Maternal inflammation regulates fetal emergency myelopoiesis.

Neonates are highly susceptible to inflammation and infection. Here, we investigate how late fetal liver (FL) mouse hematopoietic stem and progenitor cells (HSPCs) respond to inflammation, testing the hypothesis that deficits in the engagement of emergency myelopoiesis (EM) pathways limit neutrophil output and contribute to perinatal neutropenia. We show that fetal HSPCs have limited production of myeloid cells at steady state and fail to activate a classical adult-like EM transcriptional program. Moreover, we find that fetal HSPCs can respond to EM-inducing inflammatory stimuli in vitro but are restricted by maternal anti-inflammatory factors, primarily interleukin-10 (IL-10), from activating EM pathways in utero. Accordingly, we demonstrate that the loss of maternal IL-10 restores EM activation in fetal HSPCs but at the cost of fetal demise. These results reveal the evolutionary trade-off inherent in maternal anti-inflammatory responses that maintain pregnancy but render the fetus unresponsive to EM activation signals and susceptible to infection.

A maternal-effect Padi6 variant causes nuclear and cytoplasmic abnormalities in oocytes, as well as failure of epigenetic reprogramming and zygotic genome activation in embryos.

Maternal inactivation of genes encoding components of the subcortical maternal complex (SCMC) and its associated member, PADI6, generally results in early embryo lethality. In humans, SCMC gene variants were found in the healthy mothers of children affected by multilocus imprinting disturbances (MLID). However, how the SCMC controls the DNA methylation required to regulate imprinting remains poorly defined. We generated a mouse line carrying a Padi6 missense variant that was identified in a family with Beckwith-Wiedemann syndrome and MLID. If homozygous in female mice, this variant resulted in interruption of embryo development at the two-cell stage. Single-cell multiomic analyses demonstrated defective maturation of Padi6 mutant oocytes and incomplete DNA demethylation, down-regulation of zygotic genome activation (ZGA) genes, up-regulation of maternal decay genes, and developmental delay in two-cell embryos developing from Padi6 mutant oocytes but little effect on genomic imprinting. Western blotting and immunofluorescence analyses showed reduced levels of UHRF1 in oocytes and abnormal localization of DNMT1 and UHRF1 in both oocytes and zygotes. Treatment with 5-azacytidine reverted DNA hypermethylation but did not rescue the developmental arrest of mutant embryos. Taken together, this study demonstrates that PADI6 controls both nuclear and cytoplasmic oocyte processes that are necessary for preimplantation epigenetic reprogramming and ZGA.

Maternal-driven immune education in offspring.

Maternal environmental exposures, particularly during gestation and lactation, significantly influence the immunological development and long-term immunity of offspring. Mammalian immune systems develop through crucial inputs from the environment, beginning in utero and continuing after birth. These critical developmental windows are essential for proper immune system development and, once closed, may not be reopened. This review focuses on the mechanisms by which maternal exposures, particularly to pathogens, diet, and microbiota, impact offspring immunity. Mechanisms driving maternal-offspring immune crosstalk include transfer of maternal antibodies, changes in the maternal microbiome and microbiota-derived metabolites, and transfer of immune cells and cytokines via the placenta and breastfeeding. We further discuss the role of transient maternal infections, which are common during pregnancy, in providing tissue-specific immune education to offspring. We propose a "maternal-driven immune education" hypothesis, which suggests that offspring can use maternal encounters that occur during a critical developmental window to develop optimal immune fitness against infection and inflammation.

Degradation and translation of maternal mRNA for embryogenesis.

Maternal mRNAs accumulate during egg growth and must be judiciously degraded or translated to ensure successful development of mammalian embryos. In this review we integrate recent investigations into pathways controlling rapid degradation of maternal mRNAs during the maternal-to-zygotic transition. Degradation is not indiscriminate, and some mRNAs are selectively protected and rapidly translated after fertilization for reprogramming the zygotic genome during early embryogenesis. Oocyte specific cofactors and pathways have been illustrated to control different futures of maternal mRNAs. We discuss mechanisms that control the fate of maternal mRNAs during late oogenesis and after fertilization. Issues to be resolved in current maternal mRNA research are described, and future research directions are proposed.

