Prenatal screening of single-gene disorders from maternal blood

Biochemical parameters, dynamic tensiometry and circulating nucleic acids for cattle blood analysis: a review

The animal’s blood is the most complicated and important biological liquid for veterinary medicine. In addition to standard methods that are always in use, recent technologies such as dynamic tensiometry (DT) of blood serum and PCR analysis of particular markers are in progress. The standard and modern biochemical tests are commonly used for general screening and, finally, complete diagnosis of animal health. Interpretation of major biochemical parameters is similar across animal species, but there are a few peculiarities in each case, especially well-known for cattle. The following directions are discussed here: hematological indicators; “total protein” and its fractions; some enzymes; major low-molecular metabolites (glucose, lipids, bilirubin, etc.); cations and anions. As example, the numerous correlations between DT data and biochemical parameters of cattle serum have been obtained and discussed. Changes in the cell-free nucleic acids (cfDNA) circulating in the blood have been studied and analyzed in a variety of conditions; for example, pregnancy, infectious and chronic diseases, and cancer. CfDNA can easily be detected using standard molecular biological techniques like DNA amplification and next-generation sequencing. The application of digital PCR even allows exact quantification of copy number variations which are for example important in prenatal diagnosis of chromosomal aberrations.

Postnatal and non-invasive prenatal detection of β-thalassemia mutations based on Taqman genotyping assays

The β-thalassemias are genetic disorder caused by more than 200 mutations in the β-globin gene, resulting in a total (β⁰) or partial (β⁺) deficit of the globin chain synthesis. The most frequent Mediterranean mutations for β-thalassemia are: β⁰39, β⁺IVSI-110, β⁺IVSI-6 and β⁰IVSI-1. Several molecular techniques for the detection of point mutations have been developed based on the amplification of the DNA target by polymerase chain reaction (PCR), but they could be labor-intensive and technically demanding. On the contrary, TaqMan^® genotyping assays are a simple, sensitive and versatile method suitable for the single nucleotide polymorphism (SNP) genotyping affecting the human β-globin gene. Four TaqMan^® genotyping assays for the most common β-thalassemia mutations present in the Mediterranean area were designed and validated for the genotype characterization of genomic DNA extracted from 94 subjects comprising 25 healthy donors, 33 healthy carriers and 36 β-thalassemia patients. In addition, 15 specimens at late gestation (21–39 gestational weeks) and 11 at early gestation (5–18 gestational weeks) were collected from pregnant women, and circulating cell-free fetal DNAs were extracted and analyzed with these four genotyping assays. We developed four simple, inexpensive and versatile genotyping assays for the postnatal and prenatal identification of the thalassemia mutations β⁰39, β⁺IVSI-110, β⁺IVSI-6, β⁰IVSI-1. These genotyping assays are able to detect paternally inherited point mutations in the fetus and could be efficiently employed for non-invasive prenatal diagnosis of β-globin gene mutations, starting from the 9^th gestational week.

Cell-free nucleic acids as non-invasive biomarkers of gynecological cancers, ovarian, endometrial and obstetric disorders and fetal aneuploidy

BACKGROUND

Proper folliculogenesis is fundamental to obtain a competent oocyte that, once fertilized, can support the acquisition of embryo developmental competence and pregnancy. MicroRNAs (miRNAs) are crucial regulators of folliculogenesis, which are expressed in the cumulus-oocyte complex and in granulosa cells and some can also be found in the bloodstream. These circulating miRNAs are intensively studied and used as diagnostic/prognostic markers of many diseases, including gynecological and pregnancy disorders. In addition, serum contains small amounts of cell-free DNA (cfDNA), presumably resulting from the release of genetic material from apoptotic/necrotic cells. The quantification of nucleic acids in serum samples could be used as a diagnostic tool for female infertility.

METHODS

An overview of the published literature on miRNAs, and particularly on the use of circulating miRNAs and cfDNA as non-invasive biomarkers of gynecological diseases, was performed (up to January 2014).

RESULTS

In the past decade, cell-free nucleic acids have been studied for potential use as biomarkers in many diseases, particularly in gynecological cancers, ovarian and endometrial disorders, as well as in pregnancy-related pathologies and fetal aneuploidy. The data strongly suggest that the concentration of cell-free nucleic acids in serum from IVF patients or in embryo culture medium could be related to the ovarian hormone status and embryo quality, respectively, and be used as a non-invasive biomarker of IVF outcome.

CONCLUSIONS

The profiling of circulating nucleic acids, such as miRNAs and cfDNA, opens new perspectives for the diagnosis/prognosis of ovarian disorders and for the prediction of IVF outcomes, namely (embryo quality and pregnancy).

