/African PVs% of PV subjectsBlack/AfricanBlack/African VUS%VUS Black/Africanmutations% of subjects VUSBlack/AfricanCaucasian% Caucasian PVs% of PV subjects CaucasianCaucasian VUS% Caucasian Mutations% of subjects VUS CaucasianHispanic% Hispanic PVs% of PV subjects HispanicHispanic VUS% Hispanic Mutations% of subjects VUS HispanicOther% Other PVs% of PV subjects OtherOther RE VUS% Other RE Mutations% of subjects VUS Other#PV Total% Total PV#VUS TotalBRCA20.00%0.00%0.00%0.00%125.00%25.00%24.17%4.26%531.25%31.25%34.62%4.76%3414.47%16.50%122.42%2.44%815.69%18.18%45.26%5.48%211.11%12.50%36.67%6.82%5014.97%24BRCA1327.27%30.00%0.00%0.00%0.00%0.00%36.25%6.38%318.75%18.75%23.08%3.17%177.23%8.25%91.81%1.83%1631.37%36.36%11.32%1.37%211.11%12.50%24.44%4.55%4112.28%17CHEK20.00%0.00%112.50%12.50%0.00%0.00%12.08%2.13%0.00%0.00%0.00%0.00%2711.49%13.11%51.01%1.02%11.96%2.27%0.00%0.00%15.56%6.25%12.22%2.27%298.68%8ATM19.09%10.00%0.00%0.00%0.00%0.00%510.42%10.64%0.00%0.00%812.31%12.70%218.94%10.19%346.85%6.92%35.88%6.82%911.84%12.33%0.00%0.00%36.67%6.82%257.49%59CHEK2/1100delC19.09%10.00%0.00%0.00%0.00%0.00%12.08%2.13%0.00%0.00%0.00%0.00%104.26%4.85%30.60%0.61%23.92%4.55%22.63%2.74%0.00%0.00%0.00%0.00%133.89%6MUTYH0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%114.68%5.34%51.01%1.02%11.96%2.27%22.63%2.74%15.56%6.25%12.22%2.27%133.89%8PALB20.00%0.00%0.00%0.00%0.00%0.00%12.08%2.13%0.00%0.00%0.00%0.00%72.98%3.40%71.41%1.43%35.88%6.82%11.32%1.37%15.56%6.25%12.22%2.27%113.29%10BLM19.09%10.00%0.00%0.00%0.00%0.00%48.33%8.51%0.00%0.00%34.62%4.76%93.83%4.37%112.22%2.24%0.00%0.00%22.63%2.74%0.00%0.00%0.00%0.00%102.99%20MITF0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%83.40%3.88%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%82.40%0NBN0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%11.54%1.59%83.40%3.88%40.81%0.81%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%82.40%5FH327.27%30.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%41.70%1.94%40.81%0.81%0.00%0.00%11.32%1.37%0.00%0.00%0.00%0.00%72.10%5MSH619.09%10.00%112.50%12.50%0.00%0.00%0.00%0.00%0.00%0.00%4.62%4.76%31.28%1.46%132.62%2.65%23.92%4.55%22.63%2.74%15.56%6.25%0.00%0.00%72.10%19MUTYH-Biallelic/Compound Heterozygous0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%52.13%2.43%10.20%0.20%11.96%2.27%0.00%0.00%15.56%6.25%0.00%0.00%72.10%1MUTYH-Monoallelic0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%16.25%6.25%0.00%0.00%52.13%2.43%0.00%0.00%11.96%2.27%0.00%0.00%0.00%0.00%0.00%0.00%72.10%0PMS219.09%10.00%112.50%12.50%0.00%0.00%0.00%0.00%16.25%6.25%11.54%1.59%52.13%2.43%51.01%1.02%0.00%0.00%33.95%4.11%0.00%0.00%0.00%0.00%72.10%10Other00.00%0.00%562.50%62.50%375.00%75.00%3164.58%65.96%531.25%31.25%4467.69%69.84%6125.96%29.61%38377.22%78.00%1325.49%29.55%4964.47%67.12%950.00%56.25%3475.56%77.27%9127.25%546Grand Total11PV Ash108VUS Ash84PV Asi448Asi VUS4716PV Bla1665VUS Bla63235PV Cau206496VUS Cau49151PV His4476VUS His7318PV Oth1645VUS Oth44334334 PV Mutations Found738 Citation Format: Peter Beitsch, Chloe Wernecke, Kelly Bontempo, Brenna Bentley, Maureen Graham, Pat Whitworth, Rakesh Patel. Racial and ethnic groups have different clustering of common cancer genes [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-14-19.