New insights into oocyte cytoplasmic lattice-associated proteins.

Oocyte maturation and preimplantation embryo development are critical to successful pregnancy outcomes and the correct establishment and maintenance of genomic imprinting. Thanks to novel technologies and omics studies in human patients and mouse models, the importance of the proteins associated with the cytoplasmic lattices (CPLs), highly abundant structures found in the cytoplasm of mammalian oocytes and preimplantation embryos, in the maternal to zygotic transition is becoming increasingly evident. This review highlights the recent discoveries on the role of these proteins in protein storage and other oocyte cytoplasmic processes, epigenetic reprogramming, and zygotic genome activation (ZGA). A better comprehension of these events may significantly improve clinical diagnosis and pave the way for targeted interventions aiming to correct or mitigate female fertility issues and genomic imprinting disorders.

Fetal brain response to maternal inflammation requires microglia.

In utero infection and maternal inflammation can adversely impact fetal brain development. Maternal systemic illness, even in the absence of direct fetal brain infection, is associated with an increased risk of neuropsychiatric disorders in affected offspring. The cell types mediating the fetal brain response to maternal inflammation are largely unknown, hindering the development of novel treatment strategies. Here, we show that microglia, the resident phagocytes of the brain, highly express receptors for relevant pathogens and cytokines throughout embryonic development. Using a rodent maternal immune activation (MIA) model in which polyinosinic:polycytidylic acid is injected into pregnant mice, we demonstrate long-lasting transcriptional changes in fetal microglia that persist into postnatal life. We find that MIA induces widespread gene expression changes in neuronal and non-neuronal cells; importantly, these responses are abolished by selective genetic deletion of microglia, indicating that microglia are required for the transcriptional response of other cortical cell types to MIA. These findings demonstrate that microglia play a crucial durable role in the fetal response to maternal inflammation, and should be explored as potential therapeutic cell targets.

Smad4 is essential for epiblast scaling and morphogenesis after implantation, but nonessential before implantation.

Bone morphogenic protein (BMP) signaling plays an essential and highly conserved role in embryo axial patterning in animal species. However, in mammalian embryos, which develop inside the mother, early development includes a preimplantation stage, which does not occur in externally developing embryos. During preimplantation, the epiblast is segregated from extra-embryonic lineages that enable implantation and development in utero. Yet, the requirement for BMP signaling is imprecisely defined in mouse early embryos. Here, we show that, in contrast to previous reports, BMP signaling (SMAD1/5/9 phosphorylation) is not detectable until implantation when it is detected in the primitive endoderm - an extra-embryonic lineage. Moreover, preimplantation development appears to be normal following deletion of maternal and zygotic Smad4, an essential effector of canonical BMP signaling. In fact, mice lacking maternal Smad4 are viable. Finally, we uncover a new requirement for zygotic Smad4 in epiblast scaling and cavitation immediately after implantation, via a mechanism involving FGFR/ERK attenuation. Altogether, our results demonstrate no role for BMP4/SMAD4 in the first lineage decisions during mouse development. Rather, multi-pathway signaling among embryonic and extra-embryonic cell types drives epiblast morphogenesis postimplantation.

Lipid nanoparticle structure and delivery route during pregnancy dictate mRNA potency, immunogenicity, and maternal and fetal outcomes.

Treating pregnancy-related disorders is exceptionally challenging because the threat of maternal and/or fetal toxicity discourages the use of existing medications and hinders new drug development. One potential solution is the use of lipid nanoparticle (LNP) RNA therapies, given their proven efficacy, tolerability, and lack of fetal accumulation. Here, we describe LNPs for efficacious mRNA delivery to maternal organs in pregnant mice via several routes of administration. In the placenta, our lead LNP transfected trophoblasts, endothelial cells, and immune cells, with efficacy being structurally dependent on the ionizable lipid polyamine headgroup. Next, we show that LNP-induced maternal inflammatory responses affect mRNA expression in the maternal compartment and hinder neonatal development. Specifically, pro-inflammatory LNP structures and routes of administration curtailed efficacy in maternal lymphoid organs in an IL-1ß-dependent manner. Further, immunogenic LNPs provoked the infiltration of adaptive immune cells into the placenta and restricted pup growth after birth. Together, our results provide mechanism-based structural guidance on the design of potent LNPs for safe use during pregnancy.

