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Objective To explore the pathogenesis of Russell-Silver syndrome (RSS). Methods Two milliliter peripheral blood samples were collected from 6 male patients aged 6 to 8 years with suspected RSS phenotype, the parents of 2 patients and 5 healthy boys. Mononuclear cells were isolated and genomic DNA was extracted. The methylation level of the H19 imprinting control region(ICR)1 on chromosome 11p15.5 was detected by pyrosequencing.The methylation status and the copy number variation in the corresponding region of one RSS patient with positive results by pyrosequencing were analysed by methylation-specific multiplex-ligation-dependent probe amplification assay (MS-MLPA). Results Pyrosequencing analysis revealed that the methylation rates on the 6 CpG targeting sites in H19 differentially methylated region(DMR)in the 6 RSS patients were about 11%~29%, which were significantly lower than those in their parents and normal controls (44%~59%). The MS-MLPA results of one patient with positive pyrosequencing showed that the methylation rates of 4 sites in H19-DMR were about 10%,which was obviously lower than the normal level.The methylation rates of the 4 sites in KCNQ1OT1 gene were about 50%, which was in the normal range. The copy number variations from all samples detected were in the normal range. Conclusion There is methylation aberration of H19-DMR in ICR1 in children with RSS.
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<p><b>OBJECTIVE</b>To develop a rapid, simple, cost-effective, accurate and sensitive method for quantitative detection of mitochondrial DNA (mtDNA) 3243A→G mutation in order to provide reference for selecting the best detection method under different conditions.</p><p><b>METHODS</b>Genomic DNA was extracted from peripheral leucocytes of 17 individuals from a Wenzhou family featuring maternally inherited diabetes and deafness (MIDD). Heteroplasmic level of mtDNA 3243A→G mutation was determined respectively with polymerase chain reaction-restriction fragment length polymorphism (PCR-RLFP), real time-amplification refractory mutation system-quantitative PCR (RT-ARMS-qPCR) and pyrosquencing. Eleven plasmids with various heteroplasmic levels of the 3243A→G mutation (ranging from 0 to 100%)were constructed as the standards. The reliability of above methods was compared by correlation coefficient based on observed and expected values.</p><p><b>RESULTS</b>For all three methods, measurement of the standards showed a linear correlation between the expected and detected values, i.e., PCR-RFLP (R(2)=0.828), RT-ARMS-qPCR (R(2)=0.998) and pyrosquencing (R(2)=0.997). For the MIDD family, it was consistent that there are 13 members carrying the A3243G mutation with different heteroplasmic levels. And there was no significant difference between the results by RT-ARMS-qPCR and pyrosquencing.</p><p><b>CONCLUSION</b>PCR-RFLP is not appropriate for the quantitative detection but could be used for early clinical screening. Both RT-ARMS-qPCR and pyrosquencing are suitable for the detection of low heteroplasmic level of A3243G mutation. Compared with pyrosquencing, RT-ARMS-qPCR is rapid, reliable and cost-effective, and is the best choice for detecting low mutation loads.</p>