Cytosine base editors (CBEs) enable programmable genomic C·G-to-T·A transition mutations and typically comprise a modified CRISPR–Cas enzyme, a naturally occurring cytidine deaminase, and an inhibitor of uracil repair. Previous studies have shown that CBEs utilizing naturally occurring cytidine deaminases may cause unguided, genome-wide cytosine deamination. While improved CBEs that decrease stochastic genome-wide off-targets have subsequently been reported, these editors can suffer from suboptimal on-target performance. Here, we report the generation and characterization of CBEs that use engineered variants of TadA (CBE-T) that enable high on-target C·G to T·A across a sequence-diverse set of genomic loci, demonstrate robust activity in primary cells and cause no detectable elevation in genome-wide mutation. Additionally, we report cytosine and adenine base editors (CABEs) catalyzing both A-to-I and C-to-U editing (CABE-Ts). Together with ABEs, CBE-Ts and CABE-Ts enable the programmable installation of all transition mutations using laboratory-evolved TadA variants with improved properties relative to previously reported CBEs.

Cytosine base editors (CBEs), combining cytidine deaminases with the Cas9 nickase (nCas9), enable targeted C-to-T conversions in genomic DNA and are powerful genome-editing tools used in biotechnology and medicine. However, the overexpression of cytidine deaminases in vivo leads to unexpected potential safety risks, such as Cas9-independent off-target effects. This risk makes the development of deaminase off switches for modulating CBE activity an urgent need. Here, we report the repurpose of four virus-derived anti-deaminases (Ades) that efficiently inhibit APOBEC3 deaminase-CBEs. We demonstrate that they antagonize CBEs by inhibiting the APOBEC3 catalytic domain, relocating the deaminases to the extranuclear region or degrading the whole CBE complex. By rationally engineering the deaminase domain, other frequently used base editors, such as CGBE, A&CBE, A&CGBE, rA1-CBE and ABE8e, can be moderately inhibited by Ades, expanding the scope of their applications. As a proof of concept, the Ades in this study dramatically decrease both Cas9-dependent and Cas9-independent off-target effects of CBEs better than traditional anti-CRISPRs (Acrs). Finally, we report the creation of a cell type-specific CBE-ON switch based on a microRNA-responsive Ade vector, showing its practicality. In summary, these natural deaminase-specific Ades are tools that can be used to regulate the genome-engineering functions of BEs.

BACKGROUND: Germline genetic testing is routinely incorporated into clinical care for breast cancer patients to inform management decisions and reduce risk for developing subsequent cancers. While the diagnostic yield of cancer genetic testing has increased over the years due to adoption of multigene panels, a substantial portion of breast cancer patients remain without a molecular diagnosis yet are suspected to have a genetic mutation that could not be detected and/or classified with standard DNA testing techniques. We assessed the ability of a novel genetic testing approach involving simultaneous DNA and RNA analysis to increase the diagnostic yield and decrease the number of variants of unknown significance (VUS). METHODS: Women with a personal history of breast cancer were ascertained from a larger cohort of patients referred for concurrent RNA sequencing alongside DNA hereditary cancer panel testing by ordering clinicians from 18 collaborating medical centers across the United States. Test result classifications were evaluated for women whose testing included sixteen clinically-actionable hereditary breast and/or ovarian cancer (HBOC) genes (ATM, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, MLH1, MSH2, MSH6, NF1, PALB2, PMS2, PTEN, RAD51C, RAD51D, and TP53). RESULTS: In this cohort of 746 breast cancer patients, the addition of RNA sequencing increased the pathogenic variant detection rate from 8% to 9% across sixteen HBOC genes. These RNA-related positive results included two pathogenic variants in BRCA1 occurring outside the standard analytical range of DNA testing and three VUS (one each in ATM, BRCA2, and PMS2) that were reclassified as likely pathogenic as a result of additional information provided by RNA sequencing. In addition, two VUS were reclassified to benign/likely benign (one each in MSH2 and BRCA2). Together, these five variant reclassifications contributed to a 3% relative decrease in the number of unique VUS classifications (reduced from 182 to 177 unique VUS). In addition, 31 previously-tested patients received reclassification reports. CONCLUSIONS: Concurrent DNA and RNA genetic testing has shown immediate promise in this pilot study, leading to the identification of five breast cancer patients with mutations in clinically actionable genes that would otherwise have received inconclusive or negative results with DNA testing alone. By increasing the detection of germline pathogenic variants and reducing VUS classifications, concurrent DNA and RNA genetic testing increases the diagnostic yield and clinical impact of hereditary cancer testing for breast cancer patients. Citation Format: Holly LaDuca, Lily Hoang, Jill Dolinsky, Jessica Profato, Amal Yussuf, Carolyn Horton, Cara Dresbold, Cassie Garcia, Catherine Koptiuch, Danielle Dondanville, Danielle McKenna, Danielle Menashe, Deborah Wham, Deepika Nathan, Diane Samad, Elizabeth Hoodfar, Gayle Patel, Jen Moore, Jennifer Geurts, John Lee, Kara Milliron, Khateriaa Pyrtel, Meagan Farmer, Meredith Seidel, Morgan Depas, Nichole Morman, Olivia Tan, Rebekah Krukenberg, Rob Pilarski, Samantha Stachowiak, Sandra Jenkinson, Sara Pirzadeh-Miller, Shraddha Gaonkar, Tiffani Demarco, Brigette Tippin Davis, Elizabeth C Chao, Rachid Karam. Concurrent DNA and RNA genetic testing identifies more patients with hereditary breast cancer than DNA testing alone [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-08-08.

