Increased fast-twitch muscle fibers provide quicker movements in elite athletes. Carriers of this mutation potentially have exceptionally well-developed fast-twitch muscles, leading to faster and stronger athletes. But, does this narrative prove to be correct? No.
Muscles comprise up to 450,000 fibers used for flexibility, contractions, blood storage, storage of glycogen for energy (fuel), and fat storage. Fast-twitch muscle fibers provide quicker movements in elite athletes, thus their name “fast.” The emergence of this recessive allele trait of the ACTN3 has been dubbed as the “super athlete” genetic mutation.
The Claim
The claim is this trait was first formed by the supposed Darwinian mechanism of a random germline mutation. At the 577th sequential position (with a single “letter” C-to-T substitution) -1 This allele confers a gene variant to offspring related to muscle development with two variations -1 This particular variant is therefore written out as ACTN3 577X. This allelic trait provides more exceptionally developed fast-twitch muscles, which might lead to genetically faster and stronger athletes. This mutation is reportedly found more frequently among elite athletes. The claim is this mutation emerged long ago, some 40,000 – 60,000 years ago, in anatomically modern European and Asian humans.-2 ACTN3 577X may have arisen based on a global latitudinal gradient that impacts the mean annual temperature and, therefore, the fitness needs of the population. -2 Perhaps this allelic gene variant emerged based on environments where resources (calories) were more scarce; finding a more efficient muscle metabolism is beneficial for survival. -3
It is hypothesized that a shift towards a more efficient metabolism may be responsible for driving the (relatively) recent positive selection of the ACTN3 (577X) allele, which arose 40,000–60,000 years ago when anatomically modern humans migrated out of Africa.” -3 NIH
The reality
“Over the last couple of decades, research has focused on attempting to understand the genetic influence on sports performance. This has led to the identification of a number of candidate genes which may help differentiate between elite and non-elite athletes. One of the most promising genes in that regard is ACTN3, which has commonly been referred to as “a gene for speed”. Recent research has examined the influence of this gene on other performance phenotypes, including exercise adaptation, exercise recovery, and sporting injury risk.” -1
What are “alleles?”
Human parents carry gene variants in their sex cells (called gametes), which are used to transfer genetic traits to their offspring called “alleles.” Allele traits that pass most often are called “dominate,” other variants are “recessive.” The ratio (percentage) at which they are expressed in the population is called “allele frequencies.”
The most commonly discussed allele frequencies include eye, hair, or skin colorations. Unfortunately, these minor variances are insignificant but have been used to divide human beings into races. DNA mapping of the human genome has debunked this misperception of different human “races.” The mapping of the human genome and the volume of the DNA molecule has discovered a stunning 99.9999% genetic similarity between all human beings. This means there is only one race: The human race!
Other less obvious allelic traits are not as observable, including the offspring’s predisposition to diseases, mental health, height, blood type, weight, and even intellectual capacity. While genetics alone do not dictate our overall individual capacity to excel, it does illustrate that countless physiological aspects of our development are fixed. Turns out, the allele trait that assembles the amino acids to form the protein chain for a certain muscle (the genetic sequence is referred to as “ACTN3”), which variant that is expressed might express more “fast” or “slow” twitch muscle proteins. The ACTN3 is another example of allele frequencies that impact muscles and perhaps an individual’s ultimate overall potential within athletic pursuits.
ACTN3Allele Frequency of “R” vs. “X”
The two primary allele frequencies in the gene that synthesizes the protein ACTN3 for certain muscle fibers are divided between two types: “R” and “X.” The “R” allele is dominant, expressing about 56% of the time. -4The “X” allelic gene variant is recessive and expressed less often in about 44% of the population. -4 In certain populations, the rate of the 577X variant can differ by about 10%. -5 Like several other allele frequencies, such as lactose tolerance, the expression rate varies based on the population’s mix of ethnicities, sex (male or female), and geography (environment). -6
The “X” allele is claimed to be found in about 18% – 20% of super athletes (higher in males and certain ethnic groups like Africans). -5However, “both male and female elite sprint athletes have significantly higher frequencies of the 577R allele ” than the population at large. ” -5
In reality, both allele gene variants provide a clear fitness benefit. Fast-twitch (577X) might benefit an individual in a sprint (or weight lifting) based on a reliance on sudden but short bursts of strength. However, slow-twitch strength will win the marathon. All humans have a balance of these attributes, but those with the 577X lack a-actinin-3, which might result in a loss of strength (less endurance than the “R” dominant trait). Amazingly, our native genetic allele frequencies enable the expression based on survival needs (“adaptation”) caused by environmental stressors. Such stressors have been discovered to express trait variances due to epigenetic expressions.
