Maternal and fetal genetic contribution to gestational weight gain

BACKGROUND

Clinical recommendations to limit gestational weight gain (GWG) imply high GWG is causally related to adverse outcomes in mother or offspring, but GWG is the sum of several inter-related complex phenotypes (maternal fat deposition and vascular expansion, placenta, amniotic fluid and fetal growth). Understanding the genetic contribution to GWG could help clarify the potential effect of its different components on maternal and offspring health. Here we explore the genetic contribution to total, early and late GWG.

PARTICIPANTS AND METHODS

A genome-wide association study was used to identify maternal and fetal variants contributing to GWG in up to 10 543 mothers and 16 317 offspring of European origin, with replication in 10 660 mothers and 7561 offspring. Additional analyses determined the proportion of variability in GWG from maternal and fetal common genetic variants and the overlap of established genome-wide significant variants for phenotypes relevant to GWG (for example, maternal body mass index (BMI) and glucose, birth weight).

RESULTS

Approximately 20% of the variability in GWG was tagged by common maternal genetic variants, and the fetal genome made a surprisingly minor contribution to explain variation in GWG. Variants near the pregnancy-specific beta-1 glycoprotein 5 (PSG5) gene reached genome-wide significance (P=1.71 × 10-8) for total GWG in the offspring genome, but did not replicate. Some established variants associated with increased BMI, fasting glucose and type 2 diabetes were associated with lower early, and higher later GWG. Maternal variants related to higher systolic blood pressure were related to lower late GWG. Established maternal and fetal birth weight variants were largely unrelated to GWG.

CONCLUSIONS

We found a modest contribution of maternal common variants to GWG and some overlap of maternal BMI, glucose and type 2 diabetes variants with GWG. These findings suggest that associations between GWG and later offspring/maternal outcomes may be due to the relationship of maternal BMI and diabetes with GWG.

Lack of replication for the myosin-18B association with mathematical ability in independent cohorts

Twin studies indicate that dyscalculia (or mathematical disability) is caused partly by a genetic component, which is yet to be understood at the molecular level. Recently, a coding variant (rs133885) in the myosin-18B gene was shown to be associated with mathematical abilities with a specific effect among children with dyslexia. This association represents one of the most significant genetic associations reported to date for mathematical abilities and the only one reaching genome-wide statistical significance. We conducted a replication study in different cohorts to assess the effect of rs133885 maths-related measures. The study was conducted primarily using the Avon Longitudinal Study of Parents and Children (ALSPAC), (N = 3819). We tested additional cohorts including the York Cohort, the Specific Language Impairment Consortium (SLIC) cohort and the Raine Cohort, and stratified them for a definition of dyslexia whenever possible. We did not observe any associations between rs133885 in myosin-18B and mathematical abilities among individuals with dyslexia or in the general population. Our results suggest that the myosin-18B variant is unlikely to be a main factor contributing to mathematical abilities.

Gender differences in the relationships between lean body mass, fat mass and peak bone mass in young adults

The relationships between fat mass and bone mass in young adults are unclear. In 1,183 young Australians, lean body mass had a strong positive relationship with total body bone mass in both genders. Fat mass was a positive predictor of total body bone mass in females, with weaker association in males.

INTRODUCTION

Body weight and lean body mass are established as major determinants of bone mass, but the relationships between fat mass (including visceral fat) and peak bone mass in young adults are unclear. The aim of this study was to evaluate the associations between bone mass in young adults and three body composition measurements: lean body mass, fat mass and trunk-to-limb fat mass ratio (a surrogate measure of visceral fat).

METHODS

Study participants were 574 women and 609 men aged 19-22 years from the Raine study. Body composition, total body bone mineral content (TBBMC), bone area and areal bone mineral density (TBBMD) were measured using DXA.

RESULTS

In multivariate linear regression models with height, lean body mass, fat mass and trunk-to-limb fat mass ratio as predictor variables, lean mass was uniquely associated with the largest proportion of variance of TBBMC and TBBMD in males (semi-partial R(2) 0.275 and 0.345, respectively) and TBBMC in females (semi-partial R(2) 0.183). Fat mass was a more important predictor of TBBMC and TBBMD in females (semi-partial R(2) 0.126 and 0.039, respectively) than males (semi-partial R(2) 0.006 and 0.018, respectively). Trunk-to-limb fat mass ratio had a weak, negative association with TBBMC and bone area in both genders (semi-partial R(2) 0.004 to 0.034).

