1. Clinical phenotypes of spinal muscular atrophy patients with hybrid SMN gene.
- Author
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Niba ETE, Nishio H, Wijaya YOS, Lai PS, Tozawa T, Chiyonobu T, Yamadera M, Okamoto K, Awano H, Takeshima Y, Saito T, and Shinohara M
- Subjects
- Base Sequence, Chimera genetics, DNA Copy Number Variations genetics, Exons genetics, Female, Gene Deletion, Gene Dosage, Genotype, Humans, Japan epidemiology, Male, Muscular Atrophy, Spinal genetics, Muscular Atrophy, Spinal metabolism, Phenotype, Polymerase Chain Reaction, Sequence Deletion, Survival of Motor Neuron 1 Protein metabolism, Survival of Motor Neuron 2 Protein genetics, Muscular Atrophy, Spinal physiopathology, Survival of Motor Neuron 1 Protein genetics
- Abstract
Background: Spinal muscular atrophy (SMA) is a neuromuscular disease caused by homozygous deletion of SMN1 exons 7 and 8. However, exon 8 is retained in some cases, where SMN2 exon 7 recombines with SMN1 exon 8, forming a hybrid SMN gene. It remains unknown how the hybrid SMN gene contribute to the SMA phenotype., Method: We analyzed 515 patients with clinical suspicion for SMA. SMN1 exons 7 and 8 deletion was detected by PCR followed by enzyme digestion. Hybrid SMN genes were further analyzed by nucleotide sequencing. SMN2 copy number was determined by real-time PCR., Results: SMN1 exon 7 was deleted in 228 out of 515 patients, and SMN1 exon 8 was also deleted in 204 out of the 228 patients. The remaining 24 patients were judged to carry a hybrid SMN gene. In the patients with SMN1 exon 7 deletion, the frequency of the severe phenotype was significantly lower in the patients with hybrid SMN gene than in the patients without hybrid SMN gene. However, as for the distribution of SMN2 exon 7 copy number among the clinical phenotypes, there was no significant difference between both groups of SMA patients with or without hybrid SMN gene., Conclusion: Hybrid SMN genes are not rare in Japanese SMA patients, and it appears to be associated with a less severe phenotype. The phenotype of patients with hybrid SMN gene was determined by the copy number of SMN2 exon 7, as similarly for the patients without hybrid SMN gene., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)
- Published
- 2021
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