XX Genotype Research Articles

High elevation increases the risk of Y chromosome loss in Alpine skink populations with sex reversal.

The view that has genotypic sex determination and environmental sex determination as mutually exclusive states in fishes and reptiles has been contradicted by the discovery that chromosomal sex and environmental influences can co-exist within the same species, hinting at a continuum of intermediate states. Systems where genes and the environment interact to determine sex present the opportunity for sex reversal to occur, where the phenotypic sex is the opposite of that predicted by their sex chromosome complement. The skink Bassiana duperreyi has XX/XY sex chromosomes with sex reversal of the XX genotype to a male phenotype, in laboratory experiments, and in field nests, in response to exposure to cold incubation temperatures. Here we studied the frequency of sex reversal in adult populations of B. duperreyi in response to climatic variation, using elevation as a surrogate for environmental temperatures. We demonstrate sex reversal in the wild for the first time in adults of a reptile species with XX/XY sex determination. The highest frequency of sex reversal occurred at the highest coolest elevation location, Mt Ginini (18.46%) and decreased in frequency to zero with decreasing elevation. We model the impact of this under Fisher's frequency-dependent selection to show that, at the highest elevations, populations risk the loss of the Y chromosome and a transition to temperature-dependent sex determination. This study contributes to our understanding of the risks of extinction from climate change in species subject to sex reversal by temperature, and will provide focus for future research to test on-the-ground management strategies to mitigate the effects of climate in local populations.

Effect of ACTN3 R577X Genotype on Injury Epidemiology in Elite Endurance Runners.

The p.R577X polymorphism (rs1815739) in the ACTN3 gene causes individuals with the ACTN3 XX genotype to be deficient in functional α-actinin-3. Previous investigations have found that XX athletes are more prone to suffer non-contact muscle injuries. This investigation aimed to determine the influence of the ACTN3 R577X polymorphism in the injury epidemiology of elite endurance athletes. Using a cross-sectional experiment, the epidemiology of running-related injuries was recorded for one season in a group of 89 Spanish elite endurance runners. ACTN3 R577X genotype was obtained for each athlete using genomic DNA samples. From the study sample, 42.7% of athletes had the RR genotype, 39.3% had the RX genotype, and 18.0% had the XX genotype. A total of 96 injuries were recorded in 57 athletes. Injury incidence was higher in RR runners (3.2 injuries/1000 h of running) than in RX (2.0 injuries/1000 h) and XX (2.2 injuries/1000 h; p = 0.030) runners. RR runners had a higher proportion of injuries located in the Achilles tendon, RX runners had a higher proportion of injuries located in the knee, and XX runners had a higher proportion of injuries located in the groin (p = 0.025). The ACTN3 genotype did not affect the mode of onset, the severity, or the type of injury. The ACTN3 genotype slightly affected the injury epidemiology of elite endurance athletes with a higher injury rate in RR athletes and differences in injury location. However, elite ACTN3 XX endurance runners were not more prone to muscle-type injuries.

High temperature-induced masculinization in yellow catfish Tachysurus fulvidraco: A potential approach for environmental-friendly mono-sex production

Many environmental stressors, including stress temperature, high density, hypoxia, low food availability, high social pressure, and bright background colour, have been found to cause masculinization in fish. The environmental-friendly factors-induced masculinization provides a possibility of environmental-friendly mono-sex production for aquaculture. In the present work, we found high temperature (33.5 °C) or cortisol administration (300 mg kg−1 feed) covering the critical period of ovarian differentiation (15–38 days post-fertilization, DPF) caused partial masculinization of XX genotype in yellow catfish, via the application of sex-linked markers and successive histological analysis containing critical time window of ovarian and testicular differentiation and differentiated gonads, including 25 DPF, 35 DPF, 45 DPF, 65 DPF, and 125 DPH of XX female, XX male, and XY male. The masculinization modes in high temperature and cortisol administration groups were similar, including repression of primordial germ cells proliferation and retention of the ovarian cavity in XX pseudo-male. XX male was similar to XY male at both transcriptional and morphological levels, via RNA-seq analysis and morphological characteristics and gonadal histology respectively, providing a possibility to produce functional XX males and all-female XX population on a large-scale through an environmental-friendly approach for yellow catfish. The establishment and application of an environmental-friendly approach for mono-sex production will reduce the usage of steroid hormones and functionally similar chemicals in the aquaculture industry.

