BACKGROUND: Information about the appearance of gamma-, epsilon-, and zeta-globin mRNAs in fetal erythroblasts during gestation and about the presence and amounts of these mRNAs in pregnant and nonpregnant women is important from the perspective of using these molecules as a marker of fetal erythroblasts. A specific marker is necessary for isolation and identification of fetal nucleated red blood cells from maternal blood samples for use in antenatal diagnosis of fetal genetic or chromosomal abnormalities.

METHODS: We used a very sensitive reverse transcription-PCR (RT-PCR) method, coamplification analysis of gamma- and epsilon-globin cDNA, and quantitative analysis of gamma-globin mRNA based on competitive RT-PCR to investigate these aspects.

RESULTS: All adult whole-blood samples were negative for epsilon- and zeta-globin mRNA. Analyses of CD71(+) cell fractions showed that specimens from 19 of 20 nonpregnant and 10 of 14 pregnant women (at 9-13 weeks of gestation) were positive for gamma-globin mRNA (Fisher's exact test, P = 0.13), and those from 3 of 20 nonpregnant and 5 of 14 pregnant women were positive for zeta-globin mRNA (Fisher's exact test, P = 0.23). No epsilon-globin mRNA was detected in CD71(+) cell fractions from 1-mL blood samples from adults. CD71(+) cell fractions from eight fetal blood samples (at 17-20 weeks of gestation) were positive for all three globin mRNAs. We found no statistically significant difference between the amounts of gamma-globin mRNA in pregnant and nonpregnant women.

CONCLUSIONS: This study indicates that epsilon-globin mRNA might function as a marker for fetal CD71(+) cells early in pregnancy. Although gamma-globin mRNA can be detected in CD71(+) cell fractions from most adults, these transcripts also may be of use because of a marked difference between adult and fetal values.