Whole chromosome loss and genomic instability in mouse embryos after CRISPR-Cas9 genome editing

Area of Science:

• Genetics
• Developmental Biology
• Genome Editing

Background:

• CRISPR-Cas9 technology is a powerful tool for genome editing.
• Karyotype alterations are known on-target complications of CRISPR-Cas9 editing.
• The mechanisms driving these karyotypic changes in embryos post-Cas9 treatment are not well understood.

Purpose of the Study:

• To investigate the events leading to karyotype alterations in embryos after CRISPR-Cas9 treatment.
• To track spontaneous and Cas9-induced karyotype aberrations during early embryonic development.

Main Methods:

• Utilized live imaging of 8-cell stage embryos.
• Employed single-cell genome sequencing.
• Monitored embryonic development through the first three cell divisions.

Main Results:

• Observed the generation of abnormal nuclear structures, including micronuclei and chromosome bridges, due to mitotic errors.
• Demonstrated that these mitotic errors contribute to whole chromosome loss and other karyotype aberrations.
• Showed that Cas9-mediated editing can induce significant chromosome structural alterations that propagate across embryonic cell divisions.

Conclusions:

• Cas9-mediated germline genome editing can result in detrimental on-target side effects.
• Mitotic errors following Cas9 treatment are a key source of karyotype instability in early embryos.
• These findings highlight the importance of monitoring for chromosomal abnormalities after genome editing in embryos.