PSXII-34 The evaluation of the influence of FMO3 gene polymorphism on the milk productivity of Ayrshire breed cows

Abstract Russian Ayrshire population of cattle is the second largest in number the world population of animals of this breed. Trimethylaminuria (TMA) is the monogenic disease manifesting in the ‘‘fish off-flavor” of the milk from the sick cows and caused by R238X mutation in the flavin-containing monooxidase 3 gene (FMO3). The aim of our investigation was the analysis of the FMO3 gene polymorphism of Ayrshire cattle breed and its relationship with the milk productivity of the first lactation. The analysis of FMO3 gene polymorphism has been carried out on 352 animals of 5 herds, and associations with the milk productivity due 305 days have been evaluated on 20 healthy cows (RR) and 6 ones-carriers of the mutation (RX). DNA has been extracted by means of the kit “DNA-Extran” (“Syntol”, Russia). The identification of the FMO3 genotypes has been conducted by PCR-RFLP in according to the previously developed method with using TaqI restriction endonuclease. The frequency of animals-carriers of X allele associated with the defect of “fish off-flavor” of milk was in the range 10.21–12.82%. The frequencies of RR, RX and XX genotypes were 76.9, 20.5 and 2.6 %, respectively. The study of relationship between the genotypes on FMO3 gene and productivity traits has shown that the homozygous RR-individuals in comparing to RX-ones had significantly higher levels of the milk yield (+918.6 kg, P ≥ 0.05) and content of the milk protein (+28.8, P ≥ 0.05). Adaptive abilities of RR-cows of Russian selection allowed them to surpass animals of Finnish origin with a similar genotype in milk yield 5,655.6 ± 254.2 against 5,105.0 ± 238.6 kg. The investigations has shown the significant superiority the animals-non carriers of the “fish off-flavor” defect in the milk yield and content of the milk protein. This research was supported by the Ministry of science and higher education АААА-А18-118021590138-1.

Distribution of α-actinin-3 rs1815739 and angiotensin-1 converting enzyme InDel polymorphisms in Turkish bodybuilders.

The determination of the genetic profiles of successful athletes and the effects of these genetic parameters on athletic performance is gaining increasing interest. The majority of studies assessing the genetics of athletes usually analyse the most well-known genetic variations in athletes associated with the different specialties. The aim of the present study was to analyse the ACE InDel and ACTN3 rs1815739 polymorphisms in Turkish bodybuilders. A total of 11 male bodybuilders were recruited and genotyped for these polymorphisms. The respective percentage of the ACE II, ID and DD genotypes were 18, 73 and 9. For the ACTN3 genotype, the respective frequencies were 55 and 45 for the RX and RR genotypes. No XX genotype was detected. The allelic counts were 12 (55%) for I and 10 (45%) for the D alleles of ACE; and 12 (55%) and 10 (45%) for R and X alleles, respectively, for the ACTN3 genotype. Additionally, 5 athletes had ID + RX genotypes in terms of ACE InDel and ACTN3 rs1815739 polymorphisms, respectively. These results indicate the importance of endurance related alleles of ACE and ACTN3 in bodybuilders. The results of the present are in agreement with previous studies, highlighting a potential association between specific polymorphisms and the endurance-related nature of bodybuilders. Further studies with larger cohorts are required to understand the association between these polymorphisms and specific parameters performance in bodybuilders.

Identification of Y chromosome markers in the eastern three-lined skink (Bassiana duperreyi) using in silico whole genome subtraction

BackgroundHomologous sex chromosomes can differentiate over time because recombination is suppressed in the region of the sex determining locus, leading to the accumulation of repeats, progressive loss of genes that lack differential influence on the sexes and sequence divergence on the hemizygous homolog. Divergence in the non-recombining regions leads to the accumulation of Y or W specific sequence useful for developing sex-linked markers. Here we use in silico whole-genome subtraction to identify putative sex-linked sequences in the scincid lizard Bassiana duperreyi which has heteromorphic XY sex chromosomes.ResultsWe generated 96.7 × 109 150 bp paired-end genomic sequence reads from a XY male and 81.4 × 109 paired-end reads from an XX female for in silico whole genome subtraction to yield Y enriched contigs. We identified 7 reliable markers which were validated as Y chromosome specific by polymerase chain reaction (PCR) against a panel of 20 males and 20 females.ConclusionsThe sex of B. duperreyi can be reversed by low temperatures (XX genotype reversed to a male phenotype). We have developed sex-specific markers to identify the underlying genotypic sex and its concordance or discordance with phenotypic sex in wild populations of B. duperreyi. Our pipeline can be applied to isolate Y or W chromosome-specific sequences of any organism and is not restricted to sequence residing within single-copy genes. This study greatly improves our knowledge of the Y chromosome in B. duperreyi and will enhance future studies of reptile sex determination and sex chromosome evolution.