Disorders associated with the ACTN3 gene
The ACTN3 577X variant has been associated with a disorder that causes the absence of α-actinin-3. -7 This disorder causes the loss of muscle power and strength, is detrimental to force generation, and performance-enhancing isoforms might harm overall muscle function. -7 The absence of a-actinin might also cause reduced bone and muscle mass, which increases susceptibility to injury. -8 This condition is also linked to an early onset of Pompe disease, which is decreased muscle strength in boys.
The (supposed) 577X mutation has been linked to increased muscle glycogen, which is a rare condition that causes excess Glycogen Storage Disease-2. Other adverse effects include hypertension, hyperkalemia, acidosis, and expression of structural and oxidative signaling proteins associated with functional or sensory loss in neurodegenerative diseases. -9 An imbalanced metabolism and excess reactive oxygen species (ROS) generation end in a range of disorders such as Alzheimer’s disease, Parkinson’s disease, premature aging, and many other neural diseases are potentially associated with this ACTN3 gene. -10 There has also been an association between the mutation and acute mountain sickness due to a decreased rate of acclimatization, making the mutation carriers more susceptible to the effects of hypoxia during the acclimatization process and may develop AMS symptoms due to “decreased pressure of oxygen in the arterial blood.” These result in adaptation compensations that emerge as decreased oxygen, raised heart rates and cardiac output, headache, fatigue, dizziness, anorexia, and nausea. -11
“The ACTN3 gene encodes for α-actinin-3, an actin-binding protein that is specifically expressed in fast skeletal muscle fibers”…can have “a “toxic” effect on skeletal muscles.” -7
“Contrary to expectation, in vivo “doping” of ACTN3 (577X) at low to moderate doses demonstrated an absence of any change in function. At high doses, ACTN3 is toxic and detrimental to force generation…detrimental for muscle function.” -7
“Our findings demonstrate the sensitive balance of sarcomeric α-actinin expression…(the) overexpression of ACTN3 reveals insight into its metabolic role in skeletal muscle, but this is innately linked to the level of expression which can be easily disrupted causing detrimental functional effects, reminiscent of disease.” -7
Genetics function by conferring beneficial traits from the parents that are passed as allele frequencies to their offspring. Clearly, if Darwinian evolution is correct, then this is precisely where the mechanism for macro-evolution (transmutation) must reside. We discover throughout genetics that single-letter variances called genes, can cause a different amino acid to be placed in the protein chain which alters function (but not its shape). These variances in the sex cells of the parents emerge as traits and characteristics in offspring called allele frequencies.
We found that the claim that the “X” allelic variant was more abundant among elite athletes was incorrect and the dominant “R” allele is also predominantly found in elite athletes. -5
The narrative of Darwinism claims that these allelic traits emerged tens of thousands of years ago by a genetic mutation. However, these variants persist as preexisting (native) gene variants and have nothing to do with mutations. The arrangement of variant sequences in the present, despite their similarity that is almost identical, within one single “letter” out of over 1747 sequences, -13 does not prove their origin. Similarity is highly associated with design and function, not happenstance and randomness like that proposed by Darwinism. Similarity certainly does not prove the allele variants ever emerged by a germline mutation regardless of how long ago it is imagined. Additionally, while fragments of DNA have been discovered to be abundant in many fossils, these specimens when extracted are vastly fragile and incomplete. -12 This means that the sequences of fossils cannot substantiate the “emergence by fortuitous mutations” because isolating any fully mappable fossiliferous DNA sample, from tens of thousands of years ago, as a control “premutational” condition, is not just implausible, it is impossible. Therefore, any claim that these beneficial allelic variations formed by such a germline mutation are inferences largely based on speculation. There are no direct bodies of evidence to substantiate the claim. For all we know, all allele frequencies, including those of the ACTN3 that confer variances of muscles, have always persisted in the human genome since the beginning.
Sources
1- Pickering C, Kiely J. ACTN3: More than Just a Gene for Speed. Front Physiol. 2017 Dec 18;8:1080. doi: 10.3389/fphys.2017.01080. PMID: 29326606; PMCID: PMC5741991. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5741991/#:~:text=ACTN3%20is%20a%20gene%20that,premature%20stop%20codon%20(X).
