Evan Savell
ACTN3 Gene
Would you want to know if your child has the genetic predisposition to
develop into a star athlete? Scientists have long sought after a tie between genetics
and athleticism. They have noted various genetic factors contributing to athletics,
150 of which are accounted for in the Map of the Human Genome (MacArthur &
North, 2007). Recent research has found that there is a link between variants of the
ACTN3 gene and athletic performance. Based on this finding, a company from
Colorado, Atlas Sports Genetics, has introduced a 150 dollar test to the public that
screens for ACTN3 variants and that can supposedly determine if a child will thrive
in a certain sport (Lite, 2008). However, the question emerges: is there enough
substantial evidence backing the ACTN3 genes link to athleticism to pay for this
test?
In order for muscles to contraact they require a protein called actin.
However, actin needs to be stabilized, and the gene ACTN3 that codes for a protein
a-actinin three, that binds to actin and stablize it. (Yang, et al., 2009).Despite the
proteins seemingly critical function, scientist noted the lack of α-actinin-3 in more
than one billion people worldwide (North, 2008). Eventually the reason for the
proteins deficiency in the population was uncovered; it is due to a common
polymorphism R577X, which replaces an arginine with a premature stop codon.
The polymorphism inhibits the production of α-actinin-3; therefore, it leads to two
alles, an R-allele group that produces the α-actinin-3 protein, and in addition, an X-
allele group that doesn’t produce the protein (Yang, et al., 2009). The increasing
prevalence of the X-allele group, expecially in Europenas and Asain populations,
have lead some to question if, and why the X allele is selected for (North, 2008).
Scientists have conducted much research identifying the effects of the R allele
group and X allele group since the identification of the polymorphism in 1999. The
research has been conducted in elite athletes because the influence of α-actinin-3 on
muscle function should be most noticeable in these subjects. Overall, scientits have
linked the R allele with elite sprint and power performance, while they have noted
that the X allele may linked to endurance ( Enyon, et al., 2009) However, the results
have been varied, as some researcher’s information contrast with information’s
recorded by others. According to Enyon et al., ( 2009) there is a higher X allele
frequency in top level endurance runners, while the R allele is more prevalent in
top-level sprinters. From these results, the authors concluded that the R allele was
in fact linked to sprinting, and that the X allele may not be vital to endurance
running, but additive. However, there wasn’t substantial evidence recorded by
scientits to have concluded that the X allele is additive to endurance running. The
evidence showed that their was a higher X allele frequency in sprinters than in
runners, but it showed a similar X allele frequency between endurance runners. This
means that to be an endurance runner it might not matter whether or not you have
the X allele. Branching of from Enyon’s experiment, scientists studied whether or
not the R allele that is advantageous to sprinters is also advantageous to artistic
gymnastic performance. As hypothesized, the authors noted a higher degree of R
allele gymnasts than X allele gymnasts. The authors also saw that their was a lower
XX allele frequency in gymansts than in a control group ( Massida, et al, 2009). Once
again, this evidence refutes the conclusion that the X allele is additive to endurance
performance. Two more experiments have associated the R allele to sprint and
power performance, but haven’t linked the X allele to endurance running. Scientists
recorded that professional soccer players had a higher R allele frequency compared
to endurance athletes and controls; nevertheless, the experiment also indicated
extremely similar X allele distirubtion between endurance runners and contorls.
This evidence clearly doesn’t support a link between the X allele and endurance
running. ( Santiago, et al., 2009). Finally, according to Saunders et al., (2007) there
was no link between the X allele and any “ultra-endurance performance”.
In Atlas Sports Genetics test, they will screen for either the X allele, which
they say is linked to endurance events, or the R allele, which they say is related to
sprint and power events ( Lite, 2008). However, experiments conducted over the
past eight years show that the X allele is definetly not additive to endurance
perofmrance, and that the allele may not even be linked to endurance events. The
research on this topic is still relatively new, but there is not enough evidence
supporting a link between the X allele to pay 150 for this tests.
References
Enyon, N., Duarte, J.A., Oliveira, J., Sagiv, M., Yamin, C., Meckel, Y., … Goldhammer, E.
(2009). ACTN3 R577X polymorphism and Israeli top-level athletes. Int J
Sports Med, 30, 695-8.
Lite, J. (2008) Can genes predict athletic performance? Scientific American.
Retrieved from http://ScientificAmerican.com/aritcle.cfm?id=genes-sportstalent
Massidda, M., Vona, G., & Calo, C.M. (2009). Association between the ACTN3 R577X
polymorphism and artistic gymnastic performance in Italy. Genet Test Mol
Biomarkers, 13, 377-80.
Yang, N., Garton, F., & North, K. (2009). Alpha-Actinin-3 and Performance. Med Sport
Sci., 54, 88-801.
Norman, B., Esbjornsson, M., Rundqvist, H., Osterlund, T., von Walden, F., & Tesch, P.
(2009). Strength, power, fiber types, and mRNA expression in trained men
and women with different ACTN3 R577X genotypes. J Appl Physiol, 106, 959965.
North, Kathryn. ( 2008) Why is alpha-actinin-3 deficiency so common in the general
population? The evolution of athletic performance. Twin Res Human Genet,
11. 384-94.
MacArthur, D., & North, K. (2007). ACtN3: A Genetic Influence on Muscle Function
and Athletic Performance. Sport Sci. Rev, 1, 30-34.
Santiago, C., Gonzalez-Freire, M., Serratosa, L., Morate, F., Meyer, T. , Gomez-Gallego,
F., Lucia, A. (2008). ACTN3 genotype in professional soccer players. Br J
Sports Med, 42,71-3.
Saunders, C., September, A., Xenophontos, S., Cariolou, M., Anastassiades, L., Noakes,
T., Collins, M. (2007). No Association of the ACTN3 gene R577X
polymorphism with endurance performance in Ironman Triathlons. Ann
Hum Genet, 71, 777-81.
Moran, C., Yang, N., Bailey, M., Tsokanos, A., Jamurtas, A.,MacArthur, D.,
…Pitsiladis,Y., Wilson, R. (2007). Association analysis of the ACTN3 R577X
polymorphism and complex quantitative body composition and performance
phenotypes in adolescent Greeks. European Journal of Human Genetics, 15,
88-93.
Lite, J. (2008) Can genes predict athletic performance? Scientific American.
Retrieved from http://ScientificAmerican.com/aritcle.cfm?id=genes-sportstalent