Sex chromosome complement influences vulnerability to cocaine in mice

Women acquire cocaine habits faster and are more motivated to obtain drug than men. In general, female rodents acquire intravenous cocaine self-administration (SA) faster and show greater locomotor responses to cocaine than males. Sex differences are attributed to differences in circulating estradiol. We used the four core genotype (FCG) mouse to ask whether sex chromosome complement influences vulnerability to cocaine's reinforcing and/or locomotor-activating effects. The FCG cross produces ovary-bearing mice with XX or XY genotypes (XXF, XYF) and testes-bearing mice with XX or XY genotypes (XXM, XYM). A greater percentage of gonadal females acquired cocaine SA via infusions into jugular catheters as compared with XYM mice, but XXM mice were not significantly different than any other group. Discrimination of the active versus inactive nose poke holes and cocaine intake were in general greater in gonadal females than in gonadal males. Progressive ratio tests for motivation revealed an interaction between sex chromosomes and gonads: XYM mice were more motivated to self-administer cocaine taking more infusions than mice in any other group. Locomotor responses to cocaine exposure revealed effects of sex chromosomes. After acute exposure, activity was greater in XX than in XY mice and the reverse was true for behavioral sensitization. Mice with XY genotypes displayed more activity than XX mice when given cocaine after a 10-day drug-free period. Our data demonstrate that sex chromosome complement alone and/or interacting with gonadal status can modify cocaine's reinforcing and locomotor-activating effects. These data should inform current studies of sex differences in drug use.

Previous experience, aerobic capacity and body composition are the best predictors for Olympic distance triathlon performance: Predictors in amateur triathlon

Objective: Present study examines predictors of the overall race time and disciplines in the Olympic distance triathlon. Methods: Thirty-nine male and six female triathletes were evaluated for anthropometric, physiological, genetic, training, clinical and circadian characteristics. Body composition, maximum capacity for oxygen uptake (V˙O2max), maximum aerobic velocity (MAV), anaerobic threshold (AT), triathlon experience (TE) and XX genotype for α-actinin 3 affected total race time (p<0.05). Results: Total race time can be predicted by MAV (ß = -0.430, t = -3.225, p = 0.003), TE (ß = -0.378, t = -3.605, p = 0.001), and percentage of lean mass (%LM) (ß = -0.332, t = -2.503, p = 0.017). Swimming can be predicted by MAV (ß = -0.403, t = -3.239, p = 0.002), TE (ß = -0.339, t = -2.876, p = 0.007), and AT%V˙O2max (ß = 0.281, t = 2.278, p = 0.028). Cycling can be predicted by MAV (ß = -0.341, t = -2.333, p = 0.025), TE (ß = -0.363, t = -3.172, p = 0.003), and %LM (ß = -0.326, t = -2.265, p = 0.029). In running split, MAV (ß = -0.768, t = -6.222, p < 0.001) was the only parameter present in the best multiple linear regression model. Conclusion: The most important variables in multiple regression models for estimating performance were MAV, TE, AT and %LM.

Effect of ACTN3 Genotype on Sports Performance, Exercise-Induced Muscle Damage, and Injury Epidemiology.

Genetic factors play a significant role in athletic performance and its related phenotypes such as power, strength and aerobic capacity. In this regard, the lack of a muscle protein due to a genetic polymorphism has been found to affect sport performance in a wide variety of ways. α-actinin-3 is a protein located within the skeletal muscle with a key role in the production of sarcomeric force. A common stop-codon polymorphism (rs1815739; R577X) in the gene that codes for α-actinin-3 (ACTN3) produces individuals with the XX genotype that lack expression of a functional α-actinin-3. In contrast, individuals with the R-allele (i.e., RX vs. RR genotypes) in this polymorphism can express α-actinin-3. Interestingly, around ~18% of the world population have the XX genotype and much has been debated about why a polymorphism that produces a lack of a muscle protein has endured natural selection. Several investigations have found that α-actinin-3 deficiency due to XX homozygosity in the ACTN3 R577X polymorphism can negatively affect sports performance through several structural, metabolic, or signaling changes. In addition, new evidence suggests that α-actinin-3 deficiency may also impact sports performance through indirect factors such a higher risk for injury or lower resistance to muscle-damaging exercise. The purpose of this discussion is to provide a clear explanation of the effect of α-actinin-3 deficiency due to the ACTN3 XX genotype on sport. Key focus has been provided about the effect of α-actinin-3 deficiency on morphologic changes in skeletal muscle, on the low frequency of XX athletes in some athletic disciplines, and on injury epidemiology.

