False homozygous deletions of SMN1 exon 7 using Dra I PCR-RFLP caused by a novel mutation in spinal muscular atrophy.
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder, and about 95% of SMA patients are homozygous for deletions in the SMN1 gene. Herein, classical polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) using DraI yielded false homozygous deletions of SMN1 exon 7 in a patient with SMA, but multiple ligation-dependent probe amplification analysis revealed one remaining copy of SMN1 exon 7. Sequencing showed that this false deletion in the PCR-RFLP resulted from a novel mutation of one SMN1 copy that was not deleted (c.863G > T, p.R288M). This novel sequence variant introduced a mismatch that interfered with primer binding. These findings demonstrate that comprehensive analysis using PCR-RFLP, multiple ligation-dependent probe amplification, and sequencing can reliably and correctly diagnose SMA.
Kang
Seong-Ho
SH
Department of Laboratory Medicine, Seoul National University Hospital, Seoul, Korea.
Cho
Sung Im
SI
Chae
Jong-Hee
JH
Chung
Kyu Nam
KN
Ra
Eun Kyung
EK
Kim
So Yeon
SY
Seong
Moon-Woo
MW
Kim
Ji Yeon
JY
Park
Sung Sup
SS
D001483:Base Sequence; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D005091:Exons / Q000235:genetics*; D005189:False Positive Reactions; D006720:Homozygote; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis* / Q000235:genetics*; D021141:Nucleic Acid Amplification Techniques; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics*
D055533:Survival of Motor Neuron 1 Protein; D015252:Deoxyribonucleases, Type II Site-Specific; C035594:TTTAAA -specific type II deoxyribonucleases