Prenatal phenotyping: A community effort to enhance the Human Phenotype Ontology.

Technological advances in both genome sequencing and prenatal imaging are increasing our ability to accurately recognize and diagnose Mendelian conditions prenatally. Phenotype-driven early genetic diagnosis of fetal genetic disease can help to strategize treatment options and clinical preventive measures during the perinatal period, to plan in utero therapies, and to inform parental decision-making. Fetal phenotypes of genetic diseases are often unique and at present are not well understood; more comprehensive knowledge about prenatal phenotypes and computational resources have an enormous potential to improve diagnostics and translational research. The Human Phenotype Ontology (HPO) has been widely used to support diagnostics and translational research in human genetics. To better support prenatal usage, the HPO consortium conducted a series of workshops with a group of domain experts in a variety of medical specialties, diagnostic techniques, as well as diseases and phenotypes related to prenatal medicine, including perinatal pathology, musculoskeletal anomalies, neurology, medical genetics, hydrops fetalis, craniofacial malformations, cardiology, neonatal-perinatal medicine, fetal medicine, placental pathology, prenatal imaging, and bioinformatics. We expanded the representation of prenatal phenotypes in HPO by adding 95 new phenotype terms under the Abnormality of prenatal development or birth (HP:0001197) grouping term, and revised definitions, synonyms, and disease annotations for most of the 152 terms that existed before the beginning of this effort. The expansion of prenatal phenotypes in HPO will support phenotype-driven prenatal exome and genome sequencing for precision genetic diagnostics of rare diseases to support prenatal care

The birth of a human-specific neural gene by incomplete duplication and gene fusion

Background: Gene innovation by duplication is a fundamental evolutionary process but is difficult to study in humans due to the large size, high sequence identity, and mosaic nature of segmental duplication blocks. The human-specific gene hydrocephalus-inducing 2, HYDIN2, was generated by a 364 kbp duplication of 79 internal exons of the large ciliary gene HYDIN from chromosome 16q22.2 to chromosome 1q21.1. Because the HYDIN2 locus lacks the ancestral promoter and seven terminal exons of the progenitor gene, we sought to characterize transcription at this locus by coupling reverse transcription polymerase chain reaction and long-read sequencing. Results: 5' RACE indicates a transcription start site for HYDIN2 outside of the duplication and we observe fusion transcripts spanning both the 5' and 3' breakpoints. We observe extensive splicing diversity leading to the formation of altered open reading frames (ORFs) that appear to be under relaxed selection. We show that HYDIN2 adopted a new promoter that drives an altered pattern of expression, with highest levels in neural tissues. We estimate that the HYDIN duplication occurred ~3.2 million years ago and find that it is nearly fixed (99.9%) for diploid copy number in contemporary humans. Examination of 73 chromosome 1q21 rearrangement patients reveals that HYDIN2 is deleted or duplicated in most cases. Conclusions: Together, these data support a model of rapid gene innovation by fusion of incomplete segmental duplications, altered tissue expression, and potential subfunctionalization or neofunctionalization of HYDIN2 early in the evolution of the Homo lineage

The Human Phenotype Ontology in 2024: phenotypes around the world.

The Human Phenotype Ontology (HPO) is a widely used resource that comprehensively organizes and defines the phenotypic features of human disease, enabling computational inference and supporting genomic and phenotypic analyses through semantic similarity and machine learning algorithms. The HPO has widespread applications in clinical diagnostics and translational research, including genomic diagnostics, gene-disease discovery, and cohort analytics. In recent years, groups around the world have developed translations of the HPO from English to other languages, and the HPO browser has been internationalized, allowing users to view HPO term labels and in many cases synonyms and definitions in ten languages in addition to English. Since our last report, a total of 2239 new HPO terms and 49235 new HPO annotations were developed, many in collaboration with external groups in the fields of psychiatry, arthrogryposis, immunology and cardiology. The Medical Action Ontology (MAxO) is a new effort to model treatments and other measures taken for clinical management. Finally, the HPO consortium is contributing to efforts to integrate the HPO and the GA4GH Phenopacket Schema into electronic health records (EHRs) with the goal of more standardized and computable integration of rare disease data in EHRs

Understanding the genetic basis of phenotype variability in individuals with neurocognitive disorders

