Improving homology-directed repair efficiency in human stem cells

Area of Science:

• Biotechnology
• Stem Cell Biology
• Molecular Genetics

Background:

• Generating accurate human disease models using induced pluripotent stem cells (iPS cells) requires precise genetic modification.
• Efficiently editing single nucleotide variants is crucial for recapitulating diverse disease phenotypes, especially for dominant or recessive genetic disorders.

Purpose of the Study:

• To develop an improved and highly efficient protocol for engineering single nucleotide variants in human iPS cells.
• To optimize homology-directed repair (HDR) over non-homologous end joining (NHEJ) for precise genetic alterations.

Main Methods:

• Utilized a fluorescent BFP->GFP assay to monitor the efficiency of single base pair changes.
• Optimized conditions by combining cold shock, a small molecule HDR enhancer, and chemically modified single-stranded oligodeoxynucleotides (ssODNs).
• Assessed the ratio of HDR to NHEJ repair outcomes.

Main Results:

• Achieved HDR in 70% of unselected human iPS cells.
• Demonstrated a seven-fold increase in the HDR to NHEJ ratio, shifting from 0.5 to 3.7.
• The combined approach significantly enhanced the efficiency of introducing single nucleotide variants.

Conclusions:

• The developed protocol offers a robust and efficient method for precise genetic engineering of single nucleotide variants in human iPS cells.
• This advancement facilitates the creation of more accurate iPS cell-based disease models for research and therapeutic development.