Correction of a pathogenic gene mutation in human embryos

Area of Science:

• Human genetics
• Molecular biology
• Reproductive medicine

Background:

• Germline mutations can cause heritable diseases.
• Genome editing technologies offer potential for correcting genetic defects.
• Previous methods faced challenges with efficiency and off-target effects.

Purpose of the Study:

• To investigate the precise correction of a heterozygous MYBPC3 mutation in human preimplantation embryos.
• To evaluate the efficiency and safety of CRISPR-Cas9-based genome editing for germline mutation correction.
• To explore the use of endogenous DNA repair pathways for gene correction.

Main Methods:

• CRISPR-Cas9 system was employed for targeted double-strand breaks (DSBs) at the MYBPC3 mutation locus.
• Homology-directed repair (HDR) was leveraged, utilizing the wild-type maternal allele as a template.
• Cell cycle stage was modulated to optimize repair and avoid mosaicism.

Main Results:

• High targeting accuracy and homology-directed repair efficiency were achieved.
• The endogenous repair response predominantly used the wild-type maternal gene, not a synthetic template.
• Mosaicism was avoided in cleaving embryos, leading to a high yield of homozygous wild-type embryos.
• No off-target mutations were detected.

Conclusions:

• The described CRISPR-Cas9 approach demonstrates potential for correcting heritable mutations in human embryos.
• This method could complement preimplantation genetic diagnosis for reproductive applications.
• Further research is needed to confirm reproducibility with other mutations and address clinical considerations.