Maternal manipulation of offspring size can trigger the evolution of eusociality in promiscuous species.

Eusocial organisms typically live in colonies with one reproductive queen supported by thousands of sterile workers. It is widely believed that monogamous mating is a precondition for the evolution of eusociality. Here, we present a theoretical model that simulates a realistic scenario for the evolution of eusociality. In the model, mothers can evolve control over resource allocation to offspring, affecting offspring's body size. The offspring can evolve body-size-dependent dispersal, by which they disperse to breed or stay at the nest as helpers. We demonstrate that eusociality can evolve even if mothers are not strictly monogamous, provided that they can constrain their offspring's reproduction through manipulation. We also observe the evolution of social polymorphism with small individuals that help and larger individuals that disperse to breed. Our model unifies the traditional kin selection and maternal manipulation explanations for the evolution of eusociality and demonstrates that-contrary to current consensus belief-eusociality can evolve despite highly promiscuous mating.

eIF4E1b is a non-canonical eIF4E protecting maternal dormant mRNAs.

Maternal mRNAs are essential for protein synthesis during oogenesis and early embryogenesis. To adapt translation to specific needs during development, maternal mRNAs are translationally repressed by shortening the polyA tails. While mRNA deadenylation is associated with decapping and degradation in somatic cells, maternal mRNAs with short polyA tails are stable. Here we report that the germline-specific eIF4E paralog, eIF4E1b, is essential for zebrafish oogenesis. eIF4E1b localizes to P-bodies in zebrafish embryos and binds to mRNAs with reported short or no polyA tails, including histone mRNAs. Loss of eIF4E1b results in reduced histone mRNA levels in early gonads, consistent with a role in mRNA storage. Using mouse and human eIF4E1Bs (in vitro) and zebrafish eIF4E1b (in vivo), we show that unlike canonical eIF4Es, eIF4E1b does not interact with eIF4G to initiate translation. Instead, eIF4E1b interacts with the translational repressor eIF4ENIF1, which is required for eIF4E1b localization to P-bodies. Our study is consistent with an important role of eIF4E1b in regulating mRNA dormancy and provides new insights into fundamental post-transcriptional regulatory principles governing early vertebrate development.

Are fetal microchimerism and circulating fetal extracellular vesicles important links between spontaneous preterm delivery and maternal cardiovascular disease risk?

Trafficking and persistence of fetal microchimeric cells (fMCs) and circulating extracellular vesicles (EVs) have been observed in animals and humans, but their consequences in the maternal body and their mechanistic contributions to maternal physiology and pathophysiology are not yet fully defined. Fetal cells and EVs may help remodel maternal organs after pregnancy-associated changes, but the cell types and EV cargos reaching the mother in preterm pregnancies after exposure to various risk factors can be distinct from term pregnancies. As preterm delivery-associated maternal complications are rising, revisiting this topic and formulating scientific questions for future research to reduce the risk of maternal morbidities are timely. Epidemiological studies report maternal cardiovascular risk as one of the major complications after preterm delivery. This paper suggests a potential link between fMCs and circulating EVs and adverse maternal cardiovascular outcomes post-pregnancies, the underlying mechanisms, consequences, and methods for and how this link might be assessed.

Maternal Spargel/dPGC-1 is critical for embryonic development and influences chorion gene amplification via Cyclin E activity.