2- Friedlander SM, Herrmann AL, Lowry DP, Mepham ER, Lek M, North KN, Organ CL. ACTN3 allele frequency in humans covaries with global latitudinal gradient. PLoS One. 2013;8(1):e52282. doi: 10.1371/journal.pone.0052282. Epub 2013 Jan 24. PMID: 23359641; PMCID: PMC3554748.
3- Deschamps CL, Connors KE, Klein MS, Johnsen VL, Shearer J, Vogel HJ, Devaney JM, Gordish-Dressman H, Many GM, Barfield W, Hoffman EP, Kraus WE, Hittel DS. The ACTN3 R577X Polymorphism Is Associated with Cardiometabolic Fitness in Healthy Young Adults. PLoS One. 2015 Jun 24;10(6):e0130644. doi: 10.1371/journal.pone.0130644. PMID: 26107372; PMCID: PMC4480966. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480966/
4- Goleva-Fjellet, S., Bjurholt, A.M., Kure, E.H. et al. Distribution of allele frequencies for genes associated with physical activity and/or physical capacity in a homogenous Norwegian cohort- a cross-sectional study. BMC Genet21, 8 (2020). https://doi.org/10.1186/s12863-020-0813-1; https://bmcgenomdata.biomedcentral.com/articles/10.1186/s12863-020-0813-1#citeas
5- Nan Yang, Daniel G. MacArthur, Jason P. Gulbin, Allan G. Hahn, Alan H. Beggs, Simon Easteal, Kathryn North, ACTN3 Genotype Is Associated with Human Elite Athletic Performance, The American Journal of Human Genetics, Volume 73, Issue 3, 2003, Pages 627-631, ISSN 0002-9297, https://doi.org/10.1086/377590; (https://www.sciencedirect.com/science/article/pii/S0002929707620242)
6- Mattei J, Parnell LD, Lai CQ, Garcia-Bailo B, Adiconis X, Shen J, Arnett D, Demissie S, Tucker KL, Ordovas JM. Disparities in allele frequencies and population differentiation for 101 disease-associated single nucleotide polymorphisms between Puerto Ricans and non-Hispanic whites. BMC Genet. 2009 Aug 14;10:45. doi: 10.1186/1471-2156-10-45. PMID: 19682384; PMCID: PMC2734553. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2734553/
7 Garton FC, Houweling PJ, Vukcevic D, Meehan LR, Lee FXZ, Lek M, Roeszler KN, Hogarth MW, Tiong CF, Zannino D, Yang N, Leslie S, Gregorevic P, Head SI, Seto JT, North KN. The Effect of ACTN3 Gene Doping on Skeletal Muscle Performance. Am J Hum Genet. 2018 May 3;102(5):845-857. doi: 10.1016/j.ajhg.2018.03.009. Epub 2018 Apr 26. PMID: 29706347; PMCID: PMC5986729. The Effect of ACTN3 Gene Doping on Skeletal Muscle Performance;
9- Banki E, Fisi V, Moser S, Wengi A, Carrel M, Loffing-Cueni D, Penton D, Kratschmar DV, Rizzo L, Lienkamp S, Odermatt A, Rinschen MM, Loffing J. Specific disruption of calcineurin-signaling in the distal convoluted tubule impacts the transcriptome and proteome, and causes hypomagnesemia and metabolic acidosis. Kidney Int. 2021 Oct;100(4):850-869. doi: 10.1016/j.kint.2021.06.030. Epub 2021 Jul 10. PMID: 34252449. https://pubmed.ncbi.nlm.nih.gov/34252449/#:~:text=Adverse%20effects%20of%20calcineurin%20inhibitors,distal%20convoluted%20tubule%20(DCT).
10- Uttara B, Singh AV, Zamboni P, Mahajan RT. Oxidative stress and neurodegenerative diseases: a review of upstream and downstream antioxidant therapeutic options. Curr Neuropharmacol. 2009 Mar;7(1):65-74. doi: 10.2174/157015909787602823. PMID: 19721819; PMCID: PMC2724665; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2724665/
12- Mélanie Pruvost, Reinhard Schwarz, Virginia Bessa Correia, +5 “Freshly excavated fossil bones are best for amplification of ancient DNA” Jan, 2007, 104 (3) 739-744; https://doi.org/10.1073/pnas.0610257104
13 – Kim H, Song KH, Kim CH. The ACTN3 R577X variant in sprint and strength performance. J Exerc Nutrition Biochem. 2014 Dec;18(4):347-53. doi: 10.5717/jenb.2014.18.4.347. Epub 2014 Dec 6. PMID: 25671201; PMCID: PMC4322025. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4322025/
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