Maternal Genome Research Articles

Developmental trajectory of monopronucleated zygotes after in vitro fertilization when they include both male and female genomes

To examine the cause of monopronucleated zygote (1PN) formation that includes both maternal and paternal genomes. Retrospective cohort study. Private fertility clinic. A total of 44 1PN and 726 2-pronuclear zygotes from 702 patients were observed using 2 different time-lapse observation systems. Previously recorded time lapse data were reviewed to examine the mechanism of 1PN formation. The distance between the position of the second polar body extrusion and the fertilization cone or epicenter/starting position of the cytoplasmic wave was measured, and the consequent data were analyzed. Cytoplasmic waves were confirmed using vector analysis software. The cut-off value for the difference in the distance between the position of the second polar body extrusion and the fertilization cone or the epicenter/starting position of the cytoplasmic wave was 17 μm (AUC: 0.987, 95% CI: 0.976-0.999) for the Embryo Scope and 18 μm (AUC: 0.972, 95% CI: 0.955-0.988) for the iBIS time-lapse observation systems. In this study, it was found with a high degree of accuracy that a monopronucleus is formed when the fusion of the sperm takes place within 18 μm from the point of the second polar body extrusion. The theoretical chance of 1PN occurrence after invitro fertilization is 2.7% when the sperm is considered to be fused anywhere in the plasma membrane of an oocyte.

ACCURATE GENOMIC PREDICTION OF MOSAICISM THROUGH CELL DIVISION ORIGIN OF ANEUPLOIDY ANALYSIS IN THE PREIMPLANTATION EMBRYO

Simple intermediate copy number thresholds have proven to provide poor predictive value for diagnosing preimplantation mosaicism (both analytically and clinically). This study aims to validate a method to determine the cell division origin of aneuploidy from a single trophectoderm biopsy, and its ability to accurately predict mosaicism in the remaining embryo. A high throughput and PGT-validated DNA array platform was used to analyze over 800,000 SNPs within trophectoderm biopsies from a subset of PGT cases where parental DNA was available. Mendelian inheritance analyses were performed on embryonic genotypes within aneuploid chromosomes to predict their parental and cell division origins. Positive controls included embryos with a male karyotype (n=279) with known maternal origin of the X chromosome, and unbalanced embryos from PGT-SR cases (n=69) with known meiotic and parental origins of aneuploidy. The method was applied to clinical biopsies with aneuploidy and compared to rebiopsies (n=80) to evaluate the accuracy of predicting mosaicism (mitotic) and uniform (meiotic) aneuploidy. All samples were analyzed while blinded to prior results. Following validation, the incidence of mitotic origin of aneuploidy was investigated in 942 embryos. Blinded predictions of the X chromosome origin in male embryos, and parental and cell division origin of aneuploidy in PGT-SR derived unbalanced embryos were 100% concordant with expected results, demonstrating the validity of predicting parental and meiotic cell division origins of aneuploidy. Blinded analysis of rebiopsies showed that all embryos with mitotic origin of aneuploidy predicted in the original biopsy were confirmed as mosaic, and all embryos with meiotic origin were confirmed as uniform aneuploid, demonstrating the validity of predicting mitotic origins of aneuploidy and mosaicism. The overall incidence of mitotic whole chromosome aneuploidy (mosaicism) in embryos was 3%. The overall embryonic aneuploidy rate was 31% (mean maternal age 34.5+4). Aneuploid chromosomes primarily originated from the maternal genome (80%) and maternal whole chromosome aneuploidy primarily originated from meiotic errors (95%), while paternal aneuploidy more often originated from mitotic errors (35%)(p<0.05). These data indicate very high specificity in predicting mosaicism from a single aneuploid trophectoderm biopsy and a low prevalence of mosaicism (3%) in the human blastocyst. This is in stark contrast to existing methods of predicting mosaicism with intermediate copy number thresholds, where rebiopsy confirmation rates are ∼40%, and prevalence is estimated to be ∼20%. Improving the specificity of predicting mosaicism (reducing false positives) from a single biopsy may provide a unique opportunity to investigate the true clinical consequence of transferring bona fide mosaic embryos for the first time.

