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. 2015 Feb 7;16(1):11.
doi: 10.1186/s12891-015-0457-x.

Molecular characterization and copy number of SMN1, SMN2 and NAIP in Chinese patients with spinal muscular atrophy and unrelated healthy controls

Ping Fang  1 , Liang Li  2 , Jian Zeng  3 , Wan-Jun Zhou  4 , Wei-Qing Wu  5 , Ze-Yan Zhong  6 , Ti-Zhen Yan  7 , Jian-Sheng Xie  8 , Jing Huang  9 , Li Lin  10 , Ying Zhao  11 , Xiang-Min Xu  12
Affiliations

Molecular characterization and copy number of SMN1, SMN2 and NAIP in Chinese patients with spinal muscular atrophy and unrelated healthy controls

Ping Fang et al. BMC Musculoskelet Disord. .

Abstract

Background: Spinal muscular atrophy (SMA) is caused by SMN1 dysfunction, and the copy number of SMN2 and NAIP can modify the phenotype of SMA. The aim of this study was to analyze the copy numbers and gene structures of SMA-related genes in Chinese SMA patients and unrelated healthy controls.

Methods: Forty-two Chinese SMA patients and two hundred and twelve unrelated healthy Chinese individuals were enrolled in our study. The copy numbers and gene structures of SMA-related genes were measured by MLPA assay.

Results: We identified a homozygous deletion of SMN1 in exons 7 and 8 in 37 of 42 patients (88.1%); the other 5 SMA patients (11.9%) had a single copy of SMN1 exon 8. The proportions of the 212 unrelated healthy controls with different copy numbers for the normal SMN1 gene were 1 copy in 4 individuals (1.9%), 2 copies in 203 (95.7%) and 3 copies in 5 (2.4%). Three hybrid SMN genes and five genes that lack partial sequences were found in SMA patients and healthy controls. Distributions of copy numbers for normal SMN2 and NAIP were significantly different (P < 0.001) in people with and without SMA.

Conclusion: The copy numbers and gene structures of SMA-related genes were different in Chinese SMA patients and healthy controls.

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Figures

Figure 1
Figure 1
Schematic representation of SMA-related genes in MLPA assays. Gray, RAD17, SERF1B and GTF2H2, near the disease-determining gene. Arrows, relative position and 5′-to-3′ direction of SMA-related genes. Blank boxes, exons (E). Important MLPA probes are above related genes. *, probes complementary to common regions in exons 1, 4, 6, 8 of either SMN1 or SMN2; #, probes specific for SMN or NAIP genes.
Figure 2
Figure 2
Gene structures inferred from MLPA results. ( a ) NAIP gene lacking exon 5; ( b ) SMN1 gene lacking exon 7; ( c ) SMN2 gene lacking exon 7; ( d ) SMN2 gene lacking exon 1 to exon 7; ( e ) Hybrid SMN gene in which exon 8 of SMN2 was converted to exon 8 of SMN1; ( f ) Hybrid SMN gene in which exon 7 of SMN1 was converted to exon 7 of SMN2; ( g ) NAIP gene lacking exon13; ( h ) Hybrid SMN gene in which exon 8 of SMN1 was converted to exon 8 of SMN2.
See this image and copyright information in PMC

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