Fetal sex identification in maternal plasma by means of short tandem repeats on chromosome x.
Analysis of fetal DNA in maternal plasma has recently been introduced as a new method for noninvasive prenatal diagnosis. In the majority of cases, the Y chromosome-specific sequences are commonly used as a fetus-specific marker with a high risk of false-negative cases. We attempted to develop a sensitive and reliable X chromosome short tandem repeat (STR) multiplex PCR amplification system that is suitable for the amplification of short-sized templates of free fetal DNA. Because of specific characteristics of fetal DNA in maternal plasma, cell-free fetal DNA is smaller than corresponding maternal DNA, and so we selected 10 X-STR loci in which the allele size was 250 bp. In addition, fetal sex was also investigated using the amelogenin gene in the same multiplex assay. Twenty-six women were enrolled in the study. Eight of 26 total fetuses analyzed were male and 18 were female. In the whole sample, X-STRs were informative with a mean of 4.84 +/- 1.43. A mean of 2.67 +/- 1.28 X-STR markers per sample (range 1-5) of paternally inherited fetal alleles were detected in pregnant women carrying a female fetus. In all cases, blind determination of fetal sex by means of the identification of amelogenin and X-STR markers was confirmed by fetal karyotyping. This study showed that this noninvasive technique is a reliable and accurate tool to investigate free fetal DNA in pregnancies within the first trimester and could be widely used in clinical research and diagnosis.
Unità di Aterosclerosi e Trombosi, S. Giovanni Rotondo, Foggia, Italy. g.vecchione@operapadrepio.it
Gennaro
G
Vecchione
Michela
M
Tomaiuolo
Michelina
M
Sarno
Donatella
D
Colaizzo
Rosella
R
Petraroli
Maria
M
Matteo
Pantaleo
P
Greco
Elvira
E
Grandone
Maurizio
M
Margaglione
D000328:Adult; D041321:Chromosomes, Human, X / Q000235:genetics*; D005260:Female; D005333:Fetus / Q000502:physiology*; D005819:Genetic Markers; D005838:Genotype; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012732:Sex Determination Analysis / Q000379:methods*
D005819:Genetic Markers