The function of spargel/dPGC-1 in Drosophila oogenesis has been unequivocally established. Here, we sought to assess whether Spargel protein or RNA is essential for developmentally competent eggs. The trans-heterozygotic combination of two spargel mutant alleles allowed us to decrease Spargel expression to very low levels. Using this model, we now demonstrated the requirement for Spargel in eggshell patterning and embryonic development, which led us to establish that spargel is a maternal effect gene. Further examination of Spargel's potential mechanism of action in eggshell biogenesis revealed that low levels of Spargel in the adult ovary cause diminished Cyclin E activity, resulting in reduced chorion gene amplification levels, leading to eggshell biogenesis defects. Thus, another novel role for spargel/dPGC-1 is exposed whereby, through Cyclin E activity, this conserved transcriptional coactivator regulates the chorion gene amplification process.

Mating-induced increase of kynurenine in Drosophila ovary enhances starvation resistance of progeny.

The maternal nutritional environment can impact progeny development, stress tolerance, and longevity. Such phenotypic variation of offspring resulting from the maternal environment is often referred to as the 'maternal effect' and is observed across taxa, including in humans. While some mechanisms behind maternal effects have been revealed, such as histone modification, many studies rely on drastic genetic or nutritional manipulation in describing these mechanisms. Here we aimed to reveal how the maternal environment is regulated under physiological conditions to affect the progeny. Specifically, we detailed metabolic regulation in oocytes in response to mating using Drosophila melanogaster fruit flies. Using liquid chromatography-mass spectrometry, we found that upon mating, the ovary metabolites shifted, predominantly toward increasing amino acids and the tryptophan/kynurenine (Kyn) pathway. This mating-induced increase in ovary Kyn was driven by increased Kyn production in the fat body, a functional counterpart of the mammalian liver and white adipose tissue and the source of Kyn storage for the ovary after mating. Furthermore, we show that maternal Kyn repression decreased the starvation resistance of progeny and that administering exogenous Kyn to the maternal generation enhanced the starvation resistance of female progeny. Taken together, these findings point to a previously unidentified role of fat body Kyn distribution during reproduction on progeny survival.

Toward unveiling transcriptome dynamics and regulatory modules at the maternal/filial interface of developing maize kernel.

The basal region of maize (Zea mays) kernels, which includes the pedicel, placenta-chalazal, and basal endosperm transfer layers, serves as the maternal/filial interface for nutrient transfer from the mother plant to the developing seed. However, transcriptome dynamics of this maternal/filial interface remain largely unexplored. To address this gap, we conducted high-temporal-resolution RNA sequencing of the basal and upper kernel regions between 4 and 32 days after pollination and deeply analyzed transcriptome dynamics of the maternal/filial interface. Utilizing 790 specifically and highly expressed genes in the basal region, we performed the gene ontology (GO) term and weighted gene co-expression network analyses. In the early-stage basal region, we identified five MADS-box transcription factors (TFs) as hubs. Their homologs have been demonstrated as pivotal regulators at the maternal/filial interface of rice or Arabidopsis, suggesting their potential roles in maize kernel development. In the filling-stage basal region, numerous GO terms associated with transcriptional regulation and transporters are significantly enriched. Furthermore, we investigated the molecular function of three hub TFs. Through genome-wide DNA affinity purification sequencing combined with promoter transactivation assays, we suggested that these three TFs act as regulators of 10 basal-specific transporter genes involved in the transfer of sugars, amino acids, and ions. This study provides insights into transcriptomic dynamic and regulatory modules of the maternal/filial interface. In the future, genetic investigation of these hub regulators must advance our understanding of maternal/filial interface development and function.

Comparative Analysis of Maternal Gene Expression Patterns Unravels Evolutionary Signatures Across Reproductive Modes.

Maternal genes have a pivotal role in regulating metazoan early development. As such their functions have been extensively studied since the dawn of developmental biology. The temporal and spatial dynamics of their transcripts have been thoroughly described in model organisms and their functions have been undergoing heavy investigations. Yet, less is known about the evolutionary changes shaping their presence within diverse oocytes. Due to their unique maternal inheritance pattern, a high degree is predicted to be present when it comes to their expression. Insofar only limited and conflicting results have emerged around it. Here, we set out to elucidate which evolutionary changes could be detected in the maternal gene expression patterns using phylogenetic comparative methods on RNAseq data from 43 species. Using normalized gene expression values and fold change information throughout early development we set out to find the best-fitting evolutionary model. Through modeling, we find evidence supporting both the high degree of divergence and constraint on gene expression values, together with their temporal dynamics. Furthermore, we find that maternal gene expression alone can be used to explain the reproductive modes of different species. Together, these results suggest a highly dynamic evolutionary landscape of maternal gene expression. We also propose a possible functional dichotomy of maternal genes which is influenced by the reproductive strategy undertaken by examined species.

