title: X chromosome dosage by quantitative fluorescent PCR and rapid prenatal diagnosis of sex chromosome aneuploidies.
abstract: During the past few years, rapid prenatal diagnosis of chromosome aneuploidies has been successfully achieved by quantitative fluorescent PCR (QF-PCR) amplification of chromosome-specific small tandem repeats (STR). This approach has proven to be very useful in clinical settings, since it allows the detection of major numerical disorders in a few hours after sampling. For the detection of Turner's syndrome (45,X), several highly polymorphic STR on the X chromosome are needed in order to reduce the likelihood that a normal female might be homozygous for all sequences and, consequently, that the test could fail to discriminate between samples retrieved from a Turner's and a normal female fetus. Here we report a new method for rapid and accurate detection of X chromosome copy number in prenatal samples that does not depend on STR heterozygosity. The test is based on QF-PCR amplification of the X-linked HPRT together with the autosomal D21S1411 used as internal control for quantification. In the course of this study, this assay allowed the prenatal diagnosis of a rare case of a normal female homozygous for four selected highly polymorphic X chromosome STR, as well as the assessment of the normal chromosome complement of a fetus homozygous for five chromosome 21 markers.
authors.affiliation: Departament de Genética Molecular, General Lab, Barcelona 08021, Spain. v_cirigliano@hotmail.com
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cirigliano
authors.forename: Maijo
authors.initials: M
authors.lastname: Ejarque
authors.forename: Carme
authors.initials: C
authors.lastname: Fuster
authors.forename: Matteo
authors.initials: M
authors.lastname: Adinolfi
mesh_terms: D000649:Amniocentesis; D000782:Aneuploidy; D041321:Chromosomes, Human, X; D004303:Dosage Compensation, Genetic; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis* / Q000235:genetics; D005453:Fluorescence; D005819:Genetic Markers; D006579:Heterozygote; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics; D008297:Male; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D012729:Sex Chromosome Aberrations; D025064:Sex Chromosome Disorders / Q000175:diagnosis* / Q000235:genetics; D020080:Tandem Repeat Sequences; D014424:Turner Syndrome / Q000235:genetics
chemical_list: D005819:Genetic Markers; D007041:Hypoxanthine Phosphoribosyltransferase