Thesis (Ph.D.)--University of Washington, 2016-06Individuals with a diagnosis of a neurocognitive disorder, such as an autism spectrum disorder (ASD), can present with a wide range of phenotypes. Some have severe language and cognitive deficiencies while others are only deficient in social functioning. Sequencing studies have revealed extreme locus heterogeneity underlying the ASDs. Even cases with a known pathogenic variant, such as the 16p11.2 CNV, can be associated with phenotypic heterogeneity. In this thesis, I test the hypothesis that phenotypic heterogeneity observed in populations with a known pathogenic variant, such as the 16p11.2 CNV as well as that associated with the ASDs in general, is due to additional genetic factors. I analyze the phenotypic and genotypic characteristics of over 120 families where at least one individual carries the 16p11.2 CNV, as well as a cohort of over 40 families with high functioning autism and/or intellectual disability. In the 16p11.2 cohort, I assessed variation both internal to and external to the CNV critical region. Among de novo cases, I found a strong maternal bias for the origin of deletions (59/66, 89.4% of cases, p=2.38x10^-11), the strongest such effect so far observed for a CNV associated with a microdeletion syndrome, a significant maternal transmission bias for secondary deletions (32 maternal versus 14 paternal, p=1.14x10^-2), and nine probands carrying additional CNVs disrupting autism-associated genes. In the same cohort, I assessed genome wide exonic variation, including in the 27 16p11.2 CNV critical region genes and the 3 genes that lie in the flanking segmental duplications, BOLA2, SLX1A, and SULT1A3 with the hypothesis that dosage imbalance in these genes could lead to variable phenotypes. I find an absence of variation across the critical region, compared to similarly sized regions genome-wide by average heterozygosity (2nd percentile) and Tajima’s D (3rd percentile) metrics. Among the 27 critical region genes and three duplicated genes, I find no loss of function variants in 16p11.2 CNV carriers. Our genome-wide exome analysis revealed 13 likely-gene disruptive (LGD) variants in 13 probands in autism-associated genes, which is fewer than would be expected by chance (p<10^-16) and individuals having such variants trend towards being more severely affected on FSIQ (p=0.19). To understand the genetic heterogeneity associated with high-functioning autism and intellectual disability, I assessed genetic variation observed in a cohort of 43 local families of which 29 have a diagnosis of high functioning-autism. I discovered variants in novel autism candidate genes, including LPHN1 and NUMBL, find that the high functioning autism cohort tends to have more inherited loss of function and severe missense variation per individual than low functioning cohorts (p<2.2x10^-16), but fewer de novo LGD variants per individual (p=0.007). I also find that de novo variants in high functioning cases lie in a protein-protein interaction network including proteins involved in the NOTCH signaling pathway. Our findings suggest that modifiers external to, as opposed to variants internal to the critical region, may play a role in the observed phenotypic differences observed in individuals with a 16p11.2 CNV and those with ASDs in general

Genomic studies in fragile X premutation carriers.

BackgroundThe FMR1 premutation is defined as having 55 to 200 CGG repeats in the 5' untranslated region of the fragile X mental retardation 1 gene (FMR1). The clinical involvement has been well characterized for fragile X-associated tremor/ataxia syndrome (FXTAS) and fragile X-associated primary ovarian insufficiency (FXPOI). The behavior/psychiatric and other neurological manifestations remain to be specified as well as the molecular mechanisms that will explain the phenotypic variability observed in individuals with the FMR1 premutation.MethodsHere we describe a small pilot study of copy number variants (CNVs) in 56 participants with a premutation ranging from 55 to 192 repeats. The participants were divided into four different clinical groups for the analysis: those with behavioral problems but no autism spectrum disorder (ASD); those with ASD but without neurological problems; those with ASD and neurological problems including seizures; and those with neurological problems without ASD.ResultsWe found 12 rare CNVs (eight duplications and four deletions) in 11 cases (19.6%) that were not found in approximately 8,000 controls. Three of them were at 10q26 and two at Xp22.3, with small areas of overlap. The CNVs were more commonly identified in individuals with neurological involvement and ASD.ConclusionsThe frequencies were not statistically significant across the groups. There were no significant differences in the psychometric and behavior scores among all groups. Further studies are necessary to determine the frequency of second genetic hits in individuals with the FMR1 premutation; however, these preliminary results suggest that genomic studies can be useful in understanding the molecular etiology of clinical involvement in premutation carriers with ASD and neurological involvement

Non-DNA-binding cofactors enhance DNA-binding specificity of a transcriptional regulatory complex

Recruitment of cofactors to specific DNA sites is integral for specificity in gene regulation. As a model system, we examined how targeting and transcriptional control of the sulfur metabolism genes in Saccharomyces cerevisiae is governed by recruitment of the transcriptional co-activator Met4. We developed genome-scale approaches to measure transcription factor (TF) DNA-binding affinities and cofactor recruitment to >1300 genomic binding site sequences. We report that genes responding to the TF Cbf1 and cofactor Met28 contain a novel ‘recruitment motif’ (RYAAT), adjacent to Cbf1 binding sites, which enhances the binding of a Met4–Met28–Cbf1 regulatory complex, and that abrogation of this motif significantly reduces gene induction under low-sulfur conditions. Furthermore, we show that correct recognition of this composite motif requires both non-DNA-binding cofactors Met4 and Met28. Finally, we demonstrate that the presence of an RYAAT motif next to a Cbf1 site, rather than Cbf1 binding affinity, specifies Cbf1-dependent sulfur metabolism genes. Our results highlight the need to examine TF/cofactor complexes, as novel specificity can result from cofactors that lack intrinsic DNA-binding specificity.National Institutes of Health (U.S.) (Grant R01 HG003985)National Institutes of Health (U.S.) (Grant U54 LM008748)National Science Foundation (U.S.) (Postdoctoral Fellowship in Biological Informatics 630639

The birth of a human-specific neural gene by incomplete duplication and gene fusion.

