Very Long-Chain Acyl-coenzyme A Dehydrogenase (VLCAD) deficiency (OMIM 201475) is a fatty acid oxidation disorder that is detected in newborn screening. VLCAD is a metabolic disorder which prevents the converting of certain fats to energy. Defects of the ACADVL (acyl-Coenzyme A dehydrogenase, very long chain) gene are the cause of VLCAD deficiency; 80% of the cases of VLCAD deficiency are caused by mutations in the ACADVL gene, 20% of the cases are caused by complete or partial deletions of ACADVL.
Another fatty acid oxidation disorder is primary carnitine deficiency (OMIM 212140). Most cases of primary carnitine deficiency are caused by mutations in the SLC22A5 gene (solute carrier family 22 member 5), however, 20% of the cases do not show any mutation and might be caused by (partial) deletions of SLC22A5.
The ACADVL gene (20 exons) spans ~5.4 kb of genomic DNA and is located on chromosome 17p13.1, 7 Mb from the p-telomere. The SLC22A5 gene (10 exons) spans ~26 kb of genomic DNA and is located on chromosome 5q31.1, 132 Mb from the p-telomere.
The P076-B2 ACADVL-SLC22A5 probemix contains one probe for each exon of the ACADVL gene, except for exon 2. Two probes are present for exon 4. This probemix also contains one probe for each exon of the SLC22A5 gene. In addition, 12 reference probes are included in this probemix, detecting several different autosomal chromosomal locations.
This SALSA® MLPA® probemix is designed to detect deletions/duplications of one or more sequences in the aforementioned genes in a DNA sample. Heterozygous deletions of recognition sequences should give a 35-50% reduced relative peak height of the amplification product of that probe. Note that a mutation or polymorphism in the sequence detected by a probe can also cause a reduction in relative peak height, even when not located exactly on the ligation site! In addition, some probe signals are more sensitive to sample purity and small changes in experimental conditions. Therefore, deletions and duplications detected by MLPA should always be confirmed by other methods. Not all deletions and duplications detected by MLPA will be pathogenic; users should always verify the latest scientific literature when interpreting their findings. We have no information on what percentage of defects in these genes is caused by deletions/duplications of complete exons. Finally, note that most defects in this gene are expected to be small (point) mutations which will not be detected by this SALSA® MLPA® test.