CCR5 Delta 32 - Science

DNA is a made up of 4 basic molecules called nucleotides. Each human cell has billions of nucleotides.

The CCR5 Delta 32 installation is a visual explanation of a DNA deletion mutation. 

The CCR5 gene is a long strand of DNA that has the instructions for building the CCR5 protein.  The normal CCR5 gene that most of us have is called the "wild type". When a person has a slightly different version of the gene, scientists referred to that as a mutation. CCR5 Delta 32 is one such mutation. 

In each banner, the wild type is on the left half of each stripe and the Delta 32 variant is on the right half. Each sequence runs top to bottom, left to right.  So to read the DNA sequence for the CCR5 wild type, read only the left half of each stripe.

In a sequence over 1000 nucleotides long, a small 32 nucleotide deletion results in HIV resistance and gives insight into a possible treatment. 

CCR5 and HIV

The CCR5 gene produces the CCR5 protein which normally inserts into the cell membrane. The human immunodeficiency virus (HIV) infects the human cell by attaching to 2 cell membrane proteins, CD4 and CCR5.  With CCR5 Delta 32, the resultant protein is truncated and HIV is not able to properly attach to the host cell.  So people who have the mutant gene might be exposed to HIV but they are resistant to developing AIDS because the virus is unable to infect them. 

In 2009, scientists in Berlin reported the first, and only, individual to be cured of HIV. The treatment involved a bone marrow transplant from a donor with the CCR5 Delta 32 mutation. 

CCR5 Delta 32 and Evolution

It is believed that the CCR5 Delta 32 mutation first appeared about 2200 years ago.  It was a one time mutation in Northern Europe amongst the Viking population.  Those who had the mutation were protected from infection by viruses such as small pox, and survived plagues better than those with the normal CCR5 gene.  Today, about 18% of the population in Northern Europe are resistant or immune to HIV infection because they are descendants of that Viking population and they have the CCR5 Delta 32 gene.


Further on-line reading.

"Blocking HIV's Attack" by Carl June and Bruce Levine. Scientific American (March 2012), 306, 54-59 Published online: 14 February 2012 | doi:10.1038/scientificamerican0312-54

Correction: Two years after completing this piece, I noticed 2 of the tiles are the wrong colour.  I could choose to be horrified but I would rather see it as a bit of random mutation.  Contact me if you would like to know where the error is, I'll try to find it again.