Limb girdle muscular dystrophy type 2L (LGMD2L) or anoctaminopathy is a condition mainly characterised by adult onset proximal lower limb muscular weakness and raised creatine kinase (CK) values, due to recessive anoctamin 5 (ANO5) gene mutations. This gene encodes a member of the anoctamin family of transmembrane proteins, and the encoded protein is likely a calcium activated chloride channel. An exon 5 founder mutation (c.191dupA) represents 61% of mutated alleles and appears to be more prevalent in Northern European populations (Sarkozy et al. 2013 Hum Mutat). c.191dupA mutations lead to a frame shift and to premature truncation, which strongly suggests that c.191dupA is associated with a loss of ANO5 function (Bolduc et al. 2010 Am J Hum Genet).
The ANO5 gene (22 exons) ~90 kb of genomic DNA and is located at 11p14.3, 22 Mb from the p-telomere. The P436-A1 probemix contains one probe for every exon, two probes for exon 1, 7 and 19 and three probes for exon 22. Furthermore, the probemix contains a mutation specific probe for c.191dupA which will only generate a signal when the mutation is present. The exon 5 probe detects the wild-type sequence of the c.191dupA mutation, which means that its signal will decrease when the mutation is present. In addition, 10 reference probes are included in this probemix, detecting several different autosomal chromosomal locations.
SD033 Sample DNA: Please note that the mutation-specific probe for c.191dupA has only been tested on control plasmids and not on positive human DNA samples with the c.191dupA mutation! This SD033 sample DNA is provided with each probemix vial and can be used in data binning in the fragment analysis and as a positive control for the mutation-specific probe (see next page).
This SALSA® MLPA® probemix is designed to detect deletions/duplications of one or more sequences in the aforementioned gene, and to detect the presence of the aforementioned c.191dupA mutation 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.