Since the mid 90s everyones favourite carnivorous marsupial, the Tasmanian Devil, has been suffering from an unusual from of cancer called Devil Facial Tumor Disease. What’s so unusual about this cancer is that it’s transmissible. That means it can be passed onto another, unrelated animal. This occurs through biting during mating and feeding when the relatively lone devils come into close contact with each other.

It is clear that the cancer cells have all come from a single source (they are “clonal”). This was discovered when it was revealed that the DNA in cancer cells among different animals is identical. At the same time, the DNA of cancer cells is different from the DNA of other normal cells within an infected animal. Very interesting- and unusual!

So the question remained, where did those cells come from? To answer this question researchers used next generation sequencing to look at all the mRNA in tumor cells and compared it to another tissue, namely testis. The testis were chosen because lots of genes are expressed there. The goal was to understand what particular genes are active (i.e. producing mRNA) in the tumors. Because every cell type has a unique composition of active genes, if they knew the profile of the cancer cells, they could tell where they came from.

The sequencing not only gives information as to which genes are active in a tissue sample, but also how active they are. That’s because the more active a gene is, the more mRNA there will be and the more often that mRNA will be randomly sequenced. How active a gene is is an important part of the cells profile. This method is only semi-quantitative, but it gives a first impression as to which genes are really uniquely active in the cancer cells. Other quantitative experiments were performed and one particularly interesting gene was identified: MBP.

Identifying MBP as a hallmark of the cancer cells allowed the researchers to identify them as Schwann, a type of cell found in the central nervous system. MBP is central to the formation of Schwann cells, so it is likely that these cells are the origin of the disease.

This is a great example of using massively parallel sequencing to uncover unique properties in particular cell types. It’s also an important step in understanding how to control the disease, although treatment is still under development.

For further reading check out BBC’s summary.

Image: Missive Maven on Flickr

Citations

Murchison, E., Tovar, C., Hsu, A., Bender, H., Kheradpour, P., Rebbeck, C., Obendorf, D., Conlan, C., Bahlo, M., Blizzard, C., Pyecroft, S., Kreiss, A., Kellis, M., Stark, A., Harkins, T., Graves, J., Woods, G., Hannon, G., & Papenfuss, A. (2009). The Tasmanian Devil Transcriptome Reveals Schwann Cell Origins of a Clonally Transmissible Cancer Science, 327 (5961), 84-87 DOI: 10.1126/science.1180616