Non-invasive prenatal diagnosis of fetal trisomy 21 using cell-free fetal DNA in maternal blood

Since the existence of cell-free fetal DNA (cff-DNA) in maternal circulation was discovered, it has been identified as a promising source of fetal genetic material in the development of reliable methods for non-invasive prenatal diagnosis (NIPD) of fetal trisomy 21 (T21). Currently, a prenatal diagnosis of fetal T21 is achieved through invasive techniques, such as chorionic villus sampling or amniocentesis. However, such invasive diagnostic tests are expensive, require expert technicians, and have a miscarriage risk approximately 1%. Therefore, NIPD using cff-DNA in the detection of fetal T21 is significant in prenatal care. Recently, the application of new techniques using single-molecular counting methods and the development of fetal-specific epigenetic markers has opened up new possibilities in the NIPD of fetal T21 using cff-DNA. These new technologies will facilitate safer, more sensitive and accurate prenatal tests in the near future. In this review, we investigate the recent methods for the NIPD of fetal T21 and discuss their implications in future clinical practice.

4-hydroxy-2(E)-Nonenal facilitates NMDA-Induced Neurotoxicity via Triggering Mitochondrial Permeability Transition Pore Opening and Mitochondrial Calcium Overload

N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity is one of the major causes for neuronal cell death during cerebral ischemic insult. Previously, we reported that the final product of lipid membrane peroxidation 4-hydroxy-2E-nonenal (HNE) synergistically increased NMDA receptor-mediated excitotoxicity (J Neurochem., 2006). In this study, we investigated the mechanism involved in the synergistic neuronal cell death induced by co-treatment with HNE and NMDA. Although neither HNE (1 microM) nor NMDA (2 microM) alone induced the death of cortical neurons, simultaneous treatment of neuronal cells with HNE and NMDA synergistically evoked the death of the cells. However, the synergistic effect on neuronal death was observed only in the presence of calcium. HNE neither increased the cytosolic calcium level ([Ca2+]i) nor altered the NMDA-induced intracellular calcium influx. However, HNE together with NMDA elevated the mitochondrial calcium level and depolarized the mitochondrial transmembrane potential. Furthermore, HNE evoked damage of isolated mitochondria at the cytosolic calcium level (200 nM), which is maximally induced by 2 microM NMDA. Consistently, ATP was depleted in neurons when treated with both HNE and NMDA together. Ciclopirox, a potent inhibitor of mitochondrial permeability transition pore opening (Br. J. Pharmacol., 2005), largely prevented the synergistic damage of mitochondria and death of cortical neurons. Therefore, although low concentrations of HNE and NMDA cannot individually induce neuronal cell death, they can evoke the neuronal cell death by synergistically accelerating mitochondrial dysfunction.

Noninvasive Prenatal Diagnosis Using Cell-free Fetal Nucleic Acids in the Maternal Circulation / 대한주산의학회잡지

Cell-free fetal nucleic acids in the maternal circulation can be broadly divided into fetal DNA and RNA that originate from apoptotic placenta cells. Cell-free fetal nucleic acids can be detected from 4-5 weeks gestation and are undetectable in the maternal circulation after delivery. Therefore, cell-free fetal nucleic acids have been proposed as a potential material for non-invasive prenatal diagnosis (NIPD), which poses no risk to mother and child. The clinical applications of this technology fall into three categories: first, early sex determination in cases at high risk of X-linked disorders or congenital adrenal hyperplasia requiring follow-up testing or antenatal treatment; second, detection of specific paternally inherited monogenic diseases in families with high genetic risk; and third, routine antenatal care offered to all pregnant women, including prenatal screening/diagnosis of aneuploidy, particularly Down syndrome. Fetal sex determination is already performed in routine clinical care for high-risk individuals in some countries. Many researchers have explored the possibility of cell-free fetal nucleic acids on NIPD of monogenic diseases and aneuploidy. Promising results have been reported from studies using the combination of markers and the application of various experimental methods. Although these technologies can raise ethical, social, and legal concerns, a reliable noninvasive test using cell-free fetal nucleic acids may in future form a part of national antenatal programs for detection of Down syndrome and other common genetic disorders.