Analysis of the maternal genome ofElymus nutansfrom the Qinghai‐Tibet Plateau based on chloroplast genomes

AbstractElymus nutansis an important forage and ecological restoration herbage in the Qinghai‐Tibet Plateau, which is an allohexaploid species with theStStYYHHgenomes. Previous studies suggested thatPseudoroegneriais the maternal genome donor toE. nutans, but exactly whichPseudoroegneriaspecies is still unknown. Here, we report the complete chloroplast (cp) genome sequence of twoE. nutansfrom the Qinghai‐Tibet and fivePseudoroegneriaspecies. The cp genomes of the seven samples ranged narrowly from 134,924 bp to 135,142 bp in size, comprising inverted repeats of 20,808–20,814 bp, single‐copy regions of 80,536–80,754 bp (LSC) and 12,762–12,772 bp (SSC). It encoded 111 total genes, of which 78 protein‐coding genes, 29 tRNA genes, and four rRNA genes. A comparative cp genome analysis and characteristic junctions ofSt‐containing species revealed that the gene content and organization were conserved, but differences were still found in sequence variation and border regions. Further, the Bayesian inference (BI) phylogenetic tree using the whole chloroplast genome sequence demonstrated thatP. cognatamight be the most likelyStgenome donor ofE. nutansin the Qinghai‐Tibet Plateau, followed byP. strigosa. However, whetherE. nutanshas other maternal genomes still needs further research.

Vitrification protocol for immature Brycon orbignyanus ovarian tissue as an extinction escape strategy

Piracanjunba (Brycon orbignyanus) is an endangered South American fish, and ovarian tissue cryopreservation is an alternative method for preserving maternal germplasm and genetic diversity. Therefore, our aim was to test a vitrification protocol for ovarian tissue containing primary growth (PG) oocytes of B. orbignyanus as a strategy to avoid the threat of extinction. Two vitrification solutions were evaluated (VS1: 1.5 M methanol + 4.5 M propylene glycol and VS2: 1.5 M methanol + 5.5 M Me2SO) and compared using control/fresh ovarian tissue. After vitrification, the following factors were analyzed: membrane integrity using trypan blue, morphology using a histological assessment, oxidative stress (total reactive antioxidant potential (TRAP) and reduced thiol [-SH]), mitochondrial activity using MTT, and DNA damage using a comet assay. The vitrified oocytes (VS1 = 24.3 ± 0.49% and VS2 = 24.8 ± 0.69%) showed higher DNA damage than the control group (control = 20.7 ± 1.03%) (P = 0.004). In contrast, in most evaluations (membrane integrity, membrane damage, oxidative stress, and mitochondrial activity), there were no discernible differences between the control group and the vitrified samples. In addition, oocyte (P = 0.883) and nuclear diameter (P = 0.118) did not change after vitrification. VS2 treatment resulted in higher nuclear damage (15.7 ± 1.45%) than in the control treatment (3.5 ± 1.19%); however, VS1 treatment did not result in significantly more damage (9.5 ± 3.01%) than in the control (P = 0.015). Therefore, the protocol for ovarian tissue vitrification tested in this study resulted in high maintenance of PG oocyte cell integrity, making it a promising alternative for B. orbignyanus maternal genome preservation.

Maternal selenium levels and whole genome screen in recurrent spontaneous preterm birth population: A nested case control study

