Gene Expression in Placentas From Nondiabetic Women Giving Birth to Large for Gestational Age Infants

Differential gene expression in two consecutive pregnancies between same sex siblings and implications on maternal constraint

The objective of this study was to investigate how placental gene expression differs in two consecutive pregnancies in same sex siblings, and its possible association with the "maternal constraint" hypothesis. Material was gathered from the BASIC study (Biological, Affect, Stress, Imaging, and Cognition in Pregnancy and the Puerperium), a population based prospective study that was started in 2009 in Uppsala. Over 900 specimens of placenta biopsies were collected and out of these 10 women gave birth twice, to the same sex child, and were included in this study. The total RNA was isolated and prepared from frozen villous tissue from the placenta and further analyzed by use of Ion AmpliSeq Human Transcriptome Gene Expression kit. A total of 234 genes differed significantly between the first and second pregnancy placentas, when adjusting for delivery mode, maternal BMI and gestational age. Of special interest was the down-regulated group of genes in the second pregnancy. Exemplified by Pentraxin 3, SRY-Box Transcription Factor 9, and Serum Amyloid A1, which all were associated with biological processes involved in the immune system and inflammation. Further, protein-protein interaction analysis visualized them as hub genes interacting with several of the other differentially expressed genes. How these altered gene expressions affect maternal constraint during pregnancy needs further validation in lager study cohorts and also future validation in functional assays.

Cohort profile: the U-BIRTH study on peripartum depression and child development in Sweden

PURPOSE

The current U-BIRTH cohort (Uppsala Birth Cohort) extends our previous cohort Biology, Affect, Stress, Imaging and Cognition (BASIC), assessing the development of children up to 11 years after birth. The U-BIRTH study aims to (1) assess the impact of exposure to peripartum mental illness on the children's development taking into account biological and environmental factors during intrauterine life and childhood; (2) identify early predictors of child neurodevelopmental and psychological problems using biophysiological, psychosocial and environmental variables available during pregnancy and early post partum.

PARTICIPANTS

All mothers participating in the previous BASIC cohort are invited, and mother-child dyads recruited in the U-BIRTH study are consecutively invited to questionnaire assessments and biological sampling when the child is 18 months, 6 years and 11 years old. Data collection at 18 months (n=2882) has been completed. Consent for participation has been obtained from 1946 families of children having reached age 6 and from 698 families of children having reached age 11 years.

FINDINGS TO DATE

Based on the complete data from pregnancy to 18 months post partum, peripartum mental health was significantly associated with the development of attentional control and gaze-following behaviours, which are critical to cognitive and social learning later in life. Moreover, infants of depressed mothers had an elevated risk of difficult temperament and behavioural problems compared with infants of non-depressed mothers. Analyses of biological samples showed that peripartum depression and anxiety were related to DNA methylation differences in infants. However, there were no methylation differences in relation to infants' behavioural problems at 18 months of age.

FUTURE PLANS

Given that the data collection at 18 months is complete, analyses are now being undertaken. Currently, assessments for children reaching 6 and 11 years are ongoing.

Gene expression of leptin, leptin receptor isoforms and inflammatory cytokines in placentas of obese women - Associations to birth weight and fetal sex

INTRODUCTION

Leptin signaling in placentas of obese women may influence fetal growth and may be dependent on fetal sex. The aim of this study was to investigate placental gene expression of leptin, its receptor and inflammatory cytokines in obese mothers in relation to offspring birth weight and sex.

METHODS

In total, 109 placental tissue samples from severely obese women (body mass index in first trimester ≥35 kg/m²) giving birth vaginally at term to a healthy child were included. Quantitative real-time PCR was used for the analysis of leptin (LEP), its receptor LEPR with two splice variants, interleukin (IL)1B, chemokine (C-X-C motif) ligand 8 (CXCL8), tumour necrosis factor (TNF), IL6, IL10, hypoxia-inducible factor 1-alpha (HIF1A) and insulin receptor (INSR). The subjects were divided into three groups based on LEP expression percentiles (<25th percentile; 25-75th percentile and >75th percentile).

