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SALSA® MLPA® Probemix P060 SMA Carrier detects copy number variations in exons 7 and 8 of the SMN1 gene. P060 SMA has been specifically designed for SMA carrier detection.
Contents: 21 MLPA probes, including 2 probes for SMN1 (exon 7 and 8), 2 probes for SMN2 (exon 7 and 8) and 17 reference probes.
Tissue: genomic DNA isolated from human peripheral whole blood or specified prenatal samples (see Intended Purpose).
Application: spinal muscular atrophy (SMA).
CE-marked and registered for in vitro diagnostic (IVD) use in selected territories.
MRC Holland offers four different assays for SMA that fit the complete range of genetic testing needs. Compare our SMA products.
The SALSA MLPA Probemix P060 SMA Carrier is an in vitro diagnostic (IVD) or research use only (RUO) semi-quantitative assay for the detection of deletions or duplication in exons 7 and 8 of the SMN1 gene in genomic DNA isolated from human peripheral whole blood specimens, prenatal samples, from either (un)cultured amniotic fluid obtained in week 16 of pregnancy or later, free from blood contamination (un)cultured chorionic villi, free from maternal contamination fetal blood or Dried Blood Spot (DBS) cards. P060 SMA Carrier is intended to establish or confirm a potential cause for and clinical diagnosis of Spinal Muscular Atrophy (SMA), carrier testing and for molecular genetic testing of at-risk family members. This probemix can also be used for the detection of copy number changes of exons 7 and 8 of the SMN2 gene, as an interpretation aid for SMN1 copy number determination.
For the full intended purpose, see the product description.
Spinal muscular atrophy (SMA) is a neuromuscular disorder characterised by degeneration of the anterior horn cells of the spinal cord, leading to symmetrical muscle weakness and atrophy. The estimated incidence of SMA is 1:6,000-1:10,000: the second most common lethal autosomal recessive disorder in Caucasians, after cystic fibrosis (Ben-Shachar et al. 2011, Smith et al. 2007). SMA is usually divided into four clinical groups based on age of onset and maximum function obtained.
Two (highly similar) genes play a pivotal role in SMA: SMN1 and SMN2. Most individuals* have two copies of each gene. The SMA region on 5q13.2, containing the telomeric SMN1 and the centromeric SMN2, is a complicated inverted repeat area displaying high instability, leading to frequent deletions and gene conversions. SMN1 and SMN2 can only be distinguished by two single nucleotide differences: one in exon 7 and one in exon 8. The single nucleotide difference between SMN1 and SMN2 in exon 7 affects mRNA splicing in SMN2 resulting in an altered SMN protein with a limited half-life and function.
A total of 95-98% of SMA patients (this percentage is lower in SMA patients from African descent) show homozygous deletion of at least exon 7 of the telomeric SMN1 gene (Labrum et al. 2007). The remaining 3-5% present compound heterozygosity with a point mutation on one chromosome and a deletion/gene conversion on the other. Such a point mutation will not be detected by this P060 SMA Carrier MLPA assay and should be identified by sequencing. In a small number of patients, the SMN1 defect is a copy number change of SMN1 exons 1-6 which can be detected with the SALSA MLPA Probemix P021 SMA (Arkblad et al. 2006).
The great majority of SMA carriers can be identified by the presence of a single SMN1 exon 7 copy. The one copy frequency in the US is estimated to be 1:37 for Caucasians, 1:46 for Ashkenazi Jews, 1:56 for Asians, 1:91 for African-Americans and 1:125 for Hispanics. Approximately 3-8% of SMA carriers (27% of African Americans) have one functional and one defective SMN1 copy, or have two SMN1 copies on one chromosome and 0 copies on the other (2+0) (Alias et al. 2014, Ben-Shachar et al. 2011, Hendrickson et al. 2009, Miskovic et al. 2011, Smith et al. 2007). Dosage analysis cannot determine the difference between '1+1' and '2+0' (silent carriers) arrangements. Both situations are simply detected as having two SMN1 copies leading to false negative results. A thorough molecular analysis should be performed in parents of SMA patients who have two SMN1 copies. Luo et al. (2014) reported that a haplotype block specific for SMN1 duplications is present in a large percentage of Ashkenazi Jews and in other ethnic groups. Identifying this haplotype, e.g. with the use of the SALSA MLPA Probemix P460 SMA (Silent) Carrier, will, depending on ethnicity, increase the chance of identifying silent carriers.
