The Hapmap and personalized medicine

The October 2005 issue of Nature had the complete results of the first stage of the Hapmap project. I first came across the Hapmap when I heard Chris Smiths Nature podcast corresponding to that issue. The first stage marked the analysis of polymorphisms in 270 individuals who came from diverse ethnic background. Although I am no geneticist. The great thing about the hapmap data is that it finally allows us to understand human genetic variation.

We have all heard that the genetic differences between all of us is very very small. Of course the hapmap is basically a way to understand what are those differences and how small is very small. Perhaps one of the emerging facts , from studies leading up-to the hapmap project , was the extent of linkage dis-equilibrium among our differences. I will not even attempt to explain linkage-disequilibrium: suffice to say that that disequilibrium arises from differences traveling together from one generation to the next. i.e they are linked. Now why is that a big deal ?. Well it means that instead of studying the 7 million odd “polymorphisms” ( i.e the differences between you and me). Thanks to linkage disequilibrium you can possibly get at a good picture of how “generally different ” you are from me by looking at around just 10,000 places.

SO why is this big deal, because it drastically reduces the cost and effort of tracking down these differences.

Now think of a drug undergoing clinical trials. We have all heard of people who remark ” I dont respond well to amoxicillin but do just fine with zithromax ( two different antibiotics). Now imagine the scenario during a clinical trial , when that “you” and “me” is now linked in with your haplotype ( the collection of differences) and my haplotype and then at the end they might just have a clear picture of – People with haplotype X cannot tolerate this drug while people with haplotype Y , can. That is powerful information that can potentially save lives.

Also the hapmap and the study of such polymorphisms also has powerful implications for the study of human anthropology , human history and human natural selection. In this context the online seminar from science magazine explaining the process of using SNP data to examine natural selection makes very interesting viewing ( see References).

Overall, there is no denying the impact of rapid genotyping on understanding and classifying human response to clinical trials. Of course , just as the launch of Bidil -the first pre hapmap era “personalized drug” specifically targetted towards African-Americans set of a whole slew of ethical debate. I am positive that having hapmap data guide drug discovery or dosage may also be much of a mixed blessing in this era of genomic-medicine

Relevant Links :

Clues to Our Past: Mining the Human Genome for Signs of Recent Selection

Online Science Magazine flash seminar on evidence for positive selection in human lineages and the review by Sabtei et. al.

Race based drug may halt trial for better clinical markers

Nature news and Views on the Hapmap project

Wikipedia entry with an excellent description of what is a haplotype and an SNP

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One response to “The Hapmap and personalized medicine

  1. Damilola Opadeyi

    This is really fascinating. Can you help me found out any one involved in Hapmap in Nigeria?

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