Molecular analysis of SMA patients without homozygous SMN1 deletions using a new strategy for identification of SMN1 subtle mutations.
Spinal muscular atrophy (SMA) is a common autosomal recessive disease. SMA is linked to the 5q13 locus in 95% of patients, and in at least 98% of them, the SMN1 homozygous deletion is found. Compound heterozygous patients, who have an SMN1 deletion associated with a subtle mutation, appear undeleted with the common molecular diagnostic test that detects only the homozygous absence of SMN1. In these patients, mutation screening in SMN1 is hampered by the presence of several copies of the highly homologous SMN2 gene. Here, we present a rapid and reliable strategy for detecting SMN mutations using long-range PCR, which avoids cloning and cDNA analysis. Using this method, we found 10 mutations, including five mutations never reported previously and five recurrent mutations; some of them are probably population-specific. Marker analysis of the 5q13 locus in these mutations showed common haplotypes, supporting the hypothesis of a common ancestor rather than a hot spot sequence. We also evaluate the suitability of automated SSCA and DHPLC for mutation scanning.
INSERM E 0339, Faculté de Médecine X Bichat, Paris, France.
Olivier
O
Clermont
Philippe
P
Burlet
Paule
P
Benit
Dominique
D
Chanterau
Pascale
P
Saugier-Veber
Arnold
A
Munnich
Veronica
V
Cusin
D001331:Automation; D002851:Chromatography, High Pressure Liquid; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods*; D005820:Genetic Testing / Q000379:methods*; D006239:Haplotypes / Q000235:genetics; D006720:Homozygote; D006801:Humans; D008969:Molecular Sequence Data; D009134:Muscular Atrophy, Spinal / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D016601:RNA-Binding Proteins / Q000235:genetics*; D055532:SMN Complex Proteins; D012680:Sensitivity and Specificity; D017384:Sequence Deletion / Q000235:genetics; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein; D013997:Time Factors
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; C526477:SMN2 protein, human; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein