World records - WE LOVE THEM! Especially seeing them broken by our athletic heroes and the yardstick raised a little higher, according to the premise “Bigger, Stronger,Faster”. Truth is, however, some of our heroes have a dirty little secret… DOPING.
Fact is that doping is prohibited and no athlete should make use of it. It needs to be fair, just as the Olympic oath says. However, doping has been an issue for fair sports for many years. Lance Armstrong for example won the Tour the France seven times before he was caught for the use of doping. At the end of 2012, he was stripped of all of his titles since 1998, including his seven victories at the Tour de France. The cycling world was shocked. How could he have doped without being caught?
Nowadays, rapid advances in gene therapy enable athletes to use a completely different type of doping that is almost undetectable. Performance enhancing agents such as Erythropoietin (EPO) or insulin-like growth factor 1 (IGF-1) do not need to be injected anymore, but the genes that provide enhanced levels of these agents are added as plasmids, hence the name gene doping. The big advantage of gene doping is the easy bypassing of current detection methods.
The World Anti-Doping Agency (WADA) is taking the possibility of gene doping seriously (Filipp, 2007). Sooner or later, the sporting world has to deal with the phenomenon of gene doping to control athletic performance enhancement (Haisma and De Hon, 2006). The big problem is that no suitable detection method has been accepted for official use so far.
The TU Delft iGEM team is trying to tackle the problem of gene doping by designing a novel and future-oriented detection method based on CRISPR.
Currently, it is most likely that for the administration of gene doping an adenovirus or a plasmid is used. Both methods bring the doping genes into the cell nucleus, where the gene will be integrated in the genome and, subsequently, will be expressed, which results in higher hormonal and factor levels. The inserted genes, however, differ from the regular genes. Due to the size of the gene (the EPO gene with 2901 bp for example - NCBI Gene ID: 2056), introns must be removed in order to deliver it to the nucleus.
The TU Delft iGEM team therefore search for the exon-exon junctions by using a dxCas9-Tn5 transposase fusion protein (Hu et al., 2018; Picelli et al., 2014) with a library of different gRNAs that cover all different gene doping changes. When the dxCas9 finds an exon-exon junction, the Tn5 transposase will cut the doping gene and add sequencing adapters (figure 1). Only the genes with adaptor will then be sequenced with Oxford Nanopore Technologies’ next generation sequencing. This efficient, secure and versatile method for targeted sequencing will ensure that only gene doping DNA will be sequenced.
Figure 1 Schematic project overview
In October our concept will be presented at iGEM (international Genetically Engineered Machine competition), the biggest international competition on synthetic biology, where more than 340 teams from 44 countries try to solve a world problem with the use of synthetic biology.
Do you want to know more about TU Delft iGEM team’s project? Then visit their website for more information at igemtudelft.nl and sign up for their newsletter.
Also check out the clip on their project at youtube.
Get on your marks, get set and join them in the fight against gene doping.
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Written by Susan Bouwmeester and Dr Andreas Ebertz
The iGem TU Delft team - from left to right: Lisbeth Schmidtchen; Timmy Paez; Gemma van der Voort; Lisa Büller; Jard Mattens; Janine Nijenhuis; Alex Armstrong; Nicole Bennis; Kavish Kohabir; Venda Mangkusaputra; Susan Bouwmeester; Monique de Leeuw
- Filipp, F. (2007) Is science killing sport? Gene therapy and its possible abuse in doping. EMBO Rep. 8(5): 433-5. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1866212)
- Haisma, H. J., & De Hon, O. (2006) Gene doping. Int J Sports Med. 27(04): 257-66. (https://www.ncbi.nlm.nih.gov/pubmed/16572366)
- Hu, J.H., Miller, S.M., Geurts, M.H., Tang, W., Chen, L., Sun, N., Zeina, C.M., Gao, X., Rees, H.A., Lin, Z., et al. (2018) Evolved Cas9 variants with broad PAM compatibility and high DNA specificity. Nature 556:57-63. (https://www.ncbi.nlm.nih.gov/pubmed/29512652)
- Picelli, S., Björklund, A.K., Reinius, B., Sagasser, S., Winberg, G., and Sandberg, R. (2014) Tn5 transposase and tagmentation procedures for massively scaled sequencing projects. Genome Res. 24: 2033-40. (https://www.ncbi.nlm.nih.gov/pubmed/25079858)