A duplication of the Anti-Müllerian hormone gene is associated with genetic sex determination of different Oreochromis niloticus strains.

Sex determination (SD) mechanisms are ancient and conserved, yet much diversity is exhibited in primary sex-determining signals that trigger male or female development. In O. niloticus, SD is associated with a male-specific locus on linkage group (LG) 23 which harbors the Y-linked Anti-Müllerian hormone (amh) gene, and a truncated duplication, denoted amhΔy. We have evaluated the possible role of identified indels and SNPs in the amh gene on SD, based on conservation in different O. niloticus strains. A fluorescent assay for the detection of a 5 bp insertion in amhΔy exon VI, efficiently discriminated between XX, XY, and YY genotypes. Concordance rate between amhΔy and sex varied in six Oreochromis strains, from 100% (Ghana) through 90% (Swansea) to 85% (Thai-Chitralada). The association of amhΔy with sex was found to be conserved in all tested O. niloticus strains, and thus supports its key role in SD. However, the previously identified missense SNP (C/T) in amh exon II was found only in the Swansea strain, thus excluding its candidacy for the causal variation of SD across all strains. Effects of markers on LGs 1, 3, and 23 (amhΔy) fully explained sex distribution in one Thai-Chitralada family (R2 = 1.0), whereas in another family only the major effect of LG23 (amhΔy) was significant (R2 = 0.37). Thus, amhΔy on LG23 is associated with genetic SD, either as a single causal gene in different O. niloticus strains, or in combination with segregating genes on LGs 1 and 3 in the Thai-Chitralada hybrid strain.

ACTN3 R577X polymorphism related to sarcopenia and physical fitness in active older women

Background As the population is getting older, physical activity promotion becomes a good strategy to increase quality of life in the elderly; but genetic condition also plays an important role. The purpose of this study was to examine the association of the ACTN3 R577X polymorphism with physical fitness and muscle mass in physically active older women. Methods A cross-sectional study was performed with two groups of older women who practiced physical exercise regularly. The first cohort comprised 164 women (age 69.7 ± 3.2 years) and the second cohort 131 women (age 78.5 ± 3.0 years). The main outcome measures were anthropometric measures with assessment of sarcopenia and sarcopenic obesity, self-reported physical activity EXERNET questionnaire (EEPAQ), evaluation of physical fitness (muscle strength and flexibility test), and ACTN3 genotyping. Results Women above 75 years old with allele R presented a higher risk of experiencing sarcopenia compared to ACTNR XX homozygous women (odds ratio 0.356, 95% confidence interval 0.139–0.915, p = 0.026). Furthermore, statistically significant differences were found in the chair stand test (p = 0.04), as well as in the sit and reach test (p = 0.01), with better results for women below 75 years old with the ACTN3 XX genotype. Conclusions Sarcopenia and physical fitness show differences based on the ACTN3 R577X genotype in active older women.

The genetic profile of elite youth soccer players and its association with power and speed depends on maturity status.

