The muscle acetylcholine receptor consiststs of 5 subunits of 4 different types: 2 alpha isoforms and 1 each of beta, gamma, and delta subunits. CHRNA1 is an alpha subunit that plays a role in acetlycholine binding/channel gating. Alternatively spliced transcript variants encoding different isoforms have been identified. Isoform 1 is only expressed in skeletal muscle. Isoform 2 is constitutively expressed in skeletal muscle, brain, heart, kidney, liver, lung and thymus. Defects in CHRNA1 are a cause of multiple pterygium syndrome lethal type (MUPSL). Multiple pterygia are found infrequently in children with arthrogryposis and in fetuses with fetal akinesia syndrome.