Procoagulant Activity in Amniotic Fluid Is Associated with Fetal-Derived Extracellular Vesicles

Procoagulant activity in amniotic fluid (AF) is positively correlated with phosphatidylserine (PS) and tissue factor (TF)-expressing(+) extracellular vesicles (EVs). However, it is unknown if pathological fetal conditions may affect the composition, phenotype, and procoagulant potency of EVs in AF. We sought to evaluate EV-dependent procoagulant activity in AF from pregnant people with fetuses with or without diagnosed chromosomal mutations. AF samples were collected by transabdominal amniocentesis and assessed for common karyotype defects (total n = 11, 7 healthy and 4 abnormal karyotypes). The procoagulant activity of AF was tested using a fibrin generation assay with normal pooled plasma and plasmas deficient in factors XII, XI, IX, X, V, and VII. EV number and phenotype were determined by flow cytometry with anti-CD24 and anti-TF antibodies. We report that factor-VII-, X-, or V-deficient plasmas did not form fibrin clots in the presence of AF. Clotting time was significantly attenuated in AF samples with chromosomal mutations. In addition, CD24+, TF+, and CD24+ TF+ EV counts were significantly lower in this group. Finally, we found a significant correlation between EV counts and the clotting time induced by AF. In conclusion, we show that AF samples with chromosomal mutations had fewer fetal-derived CD24-bearing and TF-bearing EVs, which resulted in diminished procoagulant potency. This suggests that fetal-derived EVs are the predominant source of procoagulant activity in AF.

In silico size selection is effective in reducing false positive NIPS cases of monosomy X that are due to maternal mosaic monosomy X

OBJECTIVES

The aim of this study was to establish maternal contribution to false positive noninvasive prenatal DNA screening (NIPS) results and develop the method to distinguish maternal and fetal origin of high-risk monosomy X NIPS calls including mosaic maternal cases.

METHOD

A total of 906 women carrying singleton pregnancies have been recruited. Maternal plasma DNA semiconductor massive parallel sequencing was performed to detect common aneuploidies. For the case of high monosomy X risk call, analysis method to distinguish fetal and maternal monosomy X has been additionally applied.

RESULTS

According to NIPS results, 18 patients had a high risk of fetal monosomy X. In 11 (61%) cases, fetal aneuploidy was confirmed by karyotyping. Other 7 cases were false positives. In 3 out of 7 cases, additional analysis based on in silico size selection was allowed to assume maternal monosomy X. In these cases, fluorescence in situ hybridization analysis confirmed mosaic monosomy X in maternal blood cells.

CONCLUSION

The prevalence of mosaic monosomy X karyotype is 0.3% (3/906)-10 times higher than published before. Additional in silico size-selection and data analysis increases PPV for monosomy X from 61% to 73% for studied population.

Two Novel Mutations Associated With Ataxia-Telangiectasia Identified Using an Ion AmpliSeq Inherited Disease Panel

Ataxia-telangiectasia (A-T), or Louis-Bar syndrome, is a rare neurodegenerative disorder associated with immunodeficiency. For families with at least one affected child, timely A-T genotyping during any subsequent pregnancy allows the parents to make an informed decision about whether to continue to term when the fetus is affected. Mutations in the ATM gene, which is 150 kb long, give rise to A-T; more than 600 pathogenic variants in ATM have been characterized since 1990 and new mutations continue to be discovered annually. Therefore, limiting genetic screening to previously known SNPs by PCR or hybridization with microarrays may not identify the specific pathogenic genotype in ATM for a given A-T family. However, recent developments in next-generation sequencing technology offer prompt high-throughput full-length sequencing of genomic fragments of interest. This allows the identification of the whole spectrum of mutations in a gene, including any novel ones. We report two A-T families with affected children and current pregnancies. Both families are consanguineous and originate from Caucasian regions of Russia and Azerbaijan. Before our study, no ATM mutations had been identified in the older children of these families. We used ion semiconductor sequencing and an Ion AmpliSeq™ Inherited Disease Panel to perform complete ATM gene sequencing in a single member of each family. Then we compared the experimentally determined genotype with the affected/normal phenotype distribution in the whole family to provide unambiguous evidence of pathogenic mutations responsible for A-T. A single novel SNP was allocated to each family. In the first case, we found a mononucleotide deletion, and in the second, a mononucleotide insertion. Both mutations lead to truncation of the ATM protein product. Identification of the pathogenic mutation in each family was performed in a timely fashion, allowing the fetuses to be tested and diagnosed. The parents chose to continue with both pregnancies as both fetuses had a healthy genotype and thus were not at risk of A-T.

