Phenotypes of SMA patients retaining SMN1 with intragenic mutation.
Brain Dev
; 43(7): 745-758, 2021 Aug.
Article
em En
| MEDLINE
| ID: mdl-33892995
ABSTRACT
BACKGROUND:
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by homozygous deletion or intragenic mutation of the SMN1 gene. It is well-known that high copy number of its homologous gene, SMN2, modifies the phenotype of SMN1-deleted patients. However, in the patients with intragenic SMN1 mutation, the relationship between phenotype and SMN2 copy number remains unclear.METHODS:
We have analyzed a total of 515 Japanese patients with SMA-like symptoms (delayed developmental milestones, respiratory failures, muscle weakness etc.) from 1996 to 2019. SMN1 and SMN2 copy numbers were determined by quantitative polymerase chain reaction (PCR) method and/or multiplex ligation-dependent probe amplification (MLPA) method. Intragenic SMN1 mutations were identified through DNA and RNA analysis of the fresh blood samples.RESULTS:
A total of 241 patients were diagnosed as having SMA. The majority of SMA patients showed complete loss of SMN1 (n = 228, 95%), but some patients retained SMN1 and carried an intragenic mutation in the retaining SMN1 (n = 13, 5%). Ten different mutations were identified in these 13 patients, consisting of missense, nonsense, frameshift and splicing defect-causing mutations. The ten mutations were c.275G > C (p.Trp92Ser), c.819_820insT (p.Thr274Tyrfs*32), c.830A > G (p.Tyr277Cys), c.5C > T (p.Ala2Val), c.826 T > C (p.Tyr276His), c.79C > T (p.Gln27*), c.188C > A (p.Ser63*), c.422 T > C (p.Leu141Pro), c.835-2A > G (exon 7 skipping) and c.835-3C > A (exon 7 skipping). It should be noted here that some patients with milder phenotype carried only a single SMN2 copy (n = 3), while other patients with severe phenotype carried 3 SMN2 copies (n = 4).CONCLUSION:
Intragenic mutations in SMN1 may contribute more significantly to clinical severity than SMN2 copy numbers.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Atrofia Muscular Espinal
/
Proteína 1 de Sobrevivência do Neurônio Motor
Limite:
Adolescent
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Child
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Female
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Humans
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Infant
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Male
/
Newborn
Idioma:
En
Revista:
Brain Dev
Ano de publicação:
2021
Tipo de documento:
Article