Cited by 305CRISPR and Genetic EngineeringDNA Repair MechanismsAnimal Genetics and Reproduction

Allele-Specific Chromosome Removal after Cas9 Cleavage in Human Embryos

Open access
Zuccaro, Michael V., Xu, Jia, Mitchell, Carl, Marin, Diego, Zimmerman, Raymond, Rana, Bhavini, Weinstein, Everett, King, Rebeca T. +8 more·2020·Cell

Published version of a preprint

Abstract

Correction of disease-causing mutations in human embryos holds the potential to reduce the burden of inherited genetic disorders and improve fertility treatments for couples with disease-causing mutations in lieu of embryo selection. Here, we evaluate repair outcomes of a Cas9-induced double-strand break (DSB) introduced on the paternal chromosome at the EYS locus, which carries a frameshift mutation causing blindness. We show that the most common repair outcome is microhomology-mediated end joining, which occurs during the first cell cycle in the zygote, leading to embryos with non-mosaic restoration of the reading frame. Notably, about half of the breaks remain unrepaired, resulting in an undetectable paternal allele and, after mitosis, loss of one or both chromosomal arms. Correspondingly, Cas9 off-target cleavage results in chromosomal losses and hemizygous indels because of cleavage of both alleles. These results demonstrate the ability to manipulate chromosome content and reveal significant challenges for mutation correction in human embryos.

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Crossref · 10.1016/j.cell.2020.10.025

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  • Microhomology-mediated end-joining (MMEJ) is the dominant repair pathway in this context.

    “and that microhomology-mediated end-joining (MMEJ) is the dominant repair pathway in this context (37).”

    From Frequent loss of heterozygosity in CRISPR-Cas9–edited early human embryos (2021) · cites this paper as [37]

    The Discussion calls the MMEJ-mediated 5-bp deletion the most common repair event at the targeted EYS site, and the Results report that it accounted for 55% of edited reads. But MMEJ was not the dominant pathway among independent repair events in embryos: the Results count 14 MMEJ events versus 18 NHEJ events. The claim overgeneralizes a frequent repair outcome to the pathway overall. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • MMEJ-derived large deletions are more likely than microhomology-mediated gene conversion in this context.

    “This suggests that MMEJ-derived large deletions (14, 37) are more likely than microhomology-mediated gene conversion in this context, though protein expression has yet to be fully characterised.”

    From Frequent loss of heterozygosity in CRISPR-Cas9–edited early human embryos (2021) · cites this paper as [37]

    The Discussion reports MMEJ as a predominant repair pathway at the EYS site, but describes its common deletion as 5 bp, not a large deletion. The Background attributes segmental and whole-chromosome loss to mitotic entry with unrepaired breaks, rather than MMEJ. The paper therefore supports frequent MMEJ repair in this context, but not the claim that MMEJ-derived large deletions are more likely than gene conversion. (LLM, conf=0.85)

    Experimental — accuracy not yet measured

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Research works printed but not linked: 2

  1. EYS / Cas9 target site bioRxiv preprint doi: https://doi.org/10.1101/2020.06.17.149237; this version posted June 18, 2020. The copyright holder for this preprint · DOI
  2. % on target genotype bioRxiv preprint doi: https://doi.org/10.1101/2020.06.17.149237; this version posted June 18, 2020. The copyright holder for this preprint · DOI

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Authors
Zuccaro, M. V., Xu, J., Mitchell, C., Marin, D., Zimmerman, R., Rana, B., Weinstein, E., King, R. T., Palmerola, K. L., Smith, M. E., Tsang, S. H., Goland, R., Jasin, M., Lobo, R., Treff, N., & Egli, D.
Affiliations
  • Columbia University Irving Medical Center (US)
  • Genomic Prediction (United States) (US)
  • Columbia University (US)
  • Rutgers, The State University of New Jersey (US)
  • Memorial Sloan Kettering Cancer Center (US)
Corresponding author
Egli, Dieter
Venue
Cell
Publisher
Elsevier BV
Published
2020-12
Volume
183
Issue
6
Pages
1650-1664.e15
ISSN
0092-8674 (ISSN-L)
OpenAlex
W3095871885
Cited by
303
References
46
Citations by year
2026: 27 · 2025: 30 · 2024: 51 · 2023: 64 · 2022: 63 · 2021: 57 · 2020: 11
FWCI
15.99
Type
journal article
Language
en
Open access
Locations
  • Cell (publishedVersion)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nd)
  • PubMed (publishedVersion)
Funders
  • Irving Medical Center, Columbia University
  • New York Stem Cell Foundation
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › CRISPR and Genetic Engineering
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › DNA Repair Mechanisms
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Animal Genetics and Reproduction
Keywords
CRISPR/Cas9, human embryo, frameshift mutation, microhomology-mediated end joining, DNA double-strand break repair, zygote, paternal allele, chromosome loss, off-target cleavage, indels, embryo mosaicism, germline editing, inherited blindness
MeSH terms
Human Embryonic Stem Cells, Gene Editing, CRISPR-Associated Protein 9, Alleles, Animals, Base Sequence, Blastocyst, Cell Cycle, Cell Line, Chromosome Deletion, Chromosomes, Human, Embryo, Mammalian, Eye Proteins, Fertilization, Genotype, Heterozygote, Humans, Mitosis, Embryo Implantation, Gene Rearrangement, Genome, Human, Open Reading Frames, Polymorphism, Single Nucleotide, Mice, DNA Breaks, Double-Stranded, INDEL Mutation, Genetic Loci, DNA End-Joining Repair

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