Fetal nucleated red blood cells in peripheral blood of pregnant women: detection and determination of location on a slide using laser-scanning cytometry

Efficiency of manual scanning in recovering rare cellular events identified by fluorescence in situ hybridization: simulation of the detection of fetal cells in maternal blood

Fluorescence in situ hybridization (FISH) and manual scanning is a widely used strategy for retrieving rare cellular events such as fetal cells in maternal blood. In order to determine the efficiency of these techniques in detection of rare cells, slides of XX cells with predefined numbers (1–10) of XY cells were prepared. Following FISH hybridization, the slides were scanned blindly for the presence of XY cells by different observers. The average detection efficiency was 84% (125/148). Evaluation of probe hybridization in the missed events showed that 9% (2/23) were not hybridized, 17% (4/23) were poorly hybridized, while the hybridization was adequate for the remaining 74% (17/23). In conclusion, manual scanning is a relatively efficient method to recover rare cellular events, but about 16% of the events are missed; therefore, the number of fetal cells per unit volume of maternal blood has probably been underestimated when using manual scanning.

Combined molecular genetic and cytogenetic analysis from single cells after isothermal whole-genome amplification

BACKGROUND

Analysis of chromosomal aberrations or single-gene disorders from rare fetal cells circulating in the blood of pregnant women requires verification of the cells' genomic identity. We have developed a method enabling multiple analyses at the single-cell level that combines verification of the genomic identity of microchimeric cells with molecular genetic and cytogenetic diagnosis.

METHODS

We used a model system of peripheral blood mononuclear cells spiked with a colon adenocarcinoma cell line and immunofluorescence staining for cytokeratin in combination with DNA staining with the nuclear dye TO-PRO-3 in a preliminary study to define candidate microchimeric (tumor) cells in Cytospin preparations. After laser microdissection, we performed low-volume on-chip isothermal whole-genome amplification (iWGA) of single and pooled cells.

RESULTS

DNA fingerprint analysis of iWGA aliquots permitted successful identification of all analyzed candidate microchimeric cell preparations (6 samples of pooled cells, 7 samples of single cells). Sequencing of 3 single-nucleotide polymorphisms was successful at the single-cell level for 20 of 32 allelic loci. Metaphase comparative genomic hybridization (mCGH) with iWGA products of single cells showed the gains and losses known to be present in the genomic DNA of the target cells.

CONCLUSIONS

This method may be instrumental in cell-based noninvasive prenatal diagnosis. Furthermore, the possibility to perform mCGH with amplified DNA from single cells offers a perspective for the analysis of nonmicrochimeric rare cells exhibiting genomic alterations, such as circulating tumor cells.

Enrichment of nuclear red blood cells by membrane KCC transporter with urea intervention

Intervention by membrane KCC transporter interfering selectively could promote about 5 times enrichment of nuclear red blood cells.

Noninvasive prenatal diagnosis of fetal aneuploidies and Mendelian disorders: new innovative strategies

The application of recent technical developments, such as digital PCR or shot-gun sequencing, for the analysis of cell-free fetal DNA, have indicated that the long-sought goal of the noninvasive detection of Down syndrome may finally be attained. Although these methods are still cumbersome and not high throughput, they provide a paradigm shift in prenatal diagnosis, as they could effectively pronounce the end of invasive procedures, such as amniocentesis or chorionic villous sampling for the detection of such fetal anomalies. However, it remains to be determined how suitable these approaches are for the detection of more subtle fetal genetic alterations, such as those involved in hereditary Mendelian disorders (e.g., thalassemia and cystic fibrosis). New technical developments, such as microfluidics and reliable automated scanning microscopes, have indicated that it may be possible to efficiently retrieve and examine circulating fetal cells. As these contain the entire genomic complement of the fetus, future developments may include the noninvasive determination of the fetal karyotype.

Light-scattering spectroscopy differentiates fetal from adult nucleated red blood cells: may lead to noninvasive prenatal diagnosis

Present techniques for prenatal diagnosis are invasive and present significant risks of fetal loss. Noninvasive prenatal diagnosis utilizing fetal nucleated red blood cells (fNRBC) circulating in maternal peripheral blood has received attention, since it poses no risk to the fetus. However, because of the failure to find broadly applicable identifiers that can differentiate fetal from adult NRBC, reliable detection of viable fNRBC in amounts sufficient for clinical use remains a challenge. In this Letter we show that fNRBC light-scattering spectroscopic signatures may lead to a clinically useful method of minimally invasive prenatal genetic testing.

Prenatal diagnosis: update on invasive versus noninvasive fetal diagnostic testing from maternal blood

The modern obstetrics care includes noninvasive prenatal diagnosis testing such as first trimester screening performed between 11 and 14 weeks' gestation and second trimester screening performed between 15 and 20 weeks. In these screening tests, biochemical markers are measured in the maternal blood with or without ultrasound for fetal nuchal translucency with reported accuracy of up to 90%. Invasive procedures, including amniocentesis or chorionic villi sampling, are used to achieve over 99% accuracy. During these procedures direct fetal material is examined and, therefore, these tests are highly accurate with the caveat of a small risk for pregnancy loss. Much research now focuses on other noninvasive highly accurate and risk-free tests that will identify fetal material in the maternal blood. Fetal cells and fetal DNA/RNA provide fetal information but are hard to find in an overwhelming background of maternal cells and in the absence of specific fetal cell markers. The most experience has been accumulated with fetal rhesus and fetal sex determination from maternal blood, with an accuracy of up to 100% by using gene sequences that are absent from maternal blood. Although not clinically applicable yet, fetal cells, fetal DNA/RNA and fetal proteomics in combination with cutting edge technology are described to prenatally diagnose aneuploidies and single-gene disorders.