The SMN2 copy number is very variable with only 60-70% of individuals having two copies. Provided that at least one functional SMN1 copy is present, complete absence of the centromeric SMN2 gene has no known clinical consequences. More information on spinal muscular atrophy can be found in http://www.ncbi.nlm.nih.gov/books/NBK1352/.
*In people of African descent, the percentage of SMA patients with a homozygous exon 7 deletion may be lower (Labrum et al. 2007). This assay does not detect other causes of SMA such as pathogenic point mutations.
SALSA MLPA Probemix P060 SMA Carrier is CE-marked for in vitro diagnostic (IVD) use. This assay has also been registered for IVD use in Colombia, Costa Rica and Israel.
This assay is for research use only (RUO) in all other territories.
SALSA Reference Selection DNA SD082 can be used to aid in the selection of suitable reference samples for the P060 SMA Carrier probemix. Reference Selection DNA can only be used in initial experiments on DNA samples from healthy individuals from your sample collection with the intention to identify suitable reference samples. SD082 cannot be used as a reference sample in subsequent experiments.
A vial of SALSA Reference Selection DNA SD082 is included with every order of the P060 SMA Carrier probemix, but it is possible to order additional vials separately.
For more information, see the product description.
A general SALSA MLPA Reagent Kit is required for MLPA experiments (to be ordered separately).
A vial is included with every order of this probemix, but additional vials can also be purchased separately.
The prices above are list prices for direct orders from MRC Holland. Contact us for a quote that takes discounts and additional costs (such as shipping costs) into account. Different prices apply for orders through one of our sales partners; contact your local supplier for a quote.
Inclusion of a positive sample is usually not required, but can be useful for the analysis of your experiments. MRC Holland has very limited access to positive samples and cannot supply such samples. We recommend using positive samples from your own collection. Alternatively, you can use positive samples from an online biorepository, such as the Coriell Institute.
The commercially available positive samples below have been tested with current (B2) and have been shown to produce useful results.
Coriell Sample ID | Copy Number | |||
---|---|---|---|---|
SMN1 exon 7 | SMN2 exon 7 | SMN1 exon 8 | SMN2 exon 8 | |
NA00232; NA10684 | 0 | 2 | 0 | 2 |
NA22592; NA09677; NA03813 | 0 | 3 | 0 | 3 |
NA03815; NA20760; NA20787 | 1 | 1 | 1 | 1 |
NA23687; NA23688; NA20764 | 1 | 2 | 1 | 2 |
HG00346; HG00281 | 1 | 3 | 1 | 3 |
HG01773; HG01774; HG02132 | 1 | 4* | 1 | 4* |
NA19122; HG01941; NA19794 | 2 | 0 | 2 | 0 |
HG02514; HG03663; HG03636 | 2 | 1 | 2 | 1 |
HG01701; HG01942; HG01935 | 2 | 2 | 2 | 2 |
HG01748; HG01971; HG00329 | 2 | 3 | 2 | 3 |
HG03625 | 2 | 4* | 2 | 4* |
NA19123; HG03258; HG02891; HG00255; NA19437; HG01377 | 3 | 0 | 3 | 0 |
HG01755; HG03650; NA20775; HG01137 | 3 | 1 | 3 | 1 |
NA12548; NA20755 | 3 | 2 | 3 | 2 |
NA12552; NA20515 | 3 | 3 | 3 | 3 |
NA19235; HG03027; HG02769 | 4 | 0 | 4 | 0 |
NA19429; HG02836 | 4 | 1 | 4 | 1 |
Coriell Sample ID | Copy Number | |||
---|---|---|---|---|
SMN1 exon 7 | SMN2 exon 7 | SMN1 exon 8 | SMN2 exon 8 | |
NA19177 | 2 | 1 | 3 | 0 |
NA21527 | 2 | 2 | 1 | 3 |
NA19249 | 2 | 2 | 3 | 1 |
NA21526 | 2 | 3 | 1 | 4* |
NA19790 | 3 | 1 | 1 | 3 |
NA19327 | 3 | 1 | 2 | 2 |
NA21513 | 3 | 1 | 4 | 0 |
NA19360 | 4 | 0 | 3 | 1 |
HG02697 | 4 | 1 | 3 | 2 |
* SMN2 probes in this probemix cannot reliably distinguish between 4 or more copies. The indicated copy numbers have been validated using SALSA MLPA Probemix P021 SMA.