Genome-wide miRNA profiling in plasma of pregnant women with down syndrome fetuses

Are there foetal extracellular vesicles in maternal blood? Prospects for diagnostic biomarker discovery

Prenatal diagnosis of congenital disease improves clinical outcomes; however, as many as 50% of congenital heart disease cases are missed by current ultrasound screening methods. This indicates a need for improved screening technology. Extracellular vesicles (EVs) have attracted enormous interest in recent years for their potential in diagnostics. EVs mediate endocrine signalling in health and disease and are known to regulate aspects of embryonic development. Here, we critically evaluate recent evidence suggesting that EVs released from the foetus are able to cross the placenta and enter the maternal circulation. Furthermore, EVs from the mother appear to be transported in the reverse direction, whilst the placenta itself acts as a source of EVs. Experimental work utilising rodent models employing either transgenically encoded reporters or application of fluorescent tracking dyes provide convincing evidence of foetal-maternal crosstalk. This is supported by clinical data demonstrating expression of placental-origin EVs in maternal blood, as well as limited evidence for the presence of foetal-origin EVs. Together, this work raises the possibility that foetal EVs present in maternal blood could be used for the diagnosis of congenital disease. We discuss the challenges faced by researchers in translating these basic science findings into a clinical non-invasive prenatal test.

Liquid Biopsy in Adverse Neurodevelopment of Children: Problems and Prospects

Neurodevelopmental disorders in children have an important impact on the quality of life in the whole life cycle. Severe neurodevelopmental disorders will become a serious social and family burden and an important social and economic problem. The early and middle childhood is the critical period of children's neurodevelopment. Early diagnosis of neurological disorders plays an important role in guiding children's neurological development. Existing monitoring tools lack prenatal and even early assessment of children's neurodevelopment, so reliable biomarkers are conducive to personalized care at an earlier stage. In this review, we will discuss different methods of neurodevelopmental monitoring at different times and the role and evaluation of liquid biopsy in neurodevelopmental monitoring.

Integrative analyses of maternal plasma cell-free DNA nucleosome footprint differences reveal chromosomal aneuploidy fetuses gene expression profile

Background

Chromosomal aneuploidy is the most common birth defect. However, the developmental mechanism and gene expression profile of fetuses with chromosomal aneuploidy are relatively unknown, and the maternal immune changes induced by fetal aneuploidy remain unclear. The inability to obtain the placenta multiple times in real-time is a bottleneck in research on aneuploid pregnancies. Plasma cell-free DNA (cfDNA) carries the gene expression profile information of its source cells and may be used to evaluate the development of fetuses with aneuploidy and the immune changes induced in the mother owing to fetal aneuploidy.

Methods

Here, we carried out whole-genome sequencing of the plasma cfDNA of 101 pregnant women carrying a fetus with trisomy (trisomy 21, n = 42; trisomy 18, n = 28; trisomy 13, n = 31) based on non-invasive prenatal testing (NIPT) screening and 140 normal pregnant women to identify differential genes according to the cfDNA nucleosome profile in the region around the transcription start sites (TSSs).

Results

The plasma cfDNA promoter profiles were found to differ between aneuploid and euploid pregnancies. A total of 158 genes with significant differences were identified, of which 43 genes were upregulated and 98 genes were downregulated. Functional enrichment and signaling pathway analysis were performed based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases found that these signal pathways were mainly related to the coordination of developmental signals during embryonic development, the control of cell growth and development, regulation of neuronal survival, and immune regulation, such as the MAPK, Hippo, TGF-β, and Rap1 signaling pathways, which play important roles in the development of embryonic tissues and organs. Furthermore, based on the results of differential gene analysis, a total of 14 immune-related genes with significant differences from the ImmPort database were collected and analyzed. These significantly different immune genes were mainly associated with the maintenance of embryonic homeostasis and normal development.

Conclusions

These results suggest that the distribution characteristics of cfDNA nucleosomes in maternal plasma can be used to reflect the status of fetal development and changes of the immune responses in trisomic pregnancies. Overall, our findings may provide research ideas for non-invasive detection of the physiological and pathological states of other diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03735-7.

Detection of Embryonic Trisomy 21 in the First Trimester Using Maternal Plasma Cell-Free RNA

Prenatal trisomy 21 (T21) screening commonly involves testing a maternal blood sample for fetal DNA aneuploidy. It is reliable but poses a cost barrier to universal screening. We hypothesized maternal plasma RNA screening might provide similar reliability but at a lower cost. Discovery experiments used plasma cell-free RNA from 20 women 11−13 weeks tested by RNA and miRNA microarrays followed by qRT-PCR. Thirty-six mRNAs and 18 small RNAs of the discovery cDNA were identified by qPCR as potential markers of embryonic T21. The second objective was validation of the RNA predictors in 998 independent pregnancies at 11−13 weeks including 50 T21. Initial analyses identified 9−15 differentially expressed RNA with modest predictive power (AUC < 0.70). The 54 RNAs were then subjected to machine learning. Eleven algorithms were trained on one partition and tested on an independent partition. The three best algorithms were identified by Kappa score and the effects of training/testing partition size and dataset class imbalance on prediction were evaluated. Six to ten RNAs predicted T21 with AUCs up to 1.00. The findings suggest that maternal plasma collected at 11−13 weeks, tested by qRT-PCR, and classified by machine learning, may accurately predict T21 for a lower cost than plasma DNA, thus opening the door to universal screening.

