Mutation analysis in exons 22 and 24 of SCN4A gene in Iranian patients with non-dystrophic myotonia

  • Mohammad Mehdi Heidari Department of Biology, School of Science, Yazd University, Yazd, Iran
  • Mehri Khatami Department of Biology, School of Science, Yazd University, Yazd, Iran
  • Shahriar Nafissi Department of Neurology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
  • Faezeh Hesami-Zokai Department of Biology, School of Science, Yazd University, Yazd, Iran
  • Afshin Khorrami Department of Biology, School of Science, Yazd University, Yazd, Iran
Keywords: Nondystrophic Myotonia, Mutation, SCN4A, Polymerase Chain, Reaction Single Strand, Conformational Polymorphism


Background: Non-dystrophic myotonias are a heterogeneous set of skeletal, muscular channelopathies, which have been associated with point mutations within sodium channel α-subunit (SCN4A) gene. Because exons 22 and 24 of SCN4A gene are recognized as hot spots for this disease, the purpose of the study is to identify mutation in exons 22 and 24 of SCN4A gene in Iranian non-dystrophic myotonias patients.Methods: In this study, 28 Iranian patients with non-dystrophic myotonia analyzed for the mutation scanning in exons 22 and 24 of SCN4A gene by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and sequencing. Results: We found 29073G>C substitution in SCN4A gene in one case and 31506A>G substitution in seven cases. The 29073G>C substitution causes a missense mutation G1306A, located in the conserved cytoplasmic loop connecting repeat III and IV of the SCN4A channel but, 31506A>G substitution do not alter amino acid in SCN4A protein.Conclusion: G1306A residue is located in functionally important protein region. In “hinged-lid model” for Na+ channel inactivation in which glycines1306 act as the hinge of the lid occluding the channel pore. Mutation in this region slowed fast inactivation. Therefore, it might be a pathogenic mutation. The causal relationship of this mutation with the disease is an object for further discussion.


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How to Cite
Heidari MM, Khatami M, Nafissi S, Hesami-Zokai F, Khorrami A. Mutation analysis in exons 22 and 24 of SCN4A gene in Iranian patients with non-dystrophic myotonia. IJNL. 14(4):190-4.
Original Article(s)