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Scientists may fix faulty DNA in a man’s sperm before it fertilized an egg, CRISPR gene-editing technology has shown promise for removing bad DNA and replacing it in embryos, but as their cells multiply, the fixed DNA may make it into some cells and not others. Changing the genetic makeup of sperm cells would solve that problem. Scientists at Weill Cornell Medicine in New York made this possible by delivering an electrical pulse to the sperm, breaking its outer shell and allowing them to deliver CRISPR to the cell.
Over 10,000 genetic disorders are ‘single gene’ conditions- they are passed onto offspring through a mutation in a single piece of either parent’s DNA, carried by their sperm or egg. All single-gene disorders transmittable by the male can be treated with the use of CRISPR-Cas9 on sperm. These disorders include sickle cell disease, cystic fibrosis and muscular dystrophy.
A sperm cell has a hard exterior that allows it to penetrate an egg, but it is also sensitive and can die off if it is put under too much stress.
The Weill Cornell researchers had to find just the right voltage of pulse to use on sperm to disarm its outer shield enough to insert CRISPR-Cas9 without crippling its ability to move. The experiment eas carried out with a range of extremely high voltage shocks delivered in a very short bursts and found that the optimal pulse was a 20 milliseconds of 1,100 volts – nearly 100-times the power of a car battery, blasted at the sperm for one fiftieth of a second.
Shocking CRISPR into sperm cells did reduce their motility or ability to swim toward an egg to fertilize it – quite dramatically, but removed faulty genes, according to the new study, presented at the annual meeting of the European Society of Human Reproduction and Embryology. Fastest sperm treated with CRISPR gene-editing, will have corrected DNA to an egg, allowing an embryo to develop unhindered by genetic defects, or tampered with bio-engineering.
Gene-editing using the CRISPR-Cas9 can ‘fix’ any genetic mutation that codes for birth defects and inherited medical disorders before a child is even born. Embryonic development is a stage of rapid cell multiplication. It is unclear when – or even if – CRISPR can be used to change all and not just some of the embryo’s DNA. If some cells receive the repaired DNA, but others receive the faulty DNA, the result might be genetic mosaicism, in which a person displays traits of a disorder in some parts of their body but not others.
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