[Molecular Features of SMA-related Genes in Spinal Muscular Atrophy Patients of Han Nationality in Southwest China.]

OBJECTIVES: To investigate the molecular features of spinal muscular atrophy (SMA) related genes in SMA patients of Han nationality of southwest of China.

METHODS: We collected 62 unrelated patients of SMA and 50 unrelated healthy individuals in this study.The copy numbers of survival motor neuron gene ( SMN ) and uronal-apoptosis inhibitory protein gene ( NAIP ) were measured by using multiplex ligation-dependent probe amplification (MLPA).

RESULTS: Of 62 patients,the copy number of SMA1-4 were 30.65% (19/62),41.94%(26/62),16.13% (10/62),11.29% (7/62),respectively.The deletion of SMN1 exon 7 accounts for 98.38% (61/62).The deletion of SMN1 exon 8 accounts for 82.26% (51/62).Among SMA 1 patients,the homozygous deletion of NAIP exon 5 accounts for 68.42% (13/19) and heterzygous deletion accounts for 26.32% (5/19).Among SMA2-4patients,the homozygous deletion of NAIP exon 5 accounts for 13.95% (6/43) and heterzygous deletion accounts for 62.79% (27/43).Furthermore,68.42% (13/19) patients of SMA1have 1 copy and 2 copies of SMN2 gene,84.62% (22/26) patients of SMA 2 have more than 2 copies of SMN2 gene,90.00% (9/10) SMA3 and 85.71% (6/7) SMA4 have over 2 copies of SMN2 gene and even have 5 and 6 copy of SMN2 gene.

CONCLUSIONS: The deletion of SMN1 gene is the main cause of SMA,and the change of SMN2 and NAIP copy number can affect the severity of SMA.