We investigated the association of multiple single nucleotide polymorphisms (SNPs) with athlete status and power/speed performance in elite male youth soccer players (ESP) and control participants (CON) at different stages of maturity. ESP (n = 535; aged 8-23 years) and CON (n = 151; aged 9-26 years) were genotyped for 10 SNPs and grouped according to years from predicted peak-height-velocity (PHV), i.e. pre- or post-PHV, to determine maturity status. Participants performed bilateral vertical countermovement jumps, bilateral horizontal-forward countermovement jumps, 20m sprints and modified 505-agility tests. Compared to CON, pre-PHV ESP demonstrated a higher ACTN3 (rs1815739) XX ('endurance') genotype frequency distribution, while post-PHV ESP revealed a higher frequency distribution of the PPARA (rs4253778) C-allele, AGT (rs699) GG genotype and NOS3 (rs2070744) T-allele ('power' genotypes/alleles). BDNF (rs6265) CC, COL5A1 (rs12722) CC and NOS3 TT homozygotes sprinted quicker than A-allele carriers, CT heterozygotes and CC homozygotes, respectively. COL2A1 (rs2070739) CC and AMPD1 (rs17602729) GG homozygotes sprinted faster than their respective minor allele carrier counterparts in CON and pre-PHV ESP, respectively. BDNF CC homozygotes jumped further than T-allele carriers, while ESP COL5A1 CC homozygotes jumped higher than TT homozygotes. To conclude, we have shown for the first time that pre- and post-PHV ESP have distinct genetic profiles, with pre-PHV ESP more suited for endurance, and post-PHV ESP for power and speed (the latter phenotypes being crucial attributes for post-PHV ESP). We have also demonstrated that power, acceleration and sprint performance were associated with five SNPs, both individually and in combination, possibly by influencing muscle size and neuromuscular activation.

Differential regulation of Actn2 and Actn3 expression during unfolded protein response in C2C12 myotubes.

ACTN2 and ACTN3 encode sarcomeric α-actinin-2 and α-actinin-3 proteins, respectively, that constitute the Z-line in mammalian skeletal muscle fibers. In human ACTN3, a nonsense mutation at codon 577 that encodes arginine (R) produces the R577X polymorphism. Individuals having a homozygous 577XX genotype do not produce α-actinin-3 protein. The 577XX genotype reportedly occurs in sprint and power athletes in frequency lower than in the normal population, suggesting that α-actinin-3 deficiency diminishes fast-type muscle function. Among humans who carry 577R alleles, varying ACTN3 expression levels under certain conditions can have diverse effects on atheletic and muscle performance. However, the factors that regulate ACTN3 expression are unclear. Here we investigated whether the unfolded protein response (UPR) under endoplasmic reticulum (ER) stress regulates expression of Actn3 and its isoform Actn2 in mouse C2C12 myotubes. Among UPR-related transcription factors, XBP1 upregulated Actn2, whereas XBP1, ATF4 and ATF6 downregulated Actn3 promoter activity. Chemical induction of ER stress increased Actn2 mRNA levels, but decreased those for Actn3. ER stress also decreased α-actinin-3 protein levels, whereas levels of α-actinin-2 were unchanged. The intracellular composition of muscle contraction-related proteins was altered under ER stress, in that expression of parvalbumin (a fast-twitch muscle-specific protein) and troponin I type 1 (skeletal, slow) was suppressed. siRNA-induced suppression of Actn3 mimicked the inhibitory effect of ER stress on parvalbumin levels. Thus, endogenous expression levels of α-actinin-3 can be altered by ER stress, which may modulate muscle performance and athletic aptitudes, particularly in humans who carry ACTN3 577R alleles.

Winter syndrome: about an uncommon case report

BackgroundCongenital genital tract outflow obstruction may occur at different levels and with different clinical presentations. Winter syndrome was first described in 1968 as an association of renal, genital and middle ear anomalies. This syndrome is characterized by autosomal recessive transmission, unilateral or bilateral renal hypoplasia, distal vaginal atresia, and moderate to severe conductive hearing loss with malformation of the ossicles. The diagnosis is usually made when symptoms of obstruction are obvious. It presents most commonly with primary amenorrhea in a girl with a normal XX genotype, ovarian and hormone function; and cyclical abdominal pain. Ultrasound confirm the physical examination, revealing the presence of a normal uterus and cervix, normal ovaries and fallopian tubes, and a large hematocolpos.Case presentationThis case reports Winter syndrome in a 14-year-old girl which vaginal atresia was managed by a trans perineal vaginal pull through.ConclusionsWinter syndrome is a rare congenital condition whose clinical picture is that of an adolescent girl with primary amenorrhea and cyclic pelvic pain due to vaginal atresia, varying degrees of renal dysgenesis and deafness due to malformation of the ossicles of the middle ear. Diagnosis is based on clinical examination and imaging. Magnetic resonance imaging allows assessing the importance of atresia and thus guiding surgical management. The goals of surgical intervention are to provide relief from pain, ensure normal sexual intercourse and to preserve fertility. A thorough knowledge of embryology, pre-operative imaging with MRI and clinical examination is essential to plan an appropriate surgical management.

