J Korean Med Sci.  2004 Dec;19(6):870-873. 10.3346/jkms.2004.19.6.870.

Quantitative Analysis of SMN1 Gene and Estimation of SMN1 Deletion Carrier Frequency in Korean Population based on Real-Time PCR

• Lee TM
• Kim SW
• Lee KS
• Jin HS
• Koo SK
• Jo I
• Kang S
• Jung SC

• KMID: 1778571
• DOI: http://doi.org/10.3346/jkms.2004.19.6.870

Abstract

Spinal muscular atrophy (SMA) is an autosomal recessive disorder, caused by homozygous absence of the survival motor neuron gene (SMN1) in approximately 94% of patients. Since most carriers have only one SMN1 gene copy, several SMN1 quantitative analyses have been used for the SMA carrier detection. We developed a reliable quantitative real-time PCR with SYBR Green I dye and studied 13 patients with SMA and their 24 parents, as well as 326 healthy normal individuals. The copy number of the SMN1 gene was determined by the comparative threshold cycle (Ct) method and albumin was used as a reference gene. The homozygous SMN1 deletion ratio of patients was 0.00 and the hemizygous SMN1 deletion ratio of parents ranged from 0.39 to 0.59. The delta delta Ct ratios of 7 persons among 326 normal individuals were within the carrier range, 0.41-0.57. According to these data, we estimated the carrier and disease prevalence of SMA at 1/47 and 1/8,496 in Korean population, respectively. These data indicated that there would be no much difference in disease prevalence of SMA compared with western countries. Since the prevalence of SMA is higher than other autosomal recessive disorders, the carrier detection method using real-time PCR could be a useful tool for genetic counseling.

Keyword

Muscular Atrophy, Spinal; SMN Protein; Gene Deletion; Heterozygote; Polymerase Chain Reac-tion; PCR, Real-time

MeSH Terms

Adult
Aged
Aged, 80 and over
DNA Mutational Analysis/*methods
Female
Genetic Predisposition to Disease/epidemiology
Genetic Screening/*methods
Heterozygote
Heterozygote Detection/methods
Humans
Korea/epidemiology
Male
Middle Aged
Muscular Atrophy, Spinal/*epidemiology/genetics/*metabolism
Nerve Tissue Proteins/*genetics
Polymorphism, Genetic
*Quantitative Trait, Heritable
Reverse Transcriptase Polymerase Chain Reaction/*methods
Risk Assessment/*methods
Risk Factors

Figure

• 

  Fig. 1 Real-time amplification plots of triplicate SMN1 and albumin of: (A) healthy normal control (ΔΔCt ratio 1.04, SD SMN1 0.09, SD albumin 0.01); (B) carrier with one SMN1 copy (ΔΔCt ratio 0.5, SD SMN1 0.01, SD albumin 0.14); (C) patients with SMA of homozygous absence of SMN1 (ΔΔCt ratio 0.00, SD albumin 0.14, no amplification of SMN1).

• 

  Fig. 2 Identification of specificity of SMN1 primers in three SMA families and a normal individual by multiplex PCR with COL1A1. P, patient; F, father; M, Mother.

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