Classical lissencephaly, or isolated lissencephaly sequence (ILS), and subcortical band heterotopia (SBH) are neuronal migration disorders associated with severe mental retardation and epilepsy. Abnormalities of the PAFAH1B1 (LIS1) and DCX genes are implicated in the majority of patients with these disorders and account for approximately 75% of patients with ILS, whereas mutations of DCX account for 85% of patients with SBH. Lissencephaly may be associated with other diseases including Miller-Dieker syndrome, and Walker-Warburg syndrome. Duplications of the 17p13 region encompassing PAFAH1B1 have been reported to result in mild to moderate developmental delay.
This probemix includes probes for the lissencephaly related genes, such as; PAFAH1B1 (LIS1), DCX (SBH), POMT1 (Walker-Warburg syndrome), POMGnT1 (Muscle-Eye-Brain disease) and FLNA (periventricular nodular heterotopia, frontometaphyseal dysplasia and otopalatodigital syndrome).
The PAFAH1B1 gene (11 exons) spans ~92 kb of genomic DNA and is located on chromosome 17p13.3, ~2.5 Mb from the p-telomere. The P061-D1 probemix contains one probe for each exon of the PAFAH1B1 gene. Two probes are included for exon 1 and 2. Additionally, 8 probes flanking PAFAH1B1 are included.
The DCX gene (7 exons) spans ~118 kb of genomic DNA and is located on chromosome Xq23, ~111 Mb from the p-telomere. This probemix contains 8 probes for all exons of the DCX gene with the exception of exon 1. Two probes are included for exons 2 and 3.
The POMT1 gene (20 exons) spans ~21 kb of genomic DNA and is located on chromosome 9q34.13, ~131.5 Mb from the p-telomere. The P061-D1 probemix contains 4 probes for the POMT1 gene.
The POMGnT1 gene (23 exons) spans ~10 kb of genomic DNA and is located on chromosome 1p34.1, ~46 Mb from the p-telomere. The P061-D1 probemix contains 4 probes for the POMGnT1 gene.
The FLNA gene (48 exons) spans ~26 kb of genomic DNA and is located on chromosome Xq28, ~154 Mb from the p-telomere. This probemix contains 6 probes for the FLNA gene.
In addition, 8 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 (e.g. SNP) 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.