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Children with severe, undiagnosed developmental disorders (DDs) are enriched for damaging de novo mutations (DNMs) in developmentally important genes. We exome sequenced 4,294 families with children with DDs, and meta-analysed these data with published data on 3,287 children with similar disorders. We show that the most significant factors influencing the diagnostic yield of de novo mutations are the sex of the child, the relatedness of their parents and the age of both father and mother. We identified 95 genes enriched for damaging de novo mutation at genome-wide significance (P < 5 x 10-7), including fourteen genes for which compelling data for causation was previously lacking. The large number of genome-wide significant findings allow us to demonstrate that, at current cost differentials, exome sequencing has much greater power than genome sequencing for novel gene discovery in genetically heterogeneous disorders. We estimate that 42.5% of our cohort likely carry pathogenic de novo single nucleotide variants (SNVs) and indels in coding sequences, with approximately half operating by a loss-of-function mechanism, and the remainder being gain-of-function. We established that most haploinsufficient developmental disorders have already been identified, but that many gain-of-function disorders remain to be discovered. Extrapolating from the DDD cohort to the general population, we estimate that de novo dominant developmental disorders have an average birth prevalence of 1 in 168 to 1 in 377, depending on parental age.

Fluorescence imaging is one of the cornerstone techniques for understanding how single molecules search for their targets on DNA. By tagging individual proteins, it is possible to track their position with high accuracy. However, to understand how proteins search for targets, it is necessary to elongate the DNA to avoid protein localization ambiguities. Such structures known as "DNA tightropes" are tremendously powerful for imaging target location; however, they lack information about how force and load affect protein behavior. The use of optically trapped microstructures offers the means to apply and measure force effects. Here we describe a system that we recently developed to enable individual proteins to be directly manipulated on DNA tightropes. Proteins bound to DNA can be conjugated with Qdot fluorophores for visualization and also directly manipulated by an optically trapped, manufactured microstructure. Together this offers a new approach to understanding the physical environment of molecules, and the combination with DNA tightropes presents opportunities to study complex biological phenomena.

Protein-truncating variants protective against human disease provide in vivo validation of therapeutic targets. Here we used targeted sequencing to conduct a search for protein-truncating variants conferring protection against inflammatory bowel disease exploiting knowledge of common variants associated with the same disease. Through replication genotyping and imputation we found that a predicted protein-truncating variant (rs36095412, p.R179X, genotyped in 11,148 ulcerative colitis patients and 295,446 controls, MAF=up to 0.78%) in RNF186, a single-exon ring finger E3 ligase with strong colonic expression, protects against ulcerative colitis (overall P=6.89 × 10(-7), odds ratio=0.30). We further demonstrate that the truncated protein exhibits reduced expression and altered subcellular localization, suggesting the protective mechanism may reside in the loss of an interaction or function via mislocalization and/or loss of an essential transmembrane domain.

I studied how glutamate receptor-mediated responses, spatial arrangements, intrinsic properties and molecular specificity of cells serve cortical functions. I tested whether two somatosensory submodalities in the primary somatosensory (SI) cortex can be distinguished by glutamate receptor involvement in vivo. Low-threshold responses evoked by innocuous stimuli had a short-duration and long-duration component. The short-duration responses were mostly mediated by AMPA/kainate receptors and the long-duration responses involved the additional recruitment of NMDA receptors. High-threshold responses evoked by noxious stimuli were unimodal and mediated by both AMPA/kainate and NMDA receptors throughout the entire response. During noxious stimulus trials, an increase in baseline activity in SI cortical cells was observed. I attribute the changes in baseline activity to cells in the medial thalamic nuclei, which project to the SI cortex and are involved in the affective-motivational aspects of nociceptive signalling. To gain insight into the influence of synaptic organisation of a well-defined cortical area, I studied in vitro whether the intrinsic properties of two anatomically well-defined nonpyramidal cells in the hippocampus can provide clues into the modulation of neuronal signalling. During a depolarising current pulse, O-LM and O-Bi cells were distinguished by their accommodation of action potentials depending on the early or late part of the response. Also, during a hyperpolarising current pulse, O-LM cells displayed a prominent voltage 'sag' as compared to O-Bi cells. Both cell types contain somatostatin and I showed that O-LM cells express the metabotropic glutamate receptor type 1α. Although O-LM and O-Bi cells have a similar somatodendritic position their different axonal arbours imply that they are involved in the feedback modulation of the entorhinal and CA3 glutamatergic influences, respectively. I also found that contrary to previous reports not only somatostatin but also vasoactive intestinal polypeptide containing cells express mGluR1α, which might facilitate their oscillatory responses. To relate the action potential discharge of specific cortical cell classes to behaviourally relevant network activity, I also sought to identify hippocampal cells following in vivo recording. Novel information was provided for both the temporal and anatomical properties of cells not recorded previously. In particular, a putative interneuron targeting nonpyramidal cell and backprojection cell was recorded in relation to theta field events. A novel nonpyramidal projection cell was recorded in relation to sharp wave field events. A remarkable specificity was found in the dendritic and axonal patterns of these cells. The results show that distinct types of glutamate receptors are differentially involved in cortical function. The intrinsic properties and expression of mGluR1α in particular is highly specific in distinct nonpyramidal cell classes.

A thrust balance characterization of a low powered Quad Confinement Thruster is presented for high levels of propellant flow. The nominal flow rate for this device is between 1sccm and 2sccm of Xenon propellant. This study extends the operating range, and investigates the performance at two high flow conditions of 10sccm and 20sccm. Power is varied incrementally between 20W and 200W in order to characterize the performance versus power trends of the device. It was found that for these high flow regimes the propellant is underutilized, and a proportion of the increased thrust can likely be attributed to a hot gas expansion of the neutral Xenon rather than the generation of additional accelerated ions. The thrust was increased from 1mN (nominal) to 3.3mN at 200W of input power for the 20sccm condition. However, the performance penalty in terms of the specific impulse was considerable. The specific impulse under these conditions dropped below 200s, where the nominal condition is 1000s. A compromise between increased thrust and decreased performance was found at 10sccm of flow: 3mN of thrust at 300s specific impulse.

We show that a planar aperiodic lattice, mimicking the appearance of a sunflower, supports photonic bandgaps for weak dielectric contrast. The pattern’s high orientational order and spatially uniform modal pitch yields an isotropic Fourier space. A 2D structure of cylinders (epsilon=2) in air possesses a wide 21% TM bandgap, versus 5.6% for a sixfold lattice or 14% for a 12-fold fractal tiling. The isotropic gap frequencies imply flat bands, and thus application in nonlinear optics and low threshold lasers, where a reduced group velocity in all directions may be desired.