The frequency of SMN gene variants lacking exon 7 and 8 is highly population dependent.

Spinal Muscular Atrophy (SMA) is a disorder characterized by the degeneration of motor neurons in the spinal cord, leading to muscular atrophy. In the majority of cases, SMA is caused by the homozygous absence of the SMN1 gene. The disease severity of SMA is strongly influenced by the copy number of the closely related SMN2 gene. In addition, an SMN variant lacking exons 7 and 8 has been reported in 8% and 23% of healthy Swedish and Spanish individuals respectively. We tested 1255 samples from the 1000 Genomes Project using a new version of the multiplex ligation-dependent probe amplification (MLPA) P021 probemix that covers each SMN exon. The SMN variant lacking exons 7 and 8 was present in up to 20% of individuals in several Caucasian populations, while being almost completely absent in various Asian and African populations. This SMN1/2Δ7-8 variant appears to be derived from an ancient deletion event as the deletion size is identical in 99% of samples tested. The average total copy number of SMN1, SMN2 and the SMN1/2Δ7-8 variant combined was remarkably comparable in all populations tested, ranging from 3.64 in Asian to 3.75 in African samples.

Rapid Detection of the Three Celiac Disease Risk Genotypes HLA-DQ2.2, HLA-DQ2.5, and HLA-DQ8 by Multiplex Ligation-Dependent Probe Amplification.

BACKGROUND: Genotyping of HLA-DQ2.2, HLA-DQ2.5, and HLA-DQ8 is important in celiac disease (CD). The absence of these three genotypes has a strong negative predictive value. METHODS: We designed multiplex ligation-dependent probe amplification (MLPA) for the combined detection of HLA-DQ2.2, HLA-DQ2.5, and HLA-DQ8. The MLPA probe mix was validated against a set of 59 samples characterized by conventional techniques. RESULTS: The MLPA assay genotyped all 59 samples correctly when compared to the results obtained by PCR-SSCP/HD or PCR-SSO and PCR-SSP. CONCLUSION: The MLPA assay provides a reliable single-reaction analysis of the CD risk genotypes HLA-DQ2.2, HLA-DQ2.5, and HLA-DQ8 allowing for stratification or exclusion of disease risk.

A multiplex assay to rapidly exclude HLA-DQ2.5 and HLA-DQ8 expression in patients at risk for celiac disease.

BACKGROUND: Celiac disease (CD) is an inflammatory disorder of the small intestine induced by gluten ingestion. CD has a strong genetic association with human leukocyte antigen (HLA)-DQ2.5 and HLA-DQ8. The absence of HLA-DQ2.5 and HLA-DQ8 has a strong negative predictive value for CD. Genetic screening of HLA-DQ2.5 and HLA-DQ8 in patients at risk is of great value. METHODS: We designed, developed, and validated a multiplex assay based on multiplex ligation-dependent probe amplification (MLPA) technology, allowing the simultaneous detection of DQA1*05-DQB1*02, encoding HLA-DQ2.5, and DQA1*03-DQB1*03:02, encoding HLA-DQ8. The amplified products were separated and identified using capillary electrophoresis. RESULTS: When compared with a polymerase chain reaction followed by single-strand conformation polymorphism/ heteroduplex analysis, one discrepancy was found. Sequencing analysis showed that the developed MLPA assay result was correct. Furthermore, we demonstrated that the MLPA method is able to distinguish between the heterozygote and homozygote expression of HLA-DQ2.5 or HLA-DQ8. CONCLUSIONS: This study shows that it is possible to rapidly and accurately screen for the absence of HLA-DQ2.5 and HLA-DQ8 using MLPA, excluding patients at risk for CD for further serological or histological follow-up. In addition, MLPA might be an accurate tool to screen for other specific HLA types in the context of disease association in a diagnostic laboratory setting.