Stability of nucleosomal DNA fragments in serum.

in plasma and showed that filterable GAPDH mRNA species are present, and therefore likely to be particle bound, whereas the majority of ␤-globin DNA is not filterable and thus is not particle bound. Our study analyzed cell-free nucleic acids in amniotic fluid for the presence of particle-associated mRNA species , and like Ng et al. (7), we found the greatest decrease in GAPDH mRNA after filtration through a 0.22 ␮m filter, whereas filtration did not significantly reduce the amount of cell-free ␤-globin DNA present. Additionally, this study evaluated the difference in amounts of nucleic acids present in whole amniotic fluid containing cells and the cell-free fraction. Much more ␤-globin DNA could be isolated from whole amniotic fluid than from the cell-free fraction, but there was no statistically significant difference in the amount of GAPDH mRNA that could be isolated from the two fractions. This study demonstrates similar properties of cell-free nucleic acids in amniotic fluid and in plasma. Ng et al. (7) suggested that circulating DNA and RNA in plasma are both protected from degradation by associated particles, but the non-particle–associated form of DNA is less efficiently degraded than the non-particle–associated form of RNA and thus is present in much greater quantities relative to the particle-associated form. We extend this hypothesis to the properties of cell-free nucleic acids in amniotic fluid. These data suggest that in different body fluids, there is a universal mechanism of cell-free nucleic acid processing, possibly via packaging during apoptosis. To our knowledge, this is the first study to evaluate the properties of cell-free mRNA in amniotic fluid. We have also studied fetal gene expression in amniotic fluid (12). More research is needed to further evaluate the origin and kinetics of cell-free nucleic acids in amniotic fluid as this material has significant clinical potential for the study of health and development in living fetuses. of cell-free Epstein-Barr virus associated RNA in the plasma of patients with nasopharyngeal carcinoma. Detection of epithelial messenger RNA in the plasma of breast cancer patients is associated with poor prognosis tumor characteristics. Real-time quantification in plasma of human telomerase reverse transcrip-tase (hTERT) mRNA: a simple blood test to monitor disease in cancer patients. Plasma gamma-globin gene expression suggests that fetal hematopoietic cells contribute to the pool of circulating cell-free fetal nucleic acids during pregnancy. Global gene expression analysis of the living human fetus using amniotic fluid: a feasibility study. Circulating cell-free …