Chemotactic movement of a polarity site enables yeast cells to find their mates.

How small eukaryotic cells can interpret dynamic, noisy, and spatially complex chemical gradients to orient growth or movement is poorly understood. We address this question using Saccharomyces cerevisiae, where cells orient polarity up pheromone gradients during mating. Initial orientation is often incorrect, but polarity sites then move around the cortex in a search for partners. We find that this movement is biased by local pheromone gradients across the polarity site: that is, movement of the polarity site is chemotactic. A bottom-up computational model recapitulates this biased movement. The model reveals how even though pheromone-bound receptors do not mimic the shape of external pheromone gradients, nonlinear and stochastic effects combine to generate effective gradient tracking. This mechanism for gradient tracking may be applicable to any cell that searches for a target in a complex chemical landscape.

Fetal Nasal Bone Length in the East African Population.

OBJECTIVES: To establish normal ranges of fetal nasal bone length throughout gestation in the East African population and to subsequently compare these measurements with the standardized reference. METHODS: A retrospective cross-sectional study was performed at the University of Minnesota from January 2011 to December 2016. Fetal nasal bone length measurements were generated in a midsagittal plane at an angle of insonation of 45° from ultrasound images of 1407 nonanomalous fetuses of 1130 mothers of East African decent between 14 and 40 weeks' gestation. The proportion of fetal nasal bone lengths of less than 5.2 mm at week 20 of gestation in the East African population was then compared with the 5% noted by the standardized reference by a χ2 test. RESULTS: The fetal nasal bone length increased linearly with advancing gestational age in fetuses of East African mothers (R2 = 0.53; P < .0001). The fetal nasal bone lengths of the East African fetuses were found to be shorter at all ages of gestation compared with the standard reference. At 20 weeks' gestation 17% (95% confidence interval, 13%-22%) of the nasal bone lengths of the East African fetuses were less than 5.2 mm compared with 5% of white and African American fetuses. CONCLUSIONS: Using the standard reference may lead to a greater than 3.5-fold overdiagnosis of hypoplastic nasal bones in the East African population. To improve aneuploidy risk stratification and patient counseling in the East African population, the introduction of a standardized East African-based fetal nasal bone length reference seems warranted.

Preterm Birth of Infants Prenatally Diagnosed with Congenital Heart Disease, Characteristics, Associations, and Outcomes.

There are limited data on the relation between congenital heart disease (CHD) and preterm birth (PTB). We aimed to estimate the risk of PTB in newborns with CHD, to study associations and risk factors (modifiable and non-modifiable) as well as investigate postnatal outcomes. This was a retrospective cohort study of 336 pregnancies diagnosed with CHD between 2011 and 2016. Groups consisted of those delivered at or after 37 weeks, and those who delivered prior to 37 weeks. Collected data included maternal and fetal characteristics as well postnatal outcomes. Complete data were obtained from 237 singleton pregnancies. The overall proportion of PTB was 23.2% for all CHD, of which 38.2% were spontaneous PTB which was almost unchanged after excluding extracardiac anomalies and pathogenic chromosomal abnormalities. Significant non-modifiable risk factors were pregnancy-related HTN disorders (P < 0.001), fetal growth restriction (P = 0.01), and pathogenic chromosomal abnormalities (P = 0.046). Significant PTB modifiable risk factors included prenatal marijuana use (P = 0.01). Pregnancies delivered at 37-38 weeks had significantly more newborns with birthweight < 2500 g (P < 0.001), required more pre-operative NICU support including intubation (P = 0.049), vasopressors (P = 0.04), prostaglandins (P = 0.003), antibiotics (P = 0.01), and had longer hospital stay (P = 0.001) than those delivered at ≥ 39 weeks. Prenatally diagnosed pregnancies with CHD had higher PTB rate compared to the general population, with spontaneous PTB comprising 38.2% of these preterm deliveries. Most PTB risk factors were non-modifiable, however, significant modifiable factors included marijuana use in pregnancy. Outcomes were favorable in neonates delivered at or beyond 39 weeks.

