Case report: birth after preimplantation genetic diagnosis of a subtle mutation in SMN1 gene.
Spinal muscular atrophy (SMA) preimplantation genetic diagnosis (PGD) has been available since 1998. Protocols are based on the detection of the homozygous deletion of exon 7, which are present in 90-98% of SMA patients. A couple where the woman was a heterozygous carrier of the usual SMN1 Del7 mutation and the man was a heterozygous carrier of pMet263Arg substitution in exon 6 of SMN1 gene was referred for PGD. The usual PGD test being unsuitable for this couple, we developed a novel duplex polymerase chain reaction (PCR)-based PGD test for the detection of the mutation pMet263Arg by allele specific amplification, combined with the amplification of D5S641 extragenic polymorphic marker. PCR conditions were established using single control lymphoblasts and lymphocytes from the pMet263Arg substitution carrier. Amplification was obtained in 100% of the 86 single cells tested, amplification refractory mutation system (ARMS) PCR was specific in 100% of single cells tested and a complete genotype (mutation plus D5S641) was achieved in 88% of them. A PGD cycle was performed successfully and a pregnancy was obtained. An unaffected girl was born and postnatal diagnosis confirmed PGD results. This is the first PGD described for SMA because of another mutation than the major homozygous exon 7 deletion of SMN1. In the future, a similar strategy could be adopted for other subtle mutations of this gene.
Moutou
Céline
C
Service de Biologie de la Reproduction-SIHCUS-CMCO, CHU de Strasbourg, 19, rue Louis Pasteur, BP120, 67303 Schiltigheim cedex, France.
Machev
Nadejda
N
Gardes
Nathalie
N
Viville
Stéphane
S
D000328:Adult; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D009134:Muscular Atrophy, Spinal / Q000175:diagnosis* / Q000235:genetics; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D019836:Preimplantation Diagnosis / Q000379:methods*; D011296:Prenatal Diagnosis; D016601:RNA-Binding Proteins / Q000235:genetics*; D055532:SMN Complex Proteins; D055533:Survival of Motor Neuron 1 Protein
D017362:Cyclic AMP Response Element-Binding Protein; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D055532:SMN Complex Proteins; C526471:SMN1 protein, human; D055533:Survival of Motor Neuron 1 Protein