title: Placental methylation markers in normal and trisomy 21 tissues.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Obstetrics and Gynecology, the Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors.forename: Yu-Zhu
authors.initials: YZ
authors.lastname: Yin
authors.forename: Qin
authors.initials: Q
authors.lastname: She
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Pei-Zhen
authors.initials: PZ
authors.lastname: Zhang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jun-Wei
authors.initials: JW
authors.lastname: Lin
authors.forename: Yan-Chou
authors.initials: YC
authors.lastname: Ye
mesh_terms: D002891:Chromosomes, Human, Pair 21 / Q000737:chemistry; D004247:DNA / Q000097:blood / Q000302:isolation & purification; D019175:DNA Methylation; D004314:Down Syndrome / Q000175:diagnosis* / Q000235:genetics; D044127:Epigenesis, Genetic; D005260:Female; D005819:Genetic Markers / Q000235:genetics*; D006801:Humans; D060885:Multiplex Polymerase Chain Reaction; D010920:Placenta / Q000737:chemistry*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D017422:Sequence Analysis, DNA / Q000379:methods; D013447:Sulfites
chemical_list: D005819:Genetic Markers; D013447:Sulfites; D004247:DNA; C042345:hydrogen sulfite