Polycystins recruit cargo to distinct ciliary extracellular vesicle subtypes.

Therapeutic use of tiny extracellular vesicles (EVs) requires understanding cargo loading mechanisms. Here, we used a modular proximity label approach to identify EV cargo associated with the transient potential channel (TRP) polycystin PKD-2 of C. elegans. Polycystins are conserved receptor-TRP channel proteins affecting cilium function; dysfunction causes polycystic kidney disease in humans and mating deficits in C. elegans. Polycystin-2 EV localization is conserved from algae to humans, hinting at an ancient and unknown function. We discovered that polycystins associate with and direct specific cargo to EVs: channel-like PACL-1, dorsal and ventral membrane C-type lectins PAMLs, and conserved tumor necrosis-associated factor (TRAF) signaling adaptors TRF-1 and TRF-2. Loading of these components relied on polycystin-1 LOV-1. Our modular EV-TurboID approach can be applied in both cell- and tissue-specific manners to define the composition of distinct EV subtypes, addressing a major challenge of the EV field.

Human cytomegalovirus in breast milk is associated with milk composition and the infant gut microbiome and growth.

Human cytomegalovirus (CMV) is a highly prevalent herpesvirus that is often transmitted to the neonate via breast milk. Postnatal CMV transmission can have negative health consequences for preterm and immunocompromised infants, but any effects on healthy term infants are thought to be benign. Furthermore, the impact of CMV on the composition of the hundreds of bioactive factors in human milk has not been tested. Here, we utilize a cohort of exclusively breastfeeding full-term mother-infant pairs to test for differences in the milk transcriptome and metabolome associated with CMV, and the impact of CMV in breast milk on the infant gut microbiome and infant growth. We find upregulation of the indoleamine 2,3-dioxygenase (IDO) tryptophan-to-kynurenine metabolic pathway in CMV+ milk samples, and that CMV+ milk is associated with decreased Bifidobacterium in the infant gut. Our data indicate two opposing CMV-associated effects on infant growth; with kynurenine positively correlated, and CMV viral load negatively correlated, with infant weight-for-length at 1 month of age. These results suggest CMV transmission, CMV-related changes in milk composition, or both may be modulators of full-term infant development.

Murine isoforms of UDP-GlcNAc 2-epimerase/ManNAc kinase: Secondary structures, expression profiles, and response to ManNAc therapy.

The bifunctional enzyme UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE) catalyzes the first two committed steps in sialic acid synthesis. Non-allosteric GNE gene mutations cause the muscular disorder GNE myopathy (also known as hereditary inclusion body myopathy), whose exact pathology remains unknown. Increased knowledge of GNE regulation, including isoform regulation, may help elucidate the pathology of GNE myopathy. While eight mRNA transcripts encoding human GNE isoforms are described, we only identified two mouse Gne mRNA transcripts, encoding mGne1 and mGne2, homologous to human hGNE1 and hGNE2. Orthologs of the other human isoforms were not identified in mice. mGne1 appeared as the ubiquitously expressed, major mouse isoform. The mGne2 encoding transcript is differentially expressed and may act as a tissue-specific regulator of sialylation. mGne2 expression appeared significantly increased the first 2 days of life, possibly reflecting the high sialic acid demand during this period. Tissues of the knock-in Gne p.M712T mouse model had similar mGne transcript expression levels among genotypes, indicating no effect of the mutation on mRNA expression. However, upon treatment of these mice with N-acetylmannosamine (ManNAc, a Gne substrate, sialic acid precursor, and proposed therapy for GNE myopathy), Gne transcript expression, in particular mGne2, increased significantly, likely resulting in increased Gne enzymatic activities. This dual effect of ManNAc supplementation (increased flux through the sialic acid pathway and increased Gne activity) needs to be considered when treating GNE myopathy patients with ManNAc. In addition, the existence and expression of GNE isoforms needs consideration when designing other therapeutic strategies for GNE myopathy.

TAVR Beyond Fetal Viability: An Alternative to Preterm Delivery in Symptomatic Severe Aortic Stenosis.

