A recent study published in FEBS Open Bio revealed a novel 850K BeadChip sequencing technique capable of providing more extensive and detailed information on the pathogenesis of myasthenia gravis (MG) and the epigenetic factors affecting it.

Prior studies have shown that genetic factors are crucial in MG progression. However, with the development of more advanced detection methods, the role of epigenetics in diseases has gradually become more valued. DNA methylation is one of the most common phenomena of epigenetic alterations. It is a chemical DNA modification that changes RNA transcription without altering the DNA sequence.

The present study demonstrates genome-scale DNA methylation profiles of MG. Patients receiving MG treatment were recruited based on the following diagnostic criteria: 1) having muscle weakness of some specific striated muscles, with symptoms that were mild in the morning but severe in the afternoon; 2) positive for neostigmine test; 3) positive for repetitive nerve stimulation(RNS); and 4) with AChR antibodies found in the peripheral blood of most patients having generalized MG.

For genome-wide DNA methylation analysis, DNA was extracted from 8 MG patients and 4 healthy controls using the Illumina Human Methylation 850K BeadChip. In addition, pyrosequencing verification was conducted based on the differential methylation positions (DMPs), while cell lines derived from mice, including C2C12 and HT22, were treated with demethylation drugs. Furthermore, quantitative real-time PCR was used to detect transcribed mRNA of the screened differential genes. 

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A comparison of the control and MG groups showed that CAMK1D and CREB5 were the corresponding genes for the 2 key probe positions. On the other hand, the corresponding genes for 4 key probe positions compared to the myasthenic crisis (MC) and the non-MC group were genes SAV1, STK3, YAP1, and WWTR1.

Additionally, the pyrosequencing results revealed that the methylation level of the CAMK1D gene in the peripheral blood of MG patients decreased by 52% compared with the control group indicating a significantly different CAMK1D hypomethylation between the groups.

Moreover, the transcription of genes CREB5, PKD, YAP1, and STK3 in the C2C12 cells was decreased following the drug treatment; however, only YAP1 mRNA was downregulated in HT22 cells. Furthermore, genome-wide methylation detection results showed that the values of experimental samples were evenly distributed, signifying that the data obtained by chip detection was symmetrical.

“This study is more advantageous because Illumina 850K Beadchips, instead of the Illumina 450K, were used to cover doubled methylation sites. Therefore, more extensive and detailed information was obtained,” the authors highlighted.

Reference

Lin J, Tao L, Deng L, et al. Epigenome-wide DNA methylation analysis of myasthenia gravis. FEBS Open Bio. Published online May 31, 2023. doi:10.1002/2211-5463.13656