ObjectiveTo establish if low maternal selenium (Se) was associated with sPTB in women with recurrent sPTB and identify genetic link with maternal Se levels. DesignNested case-control study. SettingTertiary Maternity Hospital. PopulationPlasma and whole blood from pregnant women with history of early sPTB/PPROM < 34+0 and European ancestry were obtained at 20 weeks (range 15–24 weeks). ‘Cases’ were recurrent PTB/PPROM < 34+0 weeks and term (≥37+0) deliveries were classified as ‘high-risk controls.’ Women with previous term births and index birth ≥ 39 weeks were ‘low-risk controls’. MethodsMaternal plasma Se measured by ICP-MS was used as a continuous phenotype in a GWAS analysis. Se was added to a logistic regression model using PTB predictor variables. Main outcome measuresMaternal Se concentration, recurrent early sPTB/PPROM. Results53/177 high-risk women had a recurrent sPTB/PPROM < 34+0weeks and were 2.7 times more likely to have a Se level < 83.3 ppm at 20weeks of pregnancy compared with low-risk term controls (n = 179), (RR 2.7, 95%CI 1.5–4.8; p = .001). One SNP from a non-coding region (FOXN3 intron variant, rs55793422) reached genome-wide significance level (p = 3.73E−08). Targeted analysis of Se gene variant did not show difference between preterm and term births. (χ2 test, OR = 0.95; 95%CI = 0.59–1.56; p = 0.82). When Se levels were added to a clinical prediction model, only an additional 5% of cases (n = 3) and 0.6% (n = 1) of controls were correctly identified. ConclusionsLow plasma Se is associated with sPTB risk but is not sufficiently predictive at individual patient level. We did not find a genetic association between maternal Se levels and Se-related genes.

The DNA-to-cytoplasm ratio broadly activates zygotic gene expression in Xenopus

In multicellular animals, the first major event after fertilization is the switch from maternal to zygotic control of development. During this transition, zygotic gene transcription is broadly activated in an otherwise quiescent genome in a process known as zygotic genome activation (ZGA). In fast-developing embryos, ZGA often overlaps with the slowing of initially synchronous cell divisions at the mid-blastula transition (MBT). Initial studies of the MBT led to the nuclear-to-cytoplasmic ratio model where MBT timing is regulated by the exponentially increasing amounts of some nuclear component "N" titrated against a fixed cytoplasmic component "C." However, more recent experiments have been interpreted to suggest that ZGA is independent of the N/C ratio. To determine the role of the N/C ratio in ZGA, we generated Xenopus frog embryos with ∼3-fold differences in genomic DNA (i.e., N) by using X.tropicalis sperm to fertilize X.laevis eggs with or without their maternal genome. Resulting embryos have otherwise identical X.tropicalis genome template amounts, embryo sizes, and X.laevis maternal environments. We generated transcriptomic time series across the MBT in both conditions and used X.tropicalis paternally derived mRNA to identify a high-confidence set of exclusively zygotic transcripts. Both ZGA and the increase in cell-cycle duration are delayed in embryos with ∼3-fold less DNA per cell. Thus, DNA is an important component of the N/C ratio, which is a critical regulator of zygotic genome activation in Xenopus embryos.

O-209 The impact of sperm DNA fragmentation on pregnancy outcomes depends on oocyte dimorphisms