A patient with structural valve degeneration of an aortic bioprosthesis with stenosis stage 3 underwent valve-in-valve transcatheter aortic valve replacement (TAVR) at 29 weeks with improvement. This is the first reported TAVR in the third trimester. TAVR may be an alternative to preterm delivery in cases of symptomatic aortic stenosis.

Human Cytomegalovirus in breast milk is associated with milk composition, the infant gut microbiome, and infant growth.

Human cytomegalovirus (CMV) is a highly prevalent herpesvirus that is often transmitted to the neonate via breast milk. Postnatal CMV transmission can have negative health consequences for preterm and immunocompromised infants, but any effects on healthy term infants are thought to be benign. Furthermore, the impact of CMV on the composition of the hundreds of bioactive factors in human milk has not been tested. Here, we utilize a cohort of exclusively breastfeeding full term mother-infant pairs to test for differences in the milk transcriptome and metabolome associated with CMV, and the impact of CMV in breast milk on the infant gut microbiome and infant growth. We find upregulation of the indoleamine 2,3- dioxygenase (IDO) tryptophan-to-kynurenine metabolic pathway in CMV+ milk samples, and that CMV+ milk is associated with decreased Bifidobacterium in the infant gut. Our data indicate a complex relationship between milk CMV, milk kynurenine, and infant growth; with kynurenine positively correlated, and CMV viral load negatively correlated, with infant weight-for-length at 1 month of age. These results suggest CMV transmission, CMV-related changes in milk composition, or both may be modulators of full term infant development.

Human milk variation is shaped by maternal genetics and impacts the infant gut microbiome.

Human milk is a complex mix of nutritional and bioactive components that provide complete nutrition for the infant. However, we lack a systematic knowledge of the factors shaping milk composition and how milk variation influences infant health. Here, we used multi-omic profiling to characterize interactions between maternal genetics, milk gene expression, milk composition, and the infant fecal microbiome in 242 exclusively breastfeeding mother-infant pairs. We identified 487 genetic loci associated with milk gene expression unique to the lactating mammary gland, including loci that impacted breast cancer risk and human milk oligosaccharide concentration. Integrative analyses uncovered connections between milk gene expression and infant gut microbiome, including an association between the expression of inflammation-related genes with IL-6 concentration in milk and the abundance of Bifidobacteria in the infant gut. Our results show how an improved understanding of the genetics and genomics of human milk connects lactation biology with maternal and infant health.

Oral monosaccharide therapies to reverse renal and muscle hyposialylation in a mouse model of GNE myopathy.

GNE myopathy, previously termed hereditary inclusion body myopathy (HIBM), is an adult-onset neuromuscular disorder characterized by progressive muscle weakness. The disorder results from biallelic mutations in GNE, encoding UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, the key enzyme of sialic acid synthesis. GNE myopathy, associated with impaired glycan sialylation, has no approved therapy. Here we test potential sialylation-increasing monosaccharides for their effectiveness in prophylaxis (at the embryonic and neonatal stages) and therapy (after the onset of symptoms) by evaluating renal and muscle hyposialylation in a knock-in mouse model (Gne p.M712T) of GNE myopathy. We demonstrate that oral mannosamine (ManN), but not sialic acid (Neu5Ac), mannose (Man), galactose (Gal), or glucosamine (GlcN), administered to pregnant female mice has a similar prophylactic effect on renal hyposialylation, pathology and neonatal survival of mutant offspring, as previously shown for N-acetylmannosamine (ManNAc) therapy. ManN may be converted to ManNAc by a direct, yet unknown, pathway, or may act through another mode of action. The other sugars (Man, Gal, GlcN) may either not cross the placental barrier (Neu5Ac) and/or may not be able to directly increase sialylation. Because GNE myopathy patients will likely require treatment in adulthood after onset of symptoms, we also administered ManNAc (1 or 2g/kg/day for 12 weeks), Neu5Ac (2 g/kg/day for 12 weeks), or ManN (2 g/kg/day for 6 weeks) in drinking water to 6 month old mutant Gne p.M712T mice. All three therapies markedly improved the muscle and renal hyposialylation, as evidenced by lectin histochemistry for overall sialylation status and immunoblotting of specific sialoproteins. These preclinical data strongly support further evaluation of oral ManNAc, Neu5Ac and ManN as therapy for GNE myopathy and conceivably for certain glomerular diseases with hyposialylation.

