Analysis of Pools of Targeted Salmonella Deletion Mutants Identifies Novel Genes Affecting Fitness during Competitive Infection in Mice

Pools of mutants of minimal complexity but maximal coverage of genes of interest facilitate screening for genes under selection in a particular environment. We constructed individual deletion mutants in 1,023 Salmonella enterica serovar Typhimurium genes, including almost all genes found in Salmonella but not in related genera. All mutations were confirmed simultaneously using a novel amplification strategy to produce labeled RNA from a T7 RNA polymerase promoter, introduced during the construction of each mutant, followed by hybridization of this labeled RNA to a Typhimurium genome tiling array. To demonstrate the ability to identify fitness phenotypes using our pool of mutants, the pool was subjected to selection by intraperitoneal injection into BALB/c mice and subsequent recovery from spleens. Changes in the representation of each mutant were monitored using T7 transcripts hybridized to a novel inexpensive minimal microarray. Among the top 120 statistically significant spleen colonization phenotypes, more than 40 were mutations in genes with no previously known role in this model. Fifteen phenotypes were tested using individual mutants in competitive assays of intraperitoneal infection in mice and eleven were confirmed, including the first two examples of attenuation for sRNA mutants in Salmonella. We refer to the method as Array-based analysis of cistrons under selection (ABACUS)

Development of aggression subtypes from childhood to adolescence:a group-based multi-trajectory modelling perspective

The persistence of elevated subtypes of aggression beginning in childhood have been associated with long-term maladaptive outcomes. Yet it remains unclear to what extent there are clusters of individuals following similar developmental trajectories across forms (i.e., physical and indirect) and functions (i.e., proactive and reactive) of aggression. We aimed to identify groups of children with distinct profiles of the joint development of forms and functions of aggression and to identify risk factors for group membership. A sample of 787 children was followed from birth to adolescence. Parent and teacher reports, and standardised assessments were used to measure two forms and two functions of aggressive behaviour, between six and 13 years of age along with preceding child, maternal, and family-level risk-factors. Analyses were conducted using a group-based multi-trajectory modelling approach. Five trajectory groups emerged: non-aggressors, low-stable, moderate-engagers, high-desisting, and high-chronic. Coercive parenting increased membership risk in the moderate-engagers and high-chronic groups. Lower maternal IQ increased membership risk in both high-desisting and high-chronic groups, whereas maternal depression increased membership risk in the high-desisting group only. Never being breastfed increased membership risk in the moderate-engagers group. Boys were at greater risk for belonging to groups displaying elevated aggression. Individuals with chronic aggression problems use all subtypes of aggression. Risk factors suggest that prevention programs should start early in life and target mothers with lower IQ. Strategies to deal with maternal depression and enhance positive parenting while replacing coercive parenting tactics should be highlighted in programming efforts

The chronicity and timing of prenatal and antenatal maternal depression and anxiety on child outcomes at age 5

BACKGROUND: Maternal depression and anxiety have been associated with deleterious child outcomes. It is, however, unclear how the chronicity and timing of maternal mental health problems predict child development outcomes. The aim of the current study was to assess the effect of both chronicity and timing of maternal anxiety and depression in pregnancy, infancy, and the toddler period on children's internalizing and externalizing symptoms, as well as social and communication skills at age 5. METHOD: Participants were 1,992 mother-child pairs drawn from a large prospective pregnancy cohort. Mothers reported on anxiety and depression symptoms with clinical screening tools at six time points between <25 weeks gestation and 3 years postpartum. Child outcomes were assessed at age 5. RESULTS: Effect sizes were small for brief incidents of depression/anxiety and increased for intermittent and chronic problems (i.e., three or more timepoints) compared with mothers who had never experienced clinical-level anxiety or depression. Maternal anxiety/depression during pregnancy, infancy, and toddlerhood predicted all child outcomes, even after controlling for depression/anxiety during the other timepoints. However, maternal anxiety and depression during toddlerhood had a stronger association with child internalizing/externalizing symptoms and communication skills than either prenatal or postpartum depression/anxiety. CONCLUSIONS: Increasing number of exposures to clinical-level anxiety and depression is related to poorer child outcomes. Neither prenatal nor postpartum periods emerged as "sensitive" periods. Rather, maternal depression and anxiety during toddlerhood was more strongly associated with child outcomes at age 5. Results highlight the need for continued support for maternal mental health across early childhood