More CRISPR Gene Editing Babies

Nature reported that Russian molecular biologist Denis Rebrikov is planning to perform CRISPR experiments on human embryos. He’s running the experiments on the same CCR5 gene as Chinese scientist He Jiankui in 2018. This is once again raising questions on the ethics of human genetic experimentation.

The CCR5 gene editing in He’s experiment is the same one proposed for Rebrikov’s experiment. CCR5 is used by Human Immunodeficiency Virus (HIV) to enter cells. By editing the gene to make it into the Δ32 allele – a 32-base-pair deletion that introduces a premature stop codon into the CCR5 receptor locus, resulting in a nonfunctional receptor – the virus is no longer able to enter the cell. This gives increased resistance – perhaps even immunity – to HIV.

HIV-CCR5

A recent study by Xinzhu Wei and Rasmus Nielsen, titled CCR5-∆32 is deleterious in the homozygous state in humans, published in Nature, showed that homozygosity for the CCR5-∆32 variant has (drumroll) deleterious effects on long-term health. Stat News reported:

Nielsen, a professor of integrative biology at Berkeley, called ∆32 “probably not a mutation that most people would want to have. You are actually, on average, worse off having it,” including because of the influenza and West Nile consequences. The higher risk of early death, he told STAT, “likely has to do with reduced efficacy of the immune response to specific diseases. The effects depend on the environmental context, specifically the pathogenic environment.”

The problems with using CRISPR are two-fold. The first, which is potentially the case in He’s experiments, is that it’s not always known what the long-term effects of altering a gene could be. Or, even if you do, the child doesn’t get to weigh in on the cost-benefit analysis of doing the alteration. The other problem is that CRISPR can be finicky, causing off-site alterations that could have other unforeseen consequences.

I, for one, think that human genetic disease treatments – and even enhancements – is not only a good idea in the long-term, but will become necessary. Experiments like this might be premature, but will be vital to making any progress on this front.

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