[Value of early amniocentesis for prenatal diagnosis in the first trimester of pregnancy]

For the prenatal diagnosis of the fetal status, amniocentesis was performed in 9-12-week pregnancy in 31 females at risk for birth of a baby with chromosomal abnormalities and congenital malformations of the central nervous system. There were no difficulties in carrying out the procedure. A balanced translocation-bearing female was found to have a fetal chromosomal abnormality. Her pregnancy was interrupted at the 11th week; the prenatal diagnosis was evidenced by cytogenetic examination of the abortion specimen. The amniotic fluid alpha-fetoprotein estimated by radioimmunoassay ranged from 15-18 to 550-620 ng/ml. The findings suggest that early amniocentesis may be useful in the prenatal diagnosis of the fetal status and further evidence should be accumulated.

[Medical history of female carriers of chromosome aberrations]

The incidence of extragenital and gynecologic diseases, surgical procedures and menstrual, gestational and family histories have been evaluated in 50 female carriers of balanced chromosomal rearrangements (index group) and 33 women without karyotype abnormalities (control group). This study provided criteria for karyotype testing in women. Counseling guidelines were recommended for female carriage of chromosomal anomalies. These recommendations depend on karyotypic presentations of the anomalies in a carrier: alternatives are prenatal diagnosis of the fetal karyotype and adequate contraception (in robertsonian translocation involving homologous chromosomes).

[Artificial late abortion for medical genetic indications]

Late abortions have been induced for genetic indications in 96 women using intra-amniotic administration of 20% sodium chloride or Enzaprost. The results were compared within this group and with a control group of 90 women whose pregnancies were terminated for other indications at similar dates and with the same agents. The use of 20% sodium chloride was associated with significantly higher blood loss and greater lengths of abortions. Patterns and rates of complications were comparable in both groups. These data suggest a utility of 20% sodium chloride and, especially Enzaprost, in late pregnancy termination for genetic indications.

[Evaluation of diagnostic potential of various methods of chorionic sampling in the first trimester of pregnancy]

Potentials of the most common chorionic sampling methods have been examined: transcervical biopsy (TCB) (n-65), transcervical aspiration (TCA) (n-63) and transabdominal aspiration (TAA) (n-10). These procedures were done in outpatient settings at 6-12 week's gestation with sonographic guidance using accepted methodologies. TCB and TCA yielded 14.3 mg and 27.5 mg of a sample, respectively. The chorionic sample obtained with TAA was at best 3 mg. The incidence of successful chorionic sampling was 92.4% for TCB, 76.1% for TCA and 80.0% for TAA. Spontaneous abortions occurred after TAA (7.9%) and combined transcervical procedures (10%). These results suggest a potential of TCB and TCA in first-trimester prenatal diagnosis, but TCB has a number of advantages. TAA is a promising technique which, however, requires further sophistication.

Fetal skin biopsy in prenatal diagnosis of some genodermatoses

Various methods of obtaining fetal skin for prenatal diagnosis of certain autosomal-recessive congenital genodermatoses have been assessed. An attempt was made to obtain fetal skin by fetoscopy in 15 patients prior to pregnancy termination for a variety of medical reasons at 18-26 weeks. Specimens were obtained only in five cases (8 successful attempts out of 48). In twelve cases, of which five had a history of a child with junctional (Herlitz type) or dystrophic (Hallopeau-Siemens type) epidermolysis bullosa or non-bullous congenital ichthyosiform erythroderma at 16-25 weeks of pregnancy, fetal skin was obtained without fetoscopy under direct ultrasonic control. Specimens were obtained in all cases (33 successful attempts out of 39). In three cases, fetal pathology was diagnosed by the method of semi-thin and ultra-thin skin sections, and the respective pregnancies were terminated.

[The obstetrical aspects of amniocentesis and chorionic biopsy]

Threatened abortion, a history of operation or tumor-like masses of the uterus and adnexa were seen in 70 women who underwent amniocentesis or chorionic villus sampling for prenatal diagnosis. A control group comprised 40 women with similar obstetric risks who refused to have the invasive studies done. Evidence has been obtained to indicate that, with certain provisions, amniocentesis and chorionic villus sampling may be employed in situations which are regarded as contraindications.

[Prenatal diagnosis of several hereditary skin diseases]

Twenty-two control women and 5 women at risk for delivering a baby with Brocq's ichthyosiform erythroderma or fatal epidermolysis bullosa were investigated in order to make prenatal diagnosis of inherited fetal skin diseases. Fetal skin abnormalities were detected in 3 of the 5 high-risk patients, and their pregnancies were terminated. There was a spontaneous abortion with a normal fetus in 1 case. In one woman, pregnancy progressed to term delivery of a normal girl. Methodologic aspects of obtaining fetal skin samples and the results of their morphologic studies are discussed.

[Chromosomal polymorphism in patients with ovarian hypofunction of central origin]

Comparative data are reported on chromosome polymorphism in adolescent patients with ovarian hypofunction of central origin and healthy women. Chromosome variants with small and very small heterochromatin blocks were found to prevail in the adolescent patients. The incidence of pericentric inversions in chromosomes 1 and 9 was found to be significantly increased in the girls with ovarian hypofunction.