Abstract Study question Does the impact of sperm DNA fragmentation (SDF) on Intracytoplasmic sperm injection (ICSI) outcomes depend on the presence of oocyte dimorphisms? Summary answer There is a significant influence of oocyte quality on the impact of SDF on pregnancy outcomes. What is known already Sperm DNA fragmentation has been associated with ICSI outcomes. DNA damage is commonly encountered in human spermatozoa and it has been widely accepted that the oocyte assumes responsibility for the repair and remodelling of both the maternal and paternal genomes during the oocyte-embryo transition. Indeed, spermatozoa with DNA damage can fertilise oocytes and still lead to embryo development due to the oocyte DNA repair capacity. Considering the vital role played by the oocyte in the developmental process, it could be hypostatised that the oocyte quality, translated as oocyte morphology, would influence the machinery responsible for sperm DNA repair after fertilization. Study design, size, duration This cohort study included 3,035 oocytes from 525 patients undergoing ICSI cycles in a university-affiliated IVF-center, between June/2016 and July/2019. Oocytes were split into groups according to the SDF index of the sample used for ICSI: low-fragmentation (&amp;lt;30% SDF, n = 2,277) and high-fragmentation (≥30% SDF, n = 758). Oocytes were evaluated before sperm injection and the dimorphisms were recorded. The influence of SDF index on ICSI outcomes, depending on the presence of oocytes dimorphisms was evaluated. Participants/materials, setting, methods Data was evaluated using generalized linear models (GZLM) followed by Bonferroni post hoc. The results are expressed as mean ± standard error for continuous variables or percentages for dichotomous variables, and p-values. The sample size calculation suggested that a sample of at least 504 subjects had 95% power to detect a 20% effect with a significance level of 5% (α). The study was performed in a private university–affiliated in vitro fertilization (IVF) center. Main results and the role of chance The association of both factors: the presence of oocyte dimorphisms (dark cytoplasm, vacuoles in the ooplasm, and resistant membrane) and high SDF index resulted in the lowest fertilization rate among groups, while oocytes free of these dimorphisms injected with samples with &amp;lt;30% SDF had the highest fertilization rate (p = 0.05, p &amp;lt; 0.01 and p &amp;lt; 0.01 for dark cytoplasm, vacuoles in the ooplasm and resistant membrane respectively). The impact of SDF index on high quality embryos rate on cleavage stage was also influence by the presence smooth endoplasmic reticulum clusters and resistant membrane oocytes (p = 0.013 and p = 0.018). As for the clinical outcomes, the impact of SDF index on the implantation rate was influenced by the presence of vacuoles in the ooplasm (p &amp;lt; 0.01), smooth endoplasmic reticulum clusters (p &amp;lt; 0.01), large perivitelline space (p &amp;lt; 0.01), resistant membrane (p &amp;lt; 0.01), and non-resistant membrane (p &amp;lt; 0.01), while the influence of SDF index on the pregnancy rate was influenced by the presence large perivitelline space (p &amp;lt; 0.01), resistant membrane (p = 0.018) and non-resistant membrane (p &amp;lt; 0.01). The effect of SDF on the miscarriage rate was also increased in the presence of large perivitelline space (p = 0.045), non-resistant membrane (0.037) and centrally located cytoplasmic granular area (p = 0.025). Limitations, reasons for caution The retrospective nature is a limitation. It could be argued that using samples with high SDF index does not necessarily mean that a sperm cell with a fragmented DNA was injected, however, the higher the SDF index, the higher the chance of selecting one with fragmented DNA. Wider implications of the findings The findings presented here highlight the crucial role of male and female factors when facing assisted reproduction. The association of low oocyte quality and high SDF index may lead to impaired results. As the oocyte defect cannot be modified, in vivo upgrading of spermatozoa before the treatment should be encouraged. Trial registration number Not applicable

Complete maternal mitochondrial genome of the freshwater mussel Cuneopsis celtiformis (Bivalvia: Unionidae)

The genus Cuneopsis Simpson, 1900 comprises seven valid species, and Cuneopsis celtiformis (Heude, 1874) is the type species of this genus. Previous phylogenetic studies using complete mitochondrial genomes showed that Cuneopsis was not monophyletic, but the result was hampered by incomplete species sampling and lack of the type species of this genus. In this study, we collected C. celtiformis from the type locality and determined its complete maternal mitochondrial genome. This mitogenome is 15,922 bp in length and contains 14 protein-coding genes (including one F-orf), two rRNA genes, 22 tRNA genes, and 1 putative control region. Our mitochondrial phylogenomic analysis confirms that currently recognized genus Cuneopsis is polyphyletic, and C. celtiformis is the closest to C. heudei with high maximum likelihood bootstrap support value. Comprehensive sampling of all Cuneopsis species is needed for phylogenetic analysis to erect new genera in future studies.

Asymmetric epigenetic modification and homoeolog expression bias in the establishment and evolution of allopolyploid Brassica napus.