CONCLUSIONS

Lean body mass has strong positive relationship with total body bone mass in both genders. Fat mass may play a positive role in peak bone mass attainment in women but the association was weaker in men; different fat compartments may have different effects.

Childhood intelligence is heritable, highly polygenic and associated with FNBP1L

Intelligence in childhood, as measured by psychometric cognitive tests, is a strong predictor of many important life outcomes, including educational attainment, income, health and lifespan. Results from twin, family and adoption studies are consistent with general intelligence being highly heritable and genetically stable throughout the life course. No robustly associated genetic loci or variants for childhood intelligence have been reported. Here, we report the first genome-wide association study (GWAS) on childhood intelligence (age range 6-18 years) from 17,989 individuals in six discovery and three replication samples. Although no individual single-nucleotide polymorphisms (SNPs) were detected with genome-wide significance, we show that the aggregate effects of common SNPs explain 22-46% of phenotypic variation in childhood intelligence in the three largest cohorts (P=3.9 × 10(-15), 0.014 and 0.028). FNBP1L, previously reported to be the most significantly associated gene for adult intelligence, was also significantly associated with childhood intelligence (P=0.003). Polygenic prediction analyses resulted in a significant correlation between predictor and outcome in all replication cohorts. The proportion of childhood intelligence explained by the predictor reached 1.2% (P=6 × 10(-5)), 3.5% (P=10(-3)) and 0.5% (P=6 × 10(-5)) in three independent validation cohorts. Given the sample sizes, these genetic prediction results are consistent with expectations if the genetic architecture of childhood intelligence is like that of body mass index or height. Our study provides molecular support for the heritability and polygenic nature of childhood intelligence. Larger sample sizes will be required to detect individual variants with genome-wide significance.

Estimating remission from untreated major depression: a systematic review and meta-analysis

BACKGROUND

Few studies have examined spontaneous remission from major depression. This study investigated the proportion of prevalent cases of untreated major depression that will remit without treatment in a year, and whether remission rates vary by disorder severity.

METHOD

Wait-list controlled trials and observational cohort studies published up to 2010 with data describing remission from untreated depression at ≤ 2-year follow-up were identified. Remission was defined as rescinded diagnoses or below threshold scores on standardized symptom measures. Nineteen studies were included in a regression model predicting the probability of 12-month remission from untreated depression, using logit transformed remission proportion as the dependent variable. Covariates included age, gender, study type and diagnostic measure.

RESULTS

Wait-listed compared to primary-care samples, studies with longer follow-up duration and older adult compared to adult samples were associated with lower probability of remission. Child and adolescent samples were associated with higher probability of remission. Based on adult samples recruited from primary-care settings, the model estimated that 23% of prevalent cases of untreated depression will remit within 3 months, 32% within 6 months and 53% within 12 months.

CONCLUSIONS

It is undesirable to expect 100% treatment coverage for depression, given many will remit before access to services is feasible. Data were drawn from consenting wait-list and primary-care samples, which potentially over-represented mild-to-moderate cases of depression. Considering reported rates of spontaneous remission, a short untreated period seems defensible for this subpopulation, where judged appropriate by the clinician. Conclusions may not apply to individuals with more severe depression.

Changes in risk factors for preterm birth in Western Australia 1984-2006

OBJECTIVE

To characterise changing risk factors of preterm birth in Western Australia between 1984 and 2006.

DESIGN

Population-based study.

SETTING

Western Australia.

POPULATION

All non-Aboriginal women giving birth to live singleton infants between 1984 and 2006.

METHODS

Multinomial, multivariable regression models were used to assess antecedent profiles by preterm status and labour onset types (spontaneous, medically indicated, prelabour rupture of membranes [PROM]). Population attributable fraction (PAF) estimates characterized the contribution of individual antecedents as well as the overall contribution of two antecedent groups: pre-existing medical conditions (including previous obstetric history) and pregnancy complications.

MAIN OUTCOME MEASURE

Antecedent relationships with preterm birth, stratified by labour onset type.

RESULTS

Marked increases in maternal age and primiparous births were observed. A four-fold increase in the rates of pre-existing medical complications over time was observed. Rates of pregnancy complications remained stable. Multinomial regression showed differences in antecedent profiles across labour onset types. PAF estimates indicated that 50% of medically indicated preterm deliveries could be eliminated after removing six antecedents from the population; estimates for PROM and spontaneous preterm reduction were between 10 and 20%. Variables pertaining to previous and current obstetric complications (previous preterm birth, previous caesarean section, pre-eclampsia and antepartum haemorrhage) were the most influential predictors of preterm birth and adverse labour onset (PROM and medically indicated).

