Allelic methylation status of CpG islands on chromosome 21q in patients with Trisomy 21

Trisomy 21 is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. There has been limited research into the DNA methylation status of CpG islands (CGIs) in trisomy 21, therefore, exploring the DNA methylation status of CGIs in 21q is essential for the development of a series of potential epigenetic biomarkers for prenatal screening of trisomy 21. First, DNA sequences of CGIs in 21q from the USCS database were obtained and 149 sequences and 148 pairs of primers in the BGI YH database were aligned. All 300 cases were analyzed by a heavy methyl-polymerase chain reaction (HM-PCR) assay and a comparison of the DNA methylation status of CGIs was made between trisomy 21 and the control. The HM-PCR assay results did not show a difference in the DNA methylation status between individuals with trisomy 21 and the control. In total, there were 11 CGIs that showed various DNA methylation statuses between Japanese and Chinese patients. Subsequently, bisulfite genomic sequencing found variations in the methylation status of CpG dinucleotides in CGIs (nos. 14, 75, 109, 134 and 146) between trisomy 21 and the control. The different DNA methylation status of CpG dinucleotides in CGIs may be a potential epigenetic marker for diagnosing trisomy 21. No difference was identified in the DNA methylation status of 21q CGIs among Chinese individuals with trisomy 21 and the control. The homogeneity of the DNA methylation status of 21q CGIs in Chinese patients indicates that DNA methylation is likely to be an epigenetic marker distinguishing ethnicities.