Genetic Polymorphism in Corticotropin-releasing Hormone Receptor Type-1 in Preeclamptic Korean Women

PURPOSE: Placental corticotropin-releasing hormone receptor type 1 (CRHR1) expression is reduced in pregnancies with abnormal placental function such as preeclampsia (PE), and the levels and/or function of CRHR1 are genetically influenced. The aim of this study was to investigate the association between the c.33+8199C>T polymorphism in the CRHR1 gene and PE in a Korean population. MATERIALS AND METHODS: Using a case-control design, the association between the CRHR1 polymorphism and the risk of PE was investigated in 203 individuals with PE and 211 normotensive controls. Genotypes were determined using a SNapShot kit and an ABI Prism 3100 Genetic analyzer. RESULTS: Genotypes and allele frequencies for the CRHR1 polymorphism did not differ between PE and normotensive pregnancies. The variant T allele was more frequent than the ancestral C allele in both of the groups and was more frequent in the controls than in the cases. In risk analysis for PE, there was not an increased risk of preeclampsia in subjects who were concomitant homozygous rare allele genotypes (CC) (OR, 0.3; P=0.15) or heterozygous rare allele genotypes (TC) (OR, 0.8; P=0.29). There were no differences in the complications of PE such as severity or preterm delivery in patients with the CRHR1 polymorphism. CONCLUSION: Our findings indicate that the CRHR1 polymorphism was not associated with PE in the present Korean study group.

Effective Method for Extraction of Cell-Free DNA from Maternal Plasma for Non-Invasive First-Trimester Fetal Gender Determination: A Preliminary Study

PURPOSE: To find the most effective method for extraction of cell-free DNA (cf-DNA) from maternal plasma, we compared a blood DNA extraction system (blood kit) and a viral DNA extraction system (viral kit) for non-invasive first-trimester fetal gender determination. MATERIALS AND METHODS: A prospective cohort study was conducted with maternal plasma collected from 44 women in the first-trimester of pregnancy. The cf-DNA was extracted from maternal plasma using a blood kit and a viral kit. Quantitative fluorescent-polymerase chain reaction (QF-PCR) was used to detect the SRY gene and AMEL gene. The diagnostic accuracy of the QF-PCR results was determined based on comparison with the final delivery records. RESULTS: A total of 44 women were tested, but the final delivery record was only obtained in 36 cases which included 16 male-bearing and 20 female-bearing pregnancies. For the blood kit and viral kit, the diagnostic accuracies for fetal gender determination were 63.9% (23/36) and 97.2% (35/36), respectively. CONCLUSION: In non-invasive first-trimester fetal gender determination by QF-PCR, using a viral kit for extraction of cf-DNA may result in a higher diagnostic accuracy.

Tumor Necrosis Factor-alpha Gene Polymorphism (C-850T) in Korean Patients with Preeclampsia