Genomic Diversity in the Endosymbiotic Bacteria of Human Head Lice.

Insects have repeatedly forged symbioses with heritable microbes, gaining novel traits. For the microbe, the transition to symbioses can lead to the degeneration of the symbiont's genome through transmission bottlenecks, isolation, and the loss of DNA repair enzymes. However, some insect-microbial symbioses have persisted for millions of years, suggesting that natural selection slows genetic drift and maintains functional consistency between symbiont populations. By sampling in multiple countries, we examine genomic diversity within a symbiont species, a heritable symbiotic bacterium found only in human head lice. We find that human head louse symbionts contain genetic diversity that appears to have arisen contemporaneously with the appearance of anatomically modern humans within Africa and/or during the colonization of Eurasia by humans. We predict that the observed genetic diversity underlies functional differences in extant symbiont lineages, through the inactivation of genes involved in symbiont membrane construction. Furthermore, we find evidence of additional gene losses prior to the appearance of modern humans, also impacting the symbiont membrane. From this, we conclude that symbiont genome degeneration is proceeding, via gene inactivation and subsequent loss, in human head louse symbionts, while genomic diversity is maintained. Collectively, our results provide a look into the genomic diversity within a single symbiont species and highlight the shared evolutionary history of humans, lice, and bacteria.

Acquisition of 2C-like totipotency through defined maternal-effect factors.

Fully grown oocytes have the natural ability to transform 2 terminally differentiated gametes into a totipotent zygote representing the acquisition of totipotency. This process wholly depends on maternal-effect factors (MFs). MFs stored in the eggs are therefore likely to be able to induce cellular reprogramming to a totipotency state. Here we report the generation of totipotent-like stem cells from mESCs using 4MFs Hsf1, Zar1, Padi6, and Npm2, designated as MFiTLSCs. MFiTLSCs exhibited a unique and inherent capability to differentiate into embryonic and extraembryonic derivatives. Transcriptomic analysis revealed that MFiTLSCs are enriched with 2-cell-specific genes that appear to synergistically induce a transcriptional repressive state, in that parental genomes are remodeled to a poised transcriptional repression state while totipotency is established following fertilization. This method to derive MFiTLSCs could help advance the understanding of fate determinations of totipotent stem cells in a physiological context and establish a foundation for the development of oocyte biology-based reprogramming technology.

HDAC1/2/3-mediated downregulation of neurogranin is involved in cognitive impairment in offspring exposed to maternal subclinical hypothyroidism.

Subclinical hypothyroidism (SCH) in pregnancy is the most common form of thyroid dysfunction in pregnancy, which can affect fetal nervous system development and increase the risk of neurodevelopmental disorders after birth. However, the mechanism of the effect of maternal subclinical hypothyroidism on fetal brain development and behavioral phenotypes is still unclear and requires further study. In this study, we constructed a mouse model of maternal subclinical hypothyroidism by exposing dams to drinking water containing 50 ppm propylthiouracil (PTU) during pregnancy and found that its offspring were accompanied by severe cognitive deficits by behavioral testing. Mechanistically, gestational SCH resulted in the upregulation of protein expression and activity of HDAC1/2/3 in the hippocampus of the offspring. ChIP analysis revealed that H3K9ac on the neurogranin (Ng) promoter was reduced in the hippocampus of the offspring of SCH, with a significant reduction in Ng protein, leading to reduced expression levels of synaptic plasticity markers PSD95 (a membrane-associated protein in the postsynaptic density) and SYN (synaptophysin, a specific marker for presynaptic terminals), and impaired synaptic plasticity. In addition, administration of MS-275 (an HDAC1/2/3-specific inhibitor) to SCH offspring alleviated impaired synaptic plasticity and cognitive dysfunction in offspring. Thus, our study suggests that maternal subclinical hypothyroidism may mediate offspring cognitive dysfunction through the HDAC1/2/3-H3K9ac-Ng pathway. Our study contributes to the understanding of the signaling mechanisms underlying maternal subclinical hypothyroidism-mediated cognitive impairment in the offspring.