ABSTRACTGenome editing technology is a powerful tool for programming microbial cell factories. However, rat APOBEC1-derived cytosine base editor (CBE) that converts C•G to T•A at target genes induced DNA off-targets, regardless of single-guide RNA (sgRNA) sequences. Although the high efficiencies of the bacterial CBEs have been developed, a risk of unidentified off-targets impeded genome editing for microbial cell factories. To address the issues, we demonstrate the genome engineering of Corynebacterium glutamicum as a GC-rich model industrial bacterium by generating premature termination codons (PTCs) in desired genes using high-fidelity cytosine base editors (CBEs). Through this CBE-STOP approach of introducing specific cytosine conversions, we constructed several single-gene-inactivated strains for three genes (ldh, idsA, and pyc) with high base editing efficiencies of average 95.6% (n = 45, C6 position) and the highest success rate of up to 100% for PTCs and ultimately developed a strain with five genes (ldh, actA, ackA, pqo, and pta) that were inactivated sequentially for enhancing succinate production. Although these mutant strains showed the desired phenotypes, whole-genome sequencing (WGS) data revealed that genome-wide point mutations occurred in each strain and further accumulated according to the duration of CBE plasmids. To lower the undesirable mutations, high-fidelity CBEs (pCoryne-YE1-BE3 and pCoryne-BE3-R132E) was employed for single or multiplexed genome editing in C. glutamicum, resulting in drastically reduced sgRNA-independent off-targets. Thus, we provide a CRISPR-assisted bacterial genome engineering tool with an average high efficiency of 90.5% (n = 76, C5 or C6 position) at the desired targets.IMPORTANCE Rat APOBEC1-derived cytosine base editor (CBE) that converts C•G to T•A at target genes induced DNA off-targets, regardless of single-guide RNA (sgRNA) sequences. Although the high efficiencies of bacterial CBEs have been developed, a risk of unidentified off-targets impeded genome editing for microbial cell factories. To address the issues, we identified the DNA off-targets for single and multiple genome engineering of the industrial bacterium Corynebacterium glutamicum using whole-genome sequencing. Further, we developed the high-fidelity (HF)-CBE with significantly reduced off-targets with comparable efficiency and precision. We believe that our DNA off-target analysis and the HF-CBE can promote CRISPR-assisted genome engineering over conventional gene manipulation tools by providing a markerless genetic tool without need for a foreign DNA donor.

Genetic testing outcome disparities in minority racial and ethnic sub-populations within a hereditary breast and ovarian cancer program serving a diverse, urban-based population (191)

DNA-based screening and population health: a points to consider statement for programs and sponsoring organizations from the American College of Medical Genetics and Genomics (ACMG)

342 Background: Pathogenic variants (PVs) in DNA repair genes (DRG), such as in BRCA1, BRCA2, ATM, CHEK2, etc., have implications for prostate cancer (PCa) family genetic counselling, testing and risk stratification in men. However, understanding how to counsel patients with variants of unknown significance (VUS) is an unmet clinical need. On the other hand, there is the necessity to cautiously interpret VUS findings and to bolster VUS evaluations with additional evidence for pathogenicity. In this study, we aim to investigate the prevalence of germline VUS in men with PCa and their association with outcomes after robot-assisted radical prostatectomy (RARP). Methods: This is a nested cohort case study from an ongoing PCa screening, set to identify and screen men in the Italian population with a genetic predisposition (AIRC - Fondazione AIRC per la Ricerca sul Cancro project IG 2020 ID 25027). Cases for the current analysis were selected by “Adam's rib strategy” searching for germline DRG variant in men with a diagnosis of high-risk PCa who were scheduled for RARP. After informed consent was signed, a blood sample was obtained. A previously validated multigene panel test was used to assess the presence of germline variants. PVs and VUS were classified according to the American College of Medical Genetics and Genomics and Association for Molecular Pathology consensus criteria and International Agency for Research on Cancer guidelines. The primary endpoint was to describe the prevalence of VUS and the secondary to correlate VUS with pathological outcomes after RARP. Results: A total of 118 men with diagnosis of PCa who underwent RP were enrolled. The mean age at diagnosis of PCa was 65.9 (±6.42) years; pathological grade was ISUP 1-2 in 58.0% patients and 3-5 in 42.0%. Of the 76 men evaluated, 18 (23.7%) had a VUS and 1 (1.32%) a pathogenic germline variant in BRCA1 and PALB2. Among those with VUS younger men at diagnosis were more likely to carry a VUS than older at diagnosis mean (age 64 ± 6.41 vs. 66 ± 7.20 years). Additionally, 33.3% vs 16.2 % were carrier of VUS and N+ and required adjuvant androgen deprivation therapy. No difference between ISUP at final pathology and positive margin rate were found. Conclusions: Our findings showed a high prevalence of VUS germline mutations in PCa patients undergoing RARP. These mutations seem to be associated with worse pathological outcomes. Limitations includes short follow-up and absence of non-Caucasian patients.

31P Survival outcomes in BRCA pathogenetic mutated, variant of unknown significance, and wild type ovarian cancer patients treated with PARP inhibitors