CONCLUSIONS

Preterm antecedent profiles have changed markedly over the 23 years studied. Some changes may be attributable to true change, others to advances in surveillance and detection. Still others may signify change in clinical practice.

OS049. Exome sequencing identifies likely functional variantsinfluencing preeclampsia and CVD risk

INTRODUCTION

Next-generation sequencing (NGS) in family-based study designs will be pivotal in unlocking the missing heritability of common complex diseases. Whilst our prior linkage- and association-based positional cloning studies in family- and population-based Australian cohorts, respectively, have discovered novel preeclampsia candidate genes (INHBB,ACVR2A,LCT,LRP1B,RND3,GCA,ERAP2,TNFSF13B), the full complement of causal genetic variation remains largely unknown. We have now sequenced the exomes of two Australian preeclampsia families in another step forward to unlocking preeclampsia's complex allelic architecture.

OBJECTIVES

Identify family-specific exon-centric loci segregating in preeclamptic women only.

METHODS

The exomes of 18 women (7 preeclamptics,11 controls) from two Australian families contributing to our chromosome 5q (Family 1) and 13q (Family 2) susceptibility loci, respectively, were sequenced using Illumina's TruSeq Exome Enrichment assay and NGS technology. Sequence alignments, quality control assessment and variant calling were conducted on our 8000 parallel processor compute server, MEDUSA. As a first pass, we prioritized exome sequence data to non-synonymous variants within the 1-LOD drop intervals of our 5q and 13q loci. Prioritized exonic variants were also genotyped in the Western Australian Pregnancy (Raine) Cohort to assess their significance against a plethora of cardiovascular disease (CVD) related traits.

RESULTS

In Family 1 we identified two missense SNPs and in Family 2 we identified one missense SNP to segregate in the preeclamptic women but not in the unaffected women. The first SNP in Family 1 (rs62375061) resides within the LYSMD3 gene, is predicted to "possibly" damage the focal protein and the only public record of this SNP is within the Watson genome. The second SNP in Family 1 (rs111033530) resides within the GPR98 gene, is predicted to "probably" damage the focal protein and is rare (1.7% population prevalence). The SNP in Family 2 (rs1805388) resides within the LIG4 gene, is predicted to be highly deleterious (F-SNP FSS=0.849) and is common (⩾17% population prevalence). In the Raine cohort the LIG4 SNP was also significantly associated with weight (p=0.0085), total cholesterol (p=0.0007), HDL cholesterol (p=0.0067) and LDL cholesterol (p=0.0324).

CONCLUSION

Our preliminary exome data documents the substantial potential to rapidly identify likely functional variants that influence preeclampsia risk. The GPR98 finding is of major interest to us as a recent genome-wide association study reported a significant association with diastolic blood pressure for a SNP at this same gene locus. Furthermore, our findings implicate LIG4 as a novel candidate susceptibility gene for CVD and add weight to the hypothesis of shared genetic risk factors for preeclampsia and CVD.

Trends in mode of delivery during 1984-2003: can they be explained by pregnancy and delivery complications?

OBJECTIVES

To describe trends in mode of delivery, to identify significant factors which affected mode of delivery, and to describe how these factors and their impact have changed over time.

DESIGN

Total population birth cohort.

SETTING

Western Australia 1984-2003.

PARTICIPANTS

The analysis was restricted to all singleton infants delivered at 37-42 weeks of gestation with a cephalic presentation (n = 432,327).

METHODS

Logistic regression analyses were undertaken to estimate significant independent risk factors separately for elective and emergency caesarean sections compared with vaginal delivery (spontaneous and instrumental), adjusting for potential confounding variables.

MAIN OUTCOME MEASURES

Trends in mode of delivery, demographic factors, and pregnancy and delivery complications. Estimated likelihood of elective caesarean section compared with vaginal delivery and emergency caesarean section compared with vaginal delivery.

RESULTS

Between 1984-88 and 1999-2003, the likelihood of women having an elective caesarean section increased by a factor of 2.35 times (95% CI 2.28-2.42) and the likelihood of an emergency caesarean section increased 1.89 times (95% CI 1.83-1.96). These caesarean section rate increases remained even after adjustment for their strong associations with many sociodemographic factors, obstetric risk factors, and obstetric complications. Rates of caesarean section were higher in older mothers, especially those older than 40 years of age (elective caesarean section, OR 5.42 [95% CI 4.88-6.01]; emergency caesarean section, OR 2.67 [95% CI 2.39-2.97]), and in nulliparous women (elective caesarean section, OR 1.54 [95% CI 1.47-1.61]; emergency caesarean section, OR 3.61 [95% CI 3.47-3.76]).