RESULTS

A reverse U-shaped association between LEP expression and birth weight z-scores was found (R² = 0.075, p = 0.005). Placental LEPRb expression was downregulated (p = 0.034) in those with highest LEP expression. Female infants had higher birth weight z-scores than males (0.58 (-1.49-2.88) vs 0.21 (-1.50-2.93), p = 0.020) and their placental LEPRb expression was upregulated (p = 0.047). The associations between expression of different genes differed by sex.

DISCUSSION

A reverse U-shaped relationship between placental LEP expression and offspring birth weight z-scores was found together with sexual dimorphism in LEPRb expression indicating a complex regulation of fetal growth by placental leptin signaling in maternal obesity.

Genome-wide microRNA expression analysis in human placenta reveals sex-specific patterns: an ENVIRONAGE birth cohort study

There is an increasing interest in microRNAs (miRNAs) as they are of utmost importance in gene regulation at the posttranscriptional level. Sex-related susceptibility for non-communicable diseases later in life could originate in early life. Until now, no data on sex-specific miRNA expression are available for the placenta. Therefore, we investigated the difference by sex of newborn's miRNA expression in human placental tissue. Within the ENVIRONAGE birth cohort, miRNA and mRNA expression profiling was performed in 60 placentae (50% boys) using Agilent (8 × 60 K) microarrays. The distribution of chromosome locations was studied and pathway analysis of the identified sex-specific miRNAs in the placenta was carried out. Of the total 2558 miRNAs on the array, 597 miRNAs were expressed in over 70% of the samples and were included for further analyses. A total of 142 miRNAs were significantly (FDR<0.05) associated with the newborn's sex. In newborn girls, 76 miRNAs had higher expression (hsa-miR-361-5p as most significant) and 66 miRNAs had lower expression (hsa-miR-4646-5p as most significant) than in newborn boys. In the same study population, placental differentially expressed genes by sex were also identified using a whole genome approach. The placental gene expression revealed 27 differentially expressed genes by comparing girls to boys. Ultimately, we studied the miRNA-RNA interactome and identified 14 miRNA-mRNA interactions as sex-specific. Sex differences in placental m(i)RNA expression may reveal sex-specific patterns already present during pregnancy, which may influence physiological conditions in early or later life. These molecular processes might play a role in sex-specific disease susceptibility in later life.

Second Trimester Maternal Leptin Levels Are Associated with Body Mass Index and Gestational Weight Gain but not Birth Weight of the Infant

INTRODUCTION

Obesity is increasing among the pregnant population. Leptin has an important role in the regulation of energy balance and hunger. The aim of this study was to investigate the association between maternal leptin levels with maternal obesity, gestational weight gain (GWG), single nucleotide polymorphisms (SNPs) within the leptin gene, and the age-adjusted birth weight of the child.

MATERIAL AND METHODS

Maternal leptin levels (n = 740) and SNPs (n = 504) were analyzed in blood samples taken within the Uppsala Biobank of Pregnant women at pregnancy weeks 16-19.

RESULTS

Maternal leptin levels differed significantly between body mass index (BMI) groups. Normal weight women had the lowest median leptin levels and levels increased with each BMI group. Leptin SNP genotype was not associated with leptin levels or BMI. There was also no association between maternal leptin levels and age-adjusted birth weight of the child except for a negative association between leptin levels and birth weight in the morbid obese group.

DISCUSSION/CONCLUSION

Maternal BMI was identified as the best positive explanatory factor for maternal leptin levels. Leptin was a strong positive explanatory factor for GWG. Birth weight of children of uncomplicated pregnancies was, however, dependent on maternal height, BMI, GWG, and parity but not leptin levels, except for in morbid obese women where a negative association between maternal leptin levels and birth weight was found. We speculate that this indicates altered placental function, not manifested in pregnancy complication. We conclude that maternal leptin levels do not affect the birth weight of the child more than BMI, GWG, and parity.