Mechanism of commitment to a mating partner in Saccharomyces cerevisiae.

Many cells detect and follow gradients of chemical signals to perform their functions. Yeast cells use gradients of extracellular pheromones to locate mating partners, providing a tractable model for understanding how cells decode the spatial information in gradients. To mate, yeast cells must orient polarity toward the mating partner. Polarity sites are mobile, exploring the cell cortex until they reach the proper position, where they stop moving and "commit" to the partner. A simple model to explain commitment posits that a high concentration of pheromone is detected only upon alignment of partner cells' polarity sites and causes polarity site movement to stop. Here we explore how yeast cells respond to partners that make different amounts of pheromone. Commitment was surprisingly robust to various pheromone levels, ruling out the simple model. We also tested whether adaptive pathways were responsible for the robustness of commitment, but our results show that cells lacking those pathways were still able to accommodate changes in pheromone. To explain this robustness, we suggest that the steep pheromone gradients near each mating partner's polarity site trap the polarity site in place.

Pheromone Guidance of Polarity Site Movement in Yeast.

Cells' ability to track chemical gradients is integral to many biological phenomena, including fertilization, development, accessing nutrients, and combating infection. Mating of the yeast Saccharomyces cerevisiae provides a tractable model to understand how cells interpret the spatial information in chemical gradients. Mating yeast of the two different mating types secrete distinct peptide pheromones, called a-factor and α-factor, to communicate with potential partners. Spatial gradients of pheromones are decoded to guide mobile polarity sites so that polarity sites in mating partners align towards each other, as a prerequisite for cell-cell fusion and zygote formation. In ascomycetes including S. cerevisiae, one pheromone is prenylated (a-factor) while the other is not (α-factor). The difference in physical properties between the pheromones, combined with associated differences in mechanisms of secretion and extracellular pheromone metabolism, suggested that the pheromones might differ in the spatial information that they convey to potential mating partners. However, as mating appears to be isogamous in this species, it is not clear why any such signaling difference would be advantageous. Here we report assays that directly track movement of the polarity site in each partner as a way to understand the spatial information conveyed by each pheromone. Our findings suggest that both pheromones convey very similar information. We speculate that the different pheromones were advantageous in ancestral species with asymmetric mating systems and may represent an evolutionary vestige in yeasts that mate isogamously.

Targeted secretion: Myosin V delivers vesicles through formin condensates.

Secretory vesicles are often delivered to very specific targets, like pre-synaptic terminals or cell tips, to focus exocytosis. New work suggests that a biomolecular condensate focuses actin filaments that deliver incoming vesicles through the condensate to the plasma membrane.

Chemotropism and Cell-Cell Fusion in Fungi.

Fungi exhibit an enormous variety of morphologies, including yeast colonies, hyphal mycelia, and elaborate fruiting bodies. This diversity arises through a combination of polar growth, cell division, and cell fusion. Because fungal cells are nonmotile and surrounded by a protective cell wall that is essential for cell integrity, potential fusion partners must grow toward each other until they touch and then degrade the intervening cell walls without impacting cell integrity. Here, we review recent progress on understanding how fungi overcome these challenges. Extracellular chemoattractants, including small peptide pheromones, mediate communication between potential fusion partners, promoting the local activation of core cell polarity regulators to orient polar growth and cell wall degradation. However, in crowded environments, pheromone gradients can be complex and potentially confusing, raising the question of how cells can effectively find their partners. Recent findings suggest that the cell polarity circuit exhibits searching behavior that can respond to pheromone cues through a remarkably flexible and effective strategy called exploratory polarization.

Bacterial, fungal, and interkingdom microbiome features of exclusively breastfeeding dyads are associated with infant age, antibiotic exposure, and birth mode.