Use of cell-free fetal nucleic acids in maternal blood for prenatal diagnosis: the reality of this scenario in Brazil

The discovery of cell-free fetal nucleic acids in the plasma of pregnant women has allowed the development of new, noninvasive prenatal diagnostic tests for the determination of fetal gender and Rh. These tests have been implemented in the public health system in several countries of Europe for over five years. The new possibilities for diagnostic use of these technologies are the detection of fetal chromosomal aneuploidies, monogenic fetal disorders, and placental-related disorders, subjects that have been intensively studied by several groups around the world. The aim of this review was to assess the Brazilian research and clinical scenarios regarding the utilization of commercially available tests that use these plasma markers, stressing the advantages, both economic and safety-related, that non-invasive tests have when compared to those currently used in the Brazilian public health system.

Improvement in strategies for the non-invasive prenatal diagnosis of Huntington disease

PURPOSE

We focused on the improvements of prenatal diagnosis by the analysis of DNA from maternal plasma, using Huntington disease as a model of disease.

METHODS

We studied plasma from a pregnancy at risk of having a fetus affected with Huntington disease by the use of two direct analysis of the mutation and polymorphic STRs.

RESULTS

Direct methods were not informative. Analysis with STRs revealed the presence of the allele that does not co-segregate with the disease, thus the fetus was healthy.

CONCLUSIONS

This strategy is very useful to face complex cases when the direct study is not informative not only for Huntington disease but also for many other disorders.

Analysis of fetal DNA from maternal peripheral blood by lectin-polymerase chain reaction-single strand conformation polymorphism

Fetal nucleated cells in maternal peripheral blood are a non-invasive source of fetal DNA for prenatal genetic diagnosis. However, the number of fetal cells present in maternal peripheral blood is very small. Therefore, fetal cell enrichment is generally considered necessary to allow detection and subsequent genetic analysis of the rare fetal cells. In the study presented here, we performed fetal cell separation from maternal blood using galactose-specific lectin to concentrate fetal nucleated red blood cells (FNRBCs), and attempted paternal diagnosis using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP). Fetal cell separation was performed using galactose-specific lectin on a PV-MeA coated slide. Twenty cells consisting of an NRBC and its surrounding 19 maternal cells were collected using laser microdissection for stable DNA amplification. DNA analysis was performed using three sequence tagged site markers (D13S270, D17S5, and D18S474) by PCR-SSCP. All seven cases were informative because they showed heterozygosity at least one locus in D13S270, D17S5, or D18S474, and paternal-specific bands were detected in all cases. These results suggest that our proposed lectin-laser-micromanipulation-PCR-SSCP method may contribute to the development of prenatal diagnosis.

Non-invasive prenatal diagnosis: on the horizon?

The launch of the genomics and postgenomics era has greatly expanded our understanding of the genetic basis of many diseases. In conjunction with the sociocultural trend to delay childbirth and to maintain smaller family units, extra demand may be placed on the existing prenatal diagnostic services. The inherent risk of fetal loss associated with current prenatal diagnostic procedures, such as amniocentesis and chorionic villus sampling, has spurred research into non-invasive prenatal diagnosis. Much research has been conducted on the exploitation of fetal genetic material present in the maternal circulation. The initial focus was on the isolation of intact fetal cells and subsequently, the existence of extracellular fetal DNA in maternal plasma was realized. Exciting developments have been achieved in recent years. A large-scale trial to evaluate the clinical utility of fetal cell isolation from maternal blood for fetal aneuploidy diagnosis was launched and data were recently published. Much has taken place in the research of fetal DNA analysis in maternal plasma and in one example, namely prenatal RhD determination, this type of analysis has been used in the clinical setting. This paper reviews the technological developments in non-invasive prenatal diagnosis.

Molecular diagnosis of CYP21 mutations in congenital adrenal hyperplasia: implications for genetic counseling

Congenital adrenal hyperplasia (CAH) is an inherited disorder of steroid biosynthesis most often attributable to mutations in CYP21 (also termed CYP21A2) encoding the active steroid 21-hydroxylase enzyme. This review focuses on clinical and genetic aspects of CAH, and updates the reader on current methodology and applications for molecular genetic diagnosis. Genotyping patients with CAH has revealed > 50 mutations within CYP21, yet only 10 mutations account for approximately 95% of affected alleles. Many CYP21 mutations are gene conversions arising via transfer of gene sequences between the non-functional CYP21 pseudogene and CYP21. Phenotype is generally well-correlated with genotype. Historically, CAH has been divided into 3 types of disease: classic salt-wasting, classic simple virilizing (non-salt-wasting), and nonclassic. Recent findings support the notion that rather than discrete phenotypic categories, CAH is better represented as a continuum of phenotypes, from severe to mild. Molecular genetic diagnosis is most effectively employed now in prenatal diagnosis of classic CAH. As newborn screening for CAH becomes more widespread, genotyping may be implemented to resolve diagnostic difficulties encountered with hormonal testing. As automated methods of DNA diagnosis such as microarrays or gene chips are refined, it is likely that genetic screening will become less expensive and more readily available. The clinician should be aware of the potential for both false negatives and false positives with PCR-based gene screening. In short, whereas molecular genetic diagnosis is a valuable tool, it cannot replace clinical acumen and hormonal assays.