Crowding stress during the period of sex determination causes masculinization in pejerrey Odontesthes bonariensis, a fish with temperature-dependent sex determination

The pejerrey is an atherinopsid species from South America that presents a combination of genotypic and environmental (temperature-dependent) sex determination whereby low and high temperatures induce feminization and masculinization, respectively. Masculinization involves a heat-induced stress response leading to increased circulating cortisol and androgens. We tested whether crowding would elicit a similar response as high temperature and affect the sex ratios of pejerrey. Larvae with XX and XY genotypes were reared at 15, 62 and 250 larvae/L in 0.4, 1.6, and 6.4 L containers during a period considered critical for sex determination at 25 °C, a mixed-sex promoting temperature. Fish were analysed at 3–7 weeks for whole-body cortisol and 11-ketotestosterone (11-KT) titer and hydroxy-steroid dehydrogenase (hsd11b2) mRNA transcript abundance, and after completion of gonadal sex differentiation (10–14 weeks) for determination of phenotypic and genotypic sex mismatches. Crowding was associated with depressed growth, higher cortisol and 11-KT titers, increased hsd11b2 transcription, and increased frequency of masculinization compared to intermediate and/or low rearing densities. Perceived crowding (by rearing in containers with mirror-finish, reflecting walls) also caused masculinization. These results suggest the possibility that other environmental factors besides temperature can also affect sex determination in pejerrey and that a stress response leading to increased cortisol and androgen levels, which is potentially perceived by the brain, may be a common feature among different forms of environmental sex determination in this species.

Association Between rs1815739 Polymorphism of ACTN3 Gene and Athletic Ability in Chinese Sprinters

The aim of this study was to investigate the prevalence of the ACTN3 rs1815739 polymorphism and to study its association with athletes’ level of competition and lower-extremity power. Time-of-flight mass spectrometry (TOFMS) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) techniques were employed to identify the ACTN3 rs1815739 genotypes and allele frequencies in 108 elite sprinters and 206 untrained controls. Questionnaires were then used to assess subjects’ 100 m sprint, standing jump (SJ) and standing triple jump (STJ) personal best record. (1) The RR, RX and XX genotype distribution of the ACTN3 rs1815739 polymorphism is 42.6%, 49.1%, 8.3%, respectively. R and X alleles frequency is 67.1% and 32.9%, respectively, which comply with Hardy Weinberg equilibrium (HWE) through Chi-square (χ2) tests (χ2 = 0.661; df = 2; P = 0.718). (2) Significant differences were found in R allele frequency between the elite sprinter group and controls. (3) The athletes’ 100 m sprint, SJ, and STJ personal best records were better in those with RR and RX than XX genotype. A significant association was observed between the R alleles and 100 m sprint, SJ, and STJ results of male and female athletes. The present results indicate that ACTN3 rs1815739 polymorphism has a significant association with speed and lower-extremity power in sprint/power athletes.

Genetics and the Elite Athlete: Our Understanding in 2020.

Modern competitive sport has evolved so much that athletes would go to great extremes to develop themselves into champions; medicine has also evolved to the point that many genetic elements have been identified to be associated with specific athletic traits, and genetic alterations are also possible. The current review examines the published literature and looks at three important factors: genetic polymorphism influencing sporting ability, gene doping and genetic tendency to injury. The ACTN3 gene has an influence on type II muscle fibres, with the R allele being advantageous to power sports like sprinting and the XX genotype being associated with lower muscle strength and sprinting ability. The ACE gene polymorphisms are associated with cardio-respiratory efficiency and could influence endurance athletes. Many other genes are being looked at, with specific focus on those that are potentially related to enhancement of athletic ability. Recognition of these specific gene polymorphisms brings into play the concept of genetic engineering in athletes, which constitutes gene doping and is outlawed. This has the potential to develop into the next big threat in elite sports; gene doping could have dangerous and even fatal outcomes, as the knowledge of gene therapy is still in its infancy. Genetic predisposition to injury is also being identified; recent publications have increased the awareness of gene polymorphisms predisposing to injuries of ligaments and tendons due to influence on collagen structure and extracellular matrix. Ongoing work is looking at identifying the same genes from different races and different sexes to see if there are quantitative racial or sexual differences. All of the above have led to serious ethical concerns; in the twenty-first century some sports associations and some countries are looking at genetic testing for their players. Unfortunately, the science is still developing, and the experience of its application is limited worldwide. Nevertheless, this field has caught the imagination of both the public and the sportsperson, and hence the concerned doctors should be aware of the potential problems and current issues involved in understanding genetic traits and polymorphisms, genetic testing and genetic engineering.