The composition and function of early life gut bacterial communities (microbiomes) have been proposed to modulate health for the long term. In addition to bacteria, fungi (mycobiomes) also colonize the early life gut and have been implicated in health disorders such as asthma and obesity. Despite the potential importance of mycobiomes in health, there has been a lack of study regarding fungi and their interkingdom interactions with bacteria during infancy. The goal of this study was to obtain a more complete understanding of microbial communities thought to be relevant for the early life programming of health. Breastmilk and infant feces were obtained from a unique cohort of healthy, exclusively breastfeeding dyads recruited as part of the Mothers and Infants Linked for Healthy Growth (MILk) study with microbial taxa characterized using amplicon-based sequencing approaches. Bacterial and fungal communities in breastmilk were both distinct from those of infant feces, consistent with niche-specific microbial community development. Nevertheless, overlap was observed among sample types (breastmilk, 1-month feces, 6-month feces) with respect to the taxa that were the most prevalent and abundant. Self-reported antibacterial antibiotic exposure was associated with micro- as well as mycobiome variation, which depended upon the subject receiving antibiotics (mother or infant), timing of exposure (prenatal, peri- or postpartum), and sample type. In addition, birth mode was associated with bacterial and fungal community variation in infant feces, but not breastmilk. Correlations between bacterial and fungal taxa abundances were identified in all sample types. For infant feces, congruency between bacterial and fungal communities was higher for older infants, consistent with the idea of co-maturation of bacterial and fungal gut communities. Interkingdom connectedness also tended to be higher in older infants. Additionally, higher interkingdom connectedness was associated with Cesarean section birth and with antibiotic exposure for microbial communities of both breastmilk and infant feces. Overall, these results implicate infant age, birth mode, and antibiotic exposure in bacterial, fungal and interkingdom relationship variation in early-life-relevant microbiomes, expanding the current literature beyond bacteria.

Gestational Diabetes Mellitus Is Associated with Altered Abundance of Exosomal MicroRNAs in Human Milk.

PURPOSE: Human milk (HM) is a unique biological fluid that is enriched with a variety of factors, including microRNAs (miRNAs) that potentially provide both short- and long-term benefits to the infants. miRNAs are packaged within exosomes, making them bioavailable to infants. Gestational diabetes mellitus (GDM) may affect the abundance of exosomal miRNAs in HM, providing a mechanism for growth and adiposity variation in infants of mothers with GDM in early life. Therefore, the purposes of this study were to examine the impact of GDM on select miRNAs (miRNA-148a, miRNA-30b, miRNA-let-7a, and miRNA-let-7d) involved in metabolism and to examine the association of these miRNAs with measures of infant body composition in the first 6 months of life. METHODS: Milk samples were collected from a cohort of 94 mothers (62 mothers without GDM and 32 mothers with GDM) matched on body mass index strata at 1 month post partum. miRNA abundance was measured by real-time polymerase chain reaction. Linear regression models were used to examine potential differences in miRNA abundance in women with and without GDM, testing associations between miRNA abundance and infant growth and body composition measures from 1 to 6 months. FINDINGS: The abundances of miRNA-148a, miRNA-30b, miRNA-let-7a, and miRNA-let-7d were reduced in milk from mothers with GDM. Independent of GDM status, higher maternal diet quality was associated with increased abundance of each of the measured miRNAs. miRNA-148a was negatively associated with infant weight, percentage of body fat, and fat mass, whereas miRNA-30b was positively associated with infant weight and fat mass at 1 month of age. There was no association of milk miRNA-148a and miRNA-30b with infant weight at 1 month of age or with body composition measures at 3 months of age; however, miRNA-148a was negatively associated with infant weight at 6 months of age. IMPLICATIONS: If supported by randomized dietary supplementation or other intervention trials, HM miRNAs may be a therapeutic target to mitigate risk of metabolic outcomes in offspring of women with GDM.

Gestational Diabetes Mellitus Is Associated with Differences in Human Milk Hormone and Cytokine Concentrations in a Fully Breastfeeding United States Cohort.