BackgroundGene innovation by duplication is a fundamental evolutionary process but is difficult to study in humans due to the large size, high sequence identity, and mosaic nature of segmental duplication blocks. The human-specific gene hydrocephalus-inducing 2, HYDIN2, was generated by a 364 kbp duplication of 79 internal exons of the large ciliary gene HYDIN from chromosome 16q22.2 to chromosome 1q21.1. Because the HYDIN2 locus lacks the ancestral promoter and seven terminal exons of the progenitor gene, we sought to characterize transcription at this locus by coupling reverse transcription polymerase chain reaction and long-read sequencing.Results5' RACE indicates a transcription start site for HYDIN2 outside of the duplication and we observe fusion transcripts spanning both the 5' and 3' breakpoints. We observe extensive splicing diversity leading to the formation of altered open reading frames (ORFs) that appear to be under relaxed selection. We show that HYDIN2 adopted a new promoter that drives an altered pattern of expression, with highest levels in neural tissues. We estimate that the HYDIN duplication occurred ~3.2 million years ago and find that it is nearly fixed (99.9%) for diploid copy number in contemporary humans. Examination of 73 chromosome 1q21 rearrangement patients reveals that HYDIN2 is deleted or duplicated in most cases.ConclusionsTogether, these data support a model of rapid gene innovation by fusion of incomplete segmental duplications, altered tissue expression, and potential subfunctionalization or neofunctionalization of HYDIN2 early in the evolution of the Homo lineage

Beyond the exome: What\u27s next in diagnostic testing for Mendelian conditions

Despite advances in clinical genetic testing, including the introduction of exome sequencing (ES), more than 50% of individuals with a suspected Mendelian condition lack a precise molecular diagnosis. Clinical evaluation is increasingly undertaken by specialists outside of clinical genetics, often occurring in a tiered fashion and typically ending after ES. The current diagnostic rate reflects multiple factors, including technical limitations, incomplete understanding of variant pathogenicity, missing genotype-phenotype associations, complex gene-environment interactions, and reporting differences between clinical labs. Maintaining a clear understanding of the rapidly evolving landscape of diagnostic tests beyond ES, and their limitations, presents a challenge for non-genetics professionals. Newer tests, such as short-read genome or RNA sequencing, can be challenging to order, and emerging technologies, such as optical genome mapping and long-read DNA sequencing, are not available clinically. Furthermore, there is no clear guidance on the next best steps after inconclusive evaluation. Here, we review why a clinical genetic evaluation may be negative, discuss questions to be asked in this setting, and provide a framework for further investigation, including the advantages and disadvantages of new approaches that are nascent in the clinical sphere. We present a guide for the next best steps after inconclusive molecular testing based upon phenotype and prior evaluation, including when to consider referral to research consortia focused on elucidating the underlying cause of rare unsolved genetic disorders

Genome Sequencing of Autism-Affected Families Reveals Disruption of Putative Noncoding Regulatory DNA

We performed whole-genome sequencing (WGS) of 208 genomes from 53 families affected by simplex autism. For the majority of these families, no copy-number variant (CNV) or candidate de novo gene-disruptive single-nucleotide variant (SNV) had been detected by microarray or whole-exome sequencing (WES). We integrated multiple CNV and SNV analyses and extensive experimental validation to identify additional candidate mutations in eight families. We report that compared to control individuals, probands showed a significant (p = 0.03) enrichment of de novo and private disruptive mutations within fetal CNS DNase I hypersensitive sites (i.e., putative regulatory regions). This effect was only observed within 50 kb of genes that have been previously associated with autism risk, including genes where dosage sensitivity has already been established by recurrent disruptive de novo protein-coding mutations (ARID1B, SCN2A, NR3C2, PRKCA, and DSCAM). In addition, we provide evidence of gene-disruptive CNVs (in DISC1, WNT7A, RBFOX1, and MBD5), as well as smaller de novo CNVs and exon-specific SNVs missed by exome sequencing in neurodevelopmental genes (e.g., CANX, SAE1, and PIK3CA). Our results suggest that the detection of smaller, often multiple CNVs affecting putative regulatory elements might help explain additional risk of simplex autism