CONCLUSIONS

Our data show significant changes in mode of delivery in Western Australia from 1984-2003, with an increasing trend in both elective and emergency caesarean section rates that do not appear to be explained by increased risk or indication.

The effects of Neotyphodium endophytes in tall fescue on pasture mealy bug (Balanococcus poae)

The effect of different Neotyphodium endophyte strains in novel and natural tall fescue (Festuca arundinacea) associations on pasture mealy bug (Balanococcus poae) was investigated under grazing. All of the endophyte-infected tall fescue treatments had significantly lower numbers of mealy bugs compared to an endophyte-free control. Resistance to pasture mealy bug was maintained in novel associations free of the mammalian toxin ergovaline. Point analysis revealed that endophyte-free plots contained less tall fescue herbage than endophyte infected treatments. This paper raises the possibility that the pasture mealy bug was responsible.

Anti-graft-versus-host disease effect of DT390-anti-CD3sFv, a single-chain Fv fusion immunotoxin specifically targeting the CD3 epsilon moiety of the T-cell receptor

In a recent study, we showed that an immunotoxin (IT) made with a conventional monoclonal antibody targeting the CD3 epsilon moiety of the T-cell receptor (TCR) had a potent, but partial, graft-versus-host disease (GVHD) effect (Vallera et al, Blood 86:4367, 1995). Therefore, in this current study, we determined whether a fusion immunotoxin made with anti-CD3 single-chain Fv (sFv), the smallest unit of antibody recognizing antigen, would have anti-GVHD activity. A fusion protein was synthesized from a construct made by splicing sFv cDNA from the hybridoma 145-2C11 to a truncated form of the diphtheria toxin (DT390) gene. DT390 encodes a molecule that retains full enzymatic activity, but excludes the native DT binding domain. The DT390-anti-CD3sFv hybrid gene was cloned into a vector under the control of an inducible promoter. The protein was expressed in Escherichia coli and then purified from inclusion bodies. The DT390 moiety of the protein had full enzymatic activity compared with native DT and DT390-anti-CD3sFv, with an IC50 of 1 to 2 nmol/L against phytohemagglutinin-stimulated and alloantigen-stimulated T cells. Specificity was shown (1) by blocking the IT with parental anti-CD3 antibody, but not with a control antibody; (2) by failure of DT390-anti-CD3sFv to inhibit lipopolysaccharide-stimulated murine B cells; (3) by failure of an Ig control fusion protein, DT390-Fc, to inhibit T-cell responses; and (4) with in vivo immunohistochemisty studies. GVHD was studied in a model in which C57BL/6 (H-2b)-purified lymph node T cells were administered to major histocompatibility complex (MHC) antigen disparate unirradiated C.B.-17 scid (H-2d) mice to assess GVHD effects in the absence of irradiation toxicity. Flow cytometry studies showed that donor T cells were expanded 57-fold and histopathologic analysis showed the hallmarks of a lethal model of GVHD. Control mice receiving phosphate-buffered saline showed 17% survival on day 80 after bone marrow transplantation, and mice receiving 2 micrograms DT390-Fc fusion toxin control administered in 2 daily doses for 6 days (days 0 through 5) had a 43% survival rate. In contrast, 86% of mice receiving the same dose of DT390-anti-CD3sFv were survivors on day 80, a significant improvement, although survivors still showed histopathologic signs of GVHD. These findings suggest that new anti-GVHD agents can be genetically engineered and warrant further investigation of fusion proteins for GVHD treatment.

VH12 rearrangements in adult peritoneal B cells

About half of the phosphatidylcholine (PtC)-binding peritoneal B cells of B10.H-2aH-4bp/Wts mice express the VH12 gene. In these cells the D-region gene segments are restricted in length and sequence and are always rearranged to JH1, suggesting that PtC-specific B cells are clonally selected. To assess the extent to which this VH gene is used by peritoneal B cells to encode antibodies of other specificities, we have analyzed the length and sequence of D-region gene segments of VH12-D-JH1 rearrangements in peritoneal B cells independent of antigen specificity by PCR. We find that all 34 randomly chosen VH12-D-JH1 rearrangements analyzed are productive and have D regions that are restricted identically to those of PtC-specific B cells. These data suggest that essentially the entire repertoire of VH12-D-JH1 rearrangements are used by B cells that bind PtC, further illustrating the degree to which this repertoire is shaped by antigen selection.