PURPOSE: Preeclampsia is a multisystem human pregnancy-specific disorder. The pathophysiology of preeclampsia is linked with over-stimulation of inflammatory cytokines by placental ischemia via reduced uterine perfusion pressure during pregnancy. Although an increase in tumor necrosis factor (TNF)-alpha has been reported in preeclamptic women, there is little evidence of a relationship between TNF-alpha gene variations and preeclampsia. In this study, we identified a single-nucleotide polymorphism (SNP), C-850T, in the TNF-alpha gene promoter region in Korean preeclamptic women and investigated the association between this SNP and the development of preeclampsia. MATERIALS AND METHODS: This polymorphism was analyzed in peripheral blood samples from 198 preeclamptic pregnancies and 194 normotensive pregnancies using a SNapShot kit and an ABI Prism 3100 Genetic analyzer. RESULTS: Genotypes and allele frequencies for C-850T did not differ between preeclamptic and normotensive pregnancies. The distributions of genotypes (CC, CT and TT) were 74.3%, 22.2% and 3.5%, respectively, in preeclamptic pregnancies, and 71.6%, 25.8% and 2.6%, respectively, in normotensive pregnancies. The frequencies of the C and T alleles were 0.85 and 0.15 in preeclamptic pregnancies and 0.84 and 0.16 in normotensive pregnancies, respectively. There was no increased risk of preeclampsia in subjects with the CT (OR, 0.83; P=0.44) or TT genotypes (OR, 1.32; P=0.64). CONCLUSION: We found no differences in the genotypes or allele frequencies of the TNF-alpha gene polymorphism between preeclamptic and normotensive pregnancies. This study suggests that the TNF-alpha gene polymorphism may be not associated with the development of preeclampsia in pregnant Korean women.

The Y153H Variant of the STOX1 Gene in Korean Patients with Preeclampsia

PURPOSE: Preeclampsia is a multifactorial disorder with genetic and environmental components. Recently, the STOX1 gene, identified as a candidate gene for preeclampsia in Dutch women, has been shown to be placentally expressed and subject to imprinting with preferential transmission of the maternal allele. The purpose of this study is to investigate whether there is an association between the STOX1 Y153H variation and preeclampsia in Korean pregnant women. MATERIALS AND METHODS: This study involved 202 preeclamptic and 204 healthy pregnant women who were genotyped for the Y153H variant of the STOX1 gene using a commercially available SNapShot assay kit and an ABI Prism 3730 DNA Analyzer. RESULTS: There were no significant differences in genotype frequencies of the Y153H variant of the STOX1 gene between preeclamptic patients and normal controls (P>0.05). The H allele frequency of the STOX1 Y153H variation was similar in patients with preeclampsia (87.1%) and in normal controls (86.5%). In addition, multiple logistic regression analysis showed that the YH, HH, and YH/HH genotypes were not associated with an increased risk of preeclampsia when compared to the YY genotype. CONCLUSION: This is the first study to characterize the Y153H variant of the STOX1 gene in Korean patients with preeclampsia. We found no differences in the genotype and allele frequencies between preeclamptic and normal pregnancies. Although limited by a relatively small sample size, our study suggests that the STOX1 Y153H variation is not associated with the development of preeclampsia in Korean pregnant women.

Intercellular Adhesion Molecule-1 Gene Polymorphism (K469E) in Korean Preeclamptic Women

PURPOSE: Preecalmpsia is a pregnancy-specific disorder that reflects widespread endothelial dysfunction resulting from increases of adhesion molecule expression. Intercellular adhesion molecule-1 (ICAM-1) is involved in the pathogenetic mechanisms responsible for preeclampsia, and ICAM-1 plasma levels and/or function is genetically influenced. Therefore, we evaluated the distribution of ICAM-1 gene K469E polymorphism in pregnant Korean women with preeclampsia and evaluated the association between this polymorphism and preeclampsia. METHODS: The K469E polymorphism was analyzed in peripheral blood samples from 197 preeclamptic pregnancies and 193 normotensive pregnancies by a SNapShot kit and an ABI Prism 3100 Genetic analyzer. RESULTS: Genotypic and allelic frequencies of ICAM-1 gene polymorphism (K469E) did not differ between preeclamptic and normotensive pregnancies. The distributions of the KK, KE, and EE genotypes were 40.6%, 43.7%, and 15.7%, respectively, in preeclamptic pregnancies and 38.9%, 45.1%, and 16.1%, respectively, in normotensive pregnancies. The frequencies of K and E alleles were 0.62 and 0.38, respectively, in preeclamptic pregnancies and 0.61 and 0.39, respectively, in normotensive pregnancies. By multiple logistic regression analysis, there was no increased risk of preeclampsia in subjects with ICAM-1 KE (OR, 1.08; P=0.74) or EE (OR, 1.07; P=0.88) genotypes. CONCLUSION: This study suggests that the ICAM-1 gene K469E polymorphism does not associate with an increased risk of preeclampsia in pregnant Korean women.