This study explores how allopolyploidization reshapes the biased expression and asymmetric epigenetic modification of homoeologous gene pairs, and examines the regulation types and epigenetic basis of expression bias. We analyzed the gene expression and four epigenetic modifications (DNA methylation, H3K4me3, H3K27me3 and H3K27ac) of 29976 homoeologous gene pairs in resynthesized, natural allopolyploid Brassica napus and an in silico 'hybrid'. We comprehensively elucidated the biased gene expression, asymmetric epigenetic modifications and the generational transmission characteristics of these homoeologous gene pairs in B.napus. We analyzed cis/trans effects and the epigenetic basis of homoeolog expression bias. There was a significant positive correlation between two active histone modifications and biased gene expression. We revealed that parental legacy was the dominant principle in the remodeling of homoeolog expression bias and asymmetric epigenetic modifications in B.napus, and further clarified that this depends on whether there were differences in the expression/epigenetic modifications of gene pairs in parents/progenitors. The maternal genome was dominant in the homoeolog expression bias of resynthesized B.napus, and this phenomenon was attenuated in natural B.napus. Furthermore, cis rather than trans effects were dominant when epigenetic modifications potentially affected biased expression of gene pairs in B.napus.

Distinction between the effects of parental and fetal genomes on fetal growth.

Birth weight is a common measure of fetal growth that is associated with a range of health outcomes. It is directly affected by the fetal genome and indirectly by the maternal genome. We performed genome-wide association studies on birth weight in the genomes of the child and parents and further analyzed birth length and ponderal index, yielding a total of 243 fetal growth variants. We clustered those variants based on the effects of transmitted and nontransmitted alleles on birth weight. Out of 141 clustered variants, 22 were consistent with parent-of-origin-specific effects. We further used haplotype-specific polygenic risk scores to directly test the relationship between adult traits and birth weight. Our results indicate that the maternal genome contributes to increased birth weight through blood-glucose-raising alleles while blood-pressure-raising alleles reduce birth weight largely through the fetal genome.

Shedding light on the genetics of fetal growth.

Genome-wide association studies have identified genetic variants in maternal and fetal genomes associated with early-life growth traits but have been limited by the paucity of large-scale family-based cohorts that would enable the resolution of informative transmissions between parents and their offspring. A new study uses extensive pedigree data from the Icelandic population to identify genetic effects on birth weight that differ according to parental origin and to demarcate distinct contributions from the maternal intrauterine environment and offspring genetics on fetal growth.

Generating Nonmosaic Mutants in Xenopus Using CRISPR-Cas in Oocytes.

In CRISPR-Cas9 genome editing, double-strand DNA breaks (DSBs) primarily undergo repair through nonhomologous end joining (NHEJ), which produces insertion or deletion of random nucleotides within the targeted region (indels). As a result, frameshift mutation-mediated loss-of-function mutants are frequently produced. An alternative repair mechanism, homology-directed repair (HDR), can be used to fix DSBs at relatively low frequency. By injecting a DNA-homology repair construct with the CRISPR-Cas components, specific nucleotide sequences can be introduced within the target region by HDR. We have taken advantage of the fact that Xenopus oocytes have much higher levels of HDR than eggs to increase the effectiveness of creating precise mutations. We introduced the oocyte host transfer technique, well established for knockdown of maternal mRNA for loss-of-function experiments, to CRISPR-Cas9-mediated genome editing. The host-transfer technique is based on the ability of Xenopus oocytes to be isolated, injected with CRISPR-Cas components, and cultured in vitro for up to 5 d before fertilization. During these 5 d, CRISPR-Cas components degrade, preventing further alterations to the paternal or maternal genomes after fertilization and resulting in heterozygous, nonmosaic embryos. Treatment of oocytes with a DNA ligase IV inhibitor, which blocks the NHEJ repair pathway, before fertilization further improves the efficiency of HDR. This method allows straightforward generation of either nonmosaic F0 heterozygous indel mutant Xenopus or Xenopus with efficient, targeted insertion of small DNA fragments (73-104 nt). The germline transmission of mutations in these animals allows homozygous mutants to be obtained one generation (F1) sooner than previously reported.

Defects in meiotic chromosome segregation lead to unreduced male gametes in Arabidopsis SMC5/6 complex mutants.

