PMID:18650267

Citation	Chan, S, Seto, JT, MacArthur, DG, Yang, N, North, KN and Head, SI (2008) A gene for speed: contractile properties of isolated whole EDL muscle from an alpha-actinin-3 knockout mouse. Am. J. Physiol., Cell Physiol. 295:C897-904
Abstract	The actin-binding protein alpha-actinin-3 is one of the two isoforms of alpha-actinin that are found in the Z-discs of skeletal muscle. alpha-Actinin-3 is exclusively expressed in fast glycolytic muscle fibers. Homozygosity for a common polymorphism in the ACTN3 gene results in complete deficiency of alpha-actinin-3 in about 1 billion individuals worldwide. Recent genetic studies suggest that the absence of alpha-actinin-3 is detrimental to sprint and power performance in elite athletes and in the general population. In contrast, alpha-actinin-3 deficiency appears to be beneficial for endurance athletes. To determine the effect of alpha-actinin-3 deficiency on the contractile properties of skeletal muscle, we studied isolated extensor digitorum longus (fast-twitch) muscles from a specially developed alpha-actinin-3 knockout (KO) mouse. alpha-Actinin-3-deficient muscles showed similar levels of damage to wild-type (WT) muscles following lengthening contractions of 20% strain, suggesting that the presence or absence of alpha-actinin-3 does not significantly influence the mechanical stability of the sarcomere in the mouse. alpha-Actinin-3 deficiency does not result in any change in myosin heavy chain expression. However, compared with alpha-actinin-3-positive muscles, alpha-actinin-3-deficient muscles displayed longer twitch half-relaxation times, better recovery from fatigue, smaller cross-sectional areas, and lower twitch-to-tetanus ratios. We conclude that alpha-actinin-3 deficiency results in fast-twitch, glycolytic fibers developing slower-twitch, more oxidative properties. These changes in the contractile properties of fast-twitch skeletal muscle from alpha-actinin-3-deficient individuals would be detrimental to optimal sprint and power performance, but beneficial for endurance performance.
Links	PubMed Online version:10.1152/ajpcell.00179.2008
Keywords	Actinin/genetics; Actinin/metabolism; Animals; Gene Expression Regulation/physiology; Mice; Mice, Knockout; Muscle Contraction/genetics; Muscle Contraction/physiology; Muscle Fatigue/genetics; Muscle Fatigue/physiology; Muscle Fibers, Fast-Twitch/physiology; Muscle Fibers, Slow-Twitch/physiology; Muscle, Skeletal/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
MOUSE:ACTH		GO:0043415: positive regulation of skeletal muscle tissue regeneration	ECO:0000314:		P		Based on figure 6 knockout mice (alpha-actin-3 deficient)show an increased amount of EDL muscle recovery.	complete CACAO 6536

References

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