Saito Kayoko    Department   School of Medicine(Tokyo Women's Medical University Hospital), School of Medicine    Position   Professor (Fixed Term)
Article types	Original article
Language	English
Peer review	Peer reviewed
Title	Phenotypes of SMA patients retaining SMN1 with intragenic mutation.
Journal	Formal name：Brain & development Abbreviation：Brain Dev ISSN code：18727131/03877604
Domestic / Foregin	Foregin
Volume, Issue, Page	pp.10.1016/j.braindev.2021.03.006
Author and coauthor	Wijaya Yogik Onky Silvana, Är Rochmah Mawaddah, Niba Emma Tabe Eko, Morisada Naoya, Noguchi Yoriko, Hidaka Yasufumi, Ozasa Shiro, Inoue Takeshi, Shimazu Tomoyuki, Takahashi Yuya, Tozawa Takenori, Chiyonobu Tomohiro, Inoue Takushi, Shiroshita Tomoyoshi, Yokoyama Atsushi, Okamoto Kentaro, Awano Hiroyuki, Takeshima Yasuhiro, Saito Toshio, Saito Kayoko, Nishio Hisahide, Shinohara Masakazu
Publication date	2021/04
Summary	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.
DOI	10.1016/j.braindev.2021.03.006
PMID	33892995