The ACTN3 R577X Polymorphism in East and West African Athletes

Abstract

. Purpose: To determine the frequency of the ACTN3 R577X polymorphism (functional R allele and nonfunctional X allele) in a variety of African populations and to examine its influence on the success of elite East African endurance runners and West African sprinters. Methods: The R577X polymorphism was genotyped in 198 Ethiopian controls and 76 elite Ethiopian endurance athletes, 158 Kenyan controls and 284 elite Kenyan endurance runners, and 60 Nigerian controls and 62 elite Nigerian power athletes. Statistical analyses were performed by exact tests of population differentiation, using Arlequin, version 3. Analyses were carried out using 1 Â 10 6 Markov chain steps, and 1 Â 10 5 dememorization steps. Results: The frequency of the X allele was extremely low among Kenyans and Nigerians (È1% homozygosity) and higher in Ethiopians (È11% homozygosity). The low baseline frequencies of the three populations tested mean that any associations with sprint performance would likely be obscured. In Ethiopians, where baseline levels of 577XX were about 11%, there was no increased frequency in the endurance athletes. Conclusion: Our data suggest that >-actinin-3 deficiency is not a major influence on performance in African athletes. Key Words: GENETICS, ACTININ-3, AFRICA, RUNNERS, ATHLETIC PERFORMANCE T he actin-binding protein >-actinin-3, encoded by the ACTN3 gene, is a highly conserved component of the contractile machinery in fast skeletal muscle fibers in mammals (7). Homozygosity for a common nonsense polymorphism, R577X, results in complete deficiency of >-actinin-3 in about 16% of the global human population (11). We have previously demonstrated a strong association between the R577X polymorphism and elite athlete status in Australian Caucasian populations, with the >-actinin-3-deficient XX genotype being present at a lower frequency in sprint/power athletes, and at slightly higher frequency in elite female endurance athletes, relative to controls (18). The negative association of the XX genotype with sprint performance was subsequently replicated in a cohort of Finnish elite track and field athletes (10). The possible positive association of XX with endurance performance remains intriguing but uncertain, with two recent smaller studies comparing R577X genotype frequencies between 50 elite endurance cyclists, 52 elite endurance runners, and 123 controls from Spain (6), and 42 male rowers and 102 male controls from Italy (13), finding no significant differences in R577X genotype frequencies between control and athlete groups. R577X genotype has also been associated with muscle function parameters in several large nonathlete cohorts. An analysis of 355 females demonstrated an association between the XX genotype and lower baseline muscle strength (1), whereas a study of older individuals found that R577X genotype influences the response of the quadriceps muscle to strength training (2). In a large cohort of Greek adolescents, the XX genotype was associated with significantly slower performance in a 40-m sprint (9). These ...

The ACTN3 Gene and Differences between Playing Positions in Bone Mineral Content, Fat Mass and Lean Tissue Mass in the Arms, Legs and Trunk Of Rugby Union Football Players

“…Similar findings have been published for other studies [16]. The lowest frequency of the X allele has been found in Kenyan, Nigerian and South African groups (8 -11%) [17]. On the basis of playing position, Rugby Union forwards have presented as RR=28%, RX=53% and XX=19%, and backs RR=31%, RX=55%, and XX=14% (P=0.822) [18].…”

A Gene for Speed: The Emerging Role of α-Actinin-3 in Muscle Metabolism

“…However, other studies have not replicated the association between ACTN3 genotype and elite endurance performance. This suggests that the association between ␣-actinin-3 deficiency and endurance is not as strong as its association with reduced performance in sprint and power activities (2,45,53,55,59,67,84).…”

From Double Iron to Double Deca Iron Ultra-Triathlon - A Retrospective Data Analysis from 1985 to 2011

“…For example, East Africans are known as the best distance runners (Onywera, Scott, Boit & Pitsiladis 2006, Larsen 2003. The reason for this is not completely known yet, but several studies are analyzing this aspect (Ash et al 2011, Onywera, Scott, Boit & Pitsiladis 2006, Yang et al 2007). Kenyan runners have special physiological characteristics which could include favorable genetic endowment and advantageous environmental conditions (Onywera, Scott, Boit & Pitsiladis 2006) and East Africans in general seem to have a better running economy than Caucasian runners (Lucia et al 2006;Weston, Mbambo, & Myburgh 2000).…”