The SALSA MLPA probemix P015 MECP2 is an in vitro diagnostic (IVD)1
or a research use only (RUO) assay for the detection of deletions or duplications in the human MECP2 gene, in order to confirm a potential cause and clinical diagnosis for classic and atypical Rett syndrome, and for MECP2 duplication syndrome. This assay can also be used for the detection of deletions or duplications in the human NTNG1 and CDKL5 genes, in order to confirm a potential cause and clinical diagnosis for atypical Rett syndrome, and for the detection of deletions or duplications in the human ARX and CDKL5 genes, in order to confirm a potential cause and clinical diagnosis for X-linked intellectual disability syndrome. This product can also be used for molecular genetic testing of at-risk family members. This assay is for use with human DNA extracted from peripheral blood.
Deletions or duplications detected with the P015 MECP2 probemix must be confirmed by another technique. In particular, deletions or duplications detected by only a single probe always require validation by another method. Most defects in MECP2, CDKL5, ARX and NTNG1 genes are point mutations, none of which will be detected by MLPA. It is therefore recommended to use this SALSA MLPA probemix in combination with sequence analysis of the aforementioned genes. Not all exons of CDKL5, ARX and NTNG1 genes are covered. The P189 is available for deletion or duplication analysis of other CDKL5, ARX and NTNG1 exons. This assay is not intended to be used as a standalone assay for clinical decisions. The results of this test must be interpreted by a clinical molecular geneticist or equivalent.
Please note that this probemix is for In Vitro Diagnostic use (IVD) in the countries specified at the end of this product description. In all other countries, the product is for Research Use Only (RUO).
Rett syndrome is a dominant X-linked brain disorder characterized by microcephaly, loss of achieved psychomotor abilities, intellectual disability, and autistic behaviours. The prevalence of Rett syndrome is approximately 1 in 10.000 live female births. Rett syndrome is usually caused by mutations in the MECP2 gene, although patients with mutations in two other genes, CDKL5 and FOXG1, may also exhibit a Rett-like phenotype. While loss-of-function mutations in MECP2 result in Rett syndrome, gain-of-function mutations are associated with MECP2 duplication syndrome which occurs almost exclusively in males. MECP2 duplication syndrome and Rett syndrome share overlapping clinical phenotypes including intellectual disability, motor deficits, epilepsy, hypotonia, and progressive spasticity.
Atypical Rett syndrome is the early onset seizure variant of Rett syndrome and is characterized by seizures in the first months of life with subsequent development of Rett syndrome features. It has an estimated prevalence of 1 in 45.000. MECP2 alterations in Rett syndrome patients comprise mainly point mutations (approximately 80% in classical and 40% in atypical cases), while deletions or duplications are less common (8% in classical and 3% in atypical cases). Approximately 6.5-10% of patients with atypical Rett syndrome have large deletions in CDKL5 (Rett syndrome database RettBASE).
One report described a patient with atypical Rett syndrome who presented with early onset of epileptic seizures (not infantile spasms) and a de novo translocation in intron 6 of NTNG1 gene (Borg et al. 2005). Please note that MLPA will not detect balanced translocations.
Mutations in CDKL5 mainly cause X-linked early infantile epileptic encephalopathy, also called X-linked infantile spasm syndrome. ARX gene mutations account for 9.5% of all cases of X-linked intellectual disability syndromes, including X-linked lissencephaly with abnormal genitalia, X-linked infantile spasm syndrome, and Partington syndrome (neurological disorder with movement problems). Since these genes are involved in multiple syndromes and are covered in multiple probemixes, Table 1 is provided to give an overview (see product description).
More information is available at https://www.ncbi.nlm.nih.gov/books/NBK1497/
The P015-F2 probemix contains 46 probes with amplification products between 130 nt and 467 nt. The P015-F2 probemix contains 17 probes for the MECP2 gene, covering each exon. Furthermore, several probes are present for genes in close proximity to MECP2. One of these probes is located within the pseudo autosomal region 2 (PAR2). The P015-F2 probemix contains four CDKL5 probes, two ARX probes, and four NTNG1 probes. More probes for the CDKL5, ARX and NTNG1 genes are present in the P189 CDKL5/ARX/FOXG1 probemix. In addition, 10 reference probes are included in this probemix, detecting several different autosomal chromosomal locations. The identity of the genes detected by the reference probes is available online (www.mlpa.com).
This probemix 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.