[Whole-transcriptome sequencing analysis of placental differential miRNA expression profile in Down syndrome]

OBJECTIVE

To identify new biomarkers and molecular pathogenesis of Down syndrome (DS) by analyzing differentially expressed miRNAs in the placentas and their biological pathways.

METHODS

Whole transcriptome sequencing was used to identify the differentially expressed miRNAs in DS (n=3) and normal placental samples (n=3) diagnosed by prenatal diagnosis. The target genes were predicted using miRWalk, Targetscan and miRDB, and GO and KEGG pathway analyses were performed for gene enrichment studies.

RESULTS

We identified a total of 82 differentially expressed miRNAs in the placental tissues of DS, including 29 up-regulated miRNAs (fold change ≥2, P < 0.05) and 15 down-regulated miRNAs (fold change ≥2, P < 0.05), among which 10 miRNAs with relatively high expression abundance were selected for further analysis, including 4 up-regulated and 6 down-regulated miRNAs. These selected miRNAs shared the common target genes BTBD3 and AUTS2, both of which were associated with neurodevelopment. GO analysis showed that the target genes of the selected miRNAs were mainly enriched in protein binding, hydrolytic enzymes, metal ion binding protein combining, transferase activity, nucleotide, cytoplasmic constituents, nucleus composition, transcriptional regulation, RNA metabolism regulation, DNA-dependent RNA polymerase Ⅱ promoter transcriptional regulation, eye development, and sensory organ development. KEGG enrichment analysis showed that the target genes of these differentially expressed miRNAs were involved in the signaling pathways including tumor-related signaling pathway, PI3K-Akt signaling pathway, Ras signaling pathway, Rap1 signaling pathway, cytoskeletal regulatory signaling pathway, purine metabolization-related signaling pathway and P53 signaling pathway.

CONCLUSION

The differentially expressed miRNAs may play important roles in placental damage and pregnancy pathology in DS and provide clues for the prevention and treatment of mental retardation-related diseases.

Novel method of real-time PCR-based screening for common fetal trisomies

BACKGROUND

The non-invasive prenatal test (NIPT) is based on next generation sequencing (NGS) and is used for screening for fetal trisomy. However, it is time-consuming and technically difficult. Recently, peptide nucleic acid (PNA) probe-based real-time polymerase chain reaction (RT-PCR) was developed. This study aimed to examine the performance of the RT-PCR-based NIPT for screening of common fetal trisomies METHODS: From stored maternal plasma, RT-PCR was performed using Patio™ NIPT Detection Kit. In melting curve analysis, the height of melting peaks of target chromosome and reference chromosome was calculated as a peak ratio. The adjusted peak ratio of 8 markers with correction factors in each target chromosome was summated and calculated to z-score. The cut-off value for each target chromosome was established for classification (low risk vs. high risk for trisomy) whose performance was obtained in the validation phase.

RESULTS

330 plasma samples from pregnant women with normal fetus and 22 trisomy cell-line samples were used to establish the optimal cut-off values for z-score of each target chromosome. In the validation phase, 1023 samples from pregnant women including 22 cases with fetal trisomy and 1001 cases of normal control were used. The RT-PCR-based NIPT showed 95.45% sensitivity [95% confidence interval (CI) 77.16-99.88%], 98.60% specificity (95% CI 97.66-99.23%), and 98.53% accuracy (95% CI 97.59-99.18%) for the identification of trisomy 21, 18, or 13. Of 1023 samples, fifteen cases were mismatched for classification [one case as a false negative (false negative rate: 4.5%) and 14 cases as false positives (false positive rate: 1.4%)].

CONCLUSION

The RT-PCR-based NIPT showed high sensitivity and specificity for the detection of common fetal trisomies and it could be a feasible alternative to NGS-based NIPT.

Alterations of epigenetic landscape in Down syndrome carrying pregnancies: A systematic review of case-control studies

OBJECTIVE

Great attention is currently paid to both the pathogenetic mechanisms and non-invasive prenatal diagnosis (NIPD) of Down syndrome (DS). It has been posited that dysregulation of epigenetic signatures including DNA methylation and microRNAs (miRNAs) crucially contribute to the pathomechanism of DS. Therefore, we aimed to perform a systematic review of case-control publications that have examined the differences in epigenetic landscape between pregnancies bearing euploid fetuses and those affected with DS to provide a focused insight into the pathophysiology of DS and also novel biomarkers for NIPD of DS.

STUDY DESIGN

Pertinent keywords were utilized to search into PubMed, Scopus, and Google Scholar. We enrolled studies that have compared the pattern of miRNAs expression profile or DNA methylation between pregnant women who carries DS fetuses and those with euploid fetuses.

RESULTS

An assessment of 599 articles resulted in, finally, 18 eligible studies (12 miRNAs and 6 DNA methylation). The most investigated miRNAs were those that are encoded by genes on chromosome 21 and more hypermethylation regions in DS fetuses than euploids with nearly evenly distribution on all chromosomes were found. Distinct mechanisms with potential therapeutic purposes have been put forward for the involvement of epigenetic perturbations in the etiopathogenesis of DS.

CONCLUSION

There is a disagreement in the recruiting of epigenetic biomarkers for NIPD of DS. This heterogeneity in results of the qualified publications emanates from confounding factors such as differences in demographic data of participants, analytical platforms, and study design. Hence, before harnessing epigenetic signatures for NIPD of DS, more experiments are required.