Friday, March 19, 2010

Genetic engineering

We often criticize the excess geneticization of diseases whose main cause is not genetic variation but lifestyle factors of various kinds. But some diseases seem clearly to be genetic, with little environmental input, one or only a few clearly known causal genes. In such cases, genetics is the right approach, and genetics of two kinds--to detect risk factors in genetic counseling for parents planning to have children who know a serious allele is in their family, and to treat the disease when it has arisen.

A good example described in last Sunday's New York Times is epidermolysis bullosa. The disease appears to be due to a defect in a collagen gene that produces structural strength and integrity to the skin. The victims have skin described as being as delicate as butterfly wings, and as a result have very compromised lives.

EB seems to be a perfect target for gene therapy--to replace the gene in the germline of parents, or of fertilized eggs in vitro before reimplantation in the mother, or therapeutically to replace the deficient skin cells with cells competent to produce the right type of collagen. Such efforts are described in the article.

Human beings are very good at engineering, and if science is good at anything, it's technology. EB is one of many problems that seem to be engineering rather than conceptual challenges. Science ought to work, in such cases--even if that doesn't mean it can happen overnight. This kind of challenge is where genetic investment should go, in our view.

For complex diseases that are mainly due to environmental or lifestyle factors, if those were ameliorated by social behavior (like better diet) and other measures (like removal of toxins), then for most diseases what would remain would be the truly genetic instances that would fortunately be rare, and fortunately be engineering challenges.

That doesn't mean it'll be easy. If we're good at engineering and have had thousands of years to practice it, if there's one thing that organisms have evolved over countless more thousands, it's to detect and prevent the outside world from attacking its cells. So these will be battles waged mano a mano at the molecular scale.

Many techniques already exist to replace genes, engineer vectors to put genes into cells, or make microorganisms (or culturable cells) produce a gene product. The best approach, perhaps, is to engineer stem cells from the affected person, redifferentiated to be of the needed tissue type, and then somehow introduce them into the affected tissue. There's a lot of progress along these lines, but only time will tell if this is the best approach. Whatever turns out to be the case, at least these are clear-cut problems for which technological solutions seem at least possible.

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