142 words

Human embryos edited to stop disease

Scientists have used gene-editing tool CRISPR-Cas9 to fix a DNA mutation responsible for a common inherited disease – successfully replacing a gene in defective embryos that can cause heart failure

1 Injection: Sperm from man with mutated gene sequence and CRISPR-Cas9* injected simultaneously into egg cell

CRISPR-Cas9
Sperm
Egg cell
FemaleDNA

2 Molecular scissors: Enzyme called Cas9 cuts through male DNA in newly fertilised embryo

3 Small gRNA molecule guides Cas-9 scissors to damaged sequence of DNA to make cut

Male DNA
Cas9
gRNA

4 Mutated gene sequence – cut from male DNA – is replaced with healthy gene from female DNA

5 72% success: Gene editing resulted in 42 of 58 embryos with two mutation-free copies of gene in every cell


*CRISPR, Clustered regularly interspaced short palindromic repeats

Source: Nature 
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