To assess factors influencing the success of whole genome sequencing for mainstream clinical diagnosis, we sequenced 217 individuals from 156 independent cases across a broad spectrum of disorders in whom prior screening had identified no pathogenic variants. We quantified the number of candidate variants identified using different strategies for variant calling, filtering, annotation and prioritisation. We found that jointly calling variants across samples, filtering against both local and external databases, deploying multiple annotation tools and using familial transmission above biological plausibility contributed to accuracy. Overall, we identified disease causing variants in 21% of cases, rising to 34% (23/68) for Mendelian disorders and 57% (8/14) in trios. We also discovered 32 potentially clinically actionable variants in 18 genes unrelated to the referral disorder, though only four were ultimately considered reportable. Our results demonstrate the value of genome sequencing for routine clinical diagnosis, but also highlight many outstanding challenges.Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use

AMPA receptor (AMPA-R) complexes consist of channel forming subunits, GluA1–4 and auxiliary proteins including TARPs, CNIHs, synDIG1, and CKAMP44, which can modulate AMPA-R function in specific ways. Combinatorial effects of four GluA subunits binding to various auxiliary subunits amplify the functional diversity of AMPA-Rs. The significance and magnitude of molecular diversity, however, remain elusive. To gain insight into the molecular complexity of AMPA and kainate receptors (KA-Rs), we compared the proteins that co-purify with each receptor type in rat brain. This interactome study identified the majority of known interacting proteins and more importantly, provides novel candidates for further studies. We validate the claudin homologue GSG1L as a novel binding protein and unique modulator of AMPA-R gating, as determined by detailed molecular, cellular, electrophysiological, and biochemical experiments. GSG1L extends the functional variety of AMPA-R complexes and further investigation of other candidates may reveal additional complexity of ionotropic glutamate receptor function.

AMPA-type glutamate receptors (AMPARs), central mediators of rapid neurotransmission and synaptic plasticity, predominantly exist as heteromers of the GluA1-4 subunits. Here we report first AMPAR heteromer structures, which deviate substantially from existing GluA2 homomers. Crystal structures of the GluA2/3 and GluA2/4 N-terminal domains reveal a novel compact conformation with an alternating arrangement of the four subunits around a central axis. This organization is confirmed by cysteine crosslinking in full-length receptors and permitted us to determine the structure of an intact GluA2/3 receptor by cryo-EM. Two models in the ligand-free state, at 8.25 Å and 10.3 Å resolution, exhibit a substantial vertical compression and close associations between domain layers, reminiscent of NMDA receptors. Model 1 resembles a resting state, model 2 a desensitized state, providing snapshots of gating transitions in the nominal absence of ligand. Our data reveal organizational features of heteromeric AMPARs and provide a framework to decipher AMPAR architecture and signaling.Ionotropic glutamate receptors (iGluRs) are tetrameric cation channels that mediate fast excitatory signal transmission upon binding presynaptically released glutamate (1). They are essential for brain development and experience-dependent synaptic plasticity, which underlies learning. iGluR dysfunction is implicated in a number of neurological disorders including dementia, mood disorders and epilepsy (2). Three major subtypes, the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, N-methyl-D-aspartate and kainate receptors (AMPARs, NMDARs and KARs), each contribute a different component to the synaptic signal (1). AMPARs mediate the initial depolarization of the postsynaptic membrane, triggering NMDAR activation and the generation of an excitatory postsynaptic potential. The rapid kinetics of AMPARs permit moment-to-moment signaling and their trafficking to synapses is central to synaptic plasticity (3).Gating kinetics, ion permeation and trafficking are set by the subunit stoichiometry and ultimately shape the synaptic response. AMPAR tetramers are composed of the GluA1-* Correspondence to: ig@mrc-lmb.cam.ac.uk. GluA4 subunits with the vast majority containing GluA2, which renders the channel Ca 2+ -impermeable, lowers its conductance and alters its voltage dependence (1, 4). Europe PMC Funders GroupStructures of GluA2 homomers have been instrumental in clarifying AMPAR modular architecture (5). The receptor is arranged in domain layers (Fig. 1A) -a two-fold symmetrical extracellular region (ECR), composed of the N-terminal domain (NTD) and ligand-binding domain (LBD), is attached to the transmembrane ion channel domain (TMD) of approximately four-fold symmetry (Fig. 1A), while a cytoplasmic tail mediates trafficking and anchorage at synapses. The four chains (A-D) in a tetramer are conformationally nonequivalent and likely contribute differently to gating: the 'AC' pair is positioned closer to the ion conduction pore axis (at the level of...

AMPA-type glutamate receptors (AMPARs) mediate excitatory neurotransmission, and are central regulators of synaptic plasticity, a molecular mechanism underlying learning and memory. Although AMPARs act predominantly as heteromers, structural studies have focused on homomeric assemblies. Here we present a cryo-EM structure of the heteromeric GluA1/2 receptor associated with two TARP γ8 auxiliary subunits, the principal AMPAR complex at hippocampal synapses. Within the receptor, the core subunits arrange to give the GluA2 subunit dominant control of gating. This structure reveals the geometry of the Q/R-site controlling calcium flux, suggests association of TARP-stabilized lipids, and demonstrates that the extracellular loop of γ8 modulates gating by selectively interacting with the GluA2 ligand-binding domain. Collectively, this structure provides a blueprint for deciphering the signal transduction mechanisms of synaptic AMPARs.