ACTN3 (R577X) Genotype Is Associated With Australian Football League Players.

Jacob, Y, Hart, NH, Cochrane, JL, Spiteri, T, Laws, SM, Jones, A, Rogalski, B, Kenna, J, and Anderton, RS. ACTN3 (R577X) genotype is associated with Australian Football League players. J Strength Cond Res 36(2): 573-576, 2022-Genetic variants in the angiotensin-converting enzyme (ACE) and alpha actinin-3 (ACTN3) genes have been associated with elite sport athletic performance. This study aimed to investigate the frequency of each polymorphism in a cohort of elite Australian football (AF) players. To achieve this, 47 players from an Australian Football League (AFL) club and 59 healthy age matched controls with no history of elite sporting competition were recruited for this study. Each subject provided saliva samples through buccal swab for DNA extraction and genotyping, with group comparisons made using χ2 and odds ratio analysis. There was no significant difference in ACE I/D genotype between healthy control and elite AF players. The ACTN3 XX genotype was significantly underrepresented in AFL players (4.3%) compared with healthy controls (28.8%, p = 0.003). In addition, there was a greater representation of the R allele in elite AF players (70.2%) when compared with healthy controls (50%; χ2 = 8.834, p = 0.002). This is the first study to investigate genetic variants in elite AF players, with results suggesting that the ACTN3 gene may play a significant role explaining aspects of athletic performance in AF.

Strength and Endurance Training in Older Women in Relation to ACTN3 R577X and ACE I/D Polymorphisms.

The purpose of this study is to analyze the effect of two genetic polymorphisms, ACTN3 R577X, and ACE I/D, on physical condition in a sample of active older women after a two-year training period. The sample was composed of 300 healthy women over the age of 60 who underwent a two-year training program. Adapted tests from the Senior Fitness Test were used. The genotyping of the polymorphisms was obtained from the participants’ DNA via buccal swabs. The analysis of the ACE polymorphism did not reveal differences between genotypes. The analysis of the R577X polymorphism showed a favorable effect for the ACTN3 XX genotype in tests for leg strength (p: 0.001) after training, compared to the other genotypes, and also in the analysis of the combined effect of the polymorphism (ACE II + ACTN3 RX/XX). The intragroup effect revealed an improvement in arm strength for carriers of the X allele after 24 months of training (p < 0.05). The endurance values significantly worsened in all study groups. Conclusions: The R577X polymorphism of ACTN3 may have an important role in capacities related to muscle strength, providing a beneficial effect for carriers of the X allele.

Influence of the ACTN3 R577X genotype on the injury epidemiology of marathon runners.

A common single nucleotide polymorphism in the ACTN3 gene might result in the complete deficiency of α-actinin-3 (i.e., XX genotype). It has been found that ACTN3 XX individuals have several traits related to lessened muscle performance. This study aimed to determine the influence, if any, of ACTN3 genotypes on injury incidence of marathoners during the year preceding to participating in a competitive marathon race. Using a cross-sectional experimental design, the type and conditions of sports injuries were documented for one year in a group of 139 marathoners. Injuries were recorded following a consensus statement on injuries in Athletics. Afterward, ACTN3 genotyping was performed, and injury epidemiology was compared among RR, RX, and XX genotypes. The distribution of the RR/RX/XX genotypes was 28.8/42.8/23.5%, respectively. A total of 67 injuries were recorded. The frequency of marathoners that reported any injury during the previous year was not different across the genotypes (55.0/38.8/40.6%, P = 0.241). Although the overall injury incidence was not different among genotypes (2.78/1.65/1.94 injuries/1000 h of running, P = 0.084), the likelihood of suffering an injury was higher in RR than in RX (OR = 1.93: 95%CI = 0.87–4.30), and higher than in XX (OR = 1.79: 0.70–4.58). There was no difference in the conditions, severity, body location, time of year, or leading cause of injury among genotypes. However, XX presented a higher frequency of sudden-onset injuries (P = 0.024), and the OR for muscle-type injuries was 2.0 (0.51–7.79) times higher compared to RR runners. Although XX marathoners did not have a higher overall incidence of injury, the OR in these runners for muscle-type injuries was superior to RR and RX runners. The likelihood of suffering a muscle injury, especially with a sudden-onset, was twice in XX than in RR endurance runners.