The SALSA MLPA probemixes P034 DMD-1 and P035 DMD-2 are in vitro diagnostic (IVD)1
or research use only (RUO) assays for the detection of exon deletions or duplications in the human DMD
gene as a cause for Duchenne muscular dystrophy and/or Becker muscular dystrophy and for carrier screening thereof. These assays can be used with human DNA derived from peripheral blood, (un)cultured amniotic fluid obtained in week 16 of the pregnancy or later and free from blood contamination, (un)cultured chorionic villi free from maternal contamination, or fetal blood.
In the majority of patients, most defects in the DMD
gene are copy number variations (CNVs), however point mutations can occur which will not be detected by MLPA. It is therefore recommended to use these SALSA MLPA probemixes in combination with sequence analysis. Copy number changes detected by only a single probe always require validation by another method. These probemixes are not intended to be used as standalone assays for clinical decisions. The results of these tests should be interpreted by a clinical molecular geneticist or equivalent.
Please note that these probemixes are for In Vitro Diagnostic (IVD) use in the countries specified at the end of this product description. In all other countries, the product is for Research Use Only (RUO).
Germline defects in the dystrophin (DMD)
gene are the most frequent cause of Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). DMD and BMD occur almost exclusively in males as they are inherited in an X-linked recessive manner. DMD usually has an early onset in childhood with delayed milestones, which include delays in sitting and standing independently. Proximal weakness causes a waddling gait and difficulty in climbing. DMD is rapidly progressive, with affected children being wheelchair dependent by the age of 13. Respiratory complications and cardiomyopathy occur in individuals with DMD after the age of 18 and a few survive beyond the third decade of life. In contrast, BMD has a slower rate of progression and patients on average survive until their mid-40s. More information on both conditions is available at http://www.ncbi.nlm.nih.gov/books/NBK1119/.
Deletions and duplications of complete exons in the DMD
gene are the most frequent cause of DMD/BMD and are usually missed by standard sequence analysis. Most of these deletions and duplications can be detected by the MLPA technique and hence MLPA complements sequence analysis of the DMD
gene. The frequency of deletions/duplications in the DMD
gene in DMD/BMD patients has been estimated at 60-70% for deletions and 5-10% for duplications (http://www.ncbi.nlm.nih.gov/books/NBK1119/
). Best practice guidelines on molecular diagnostics in Duchenne/Becker muscular dystrophies have been published by Abbs et al. (2010).
The SALSA MLPA Probemix P034-B2 DMD-1 contains 49 MLPA probes with amplification products between 130 and 500 nucleotides (nt). The SALSA MLPA Probemix P035-B1 DMD-2 contains 48 MLPA probes with amplification products between 130 and 500 nt.
The P034-B2 and P035-B1 probemixes together contain one probe for each of the 79 DMD
exons included in transcript variant Dp427m. In addition, one probe is present in P035-B1 for the alternative promoter/exon 1 found in transcript variant Dp427c. Performing two MLPA reactions, one with P034-B2 and one with P035-B1, is thus sufficient to investigate the copy number of all DMD
exons. P034-B2 and P035-B1 contain nine and eight reference probes, respectively. These reference probes detect locations on the X-chromosome. Complete probe sequences and the identity of the genes detected by the reference probes are available online (www.mlpa.com
These probemixes contains nine quality control fragments generating amplification products between 64 and 105 nt: four DNA Quantity fragments (Q-fragments), two DNA Denaturation fragments (D-fragments), one Benchmark fragment, and one chromosome X and one chromosome Y-specific fragment. More information on how to interpret observations on these control fragments can be found in the MLPA General Protocol and online at www.mlpa.com