No association between endothelin-1 gene polymorphisms and preeclampsia in Korean population

PURPOSE: Preeclampsia is a major cause of maternal and perinatal mortality and morbidity and is considered to be a multifactorial disorder involving a genetic predisposition and environmental factors. Endothelin-1 (ET-1) is a potent vasoconstrictor peptide, and alterations in the ET-1 system are thought to play a role in triggering the vasoconstriction seen with preeclampsia. The aim of this study was to examine the frequency of the 4 common single-nucleotide polymorphisms (SNPs) (c.1370T>G, c.137_139delinsA, c.3539+2T>C, and c.5665G>T) of the ET-1 gene in normotensive and preeclamptic pregnancies and to investigate whether these SNPs are associated with preeclampsia in pregnant Korean women. METHODS: We analyzed blood samples from 206 preeclamptic and 216 normotensive pregnancies using a commercially available SNapShot kit and an ABI Prism 3100 Genetic analyzer. RESULTS: There were no significant differences in genotype or allele frequencies of the 4 SNPs in the ET-1 gene between preeclamptic and normotensive pregnancies. The respective frequencies of the 3 haplotypes (TDTG, GDCT, and TICT; >10% haplotype frequency) were 61%, 13% and 13%, respectively, in preeclampsic pregnancies and 62%, 14% and 12%, respectively, in normotensive pregnancies. The frequencies of these haplotypes were similar for both groups. Using multiple logistic regression analysis, we did not observe an increase in the risk of preeclampsia for the 4 SNPs of the ET-1 gene under either a recessive or dominant model. CONCLUSION: This study suggests that the 4 SNPs of the ET-1 gene are not associated with an increased risk for preeclampsia in pregnant Korean women.

The association between polymorphisms of beta-adrenoceptors and preeclampsia

PURPOSE: The beta-adrenoceptors are pharmacologically classified into beta1-, beta2- and beta3-adrenoceptor. The gene of each subtype has polymorphisms related to their function (beta1-adrenoceptor: Ser49Gly, beta2- adrenoceptor: Gln27Glu, beta3-adrenoceptor: Trp64Arg). The objectives of this study were to analyse the allelic and genotypic distribution of the representative polymorphism of beta-adrenoceptors in preeclampsia and to investigate whether combined genotype of beta-adrenoceptors may be associated with preeclampsia. METHODS: Blood samples were collected from a Korean population (159 preeclamptic pregnancies and 168 normotensive pregnancies). The beta1-, beta2- and beta3-adrenoceptor genotypes was determined using polymerase chain reaction-restriction fragment length polymorphism. RESULTS: There were no differences in allelic and genotypic distribution of beta1- and beta2-adrenoceptor polymorphisms between the two groups. However, the Arg allele of beta3-adrenoceptor polymorphism were more frequent in preecalmpsia than in controls (P<0.05, OR=1.57, 95% CI=1.01-2.46). Moreover, prevalence of genotype carrying heterozygote of beta3-adrenoceptor polymorphism was increased in preeclampsia compared with controls (P<0.05, OR 1.76, 95% CI 1.06-2.92). When combination of the three polymorphisms were evaluated, pregnancies with the particular combined genotype that is consisted of heterozygote of beta1-, beta3-adrenoceptor and wild homozygote of beta2-adrenoceptor (Ser/Gly, Gln/Gln, Trp/Arg), showed a significant increase in the risk of preeclampsia (P<0.05, OR=3.01, 95% CI 1.12-8.08). CONCLUSION: A particular combined genotype (Ser/Gly, Gln/Gln, Trp/Arg) of - adrenoceptors was associated with the risk of preeclampsia.