title: Confirmation of mosaicism and uniparental disomy in amniocytes, after detection of mosaic chromosome abnormalities in chorionic villi.
abstract: Chromosome mosaicism is detected in about 1-2% of chorionic villi samples (CVS), and may be due to a postzygotic nondisjunction event generating a trisomic cell line in an initially normal conceptus (mitotic origin) or the postzygotic loss of one chromosome in an initially trisomic conceptus (meiotic origin and trisomy rescue). Depending on the distribution of the abnormal cell line, the mosaic can be confined to the placenta (CPM) or generalised to the fetus (TFM, true fetal mosaicism). Trisomy rescue could theoretically be associated with a 33.3% probability of uniparental disomy (UPD) in the fetus. The aim of this study was to determine the risk of fetal involvement in a cohort of numerical and structural chromosome mosaics revealed in chorionic villi by means of combined direct and long-term culture analyses; we also determined the incidence of UPD associated with mosaic aneuploidies and supernumerary markers involving imprinted chromosomes. A total of 273 of a consecutive series of 15,109 CVS evaluated during a period of 5 years showed a mosaic condition in direct preparations and/or long-term cultures; confirmatory amniocentesis was performed in 203 cases. The abnormal cell line was extended to the fetus in 12.8% cases in terms of structural and numerical abnormalities involving autosomes and sex chromosomes; the risk of TFM varied and depended on the placental tissue distribution of the abnormal cell line. One of the 51 cases in which the mosaic involved an imprinted chromosome showed UPD, thus indicating a risk of 1.96%.
authors.affiliation: Unit of Cytogenetics, TOMA Laboratory, Busto Arsizio, Varese, Italy. fgrati@tomalab.com
authors.forename: Francesca R
authors.initials: FR
authors.lastname: Grati
authors.forename: Beatrice
authors.initials: B
authors.lastname: Grimi
authors.forename: Giuditia
authors.initials: G
authors.lastname: Frascoli
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Di Meco
authors.forename: Rosaria
authors.initials: R
authors.lastname: Liuti
authors.forename: Silvia
authors.initials: S
authors.lastname: Milani
authors.forename: Anna
authors.initials: A
authors.lastname: Trotta
authors.forename: Francesca
authors.initials: F
authors.lastname: Dulcetti
authors.forename: Enrico
authors.initials: E
authors.lastname: Grosso
authors.forename: Monica
authors.initials: M
authors.lastname: Miozzo
authors.forename: Federico
authors.initials: F
authors.lastname: Maggi
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Simoni
mesh_terms: D000653:Amniotic Fluid / Q000378:metabolism*; D000782:Aneuploidy; D002460:Cell Line; D002824:Chorionic Villi / Q000378:metabolism*; D015193:Chorionic Villi Sampling / Q000379:methods*; D002869:Chromosome Aberrations; D025063:Chromosome Disorders; D002874:Chromosome Mapping; D004247:DNA / Q000378:metabolism; D005260:Female; D006801:Humans; D007621:Karyotyping; D009030:Mosaicism; D009630:Nondisjunction, Genetic; D010920:Placenta; D011247:Pregnancy; D011336:Probability; D012307:Risk Factors; D014018:Tissue Distribution; D024182:Uniparental Disomy
chemical_list: D004247:DNA