Structural maintenance of chromosome 5/6 (SMC5/6) complex is a crucial factor for preserving genome stability. Here, we show that mutants for several Arabidopsis (Arabidopsis thaliana) SMC5/6 complex subunits produce triploid offspring. This phenotype is caused by a meiotic defect leading to the production of unreduced male gametes. The SMC5/6 complex mutants show an absence of chromosome segregation during the first and/or the second meiotic division, as well as a partially disorganized microtubule network. Importantly, although the SMC5/6 complex is partly required for the repair of SPO11-induced DNA double-strand breaks, the nonreduction described here is SPO11-independent. The measured high rate of ovule abortion suggests that, if produced, such defects are maternally lethal. Upon fertilization with an unreduced pollen, the unbalanced maternal and paternal genome dosage in the endosperm most likely causes seed abortion observed in several SMC5/6 complex mutants. In conclusion, we describe the function of the SMC5/6 complex in the maintenance of gametophytic ploidy in Arabidopsis.

Maternal Effect Mutations: A Novel Cause for Human Reproductive Failure.

Genetic alterations significantly contribute to the aetiology of reproductive failure and comprise monogenic, chromosomal and epigenetic disturbances. The implementation of next-generation sequencing (NGS) based approaches in research and diagnostics allows the comprehensive analysis of these genetic causes, and the increasing detection rates of genetic mutations causing reproductive complications confirm the potential of the new techniques. Whereas mutations affecting the fetal genome are well known to affect pregnancies and their outcome, the contribution of alterations of the maternal genome was widely unclear. With the recent mainly NGS-based identification of maternal effect variants, a new cause of human reproductive failure has been identified. Maternal effect mutations affect the expression of subcortical maternal complex (SCMC) proteins from the maternal genome, and thereby disturb oocyte maturation and progression of the early embryo. They cause a broad range of reproductive failures and pregnancy complications, including infertility, miscarriages, hydatidiform moles, aneuploidies and imprinting disturbances in the fetus. The identification of women carrying these molecular alterations in SCMC encoding genes is therefore essential for a personalised reproductive and genetic counselling. The diagnostic application of new NGS-based assays allows the comprehensive analysis of these factors, and helps to further decipher these functional links between the factors and their disturbances. A close interdisciplinary collaboration between different disciplines is definitely required to further decipher the complex regulation of early embryo development, and to translate the basic research results into clinical practice.

Women and babies are dying from inertia: a collaborative framework for obstetrical drug development is urgently needed

Obstetrical complications, often referred to as the "great obstetrical syndromes," are among the most common global causes of mortality and morbidity in young women and their infants. However, treatments for these syndromes are underdeveloped compared with other fields of medicine and are urgently needed. This current paucity of treatments for obstetrical complications is a reflection of the challenges of drug development in pregnancy. The appetite of pharmaceutical companies to invest in research for obstetrical syndromes is generally reduced by concerns for maternal, fetal, and infant safety, poor definition, and high-risk regulatory paths toward product approval. Notably, drug candidates require large investments for development with an unguaranteed return on investment. Furthermore, the discovery of promising drug candidates is hampered by a poor understanding of the pathophysiology of obstetrical syndromes and their uniqueness to human pregnancies. This limits translational extrapolation and de-risking strategies in preclinical studies, as available for other medical areas, compounded with limited fetal safety monitoring to capture early prenatal adverse reactions. In addition, the ethical review committees are reluctant to approve the inclusion of pregnant women in trials, and in the absence of regulatory guidance in obstetrics, clinical development programs are subject to unpredictable regulatory paths. To develop effective and safe drugs for pregnancy complications, substantial commitment, and investment in research for innovative therapies are needed in parallel with the creation of an enabling ethical, legislative, and guidance framework. Solutions are proposed to enable stakeholders to work with a common set of expectations to facilitate progress in this medical discipline. Addressing this significant unmet need to advance maternal and possibly perinatal health requires the involvement of all stakeholders and specifically patients, couples, and clinicians facing pregnancy complications in the dearth of appropriate therapies. This paper focused on the key pharmaceutical research and development challenges to achieve effective and safe treatments for obstetrical syndromes.