Age-, sex- and disease subtype-related foetal growth differentials in childhood acute myeloid leukaemia risk: A Childhood Leukemia International Consortium analysis

AIM

Evidence for an association of foetal growth with acute myeloid leukaemia (AML) is inconclusive. AML is a rare childhood cancer, relatively more frequent in girls, with distinct features in infancy. In the context of the Childhood Leukemia International Consortium (CLIC), we examined the hypothesis that the association may vary by age, sex and disease subtype using data from 22 studies and a total of 3564 AML cases.

METHODS

Pooled estimates by age, sex and overall for harmonised foetal growth markers in association with AML were calculated using the International Fetal and Newborn Growth Consortium for the 21st Century Project for 17 studies contributing individual-level data; meta-analyses were, thereafter, conducted with estimates provided ad hoc by five more studies because of administrative constraints. Subanalyses by AML subtype were also performed.

RESULTS

A nearly 50% increased risk was observed among large-for-gestational-age infant boys (odds ratio [OR]: 1.49, 95% confidence interval [CI]: 1.03-2.14), reduced to 34% in boys aged <2 years (OR: 1.34, 95% CI: 1.05-1.71) and 25% in boys aged 0-14 years (OR: 1.25, 95% CI: 1.06-1.46). The association of large for gestational age became stronger in boys with M0/M1subtype (OR: 1.80, 95% CI: 1.15-2.83). Large birth length for gestational age was also positively associated with AML (OR: 1.38, 95% CI: 1.00-1.92) in boys. By contrast, there were null associations in girls, as well as with respect to associations of decelerated foetal growth markers.

CONCLUSIONS

Accelerated foetal growth was associated with AML, especially in infant boys and those with minimally differentiated leukaemia. Further cytogenetic research would shed light into the underlying mechanisms.

Genome-wide DNA methylation changes in placenta tissues associated with small for gestational age newborns; cohort study in the Chinese population

Aim: To investigate DNA methylation changes in placenta tissues associated with small for gestational age (SGA). Materials & methods: A prospective cohort study consisting of 1292 pregnant women from China (including 39 SGA with placenta tissues) was performed, microarray and pyrosequencing were conducted. Results: Total 2012 methylation variable positions stood out from all probes (p < 0.05; Δβ > 0.2). In SGA cases, a CpG site within ANKRD20B showed lower methylation level (p = 0.032) than appropriate for gestational age in validation cohort. Five sites within FAM198A (p = 0.047, 0.050, 0.039, 0.026 and 0.043, respectively) had a reduced methylation in male newborns whose mother had preconception folic acid supplementation. Conclusion: DNA methylation changes in placenta tissues may be associated with SGA, maternal preconception folic acid supplementation status and also be fetal sex-specific.

A Co-expression Analysis of the Placental Transcriptome in Association With Maternal Pre-pregnancy BMI and Newborn Birth Weight

Maternal body mass index (BMI) before pregnancy is known to affect both fetal growth and later-life health of the newborn, yet the implicated molecular mechanisms remain largely unknown. As the master regulator of the fetal environment, the placenta is a valuable resource for the investigation of processes involved in the developmental programming of metabolic health. We conducted a genome-wide placental transcriptome study aiming at the identification of functional pathways representing the molecular link between maternal BMI and fetal growth. We used RNA microarray (Agilent 8 × 60 K), medical records, and questionnaire data from 183 mother-newborn pairs from the ENVIRONAGE birth cohort study (Flanders, Belgium). Using a weighted gene co-expression network analysis, we identified 17 correlated gene modules. Three of these modules were associated with both maternal pre-pregnancy BMI and newborn birth weight. A gene cluster enriched for genes involved in immune response and myeloid cell differentiation was positively associated with maternal BMI and negatively with low birth weight. Two other gene modules, upregulated in association with maternal BMI as well as birth weight, were involved in processes related to organ and tissue development, with blood vessel morphogenesis and extracellular matrix structure as top Gene Ontology terms. In line with this, erythrocyte-, angiogenesis-, and extracellular matrix-related genes were among the identified hub genes. The association between maternal BMI and newborn weight was significantly mediated by gene expression for 5 of the hub genes (FZD4, COL15A1, GPR124, COL6A1, and COL1A1). As some of the identified hub genes have been linked to obesity in adults, our observation in placental tissue suggests that biological processes may be affected from prenatal life onwards, thereby identifying new molecular processes linking maternal BMI and fetal metabolic programming.

