Evan Eichler and colleagues use single-molecule molecular-inversion probes to sequence the coding and splicing regions of 208 candidate genes in more than 11,730 individuals with neurodevelopmental disorders. They report 91 genes with an excess of de novo or private disruptive mutations, identify 25 genes showing a bias for autism versus intellectual disability, and highlight a network associated with high-functioning autism. Gene-disruptive mutations contribute to the biology of neurodevelopmental disorders (NDDs), but most of the related pathogenic genes are not known. We sequenced 208 candidate genes from >11,730 cases and >2,867 controls. We identified 91 genes, including 38 new NDD genes, with an excess of de novo mutations or private disruptive mutations in 5.7% of cases. Drosophila functional assays revealed a subset with increased involvement in NDDs. We identified 25 genes showing a bias for autism versus intellectual disability and highlighted a network associated with high-functioning autism (full-scale IQ >100). Clinical follow-up for NAA15, KMT5B, and ASH1L highlighted new syndromic and nonsyndromic forms of disease.

This study characterizes the properties of disease-causing mutations that produce sporadic amino acid replacements in proteins of people with autism and developmental delay. The mutations tend to cluster and reoccur at specific regions important to protein function, highlighting for future follow-up ∼200 candidate genes, many involved in neuronal signaling. Although de novo missense mutations have been predicted to account for more cases of autism than gene-truncating mutations, most research has focused on the latter. We identified the properties of de novo missense mutations in patients with neurodevelopmental disorders (NDDs) and highlight 35 genes with excess missense mutations. Additionally, 40 amino acid sites were recurrently mutated in 36 genes, and targeted sequencing of 20 sites in 17,688 patients with NDD identified 21 new patients with identical missense mutations. One recurrent site substitution (p.A636T) occurs in a glutamate receptor subunit, GRIA1. This same amino acid substitution in the homologous but distinct mouse glutamate receptor subunit Grid2 is associated with Lurcher ataxia. Phenotypic follow-up in five individuals with GRIA1 mutations shows evidence of specific learning disabilities and autism. Overall, we find significant clustering of de novo mutations in 200 genes, highlighting specific functional domains and synaptic candidate genes important in NDD pathology.

Genotype-first combined with reverse phenotyping has shown to be a powerful tool in human genetics, especially in the era of next generation sequencing. This combines the identification of individuals with mutations in the same gene and linking these to consistent (endo)phenotypes to establish disease causality. We have performed a MIP (molecular inversion probe)-based targeted re-sequencing study in 3,275 individuals with intellectual disability (ID) to facilitate a genotype-first approach for 24 genes previously implicated in ID. Combining our data with data from a publicly available database, we confirmed 11 of these 24 genes to be relevant for ID. Amongst these, PHIP was shown to have an enrichment of disruptive mutations in the individuals with ID (5 out of 3,275). Through international collaboration, we identified a total of 23 individuals with PHIP mutations and elucidated the associated phenotype. Remarkably, all 23 individuals had developmental delay/ID and the majority were overweight or obese. Other features comprised behavioral problems (hyperactivity, aggression, features of autism and/or mood disorder) and dysmorphisms (full eyebrows and/or synophrys, upturned nose, large ears and tapering fingers). Interestingly, PHIP encodes two protein-isoforms, PHIP/DCAF14 and NDRP, each involved in neurodevelopmental processes, including E3 ubiquitination and neuronal differentiation. Detailed genotype-phenotype analysis points towards haploinsufficiency of PHIP/DCAF14, and not NDRP, as the underlying cause of the phenotype. Thus, we demonstrated the use of large scale re-sequencing by MIPs, followed by reverse phenotyping, as a constructive approach to verify candidate disease genes and identify novel syndromes, highlighted by PHIP haploinsufficiency causing an ID-overweight syndrome.

Next-Generation Sequencing (NGS) techniques have become a cornerstone of molecular diagnostics, enabling high-throughput, parallel analysis of multiple disease-associated genes. Their targeted design allows streamlined interpretation and optimised diagnostic yield, especially in disorders with known genetic heterogeneity. In this review, we provide a comprehensive overview of the clinical application of NGS techniques—targeted gene panels, whole exome sequencing (WES) and whole genome sequencing (WGS)—detailing the methodological workflow and the critical steps involved in their implementation. Particular emphasis is placed on the genes identified through NGS that are implicated in neurodevelopmental, neurodegenerative, psychiatric, neuromuscular, cardiovascular, and metabolic disorders. We also compare the advantages and limitations of panel-based diagnostics versus WES and WGS, and discuss future directions, including the integration of long-read sequencing technologies into multidisciplinary clinical practice. Finally, we consider how these advances may ultimately bridge biomedical research and clinical practise to improve the diagnosis and management of multifactorial diseases.