Exosome-Derived MicroRNAs of Human Milk and Their Effects on Infant Health and Development

Multiple biologically active components of human milk support infant growth, health and development. Milk provides a wide spectrum of mammary epithelial cell-derived extracellular vesicles (MEVs) for the infant. Although the whole spectrum of MEVs appears to be of functional importance for the growing infant, the majority of recent studies report on the MEV subfraction of milk exosomes (MEX) and their miRNA cargo, which are in the focus of this review. MEX and the dominant miRNA-148a play a key role in intestinal maturation, barrier function and suppression of nuclear factor-κB (NF-κB) signaling and may thus be helpful for the prevention and treatment of necrotizing enterocolitis. MEX and their miRNAs reach the systemic circulation and may impact epigenetic programming of various organs including the liver, thymus, brain, pancreatic islets, beige, brown and white adipose tissue as well as bones. Translational evidence indicates that MEX and their miRNAs control the expression of global cellular regulators such as DNA methyltransferase 1—which is important for the up-regulation of developmental genes including insulin, insulin-like growth factor-1, α-synuclein and forkhead box P3—and receptor-interacting protein 140, which is important for the regulation of multiple nuclear receptors. MEX-derived miRNA-148a and miRNA-30b may stimulate the expression of uncoupling protein 1, the key inducer of thermogenesis converting white into beige/brown adipose tissue. MEX have to be considered as signalosomes derived from the maternal lactation genome emitted to promote growth, maturation, immunological and metabolic programming of the offspring. Deeper insights into milk’s molecular biology allow the conclusion that infants are both “breast-fed” and “breast-programmed”. In this regard, MEX miRNA-deficient artificial formula is not an adequate substitute for breastfeeding, the birthright of all mammals.

Methylation profile of imprinted genes provides evidence for teratomatous origin of a subset of mucinous ovarian tumours.

Mucinous ovarian tumours are sometimes associated with mature teratomas. It is suggested that the mucinous tumours in this setting are derived from teratomas, but there remains the possibility of collision or metastasis from extra-ovarian sites. Because mature ovarian teratomas are considered to be parthenogenetic tumours that arise from a single oocyte/ovum, they have only a maternal genome and therefore show maternal genome imprinting. If mucinous ovarian tumours originate from teratomas, their genome imprinting is theoretically maternal. One of the most important mechanisms of genome imprinting is DNA methylation. In the present study, we analysed a total of 28 mucinous ovarian tumours (7 with teratomas, 21 without teratomas; 14 malignant, 14 borderline) to clarify the methylation profiles of their imprinted genes using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) of 21 imprinting control regions (ICRs) of nine imprinted genes/gene clusters using formalin-fixed, paraffin-embedded samples. All cases lacked evidence of an extra-ovarian primary mucinous tumour. In all seven mucinous tumours with teratomas, the overall methylation profile of mucinous tumours was comparable to that of teratomas, although some ICRs showed aberrant methylation. In contrast, all but one of the mucinous tumours without teratomas showed somatic or irregular methylation patterns. Morphologically, there was little teratomatous tissue in some mucinous tumours carrying teratoma-type methylation profiles, suggesting that mucinous tumours overwhelmed ancestral teratomas. In conclusion, the methylation profile of imprinted genes provides evidence that a subset of mucinous ovarian tumours originated from mature teratomas. Genome imprinting-based analysis is a promising strategy to verify the teratomatous origin of human tumours. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Complementary role of p57kip2 immunostaining in diagnosing hydatidiform mole subtypes.

