CRISPR-Cas9 Delivered Directly to Human Sperm
In a new study, presented at the annual meeting of the European Society of Human Reproduction and Embryology 2018, the CRISPR genome editing method has been delivered directly in human sperm cells. This differs from the usual approach in which the fertilised embryo is usually the target for gene editing.
The method uses a single 1100-volt electrical pulse, a fiftieth of second long, to allow the CRISPR components to break through the tough outer exterior of the sperm cells without killing them. With these optimal parameters in place, the sperm was still viable and able to retain enough mobility to fertilise an egg.
The team are planning to use the CRISPR-Cas 9 system to knockout LAMA1, a gene that is found to be upregulated in male infertility patients.
It has not yet been shown whether the genome editing system actually works once inside the sperm cells and Dr Choi added that there is still a lot to understand and discover about the sperm nucleus. It is also possible that editing may take place after the sperm fertilises an egg, in which case mosaicism may still be a problem. Mosaicism occurs when the DNA is not repaired in all of the embryonic cells.
The study gives hope that correcting mutations in human sperm cells is possible and may lead to the prevention of disease being passed on by fathers.
‘If we could do the editing in sperm, this would be fantastic,’ said Professor Tony Perry of the University of Bath in the UK, a leading expert on genome editing who was not involved in the study. ‘But it’s a big “if”. I think it’s unlikely but I would love to be proved wrong,’ he concluded.