IL1ß-NFκß-Myocardin signaling axis governs trophoblast-directed plasticity of vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) plasticity is fundamental in uterine spiral artery remodeling during placentation in Eutherian mammals. Our previous work showed that the invasion of trophoblast cells into uterine myometrium coincides with a phenotypic change of VSMCs. Here, we elucidate the mechanism by which trophoblast cells confer VSMC plasticity. Analysis of genetic markers on E13.5, E16.5, and E19.5 in the rat metrial gland, the entry point of uterine arteries, revealed that trophoblast invasion is associated with downregulation of MYOCARDIN, α-smooth muscle actin, and calponin1, and concomitant upregulation of Smemb in VSMCs. Myocardin overexpression or knockdown in VSMCs led to upregulation or downregulation of contractile markers, respectively. Co-culture of trophoblast cells with VSMCs decreased MYOCARDIN expression along with compromised expression of contractile markers in VSMCs. However, co-culture of trophoblast cells with VSMCs overexpressing MYOCARDIN inhibited their change in phenotype, whereas, overexpression of transactivation domain deleted MYOCARDIN failed to elicit this response. Furthermore, the co-culture of trophoblast cells with VSMCs led to the activation of NFκß signaling. Interestingly, despite producing IL-1ß, trophoblast cells possess only the decoy receptor, whereas, VSMCs possess the IL-1ß signaling receptor. Treatment of VSMCs with exogenous IL-1ß led to a decrease in MYOCARDIN and an increase in phosphorylation of NFκß. The effect of trophoblast cells in the downregulation of MYOCARDIN in VSMCs was reversed by blocking NFκß translocation to the nucleus. Together, these data highlight that trophoblast cells direct VSMC plasticity, and trophoblast-derived IL-1ß is a key player in downregulating MYOCARDIN via the NFκß signaling pathway.

Role of the GLP2-Wnt1 axis in silicon-rich alkaline mineral water maintaining intestinal epithelium regeneration in piglets under early-life stress.

Stress-induced intestinal epithelial injury (IEI) and a delay in repair in infancy are predisposing factors for refractory gut diseases in adulthood, such as irritable bowel syndrome (IBS). Hence, it is necessary to develop appropriate mitigation methods for mammals when experiencing early-life stress (ELS). Weaning, as we all know, is a vital procedure that all mammalian newborns, including humans, must go through. Maternal separation (MS) stress in infancy (regarded as weaning stress in animal science) is a commonly used ELS paradigm. Drinking silicon-rich alkaline mineral water (AMW) has a therapeutic effect on enteric disease, but the specific mechanisms involved have not been reported. Herein, we discover the molecular mechanism by which silicon-rich AMW repairs ELS-induced IEI by maintaining intestinal stem cell (ISC) proliferation and differentiation through the glucagon-like peptide (GLP)2-Wnt1 axis. Mechanistic study showed that silicon-rich AMW activates GLP2-dependent Wnt1/ß-catenin pathway, and drives ISC proliferation and differentiation by stimulating Lgr5+ ISC cell cycle passage through the G1-S-phase checkpoint, thereby maintaining intestinal epithelial regeneration and IEI repair. Using GLP2 antagonists (GLP23-33) and small interfering RNA (SiWnt1) in vitro, we found that the GLP2-Wnt1 axis is the target of silicon-rich AMW to promote intestinal epithelium regeneration. Therefore, silicon-rich AMW maintains intestinal epithelium regeneration through the GLP2-Wnt1 axis in piglets under ELS. Our research contributes to understanding the mechanism of silicon-rich AMW promoting gut epithelial regeneration and provides a new strategy for the alleviation of ELS-induced IEI.