Placental methylation markers in normal and trisomy 21 tissues

The objective of this study is to combine multiplex ligation-dependent probe amplification (MLPA) and bisulfite sequencing to determine DNA methylation markers for noninvasive prenatal diagnosis of Down syndrome.

DNA methylation ratios (MR) of four fragments (CGI149, CGI045, HLCS-1, and HLCS-2) on chromosome 21 were evaluated in blood cells from 13 nonpregnant women, 15 euploidies, and 11 Down Syndrome (DS) placentae. Ratios were measured by bisulfite sequencing and methylation-specific (MS)-MLPA.

The MS-MLPA and bisulfite sequencing results were concordant. CGI149, CGI045, and HLCS-2 were unmethylated in all nonpregnant blood cells. CGI149, CGI045, HLCS-1, and HLCS-2 were methylated in most of the euploid (13, 11, 15, and 15, respectively) and DS placentae (10, 11, 11, and 11, respectively). The median placental DNA MR in CGI149 was 0.4578 (interquartile range, 0.3568-0.5169) and 0.5918 (interquartile range, 0.5618-0.6659) in euploid and DS placentae, respectively (p = 0.001). Using placental MR at 0.5390 as a threshold, we detected DS at 90.9% sensitivity and 93.3% specificity.

The MS-MLPA is an effective alternative to bisulfite sequencing in assessing placental MR. CGI149 is a potential marker for the noninvasive diagnosis of Down syndrome.