ACTN3
ACTN3 encodes alpha-actinin-3, a structural protein found almost exclusively in fast-twitch (type II) skeletal muscle fibers, where it anchors the actin cytoskeleton at the sarcomere's Z-disc to support rapid, forceful contractions. The common R577X nonsense variant (rs1815739) causes complete loss of alpha-actinin-3 protein in roughly one-fifth of people worldwide; XX (null) genotypes trend toward endurance-oriented muscle performance, while carriers retaining the protein trend toward sprint/power performance.
Traits ACTN3 shapes
Markers (rsIDs)
Reference databases
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