Maternal body mass index moderates antenatal depression effects on infant birthweight

Obesity and depression are two common medical problems that pregnant women present with in antenatal care. Overweight and obesity at the beginning of the pregnancy, and excessive weight gain during pregnancy, are independent explanatory variables for fetal birthweight and independent risk factors for giving birth to a large for gestational age (LGA) infant. However, the effect of co-morbid depression has received little attention. This study set out to investigate if maternal body mass index (BMI) in early pregnancy moderates antenatal depression effects on infant birthweight. 3965 pregnant women participated in this longitudinal cohort study, where cases (n = 178) had Edinburgh Postnatal Depression Scale (EPDS) score ≥ 17 in gestational week 17 or 32, and remaining women (n = 3787) were used as controls. The influence of maternal BMI and antenatal depressive symptoms on standardized birthweight was evaluated by analysis of covariance, with adjustment for relevant confounders. Depressed women with BMI 25.0 kg/m² or more gave birth to infants with significantly greater standardized birthweight than non-depressed overweight women, whereas the opposite pattern was noted in normal weight women (BMI by antenatal depressive symptoms interaction; F(1,3839) = 6.32; p = 0.012. The increased birthweight in women with co-prevalent overweight and depressive symptoms was not explained by increased weight gain during the pregnancy. Maternal BMI at the beginning of pregnancy seems to influence the association between antenatal depressive symptoms and infant birthweight, but in opposite directions depending on whether the pregnant women is normal weight or overweight. Further studies are needed to confirm our finding.

Maternal Pre-Pregnancy Obesity Is Associated with Altered Placental Transcriptome

Maternal obesity has a major impact on pregnancy outcomes. There is growing evidence that maternal obesity has a negative influence on placental development and function, thereby adversely influencing offspring programming and health outcomes. However, the molecular mechanisms underlying these processes are poorly understood. We analysed ten term placenta’s whole transcriptomes in obese (n = 5) and normal weight women (n = 5), using the Affymetrix microarray platform. Analyses of expression data were carried out using non-parametric methods. Hierarchical clustering and principal component analysis showed a clear distinction in placental transcriptome between obese and normal weight women. We identified 72 differentially regulated genes, with most being down-regulated in obesity (n = 61). Functional analyses of the targets using DAVID and IPA confirm the dysregulation of previously identified processes and pathways in the placenta from obese women, including inflammation and immune responses, lipid metabolism, cancer pathways, and angiogenesis. In addition, we detected new molecular aspects of obesity-derived effects on the placenta, involving the glucocorticoid receptor signalling pathway and dysregulation of several genes including CCL2, FSTL3, IGFBP1, MMP12, PRG2, PRL, QSOX1, SERPINE2 and TAC3. Our global gene expression profiling approach demonstrates that maternal obesity creates a unique in utero environment that impairs the placental transcriptome.

Metabolic targets of endocrine disrupting chemicals assessed by cord blood transcriptome profiling

Early life exposure to endocrine disrupting chemicals (EDCs) has been frequently associated with impaired perinatal growth, an important risk factor for later onset of metabolic disorders. We analyzed whether the cord blood transcriptome showed early indications of alterations in metabolic processes in 195 human samples in relation to cord blood levels of dichlorodiphenyldichloroethylene (p,p'-DDE), polychlorinated biphenyl-153 (PCB-153), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS). Overall, 39 metabolically relevant transcription factors were significantly enriched (31 by p,p'-DDE, 10 by PCB-153, 8 by PFOA, and 2 by PFOS). These included the glucocorticoid receptor (p,p'-DDE and PCB-153) and the progesterone receptor (PFOA and PFOS). The 'insulin receptor signaling', 'acute phase response signaling', 'Interleukin(IL)-6 signaling', and 'prolactin signaling' pathways were significantly enriched in relation to p,p'-DDE. Transcriptional changes at birth suggest a role for specific metabolic targets as a link between prenatal EDC exposure and metabolic disorders later in life.