Spinal muscular atrophy patient detection and carrier screening using dried blood spots on filter paper.

AIM: Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder. It is caused by mutations in the SMN1, and its clinical severity is modified by copy number variations of the SMN2. According to previous studies, deletion of SMN1 exon 7 is the most frequently observed in patients with SMA. Therefore, molecular analyses exploiting this genetic lesion could be beneficial in the diagnosis of SMA. Unfortunately, in many geographical regions, physicians do not have the latest molecular screening technologies at their immediate disposal. Thus, to overcome this issue, we developed an SMA-diagnosing system using dried blood spots (DBS) placed on filter paper to facilitate remote diagnosis. METHODS: In this study, we validate the applicability of DBS on Flinders Technology Associates (FTA) filter paper for detecting SMN1 exon 7 deletions and copy number variations of SMN1 and SMN2. To detect exon 7 deletions in SMN1, polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis was conducted by using DNA extracted from the DBS on FTA filter paper that had been stored at room temperature for a period of up to 4 years. To determine the copy numbers of SMN1 and SMN2, we carried out SYBR green-based real-time PCR by using the same blood specimens. RESULTS: The results obtained from the DBS on FTA filter paper were in complete concordance with those analyses using fresh blood specimens. This indicates that DBS on filter papers is a reliable method for SMA patient detection and carrier screenings. CONCLUSION: The SMA-diagnosing system, combined with the mailing of DBS on filter paper, will be beneficial for patients suffering from neuromuscular disorders in areas with limited or no access to diagnostic facilities with molecular capabilities.

Diagnosis of spinal muscular atrophy via high-resolution melting analysis symmetric polymerase chain reaction without probe: a screening evaluation for SMN1 deletions and intragenic mutations.

AIM: Spinal muscular atrophy (SMA) is a well-defined autosomal recessive neuromuscular disorder caused by mutations in the survival motor neuron 1 (SMN1) gene. The most frequently observed mutation is a deletion of exon 7, which has been documented in >95% of SMA patients. A novel technique for detecting mutations known as high-resolution melting analysis (HRMA) has rapidly become the tool of choice for screening pathogenic genetic variants. In the present study, we attempt to validate the applicability of HRMA to the detection of exon 7 deletions and other intragenic mutations in SMN1. RESULTS: Three primer sets were adopted in our HRMA screening for deletion of SMN1 exon 7. In screening attempts utilizing two primer sets, the results of HRMA were not compatible with those obtained by polymerase chain reaction-restriction fragment length polymorphism. Therefore, we applied a modified protocol using revised primer sets, which resulted in an absolute compatibility of results between HRMA and polymerase chain reaction-restriction fragment length polymorphism. With regard to screenings for intragenic mutations in SMN1 exon 3, two primer sets were adopted for use in HRMA. In the initial HRMA screening using the first primer set, we failed to identify any intragenic mutations; however, when using a revised primer set, HRMA successfully detected the presence of a c.275G>C mutation. CONCLUSION: HRMA is a simple but versatile tool to add to the existing arsenal of diagnostic techniques that could aid clinicians/researchers in diagnosing SMA. However, as we demonstrate in the present study, the design and selection of primers is of monumental importance in ensuring the successful application of HRMA to screening for pathogenic variants.