Numerous erythroblasts in maternal blood are impervious to fluorescent in situ hybridization analysis, a feature related to a dense compact nucleus with apoptotic character.
OBJECTIVE
The analysis by fluorescence in situ hybridization (FISH) of fetal erythroblasts enriched from maternal blood remains an attractive alternative for risk-free prenatal diagnosis of aneuploidies. However, current results are discouraging because of the low levels of sensitivity or the inability to detect fetal erythroblasts by FISH.


METHODS
Erythroblasts were enriched from 35 maternal blood samples by magnetic cell sorting (MACS), identified morphologically following May-Grünwald Giemsa staining and examined by FISH for chromosomes X, Y and 18.


RESULTS
We observed that circulating erythroblasts comprised two distinct groups: one was clearly of maternal origin and could be reliably analyzed by FISH, whereas the other, which appeared to be of fetal origin, was largely impervious to FISH analysis. This latter feature seemed to be related to an abnormally dense nucleus with an apoptotic character. Since the oxygen tension in the maternal circulation is higher than that in the fetus, we cultured fetal cord blood erythroblasts in conditions mimicking this difference in oxygen concentrations and found that high oxygen concentrations rapidly induced shrinkage of the erythroblast nucleus, rendering it impervious to FISH analysis.


CONCLUSIONS
Our data show that circulating erythroblasts of presumed fetal origin cannot be reliably analyzed by FISH because of an abnormally dense nucleus. This nuclear phenotype appears to be induced by the higher oxygen tension present in the maternal circulation than in fetal blood.
Babochkina
Tatiana
T
University Women's Hospital, Basel, Switzerland.
Mergenthaler
Susanne
S
De Napoli
Giuseppina
G
Hristoskova
Sashka
S
Tercanli
Sevgi
S
Holzgreve
Wolfgang
W
Hahn
Sinuhe
S
D000782:Aneuploidy; D017209:Apoptosis; D002467:Cell Nucleus / Q000378:metabolism*; D002469:Cell Separation; D004900:Erythroblasts / Q000166:cytology*; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D020287:In Situ Nick-End Labeling; D008297:Male; D018895:Microsatellite Repeats; D010100:Oxygen / Q000378:metabolism; D011247:Pregnancy; D011296:Prenatal Diagnosis
D010100:Oxygen