Post-genomics studies and their application to non-invasive prenatal diagnosis

Non-invasive prenatal diagnosis (NIPD) offers the opportunity to eliminate completely the risky procedures of amniocentesis and chorionic villus sampling. The development of NIPD tests has largely centred around the isolation and analysis of fetal cells in the maternal circulation and the analysis of free fetal DNA in maternal plasma. Both of these techniques offer difficult technical challenges, and at the current moment in time the use of free fetal DNA is the simplest and most effective method of defining paternally inherited fetal genes for diagnosis. Post-genomics technologies that explore the proteins (proteomics) and transcripts (transcriptomics) released by the placenta into the maternal circulation offer new opportunities to identify genes and their protein products that are key diagnostic markers of disease (in particular Down syndrome), and might replace the current screening markers in use for prediction of risk of Down syndrome. In the ideal situation, these markers are sufficiently diagnostic not to require invasive sampling of fetal genetic material. Post-genomics techniques might also offer better opportunities for defining fetal cell-specific markers that might enhance their isolation from maternal blood samples. This review describes progress in these studies, particularly those funded by the Special Non-invasive Advances in Fetal and Neonatal Evaluation (SAFE) Network of Excellence.

Accurate Diagnosis of a Homozygous G1138A Mutation in the Fibroblast Growth Factor Receptor 3 Gene Responsible for Achondroplasia

Achondroplasia is the most common genetic form of dwarfism inherited as an autosomal dominant disorder. Individuals affected with achondroplasia have impaired ability to form bone from cartilage (endochondral bone formation). Homozygous achondroplasia is a neonatal lethal condition. The vast majority of patients with achondroplasia have a G-to-A transition at position 1138 of the fibroblast growth factor receptor 3 (FGFR3) cDNA sequence, resulting in the Gly-to-Arg substitution at position 380 of the FGFR3 protein. This mutation has been diagnosed by SfcI digestion of amplified genomic DNA. However, it has also been demonstrated that the SfcI digestion protocol does not consistently distinguish between DNA samples heterozygous and homozygous for the G1138A substitution. This study was designed to improve the molecular diagnosis based on the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques for the FGFR3 G1138A mutation. The newly designed forward primer contains one mismatch (G at position 1136) from the FGFR3 cDNA sequence (A at position 1136), thereby creating a PstI site (CTGCAG at positions 1134 to 1139) in the amplified DNA from alleles containing the G1138A mutation. The PCR-RFLP technique based on the PstI digestion of amplified genomic DNA with a novel forward primer shows 100% accuracy in diagnosis of the G1138A mutation in heterozygous and homozygous individuals.

Slide-based cytometry and predictive medicine: The 8th Leipziger workshop and the 1st international workshop on slide-based cytometry

Slide-based cytometry (SBC) and related techniques offer unique tools to perform complex diagnostic procedures at very early disease stages. Multicolor or polychromatic analysis of cells by SBC is of special importance, not only as a cytomics technology platform, but for patients with low blood volume such as neonates. The exact knowledge of the location of each cell on the slide allows the specimen to be restained and subsequently reanalyzed. These separate measurements can be fused to one data file (merging), increasing the information obtained per cell. Relocalization and optical evaluation of the cells, a typical feature of SBC, can be of integral importance for cytometric analysis. Predictive medicine is aimed at the detection of changes in the patient's state prior to the manifestation of deterioration or improvement. Such instances are concerned with multiorgan failure in sepsis or noninfectious posttraumatic shock in intensive care patients, or the pretherapeutic identification of high risk patients in cancer cytostatic therapy. Early anti-infectious or anti-shock therapy, as well as curative chemotherapy in combination with stem cell transplantation, may provide better survival chances for the patient as well as concomitant cost containment. Predictive medicine-guided, individualized, early reduction or cessation of therapy may lower or abrogate potential therapeutic side effects (individualized medicine). With the 8th Leipziger Workshop and the 1st International Workshop on Slide-Based Cytometry, cytomics technologies moved to more practical applications in the clinics and the clinical laboratory. This development will be continued in 2004, at the upcoming Leipziger Workshop and the International Workshop on Slide-Based Cytometry.

Fetal cells and DNA in maternal blood

Although fetal cells have been known to escape to the maternal circulation for a number of years, research attempts to use them for prenatal diagnosis have not had any consistent success. This review attempts to trace the history of such attempts and to document their progress and reasons for success or failure. The opinions of recent conferences including that of the US National Institute of Child Health and Human Development, a sponsor of major US research in the field, are reported and discussed. It is concluded that although basic work has demonstrated the biologic availability of both fetal cells and their free DNA representatives in the maternal circulation at gestational ages relevant to prenatal diagnosis, much work remains to develop practical technology for their consistent recovery and assay.