It is unclear whether gestational diabetes mellitus (GDM) alters breast milk composition. We prospectively examined associations of GDM status with concentrations of six potentially bioactive elements (glucose, insulin, C-reactive protein (CRP), interleukin-6 (IL-6), leptin, and adiponectin) in human milk. These were measured at both 1 and 3 months postpartum in 189 fully breastfeeding women. Mixed-effects linear regression assessed GDM status-related differences in these milk bioactives, adjusting for demographics, maternal factors, and diet. At 1 and 3 months postpartum, milk CRP was higher (1.46 ± 0.31 ng/mL; p < 0.001 and 1.69 ± 0.31 ng/mL; p < 0.001) in women with GDM than in women without GDM, whereas milk glucose (−5.23 ± 2.22 mg/dL; p = 0.02 and −5.70 ± 2.22; p = 0.01) and milk insulin (−0.38 ± 0.17 µIU/mL; p = 0.03 and −0.53 ± 0.17; p = 0.003) were lower in women with GDM. These significant associations remained similar after additional adjustment for maternal weight status and its changes. No difference was found for milk IL-6, leptin, and adiponectin. There was no evidence of association between these milk bioactive compounds and 1 h non-fasting oral glucose challenge serum glucose in the women without GDM. This prospective study provides evidence that potentially bioactive elements of human milk composition are altered in women with GDM.

Identification, tissue distribution, and molecular modeling of novel human isoforms of the key enzyme in sialic acid synthesis, UDP-GlcNAc 2-epimerase/ManNAc kinase.

UDP-GlcNAc 2-epimerase/ManNAc kinase (GNE) catalyzes the first two committed steps in sialic acid synthesis. In addition to the three previously described human GNE isoforms (hGNE1-hGNE3), our database and polymerase chain reaction analysis yielded five additional human isoforms (hGNE4-hGNE8). hGNE1 is the ubiquitously expressed major isoform, while the hGNE2-hGNE8 isoforms are differentially expressed and may act as tissue-specific regulators of sialylation. hGNE2 and hGNE7 display a 31-residue N-terminal extension compared to hGNE1. On the basis of similarities to kinases and helicases, this extension does not seem to hinder the epimerase enzymatic active site. hGNE3 and hGNE8 contain a 55-residue N-terminal deletion and a 50-residue N-terminal extension compared to hGNE1. The size and secondary structures of these fragments are similar, and modeling predicted that these modifications do not affect the overall fold compared to that of hGNE1. However, the epimerase enzymatic activity of GNE3 and GNE8 is likely absent, because the deleted fragment contains important substrate binding residues in homologous bacterial epimerases. hGNE5-hGNE8 have a 53-residue deletion, which was assigned a role in substrate (UDP-GlcNAc) binding. Deletion of this fragment likely eliminates epimerase enzymatic activity. Our findings imply that GNE is subject to evolutionary mechanisms to improve cellular functions, without increasing the number of genes. Our expression and modeling data contribute to elucidation of the complex functional and regulatory mechanisms of human GNE and may contribute to further elucidating the pathology and treatment strategies of the human GNE-opathies sialuria and hereditary inclusion body myopathy.

Polyhydramnios with bidirectional fetal ductus arteriosus flow in a fetus with congenital diaphragmatic hernia: case report.

The etiology of polyhydramnios may be attributed to either increased production of amniotic fluid (fetal polyuria or high-output cardiac failure) or decreased fetal swallowing (obstruction or neurological impairment). Although idiopathic polyhydramnios occurs in nearly half of all cases, it is often associated with fetal abnormalities. Fetal ductus arteriosus flow is normally from right to left. We report a case of antenatally detected bidirectional fetal ductus arteriosus flow diagnosed concomitantly with polyhydramnios. Amnioreduction was performed due to severe maternal symptoms, which resulted in correction of the fetal ductus arteriosus flow. Postnatal diagnosis of a Morgagni diaphragmatic hernia indicates that our sonographic findings collectively may have been a diagnostic clue.