Gestational trophoblastic disease comprises of a spectrum of pregnancy-related tumours which includes complete (CHM) and partial hydatidiform moles (PHM). Accurate diagnosis and subclassification of HM subtypes are crucial as prognosis differs. Histopathological examination using haemotoxylin and eosin (H&E) staining remains the basis for diagnosing HM, with only 80% accuracy. p57kip2 is a cyclin-dependent kinase inhibitor (CDKI) protein and is strongly paternally imprinted, being expressed from maternal allele. Therefore, complete mole (CHM) with only paternal genome has nearly absent expression of p57kip2 compared to partial mole (PHM) having both paternal and maternal genomes. This study is aimed to determine usefulness of p57kip2 immunohistochemistry (IHC) analysis in the diagnosis of HM subtypes. A total of 82 archived paraffin embedded HM tissues with subtypes classified based on H&E staining- 39 (47.5%) CHM, 41 (50.0%) PHM and two (2.43%) unclassified molar pregnancy were retrieved. All tissue samples were subjected for p57kip2 IHC analysis and HM subtypes were then reclassified. A total of 66 cases (80.5%) were re-classified as CHM, 14 cases (17.1%) as PHM and two cases (2.4%) were decidual and cystic tissues. Analysis using p57kip2 immunostaining showed a diagnostic discrepancy of 33.0% from routine H&E staining and helps to improve the characterisation of the HM subtypes specifically at early gestations which have less distinctive morphologies. IHC using p57kip2 monoclonal antibody should be considered as a routine ancillary test to H&E in improving the diagnosis of HM subtypes particularly in developing countries with limited resources.

Growth Restriction and Genomic Imprinting-Overlapping Phenotypes Support the Concept of an Imprinting Network.

Intrauterine and postnatal growth disturbances are major clinical features of imprinting disorders, a molecularly defined group of congenital syndromes caused by molecular alterations affecting parentally imprinted genes. These genes are expressed monoallelically and in a parent-of-origin manner, and they have an impact on human growth and development. In fact, several genes with an exclusive expression from the paternal allele have been shown to promote foetal growth, whereas maternally expressed genes suppress it. The evolution of this correlation might be explained by the different interests of the maternal and paternal genomes, aiming for the conservation of maternal resources for multiple offspring versus extracting maximal maternal resources. Since not all imprinted genes in higher mammals show the same imprinting pattern in different species, the findings from animal models are not always transferable to human. Therefore, human imprinting disorders might serve as models to understand the complex regulation and interaction of imprinted loci. This knowledge is a prerequisite for the development of precise diagnostic tools and therapeutic strategies for patients affected by imprinting disorders. In this review we will specifically overview the current knowledge on imprinting disorders associated with growth retardation, and its increasing relevance in a personalised medicine direction and the need for a multidisciplinary therapeutic approach.

Analysis of DNA variants in miRNAs and miRNA 3ʼUTR binding sites in female infertility patients

Early human embryogenesis relies on maternal gene products accumulated during oocyte growth and maturation, until around day-3 post-fertilization when human zygotic genome activation occurs. The maternal-to-zygotic transition (MZT) is a tightly coordinated process of selective maternal transcript clearance and new zygotic transcript production. If MZT is disrupted, it will lead to developmental arrest and pregnancy loss. It is well established that microRNA (miRNA) mutations disrupt regulation of their target transcripts. We hypothesize that some cases of embryonic arrest and pregnancy loss could be explained by the mutations in the maternal genome that affect miRNA-target transcript pairs. To this end, we examined mutations within miRNAs or miRNA binding sites in the 3ʼ untranslated regions (3ʼUTR) of target transcripts. Using whole-exome sequencing data from 178 women undergoing in vitro fertilization (IVF) procedures, we identified 1197 variants in miRNA genes, including 93 single nucleotide variants (SNVs) and 19 small insertions/deletions (INDELs) within the seed region of 100 miRNAs. Eight miRNA seed-region variants were significantly enriched among our patients when compared to a normal population. Within predicted 3ʼUTR miRNA binding sites, we identified 7393 SNVs and 1488 INDELs. Between our patients and a normal population, 52 SNVs and 30 INDELs showed significant association in the single-variant testing, whereas 51 genes showed significant association in the gene-burden analysis for genes that are expressed in preimplantation embryos. Interestingly, we found that many genes with disrupted 3ʼUTR miRNA binding sites follow gene expression patterns resembling MZT. In addition, some of these variants showed dramatic allele frequency difference between the patient and the normal group, offering potential utility as biomarkers for screening patients prior to IVF procedures.