Genome Sequencing and Comprehensive Rare Variant Analysis of 465 Families with Neurodevelopmental Disorders

Purpose Despite significant progress in unravelling the genetic causes of neurodevelopmental disorders (NDDs), a substantial proportion of individuals with NDDs remain without a genetic diagnosis following microarray and/or exome sequencing. Here we aimed to assess the power of short-read genome sequencing (GS), complemented with long-read GS, to identify causal variants in NDD participants from the NIHR BioResource project. Methods Short-read GS was conducted on 692 individuals (489 affected and 203 unaffected relatives) from 465 families. Additionally, long-read GS was performed on five affected individuals who had structural variants (SVs) in technically challenging regions, complex SVs, or required distal variant phasing. Results Causal variants were identified in 36% affected individuals (177/489) and a further 26% (129/489) had a variant of uncertain significance, after multiple rounds of re-analysis. Among all reported variants, 88% (333/380) were SNVs/indels, and the remainder were structural variants (SVs), non-coding, and mitochondrial variants. Furthermore, long-read GS facilitated resolution of challenging SVs and invalidated variants of difficult interpretation from short-read GS. Conclusion This study demonstrates the value of short-read GS, complemented with long-reads, to investigate the genetic causes of NDDs. GS provides a comprehensive and unbiased method to identify all types of variants throughout the nuclear and mitochondrial genome in NDD individuals. ### Competing Interest Statement K.J.C and K.M. are currently employees of AstraZeneca. L.C.D. is currently an employee of Healx Ltd. ### Funding Statement This work was supported by The National Institute for Health Research England (NIHR) for the NIHR BioResource project (grant number RG65966). This work is partly funded by the NIHR GOSH BRC. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the Department of Health. This research was supported by the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All participants provided written informed consent to participate in the study. The study was approved by the East of England Cambridge South national institutional review board (13/EE/0325). The research conforms with the principles of the Declaration of Helsinki. Written informed consent to participate was obtained to publish clinical information. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Genome data has been deposited at the European Genome-phenome Archive (EGA) under accession number EGAD00001004522.